Engineering, Construction, and Operations in Space V

The threat of damage from high speed meteoroid and orbital debris particle impacts has become a significant design consideration in the development and construction of long duration earth-orbiting spacecraft. Historically, significant amounts of resources have been devoted to developing shielding for such structures as a means of reducing the penetration potential of high speed on-orbit impacts. These efforts have typically focused on simply whether or not the inner (or pressure) walls of candidate multi-wall structural systems would be perforated. Only recently the nature and extent of pressure wall penetration damage have begun to be explored. This paper presents the results of a study whose objective was to characterize the hole formation and cracking phenomena associated with the penetration of some of the multi-wall systems being considered for the International Space Station Alpha (ISSA). Empirical equations were developed for effective hole size and maximum tip-to-tip crack length in the event of a module penetration. These equations can be used in a survivability analysis to determine whether or not module unzipping would occur under a specific set of impact conditions and the time available for module evacuation prior to the onset of incapacitation due to air loss.

Understanding high-pressure material behavior is crucial to address the physical processes associated with a variety of hypervelocity impact events related to space sciences such as orbital-debris impact on a debris shield. At very high impact velocities material properties will be dominated by phase-changes, such as melting or vaporization, which cannot be achieved at lower impact velocities. Development of well-controlled and repeatable hypervelocity launch capabilities is the first step necessary to improve our understanding of material behavior at extreme pressures and temperatures not currently available using conventional two-stage light-gas gun techniques. In this paper, techniques used to extend the launch capabilities of a two-stage light gas gun to 16 km/s are described. It is anticipated that this technology will be useful in testing, evaluating, and design of various debris shields proposed for use with many different spacecrafts before deployment.

Impact probabilities are calculated for Leonid meteoroids acting upon space platforms in low Earth orbit. It is found that at times of meteor storm activity the meteoroid impact probability increases by factors in excess 10⁴ of that from the sporadic background of meteoroids. Currently, the most likely stream to yield a meteor storm is that of the Leonids. It is probable that the Leonid stream will produce at least one and perhaps several meteor storms during the last years of the 1990's. We present impact probabilities on satellites based on the historically observed flux of Leonids. In addition, we present our current predictions for the peak strength and time of occurrence for Leonid showers during the late 1990's and early 21st Century based on numerical simulation of the formation and evolution of the stream. The impact shielding presently incorporated into space platform design may not be adequate under Leonid storm conditions. Several risk curtailment scenarios are, however, open to space platform operators. An analysis of space platform impact probabilities from meteoroids within the Leonid stream suggests that the critical shielding concept outlined for the proposed Space Station will result, even under the most extreme of circumstances, in probabilities of no penetrative impacts above 99%.

Space debris could present a hazard to defense systems. Recent data indicate that impact rates from small particles at low altitudes may have been overestimated, impacts at high altitudes would only reduce the lifetimes of large satellites slightly, and fragmentation and cascade rates are small.

Detection of near-Earth Objects (NEOs) has concentrated on long-warning threats. LPCs and smaller objects do not offer such warning. Their detection on final approach is a more demanding search problem. Improvements in ground- and space-based search sensors and strategies could provide adequate search capability.

The US Air Force has developed considerable technology and operational experience applicable to the construction of a planetary defense system. This technology includes wide field of view sensors equipped with large format focal planes, detection techniques for identifying moving targets in cluttered backgrounds, methods for maintaining catalogs of space objects and satellite technology applicable to in-situ asteroid characterization. Much of this technology has been developed in order to support the US space surveillance program. The space surveillance program was initiated in response to the launch of Sputnik and now maintains a world wide network of sensors tasked with maintaining the location of all manmade space objects. The conduct of space surveillance requires that large portions of the sky be observed on a timely basis with high sensitivity. This requirement initially led to the construction of a network of wide field of view optical instruments called Baker Nunn cameras, after the developers. The Baker Nunns were quite successful, but suffered from two drawbacks (1) they used film as the detector in the focal plane which, since it had to be developed, limited how quickly the results were available and ignore the film was scanned manually, by personnel looking for streaks, to detect targets. In the late 1970's, advances in the capability of computers and high quality, intensified television cameras promised the development of "film free" electro-optic systems with automatic target detection capability. In order to develop such a system and determine its performance, the US Air Force constructed the Experimental Test Site (ETS) in Socorro, New Mexico. At the ETS a prototype space surveillance sensor system, consisting of meter class telescopes, equipped with intensified EBSICON television cameras, was constructed under the technical direction of MIT Lincoln Laboratory. The system employed automated computer algorithms to process the data and relieve the operators of manual tasks. The system performed quite well and specifications were developed for an operational system called GEODSS. The procurement contract was won by TRW Inc. and operational sites were established in New Mexico (across the parking lot from the ETS), Korea and Diego Garcia, in the Indian Ocean. The GEODSS network has been a cornerstone in the US Space Surveillance network since its deployment. However, the advance of detector and computer capability has left the current operational system equipped with obsolete technology. In order to improve the performance of the GEODSS to that provided by the current state of the art, the Air Force is in the process of upgrading the system. Under Air Force sponsorship, Lincoln Laboratory has developed a new generation of sensitive, large format, frame transfer CCD focal planes for GEODSS. These focal planes have been installed in a new generation of camera and are currently undergoing testing at the ETS. When equipped with the new focal plane and camera technology, the modest sized GEODSS telescopes have considerable capability to conduct large coverage, sensitive searches for earth crossing objects. Based on analysis, to be validated by field measurements, the CCD equipped GEODSS telescope will be capable of achieving a limiting magnitude of 22, over a 2 sq/deg field of view, with about 100 seconds of integration. This is comparable to the sensitivity of considerably larger telescopes equipped with current cameras. In addition to the high sensitivity, the CCD is configured for frame transfer operations which are well suited to asteroid search operations. Other Air Force programs have demonstrated technology applicable to the in-situ characterization of asteroids. This approach offers an unprecedented opportunity to understand the composition, structure and behavior of asteroids. The Clementine 2 program, currently planned as a joint venture between the Air Force Space Warfare Center, Phillips Laboratory and NASA, is intended to rendezvous with a number of near-earth asteroids and characterize each via probe impact.

Over the past several years, the Air Force has been developing new devices and technology for the detection and tracking of earth orbiting satellites. This technology has been targeted to provide an upgraded capability for an operational space surveillance system called GEODSS. Currently, a number of GEODSS systems are deployed around the world as part of the world-wide space surveillance system operated by the US Air Force. Each GEODSS site is currently equipped with 1-meter class telescopes and EBSICON detector systems which represent 1970's technology. The Air Force is now in the process of upgrading the GEODSS system to achieve the performance offered by state of the art detector systems. Under Air Force sponsorship, Lincoln Laboratory has developed a new generation of sensitive, large format, frame transfer CCD focal planes for GEODSS. These focal planes have been installed in a new generation of cameras and are currently undergoing testing at the Lincoln Laboratory Experimental Test Site (ETS). When equipped with the new focal plane and camera technology, the modest sized GEODSS telescopes have considerable capability to conduct large coverage, sensitive searches for earth crossing asteroids. Theoretical analysis has indicated that the CCD equipped GEODSS telescope will be capable of achieving a limiting magnitude of 22, over a 2 sq/deg field of view, with about 100 seconds of integration. This is comparable to the sensitivity of considerably larger telescopes equipped with current cameras. In addition to the high sensitivity, the CCD is configured for frame transfer operations which are well suited to asteroid search operations. This paper will present the results of the initial system tests conducted at the ETS and will discuss how this technology fits into a concept of operations for a planetary defense system based on the Air Force developed technology.

Orbital and landing operations at near-Earth asteroids involve a variety of difficulties due to the irregular shape of these asteroids and their potential for non-uniform rotation. These difficulties make it common to find trajectories that evolve from stable, near-circular orbits to crashing or escaping orbits in a matter of days. Even in less dramatic situations the nature of orbital mechanics about asteroids are different than the familiar planetary orbiter cases. The understanding and control of orbits about asteroids is essential if a human or robotic presence at asteroids is to become commonplace. A complementary issue to understanding these dynamics is the modeling of the asteroid environment. Much of the difficulty in planning missions to a small body stems from ignorance of the shape, spin state and gravity field of the target prior to asteroid rendezvous. For this reason, realistic a priori physical models of the targets can dramatically reduce the cost and risk of asteroid missions. This paper defines and discusses a variety of asteroid landing scenarios, gives a simple analysis of the benefits and difficulties involved with each of them and addresses the benefits of having accurate information about the target asteroid and about asteroids in general. In conjunction with this paper some examples of orbiter and lander trajectories about asteroids will be available in a video format. These examples use shape models of asteroids 4769 Castalia and 4179 Toutatis obtained by inversion of radar images.

Recent discoveries with Spacewatch telescope and optical orbital measurements show that there is enhanced population of small Near-Earth Objects with size smaller than 50 m defined for this paper as Near-Earth-Missing Asteroids (NEMA). Analysis of their orbits results in their perihelia distribution concentration near 1 AU, low eccentricities, and low velocities relative to the Earth. It is discussed here opportunities to use them (1) to obtain basic data on NEO and their origin, (2) to work out the technologies of NEO threat interdiction and components of future Space Defense System, (3) to study possibility to use them for space industrial technologies development, (4) to develop and implement various types of scientific and industrial space station, (5) to test some technologies of NEO orbit changing for Space Defense of the Earth and future space industry. NEMAs provides favorable conditions for implementation of this program. Small ΔV allows to use flexible space vehicles civilian and retired form military programs. Groundbased optical and radars systems could be efficiently upgraded and developed to provide needed observational support. Military and civilian space support systems could be developed to provide space navigation and control of spacecraft exploration of NEMA. Some preliminary components for the proposed program were analyzed and developed in Space Patrol project proposed by Lavochkin SPA. The results of this program would be of great value also for missions to long-distant asteroids and comets.

To study the nature of asteroids and comets, to determine possible methods and means of impact on threatening asteroid and also to predict consequences of collision with Earth we need to research into their physical properties. They include: 1. Dimensions, mass and shape of an asteroid, 2. Density of asteroid material and its distribution over depth. Grain density of grain (or porosity), 3. Chemical composition of an asteroid, 4. Data on shock compressibility of asteroid material, and 5. Elastic-plastic and strength parameters. A number of these parameters can be determined through astronomical observations. But some of them, very important, indeed, can be obtained only through performing space mission to an asteroid using research probes. We discuss feasibility of experimental research of various asteroid parameters depending on reciprocal kinematics of research probe and asteroid. Requirements to research apparatus, probe, registration system are formulated. Some existing techniques of information acquisition that can be utilized in research probe are shown. Therefore, reverse problem is also being solved: what experimental information can be gained for specific velocity of research probe and asteroid impact.

Paper provides calculated estimates of results of affecting the asteroid with buried explosion, surface explosion, and stand-off nuclear explosions and kinetic impact.

A new semi-analytical model describing the entry and deformation of meteoroids entering planetary atmospheres has been developed and calibrated against numerical simulations performed using the CTH shock-physics computational hydrocode. The model starts with the classical treatment of meteoroid ablation which is modified to include an explicit treatment of energy conservation during the ablative process. This is reconciled with terrestrial observations by modeling the formation of a vapor/debris layer (the visible bolide) surrounding the central meteoroid. A mechanical deformation model based on long-wavelength hydrodynamic instability growth is added and calibrated against numerical simulations performed with CTH. The analytical model provides initial conditions for numerical fireball simulations which are compared with observations of the Comet Shoemaker-Levy 9 impact on Jupiter and can be used to assess the terrestrial impact hazard.

The knowledge gained from the observations and simulations of the impact of comet Shoemaker-Levy 9 (SL9) with Jupiter has led us to consider the threat of impact-generated plumes to satellites in low-Earth orbit (LEO). Preliminary simulations suggest that impacts of a size that recur about once per century on Earth generate plumes that rise to nearly 1000 km over an area thousands of km in diameter. Interacting plumes from multiple impacts rise to higher altitudes. Detailed modeling of such plumes is needed to quantify this threat to satellites in LEO. Careful observations of high-energy atmospheric entry events using both satellite and ground-based instruments would provide validation for these computational models.

Influx of meteoroids onto Earth is reasonably well known for sizes of up to about 1 meter applying results from three independent Photographic Bolide (Fireball) Networks. The change of cumulative numbers with increasing mass was recently improved by new calibration at 100 kg masses from a very self-consistent solution for motion and ablation of the Lost City bolide (bulk density and terminal mass known from the recovered meteorite). The influx onto Earth of small asteroids observed in reflected sunlight is also reasonably well established from observations of the Space-Watch Telescope down to sizes of somewhat less than 10 meters. Cumulative fluxes as function of total kinetic energy at entry of these bodies into the Earth's atmosphere are used as standards for comparison with relative fluxes derived from cumulative numbers of 21 meteoric events observed by satellites (SA bolides). Absolute calibration is realized by comparing cumulative numbers of 43 Prairie Network (PN) bolides brighter than absolute magnitude –10 with the same flux curve and using the same method. Dynamically determined masses of the 43 PN bolides are used to define the mass scale of the satellite-observed (SA) bolides. Definitions of differential and total luminous efficiency are presented, and data on total luminous efficiencies as well as on velocities, masses, ablation coefficients, and on total radiated energies of 33 PN bolides are given. For the average luminous efficiency, the masses of the SA bolides resulted between 6 x 10⁶ kg and 3500 kg with the median value of 80000 kilograms. Corresponding sizes are from 15 m to 1.2 m with the median at 3.4 m.

ReVelle has recently presented a summary of available infrasonic signals from near-earth objects (NEOs) that entered the earth's atmosphere from about 1960–1980. Using an approach developed by Cox we have calculated the acoustic conversion efficiency for a number of these events that were detected by the U.S. Air Force. Based on results with conventional explosions, this quantity is expected to depend weakly on the range from the source. In our analysis of these events, we have used well-known, and independently calibrated, semi-empirical source energy (E_s) and wave period at maximum amplitude scaling relations developed by the U.S. Air Force along with various observed signal and atmospheric properties. With this knowledge of the source energy and the range, the efficiency can be computed. Our acoustic efficiencies range typically from about 0.1 to a few percent. In comparison, measurements of thunder by Holmes and co-workers determined an acoustic conversion efficiency from about 0.18 to 0.42 %. Previously, Astapovich also estimated the acoustic efficiency for meteor-fireballs on the basis of only fireball sound reports from a single event and determined a value of ⩽ 0.01 %. Using the efficiencies derived from analysis of the Air Force data, we hope eventually to predict the detection rate of NEOs for the proposed global scale CTBT (Comprehensive Test Ban Treaty) infrasonic system (60 arrays, each of 4 elements) and to establish the expected false alarm rate for such sources.

This paper will identify and examine issues encountered in past international space ventures, regarding management structures, differing parameters of operation, decision-making and expectations, for future consideration in the planning of an international moon mission. Recognizing and avoiding likely impediments whenever possible can save all of those involved time, money, considerable frustration, and, perhaps most importantly, increase the potential for success. Toward this end, information-based planning is crucial.

On July 20, 1989, the 20th anniversary of the Apollo Moon landing, President George Bush shared his Administration's bold vision for America's space program. He called for a completion of Space Station Freedom followed by human expeditions to the Moon and Mars. He talked about a permanent journey into space as a part of not only the destiny of America, but of all humankind. While Bush did not call for an "Apollo" type of crash effort, he did provide a highly visible and eloquent articulation of America's future in space. Thus began the short-lived effort that came to be known as the Space Exploration Initiative (SEI). And as we shall see, eloquence alone was not enough to secure America's future in space.

American supporters of human space exploration, identified in this essay as space proponents, want the United States to pursue a policy of establishing human settlements on other worlds in the Solar System. Human space exploration is a matter of public policy because a substantial expenditure of public resources is necessary to achieve this goal. A new approach to this policy question can be realized by critically examining the fundamental assumptions and beliefs of the space proponents. The theory of myth-systems provides a means to examine these principles. This theoretical framework demonstrates that the space proponents lack insight into their beliefs, misinterpret political events associated with human spaceflight, and thus unintentionally narrow their perspective on how to achieve their goal.

Although the Moon remains an obvious target for a new generation of human exploration missions, the demise of heavy-lift launch capabilities and the decline in space program expenditures might appear to place the Moon beyond our grasp. This paper will propose a strategy for renewing human exploration by fully exploiting existing space systems and establishing a staging point at the edge of the lunar gravity well. This plan is aimed at returning humans to the Moon by the end of this century and surpassing the accomplishments of Project Apollo through a sustained and affordable program of exploration with progressive growth in size and scope.

We have studied construction systems on the moon. The investigation of construction methods was performed on seven tasks. Through discussion, we generated several concepts for new construction methods. Then, we performed trade studies to get the most suitable system for lunar base construction. Construction processes and equipment which consume large amounts of electric power have also been discussed. Construction planning for lunar base depends on energy consumption policy. In this paper, we calculated the energy used for construction work on the moon. Estimation of energy consumption shows that the development of energy saving construction method is very much important where soil excavation and movement are concerned.

ESA's "Space 2020" initiative attempts to assess today's situation in terms of tomorrow's potential development within the space sector, in order to support a strategic long term programme. The European space sector and ESA are part of a complex network of socio-economic factors. It is expected that the structural changes, on a global as well as on a continental scale, which are most likely to occur during the next few decades will strongly affect the future of the space sector in general, and thus the role of ESA. In the first phase of the Space 2020 study, two important scenarios were selected as reference models for the time horizon chosen: the `Greater Europe Scenario' and the `Little Europe Scenario'. The Greater Europe Scenario held that, around the end of the decade, the European Union would in principle, have monetary union, convergence of economic policies, an integrated defence system, and a common foreign policy. The Little Europe Scenario, on the other hand, held that no real progress towards European integration was expected up to the end of the decade, particularly as far as monetary union and the convergence of foreign and defence policies were concerned. 3 areas have been assessed extensively and are discussed in more detail below: (1) concepts for cost reduction, (2) new services and potential synergies, and (3) trends in research and development.

Project Space Vision is a voluntary and independent effort by the young international space community, initiated to provide input to the Long-Term Space Policy Committee of the European Space Agency. The project reflects visions and priorities for the coming 50 years of space activities through the eyes of the post-Apollo generation. Using the Internet, the growing potential of professional networking in an emerging information society is explored. Several thousands of potential contributors could be reached internationally, within a few weeks, and responses were received from agencies, industries and institution related to space on a global basis. The dominating rationale for future space activities were found to be space exploration, space services and scientific progress. Main perceived barriers are lack of public and political support and high cost of access to space. Other results indicate drastic overestimates regarding the magnitude of current space expenditures and a trend towards a relatively more service- and Earth-oriented paradigm for space activities. The paper summarises the results and highlights the process that enabled its conclusion in a single month. Final recommendations are eventually expressed in the form of potential components of a long-term space policy based on the received contributions.

The U.S. government and NASA began placing emphasis and resources on commercial space beginning in the early 1980s. Through its funding of Centers for the Commercial Development of Space (CCDS) and commercial space policies, the U.S. government has worked to promote the development of a private space sector. This paper examines the progression of commercial space in the U.S. over the past fifteen years at a high-level. Many changes have occurred in the field of commercial space, both in perceptions and actual activities. In the eighties, emphasis was placed on the prospect of conducting materials processing leading to predictions of huge profits that never materialized. This contributed to a distorted understanding of the meaning of commercial space, and tended to overshadow more established and revenue-producing sectors of satellite-based communications and satellite launch insurance. Eventually in the late 1980s, and early 1990s, the markets that emerged were a variety of new market niches in telecommunications, remote sensing, and to a limited extent, small launch vehicles. The types of companies that have entered the private space business during this time period has been a dynamic all of its own. The "go-go" days of the 1980s were characterized by Texas-based start-up companies, and were inspired by the early success and promise of the space shuttle program. In the 1990s large aerospace corporations have formed multinational strategic alliances in an effort to posture for international markets. Space business education has emerged as an important force contributing to the organized growth of commercial space. This paper examines at a high-level, the trends and issues that have occurred during the past fifteen years in commercial space and puts forth a short view of where the industry is heading.

A new commercial business to lease existing space assets is described. Called Pathfinder, this collaboration between The Boeing Company, RSC Energia and Honeywell provides quick, cost-effective, near-term access to external payload sites on the Mir space station beginning in mid-1996. The paper outlines this payload service, including: (1) appropriate payload types and profiles, restrictions and qualification requirements, (2) system and operations descriptions, (3) payload integration services available to take a payload from any stage of development through flight, and (4) reference schedule for mission development and deployment. Some key legal, regulatory, warranty, contingency, export, data privacy and payload decommissioning issues are addressed. Finally, Pathfinder's current program status is reported.

This paper examines real options for providing the wide-ranging system of civil and criminal law required for significant expansion of commercial business in low Earth orbit. The critical role for such a framework in developing large-scale permanently inhabited Space Business Parks (SBPs) over the next twenty years is detailed in the following areas: enabling investment resources, managing human conduct, and operating viable businesses based on such orbital assets. The need for bodies of regulation in matters of property rights, lienholder security, building codes, operating license procedures, tax matters, and matters of criminal conduct are discussed. Issues of Constitutional authority to regulate civil and criminal behavior are addressed. Five alternate models of governance are described, and their potential application to the space business environment is evaluated. An Orbital Trust Territories Act, modified by elements of the Law of the Sea model, is recommended for implementation by the U.S. Congress. This Act will facilitate American development of SBP's, and is justified as the best approach to securing a leading role for the United States in this high-potential growth market area.

The governmental role in the successful development of commercial, large-scale Space Business Parks in low Earth orbit is vital but has not been characterized. This paper presents a specific agenda for such enabling action, tailored for the U.S. Government, in the following four areas: existing NASA programs to be completed; Earth-to-orbit transportation service performance goals to be met; the framework of laws and regulations to be established; and technologies to be developed and demonstrated. Without all these components, significant private investment in commercial space development is foreclosed. This agenda of government actions is presented to help advance the discussion among those government leaders, investors, developers and aerospace professionals interested in working together to establish Space Business Parks as a freely profit-driven focus for human spacefaring activity.

The return of extraterrestrial minerals was the culmination of a 10 year, $40 Billion dollar public effort to expand human presence into the next frontier. The symbol of the U.S. Apollo program was the unique rock and soil that was brought back by the astronauts. It is now possible to mount a. private sample return mission in an area of high scientific interest on the Moon using proven technology. The economic potential comes from the identification of a market for a known lunar product, rather than a drop in the price of space access.

In future, as orbiting hotels become more sophisticated, more advanced facilities will be developed. One direction of such development will be to include larger rooms for guests to experience activities in "zero gravity", as it is popularly known. The paper considers the design of a small gymnasium that might be the first of such sports centers to be built and used in orbit.

US federal government policy should be changed immediately to permit use of excess ballistic missile assets for commercial launches. While unrestricted use should not be promoted, the federal government should distribute five missile shipsets per year to industry and make an additional five shipsets available to academe per year through the year 2002. A Department of Transporation office should be established to manage the distribution of these assets, A distribution procedure, consistent with a revised national policy, should include pricing standards, usage targets, incentives (for users, competing technologies, and complementary goods), quotas, and tax credits for infrastructure and commercial launcher developers,. Missile assets can then be expected to contribute to improved near-term access to orbit without undue damage to the US small launcher industry.

Technical progress in the areas of post processing and adaptive optics wavefront compensation have enabled routine high resolution imaging of satellites in low earth orbit using ground based telescopes. However, the requirement to ascertain and monitor the status of spacecraft operating in orbits extending out to geostationary altitude presents an extremely complex imaging problem for which there is no demonstrated technical solution(s). Very high angular resolution at such extreme ranges generally requires the implementation of synthetic aperture techniques which, in turn, generate very demanding operational requirements in the areas of low-light-level array aperture co-phasing and adequate spectral sampling for imaging. As an example, geostationary satellites may range from the equivalent of a stellar visual magnitude of 10 to considerably fainter while possessing angular subtenses as seen from the ground on the order of a fraction of a milliradian. The Deep Space Surveillance Branch of the Phillips Laboratory has been studying the application of adaptive optics technology designed to enable low-light-level co-phasing of optical interferometric arrays as well as the number and configuration of array apertures required for good imagery. We find that it is possible in principle to modify or upgrade a variety of the optical interferometer programs being planned or in development to a level where this mission can be enabled.

Kestrel Corporation is designing and building the first Fourier transform hyperspectral imager (FTHSI) to be operated from a spacecraft. Performance enhancements offered by the Fourier transform approach have shown it to be one of the more promising spaceborne hyperspectral concepts. Simulations of the payload's performance have indicate that the instrument is capable of separating a wide range of subtle spectral differences. Variations in the return from the Georges Bank and shoals are discernible and various types of coastal grasses (sea oats and spartina) can be isolated against a sand background.

Efficient commercial operations in space will necessitate the remote selection of sites for operating facilities as well as for transportation routes for vehicles, supplies, equipment, and resources. A method for choosing a least cost path for an oil pipeline in the Former Soviet Union, which has lunar and planetary applications, is described here. The prototype least cost analysis for pipeline routing was performed using remotely sensed satellite imagery of the Earth and Geographic Information Systems (GIS) analysis. The work was performed and funded by Bechtel Corporation and NASA, John C. Stennis Space Center, Commercial Remote Sensing Program, under a Domestic Nonreimbursable Space Act Agreement.

Geologists have been in the vanguard of research aimed at applying remotely sensed imagery in the search for mineral resources since the first Landsat satellite was launched in 1972. Since then, each advancement of imaging sensor technology introduced new capabilities and brought further refinement of technique. By the end of this decade, the next generation of resource satellites will begin providing geologists with global coverage of diverse data types at spatial and spectral resolutions now available only from airborne sensors. In order to meet the challenges of locating new mineral deposits in less than ideal environments, geoscientists are developing new and innovative approaches to the practical application of remote sensing imagery.

The wide range of Earth observing satellites scheduled for launch between 1996 and 2004; the variety of their intended science and research missions; the growth of commercial sensor systems and private launch capabilities; and the miniaturization of sensor systems for orbit insertion from small vehicles testify to significant changes in Earth data collection technology. In the government sector, small satellites designed for filling gaps in atmospheric, geophysical, and biological measurements that can be fused with data being collected by EOS observatories are preferred over larger and more costly systems. In the private sector, niche satellites that collect data for specific commercial markets and that can be launched at low cost, are preferred over more complex or more general purpose systems that must then search for markets. Commercial spaceports represent a place for these smaller, more frequent, and less costly activities to be undertaken, even those that are federally sponsored. A national and international network of spaceports for launching and recovering payloads on reusable launch vehicles offer a quantum leap in applications for Earth sensing that are time-critical or site-specific in their execution.

The solar power satellite (SPS) concept is an option for providing the Earth with almost a continuous running and nondepletable power source. Solar radiation is collected in space on a large solar cell array located in geosynchronous orbit. The energy is converted into microwaves at 2.45 GHz and beamed to a receiving antenna located on Earth. The receiving antenna converts the microwave power into useful alternating current power to supply an electrical power grid.

This paper discusses the viability of beaming solar power from space as a terrestrial energy source in the future. It presents an analytic method for evaluating space solar power (SSP) as an investment, and discusses sources of data for determining both costs and benefits. Much of the research and analysis on which this paper is based was conducted as part of an on-going study for the Advanced Concepts Office of NASA's Office of Space Access and Technology and the Advanced Space Analysis Office of Lewis Research Center. This study is designed to be a fresh look at space solar power, updating a major study conducted by NASA and DOE in the late 1970's, and reconsidering assumptions made in that earlier analysis. Encouraging results have led to a second phase of the current study. This study has focused on whether space solar power is an advanced concept appropriate for investment by NASA. The criteria used by this study in assessing the value of space solar power reflect a changing NASA paradigm, by considering technologies in the context of the economic and financial issues. This paper summarizes the overall study approach, and reports on the methodology used for assessing the economic viability of space solar power: (1) presents an analytic structure for considering space solar power investments in terms of internal rate of return and net present value, (2) demonstrates how findings from research conducted in the late 1970's can be used to develop cost estimates for systems that use newer technology and different architectures, (3) summarizes trends in world energy consumption that can be used to estimate future demand, and (4) discusses externalities associated with energy production and their impacts on the financial and economic viability of space solar power systems.

The paper describes the "SPS 2000" system currently being designed to operate as a pilot plant delivering 10 MW of microwave power from low Earth orbit to receiving antennas at the Earth's surface. Research under way on different aspects of the satellite and the ground segment, and field research under way in a number of equatorial countries is described. A number of issues other than the technical design of the system which are also of importance both in planning the system and in assessing its potential value, are also discussed.

We believe nothing is more effective for the development of the microwave power transmission technology than to operate step-by-step experiments and thus to accumulate critical data. We succeeded in two rocket experiments called by MINIX in 1983 and ISY-METS in 1993 of the ISY year, and three demonstrations called by MILAX in 1992, Kansai-demo in 1994 and ETHER in 1995. The objectives of the rocket experiments are to study nonlinear interactions of the microwave power beam in the space plasma environment and to demonstrate the power transmission in space. Both of the rockets were successfully launched to observe interesting plasma wave excitations. We succeeded in the demonstration of the microwave power transmission using a model airplane. The objective of the MILAX is to verify a newly developed active phased array antenna and to demonstrate the feasibility of the microwave power transmission by flying the small model airplane. We also performed a point-to-point microwave power transmission demonstration (Kansai-demo) for ground use, and the power transmission demonstration toward a small airship for the future stratospheric platforms during the WPT'95 conference held at Kobe University. These rocket experiments and demonstrations are reviewed in this paper.

Solar power satellite needs for the deployment of an extensive amount of solar cells on orbit, has driven the pursuit of an alternate technology for the fabrication of solar cells on orbit instead of transportation of solar cells from earth to space. Preliminary proof-of-concept experiments on the Wake Shield Facility have shown the ability to grow high quality crystalline thin film materials in the vacuum of space. Such direct growth and processing of thin film solar cells in the vacuum of space can lead to significant reductions in launched up-mass and consequent major reductions in cost for solar cell deployment on a solar power satellite.

The proposed Lunar-Solar Power (LSP) System collects solar power on the moon and delivers it, via microwave beams, to regional electric power grids on Earth. Rectennas are the major cost element. LSP space costs decrease as component and systems technology improve and portions of the production facilities on the moon are made of lunar materials. Lowering Earth-to-orbit transportation costs decreases the up-front cost of LSP. Terrestrial power systems are far more expensive.

Although the current space climate is focused on developing cheaper access to space and performing smaller, well-defined science payloads, the ultimate future calls for a permanent human presence in space, crowned with the achievement of interstellar travel. Whether that expansion comes from practical drives — the taxation of the limits of the carrying capacity of Earth — or more romantic, exploratory impulses, prudence dictates that we begin preparations far in advance of our departure date. There are numerous technological feats to master, in the guise of physical systems such as propulsion and shielding, and biological systems such as life support. But serious issues of design and systems integration also emerge, and their scope and difficulties may need several testing iterations for even their definition. A Solar System Cruiser that cycles between inner and outer planets, improving and evolving along each voyage, represents a phased mission architecture that both utilizes existing infrastructure while validating future technologies and testing human factors limits. As such, it might provide a valuable exercise in design learning that will serve humankind well in future grand undertakings such as interstellar travel. In addition, it may provide valuable infrastructure, material resource and science development for its useful lifetime.

If someone were offered a trip to the stars, he or she might be captured by the glamour of the "trip of a lifetime." Yet, unless a new physics dethrones E=mc², it would not only mean the trip of a lifetime, but of several lifetimes. Furthermore, as manned platforms are currently conceived, some future mastery of all pertinent technological, economic and social hurdles would still not produce a starship hospitable to life. Spacecraft are designed first and foremost to meet mission specificiations, with human factors concerns as an appendix. On an interstellar journey, humans are the mission. Therefore, a new approach to large and small-scale design issues must be taken that is dictated first by habitability criteria. An approach might be applied whereby the ship is viewed as a self-contained city, an entire ecosystem in which the ecology is in complete harmony with the human presence. Such systems of city architecture were envisioned by Paolo Soleri and others, and are applied here to derive human-driven design constraints for the meso-level design principles of this spaceship. These specifications then suggest solutions to issues as varied as gravity, shielding, life support systems, food production, clustering and separation of human spaces, and accommodation of crew growth.

"Bootstrapping" means to start with the least expensive manufacturing and transportation system, which then increases its own capacity using materials already in space. This proposal optimizes the locations of manufacturing, initially in LEO for lower launch and servicing costs; later in high orbit to use continuous solar power. It starts with a few hundred kilograms of equipment on the Lunar surface, just to load dirt into spacecraft. For inexpensive transportation: Rotating Tethers catch raw materials coming from the Lunar surface, recover their kinetic energy, and throw additional mining equipment back. Later, "Regolith Rockets" use preheated Lunar dust for reaction mass to lift off the Lunar surface to catch the tip of a tether; rugged miniature spacecraft are launched from an Electromagnetic Mass Driver. This system becomes self financing and grows by producing oxygen, fiberglass tethers; metals for spacecraft, rovers, and habitats; solar panels; and slag for shielding. This breaks an economic barrier to enable the settlements beyond Earth, the most significant migration in history.

The emerging field of nanotechnology with its nanosatellite potential is related to the problem of interaction with the space environment, especially with orbital debris populations. This is done by using the Livingston curve, widely cited in high-energy physics when discussing advanced technology and the future development of particle accelerator populations, as a universal quantitative relationship for the time evolution of technology.

Man-made orbital debris is fast becoming a threat to safe operations all around the Earth's orbital domain. Even submillimeter particles traveling at orbital velocities can cause significant amounts of damage to exposed hardware in Earth orbit. Spent upper stages accidental explosions of propellant tankage, colliding micrometeorites, thermal insulation and paint flakes, tools and accessories unintentionally left behind, and several other factors including decommissioned, degrading satellites in graveyard orbits contribute to the increase of this dangerous phenomenon. A basic architectural concept is presented on a space vehicle designed to remove orbital debris from LEO. The vehicle uses a "snowplow" approach to deflect incoming debris particles to lower orbits, where the particles will burn up upon reentry into the Earth's atmosphere. As an additional tool, a laser is mounted to destroy smaller particles.

Many of today's artificial intelligence methods are simply another type of algorithm or model. The key to real intelligent systems lies in making the systems adaptive. It is toward this goal that we must work, in cooperation with technical staff from all affected disciplines. This paper stresses the introduction of adaptation in intelligent systems for space or planetary science systems applications. Adaptation is important to the long-term use of intelligent systems. In this direction, a practical framework, or construct, is suggested for the construction of an intelligent Agent for use in space or planetary science systems. The construct proposed is based upon integrated/hybrid artificial intelligence systems (neural networks, expert and procedural systems combined with intelligent, microelectronic sensors and hardware).

Extreme environments, whether they be the frigid nights of the poles, the burning sands of the desert or the harsh environment of space, pose interesting challenges to the Architect, the Engineer and the Constructor in their efforts to create habitats far mankind. On Earth the major issue is thermal management, with related issues being protection from the elements and illumination. The current approach is to confine people in boxes. In space, additional environmental issues are the retention of atmosphere and protection from ionizing cosmic and solar radiation. Proposals for space habitats range from tubes and spheres to fanciful artist's concepts of large glass domes. The challenge of design for both Earth and space habitats is to create dwellings which speak to the human spirit, beyond providing the minimum physical requirements for survival. In hot, arid regions of the world, the prime goal is to minimize heat gain while preserving water. In the Arctic and Antarctic regions, the prime goal is to minimize heat loss. Malls, air bridges and underground shopping areas in northern cities point to potential design solutions for Earth-based habitats in these and other cold climates. In each case of environmental extremes the goal is to create a comfortable oasis for human life. If only minimum requirements for temporary terrestrial encampment are to be met (without consideration for long-term or permanent settlements) then tubes and boxes are most cost-effective (the navy has shown that it is possible to keep over one hundred thirty people working effectively in a confined and isolated tube, a submarine, for up to ninety days). On the other hand, experience in the Arctic oil fields has shown that, for assignments that are longer-term, more spaces and amenities are needed Domes allow far the separation of environmental considerations from those of interior habitability. However, construction technology and economics must develop band-in-band in order for domed habitats to become cost-effective functional solutions, as well as aesthetic ones. For long duration terrestrial missions or assignments to other planets, the minimum goals are to protect (physically isolate) inhabitants from lethal cosmic and solar radiation and to provide a habitable, semi-closed environment, where all possible water would be recycled, treated and re-used (some even captured from the air after being respired by people and plants). On Earth and in extra-terrestrial planetary environments, dome concepts would allow this and other (apparently luxurious) features to be included, such as tertiary water treatment and filtration systems for the creation of gardens, complete with waterfalls. For extra-terrestrial construction, alternatives more cost effective than domes range from regolith-covered inflatables (protected under lunar "sandbags"), to tensile structures and one author's proposal of an innovative hybrid cable-membrane structure which would suspend regolith (lunar "topsand") as a radiation and micro-meteorite shield over a spacious crater habitat.

We propose a new type of energy storage device designed specifically for space applications. It consists of flywheels using superconducting bearings, and conceivably could support an international Space Station in Earth orbit as well as a lunar colony or planetary outpost.

The human settlement of space will involve the design, fabrication, testing, deployment, operation, replenishment, maintenance, repair, and disposal of a wide spectrum of space operations and transportation systems. These will include reusable launch vehicles, orbiting space stations, space tugs, interplanetary transports, and planetary bases. This paper discusses the importance of carefully and systematically undertaking the systems engineering planning of the basic infrastructure for the first phase of this settlement. Further, this paper proposes a basic space infrastructure planning requirement, derived functional requirements, functional elements and functional interfaces that may serve as a starting point for further analysis and refinement.

Opening the space frontier to human settlement and enterprise requires that a basic infrastructure be developed that will provide the necessary services to support these human activities. One of the first steps in establishing this basic infrastructure is to build large space bases in low Earth orbit that will serve as the terminus for the reusable launch vehicles or planetary shuttles now under development. This paper discusses a proposed approach for building such large space bases using the current Space Shuttle's technology base.

Organic crystal growers now have access to a wide array of facilities and hardware on space shuttle missions and other international carriers. Agencies providing such access include governmental organizations (such as the NASA Marshall Space Flight Center and the European Space Agency), educational institutions (e.g., the Birmingham and Huntsville campuses of the University of Alabama, the University of Colorado-Boulder, Kansas State University, Massachusetts Institute of Technology, and the University of California-Riverside), and private companies (such as Instrumentation Technology Associates, Intospace GmbH, and Payload Systems Inc.). These organizations have published descriptions of the hardware they have designed for space flight, including hanging-drop vapor diffusion chambers, membrane-based solute diffusion and solvent-transport cells, sliding-block free diffusion cells, sliding film diffusion cells, batch mixing devices, and submerged crystal growth chambers. In recent years one or more of these facilities has been present on nearly every space shuttle mission, and, in most cases, a high level of automation makes this high frequency of experimentation possible. The total number of individual tests of organic crystallization using this array of devices now numbers into the thousands, making organic crystal growth the most frequently practiced low gravity research procedure in the history of space flight. The services of these facilities have been available for several years to corporate entities wishing to determine the structure of organic molecules having high commercial value. Current hardware can be used to perform any of the widely-utilized (and some of the newly-developed) techniques used for organic crystal growth. These techniques include vapor diffusion (hanging and sessile drop), batch growth (thermal gradient and isothermal), dialysis diffusion, osmotic dewatering, step osmotic dewatering, step dialysis diffusion, liquid-liquid (also known as interfacial or double) diffusion, step diffusion, and boundary-layer diffusion. Every one of these methods has resulted in the growth of diffraction-quality crystals in low gravity. In many cases crystals grown in low gravity have been of higher quality than those grown at 1 g. Some of the methods that have yielded superior crystals (e.g., liquid-liquid diffusion) cannot be practiced successfully at 1 g because of buoyancy-driven motions (convection and sedimentation). The practice of crystallization in low gravity, therefore, widens the variety of techniques available to researchers, and the high frequency of access to this microgravity environment allows researchers to continually improve and broaden their crystal growing capability.

The industry/NASA Reusable Launch Vehicle (RLV) Technology program is intended to mature and demonstrate technologies leading to a viable, reusable commercial launch system that can satisfy national needs and achieve acceptable recurring costs. This paper reviews the current status of the RLV Technology program including the DC-XA, X-33, X-34 flight systems and associated technology programs and examines some lessons learned from the recently completed DC-X reusable rocket demonstrator program.

A NASA Johnson Space Center team of engineers has been organized to design a crew return vehicle for returning International Space Station crew members from orbit. A lifting body based on the X-23/X-24A configuration with Shuttle derived, guidance and control algorithms is providing a baseline for the re-entry phase of flight. A thermal protection system utilizing a number of materials is providing the capability for up to a 1300 km (700 nm) crossrange goal. A ram air inflated parafoil system is being incorporated to increase the landing performance characteristics.

In spring 1993 the Japanese Rocket Society started a formal study program on space tourism. The objective of this research is to determine how to establish a successful commercial service offering short visits to low Earth orbit to fare-paying passengers. To date the services required have been studied; the "Kankoh-maru" passenger vehicle has been designed; and the necesssary propulsion and propellant supply systems have been analysed. Currently Kankoh-maru's development and manufacturing costs are being studied, as well as the facilities required at airports, the accommodation facilities required in orbit, and potential business development scenarios.

The decommissioning of U.S. ICBMs presents the space launch community with a unique opportunity. Over 400 Minuteman missiles are currently in storage, and the Air Force is already working to refurbish these assets for suborbital launchers. Orbital versions could place over 300 kg in low orbit at low cost, but the 1994 National Space Transportation Policy (NSTP) severely limits this option. The high costs and questionable reliability of today's commercial small launchers dictate a revision of that policy. Payloads suitable for ICBM-based launchers include communications, military, and science satellites. These launchers could also give the military a capability it currently lacks by facilitating rapid launch on demand during during a crisis. Finally, by expanding the uses for lightsats, such use may create a larger market for commercial vehicle builders over the long run. The United States should not waste the assets built up in its missile programs. It should allow use of ICBMs to provide access to orbit until the commercial companies can offer routine, affordable alternatives.

The CSG 2000 programme was decided in 1988 to upgrade the ground infrastructure at the Guiana Space Centre (CSG) for Ariane-4 and Ariane-5 launches with increased reliability and reduced cost through to the period 2010/2015. It consists of a thorough modernisation of all major systems: tracking and position-plotting, flight safety, telemetry and down range stations, ground operations and safety coordination, telecommunications, meteorology services and general infrastructure.

Based on the experiences of Sea Launch, a new venture in space transportation, this paper presents the necessary traits that launch service providers must meet in order to survive in the competitive commercial market. It identifies 1) low price, 2) tailorable performance, 3) high availability, and 4) reliable delivery as the key customer requirements that must be met. The ability of a company to satisfy these requirements is a delicate balance between technology drivers, operational constraints, and intra-industry "co-opetition." This paper illustrates one approach by Sea Launch to find this balance. Factors that are critical to continuing competitiveness include: cost structure, operational flexibility, launch rate capacity, and payload-vehicle interfaces. Examination of the programmatic issues faced by Sea Launch illustrates the needs and obstacles in each of these areas.

The Space Shuttle program development is reviewed to derive the fundamentals of a new paradigm for launch system development that could provide safe, reliable and inexpensive access to space.

This paper discusses the scheduling considerations when developing the International Space Station (ISS) Assembly Sequence. Assembly of the space station requires 44 space launches (not including additional launches for resupply) on 5 different launch vehicles from 3 different countries. The assembly sequence has to be developed such that sufficient resources (space station docking ports, power systems, thermal systems, on-orbit stowage, etc.) are available at each stage of assembly. Therefore space station system functionality must periodically be increased to meet the needs of the growing configuration. Interdependence and development schedules of international elements are crucial to the success of the space station assembly. The scheduling of the necessary launch vehicles to deliver the assembly elements is just one aspect of the overall traffic planning. Along with transportation to space on-orbit activities also play a main role in the assembly sequence schedule. Assembly of the International Space Station is currently scheduled to occur over a 4.5 year lime period beginning with the First Element Launch (PEL) in November of 1997. June of 2002 marks the completion of the largest cooperative international construction project in history, the International Space Station (ISS)

The NASA Space Station Program Office is responsible for integrated traffic planning for the International Space Station (ISS). Traffic planning involves the scheduling of earth-to-orbit vehicles arriving at and departing from the ISS. The main objective of ISS traffic planning is the development of sound ISS long-term traffic plans that optimize utilization of ISS transportation assets within program constraints. The development of a traffic model tool to support this objective began in late 1993. The original traffic model (TM1) was developed in the Excel spreadsheet environment and has been a powerful and effective tool, mainly used in design analysis to assess station design characteristics, such as resupply vehicle capacity. However, TM1 has some limitations. The main limitation is that only the developer clearly understands how the model works and is the only one who can use the model to generate any meaningful results. This restricts the Space Station program's ability to utilize multiple analysts to arrive at the "best" traffic plan. Another TM1 drawback is the lack of configuration control To alleviate these problems, ISS Traffic Model Version 2 (TM2) was developed. Development of TM2 began with a nation-wide search of on-going traffic modeling activity in the private and public sectors. This search answered several critical questions important to the development of a comprehensive traffic model. The TM2 development effort has emphasized structure and consistency to support a multi-user environment. The model structure promotes data control, while allowing a high degree of flexibility to support multiple traffic planning analyses. The model structure was also built to be conducive to model enhancements, such as functions that are planned to include schedule/loading optimization and launch schedule uncertainty management.

Developing hardware from requirements is like walking on water; it's a lot easier if it is frozen. This credo is especially true if one is tasked with controlling the International Space Station (ISS) technical baselines and documentation for the 6 international partner (IP) space agencies of the US, Russia, Canada, Japan, Italy, and Europe. However, no matter how well designed a project is initially, having requirements that change cannot be avoided in any design, much less the complex design and integration requirements necessary for the ISS. The most important factor to consider is how to process the changes to the technical baselines such that all affected parties understand and have agreed to the change. The purpose of this paper is to describe, on a high level, an overall nominal path change process that has been successfully used on the ISS Program to maintain the program baseline and integrated design.

This paper describes the command and control concept for the International Space Station (ISS), including roles, responsibilities, functions, and interfaces. It emphasizes the internationally distributed nature of command and control functions and processes. The NASA model for command and control for human space flight is outlined, and a synopsis of the evolution of the command and control concept for ISS is provided. The paper addresses only ISS core systems operations, science operations are not discussed.

In the Freedom program the Flight Crew Equipment (FCE) hardware was provided solely by NASA and used by all Space Station partners during all phases of the program. With the addition of Russia as a partner in the International Space Station (ISS) program U.S. crew members will be living in modules that are provided and supported by Russian hardware during the assembly and assembly complete phase's. Because of differences in design approaches, requirements, system constraints and respective cultures there are considerable differences between the NASA and Russian FCE hardware. This is further complicated by different resupply intervals and methods each partner has available to support their segment. These differences pose potential problems for a crew that is living in a confined environment, required to act and perform as a team while at the same time being subjected to two fundamentally different and unequal lifestyles.

The International Space Station (ISS) relies heavily on Extravehicular Activity (EVA) for assembly and maintenance. The ISS EVA System provides the translation aids, tools and support hardware to allow the crew to assemble and maintain the US portion of the ISS. The EVA System supports the three primary phases of an EVA: translation of crew and hardware to the worksite, worksite setup and restraint and conducting the actual EVA task. The primary hardware items in the EVA System and the uses of the hardware are described. Other hardware items crucial to EVA but not part of the EVA system are also discussed. In addition, a brief overview of the Russian ISS EVA capability is provided along with plans for interoperability between US and Russian EVA.

The International Space Station (ISS) is a low Earth orbiting facility for conducting research in the life science, microgravity, earth observations, astrophysics, space processing, and engineering disciplines. The ISS will be assembled on-obit at an altitude of 220 nautical miles with contributions from the United States, Canada, Japan, the European Space Agency, and Russia. The ISS provides a shirt sleeve environment for conducting research in the US Laboratory (US Lab), the Centrifuge Accommodations Module (CAM), the Japanese Experiment Module (JEM), and the European Columbus Orbiting Facility (COF). The Mini Pressurized Logistics Module (MPLM) provided by Italy serves as a conditioned pressurized transport carrier to replenish and return passive and perishable payload cargo. External Earth observations can be performed by utilizing the payload attachment points on the truss and the JEM Exposed Facility. The pressurized and external locations are equipped with a variety of electrical, avionics, fluids, and gas interfaces to support the experiments. ISS solar arrays, thermal radiators, communication system, propulsion, environmental control, and robotic devices provide the infrastructure to support sustained research. The Russian payload accommodations are presently being defined by the Russian Space Agency. This paper reflects the design maturity of data regarding payload accommodations at the time of its submittal. This paper is based on the assembly complete configuration of the station. As the design matures (qualification tests of components and associated analyses of the integrated performance are updated), the ISS Payload Accommodations Customer Documentation Tree will be updated accordingly to reflect this design maturity.

The success of the International Space Station (ISS) is dependent upon Extra Vehicular Robotics (EVR) for assembly and maintenance. The ISS EVR System encompasses two major types of robotic systems: Single-Manipulator operations and Dexterous Manipulator operations. The three single-manipulator robots on the ISS include the Canadian Space Station Remote Manipulator System(SSRMS), the Japanese Experimental Module Robotic Manipulator System (JEM RMS) and the Russian European Robotic Assembly (ERA) and provide for assembly, maintenance, viewing and Extravehicular crew support. The Canadian Space Agency built Special Purpose Dexterous Manipulator (SPDM) is primarily used for maintenance activities requiring great accuracy. The robotic systems are crucial for the ISS in the roles of assembly; translation of payloads and crew to worksites; providing power; data and video to "dead" payloads; providing viewing to remote areas; providing assistance to extravehicular activities; and providing maintenance. The primary uses of the EVR systems and the uses of the hardware are described. Other hardware items crucial to EVR but not part of the EVR system are also discussed.

The International Space Station (ISS) relies on the use of Extra Vehicular Robotics (EVR) to assemble, maintain, and perform payload handling operations. These activities will be performed utilizing "large arm" and dexterous manipulators. This paper focuses on the operations of the three "large" manipulators: Canadian Space Station Remote Manipulator System (SSRMS); Japanese Experiment Module Remote Manipulator System (JEMRMS) Main Arm (MA); and the Russian European Robotic Arm (ERA). A brief overview of the manipulators is provided, followed by a description of manipulator control, examples of operations, and plans for interoperability between the ISS robotic systems.

Extra Vehicular Robotics (EVR) is crucial to the International Space Station (ISS) for external activities including assembly, maintenance, handling and inspection of the ISS. The success or failure of the ISS is based largely on the ability of the robotic system to accomplish its assigned tasks successfully. Verification of not only the robotic arms and Mobile Transporter but also the hardware used to support the robotic tasks is crucial to the ISS. The purpose of the EVR verification process is to verify not only the End-to-End Robotic system but also that the integrated ISS hardware can support EVR assembly and maintenance functions for a successful ISS.

Mission concepts for the early 21st century—the next 25 years—include establishing outposts on the Moon or Mars that will begin what amounts to a new era in history, the era in which human beings inhabit environments beyond the Earth. Looking beyond the space station program, succeeding generations of human missions into space will embody successively greater levels of self-sufficiency and more complex technological requirements. The extension of human life to other planets will require that the explorers be equipped with a spectrum of technologies to support life and make use of the resources available in the Martian or lunar environment. To live on another planet and to make use of what is discovered in a new environment will require ingenuity, certainly. But beyond ingenuity, explorers will need to have available the technologies that have been developed on Earth over the past hundred years to create and use energy, produce essential chemicals like oxygen and water, and other purposes. These technologies, however, have been developed and optimized on Earth, in largely empirical efforts, and many — those involving fluid processes- may perform quite differently in non-Earth environments. There is a real challenge to the research community to build an understanding that will allow the technological processes that have been developed on Earth to be exported to new, non-Earth environments. The intent of this paper is to outline a program through which the talents of the nation in engineering science can be effectively enlisted for this effort. Many of the potential participants are already at work in the microgravity program, where the control of gravity in pursuit of scientific knowledge by researchers from physics and the engineering disciplines has led to many new insights in fluid physics, combustion science, and materials science. The ultimate objective of an engineering research program in exploration processes would be a comprehensive body of knowledge that would serve as a lasting foundation for space development, in much the same way that NACA's early work in wing section performance was a foundation for most of this century's progress in aircraft design and remains today an important archival reference. Another useful conceptual comparison is the evolution of engineering knowledge with the development of the chemical industry from the 1940's to the 1960's. In this period, engineers attempting to meet the demands of a rapidly growing industry found that the "art and practice" basis of process technology up to that time was not adequate for new technologies. The attempt to put process technologies on a rational and systematic footing produced a conceptual framework of common underlying building blocks, called unit operations, for chemical processes that has proven to be of immense value in engineering design. What would be required to perform a similar role in space exploration and development is essentially an updating of the understanding of "unit operations" to a level of science and mechanistic detail that would permit extrapolation of Earth-based engineering to new environments. Having this knowledge as a foundation for space development will be essential to effective, economical, and timely solution of many of the challenges that will be encountered in human exploration of the solar system. This knowledge will also stimulate development in Earth-based technologies, as the physics that underlie industrial operations is more intimately understood.

The microgravity environment induced by near-earth orbits of spacecraft, along with the hard-vacuum, of space through the use of a wake shield, provide unique experimental opportunities for testing theories related to the mechanical behavior of terrestrial materials that are essentially granular without any physical or chemical cementation between the grains. Such materials may include cohesion less soils, industrial powders, pharmaceutical products, industrial or agricultural grains, crushed coal, etc. This paper will focus on such issues and will include a microgravity experiment currently planned to study the behavior of dry and saturated sands at very low effective stress levels. This experiment is scheduled to be performed during a Space Shuttle-MIR mission in 1996.

The effective management and control of fluids in future space-based operations continue to present challenges to the designers and implementers of new spacecraft and space systems. A recurring problem in overcoming these challenges has been the lack of verified data bases and analytical tools which can accurately predict the behavior of fluids and processes involving fluids when they are subjected to the low-gravity environment of space. White the focus of the NASA Microgravity Science and Applications Program has not been on fluid behavior in low-gravity, the Program has enabled advances in our basic understanding of fluid dynamics and transport processes which can clearly benefit space system designers and technology developers. This paper describes how low-gravity fluid behavior impacts the operation of space systems, outlines where significant advancements in knowledge are needed to guide future system designs, and reviews some of what has been learned recently about the effects of reduced-gravity levels on relevant fluid phenomena/processes.

Combustion experiments have taken place over the last decade in an attempt to understand the importance of gravity in the flammability and fire spread rates of gaseous, liquid, and solid fuels. The principal output of the microgravity combustion modelling and experiments has been: (1) new fundamental understanding which requires modification of many aspects of combustion science textbooks, (2) recommendations on research, practices and policies as they relate to NASA's crew-inhabited spacecraft, and (3) spinoff technologies principally in miniaturized and/or new instrumentation. In anticipation of space exploration outside of low-Earth orbit, some of the experiments considered Lunar and Martian gravitational settings. The results of such experiments and those in microgravity are described below.

On-orbit servicing, such as supplying, refueling, and retrieval, is planned to support various space activities. On-orbit servicing robots would become one of the key elements of the on-orbit servicing systems providing specific services for satellites, platforms and space stations. NASDA is currently developing an experimental satellite Engineering Test Satellite VII (ETS-VII) in order to study the feasibility of space robot as future on-orbit servicing tool. This paper describes latest study of the on-orbit servicing robot, and general concepts of space cranes and dexterous servicing robots.

New developments in the advanced technology of high-temperature superconducting (HTS) material are applied to vibration isolation in microgravity. The possibility of designing a magnetic isolation device which could eliminate or attenuate acoustic noise backgrounds is briefly addressed and its potential for filtering out perturbations to space and life science experiments onboard the international Space Station is explored.

Microgravity experiments on free fluid surfaces of large length scale could be subject to experimental artifact from flow induced charging. Under conditions favorable for flow induced charging, flowing liquids develop a static electrical charge which manifests itself as a force whose magnitude approaches that of surface tension force. Favorable conditions are: a non-conducting liquid, a small diameter non-conducting flow passage, a large flow volume, and a small separation distance between the fluid and another object. We present a method for calculating the magnitude of flow induced charging and scaling arguments so that potential problems can be determined and dealt with at the experimental design phase. A dimensionless ratio of charge force to surface tension force we call the Hula Number should be less than 0.5 to prevent artifact or unwanted fluid motion.

The current practice of using flight-type pressure suits for neutral buoyancy simulation is prohibitively expensive and severely limits testing opportunities. While final flight crew training is best performed in these high fidelity suits, many of the required neutral buoyancy activities, including basic research, engineering design validation, and procedures development, could be performed in lower fidelity pressure suit simulators without significant impact on test results. This paper reviews the Space Systems Laboratory's development of a simulation suit, specifically designed for neutral buoyancy operations. The Maryland Advanced Research/Simulation (MARS) Suit is designed to replicate the critical parameters of pressure suit activity, while greatly reducing the operational requirements of a high-fidelity suit system. The design incorporates a hard upper torso with integral helmet and backpack, and multilayer fabric arms and lower body unit. Rather than simply replicating an existing pressure suit, the MARS Suit design team has incorporated advanced features, including a rear-entry hatch and an oversized visor assembly which can accommodate high-resolution displays and experimental crew interfaces. Several design features have been selected in order to minimize the fabrication and operational costs of the system. Rather than support significant internal pressure, the MARS Suit is maintained at local ambient pressure, and motion limitations and force requirements of any desired existing pressure suit are replicated by mechanical design of the arm and leg garments. The internal environment of the suit is dry, enabling the use of biomedical sensors and communications systems without the complication of water immersion. In contrast to the existing Hamilton-Standard Extravehicular Mobility Unit (EMU) pressure suit, which requires intensive preparation and sizing for individual runs, the MARS Suit is designed to be easily reconfigurable. Simple, low-cost soft goods units for the arms and legs are specifically tailored for each subject, and can be quickly mated to a system of sized torso/visor/backpack assemblies. The backpack incorporates built-in systems for neutral buoyancy testing, including doubly redundant breathing air sources, suit instrumentation systems, and surface communications electronics. The backpack has also been designed as an extensive support base for future experimental systems, and includes a wiring harness leading into the suit as well as a sealed compartment for supporting electronics. This paper reviews the design of the MARS Suit, and details the current status of the development process for the MX-1 prototype unit. Plans are also presented for future testing with the MX-1, including verification of suit characteristics and biomedical data collection.

Possible ways of traveling on external surfaces of orbital stations (OS), requirements to guiding tracks (GT) for mobile bogies, some approaches to running gear design ensuring optimum interaction with guiding tracks and transported equipment in all modes of operations are discussed including behavior of the system during its speed-up, uniform movement, braking and parking.

Concrete has long been advocated as a construction material for a permanent lunar base. The advantage of lunar concrete is that all of the components can be derived from local materials, thus saving the huge costs of launching large structures from Earth. Lunar cement manufacturing, however, will require several complex, high-energy steps, due to the nature of lunar surface materials. Concrete may be a considerably more practical construction alternative for a Mars base. The martian environment is no more challenging to permanent structures than that of the Moon. Moreover, key materials required for the manufacture of concrete are much more readily available on Mars than on the lunar surface.

In this paper we review the design principles for optimized two-stage concentrators in the context of applications in the lunar environment and discuss the characteristics and properties of some of the nonimaging secondaries which could be employed. In particular we address the potential for using solar energy for the production of cement from lunar materials which will require extremely high temperatures. The generation of such temperatures, in the range 1400 degrees C to 2200 degrees C, will require very high levels of solar flux concentration incorporating some form of ideal or near ideal nonimaging concentrator. The maximum relative benefit will be provided by the secondary in cases where φ, the rim angle of the primary, is small, that is, for systems with relatively large focal length to diameter (F/D) ratios. The design parameters and trade-offs for each of these systems including strategies for choice of particular secondary and degree of truncation, are discussed. The principles underlying the design of these optical systems are summarized with specific emphasis on their comparative advantages for deployment in space and lunar environments.

Multinational space stations are being built in Earth orbit. These stations offer humans a place to live and work in the environment of space. However, for the men and women who will occupy the stations for extended periods, a two-fold problem will persist. They will be in imminent danger from the debilitating effects of micro-gravity, and intense radiation from solar, interstellar and intergalactic sources. Practical solutions to these problems are within reach of today's technology. Rotating, and heavily shielded structures could be build in lunar orbit. Rotation would simulate artificial gravity, and each structure would have walls of sufficient mass and thickness to shield against radiation. Concrete, manufactured from materials found almost entirely on the Moon's surface, and moulded into pre designed shapes would be the primary building component of choice. Lunar Concrete offers the many advantages of readily available raw materials, structural integrity as a building material, and effective capacity as a radiation shield. Precast concrete components and modules could be manufactured on the lunar surface, transported to orbit via a Lunar Maglev, and assembled in lunar orbit to form Precast Concrete Space Stations.

This paper presents test data on heat evolved by exposing cement and its compounds, tricalcium silicate (C₃S), dicalcium silicate (C₂S), tricalcium aluminate (C₃A), and tetracalcium aluminoferrite (C₄AF), individually to a pressurized steam environment for 6 hours. It also reveals morphological characteristics of their hydrates. For example, a 209 cal/g of hydration heat was measured for the pellet specimen made with the C₃S compound. It is about 90% more than that of the same compound mixed with water. All specimens hardened, except C₃A which reacted very rapidly with steam and registered an 91°C temperature rise during the test. This paper also discusses the effects of particle sizes and compaction on heat evolution in the steaming process. The test results verify the validity of the Dry-Mix/Steam- Injection (DMSI) concept which, in our judgment, will pave ways for concrete construction in outer space after the turn of century.

To cast concrete on the Moon requires a new procedure to overcome the ill-suited vacuum condition. The proposed new procedure is to mix cement and aggregate in a dry state and expose the mixture to steam in a confined chamber to enforce hydration at elevated temperatures and pressures. A test program was carried out at the National Chiao Tung University in 1993 to verify the concept of the proposed Dry-Mix/Steam-Injection (DMSI) procedure. The hydration mechanism of a dry cement mixture with high temperature steam differs from that of the conventional wet mix procedure in two ways. First, a rapid transfer of thermal energy from steam causes the cement particles to raise their activation energy to expedite a complete hydration. Second, steam particles are very small, in the order of 3 Angtron in diameter, capable of penetrating micron pores inhibited in cement particles. Concrete thus made developed a high strength of 700 kgf/cm² (10,000 psi) after 18 hours of steaming at 180 C. It is approximately 2.5 times that of companion concrete made with the conventional wet-mix procedure after 28 days of moist curing. Another test series revealed that the DMSI method required only 50% of the cement needed in making concrete of an equivalent strength of 560 to 630 kgf/cm2 (8000 to 9000 psi) through the wet-mix procedure.

The development of microstructure in cement pastes and its resistance to harsh environments is of considerable current interest. In this work we have studied the effects of cryogenic temperatures on hydrating white cement pastes using Nuclear Magnetic Resonance (NMR) techniques. These methods are non-destructive and are applied in situ. NMR relaxation analysis has been used to interpret the evolution of the micropore structure in a cement paste during hydration, permitting a basic understanding of the state of water and change of pore structure undergoing wet-dry and freeze-thaw cycles. The pore structure evolution has been investigated by the suppression of the freezing temperature of water and compared with relaxation analysis performed at room temperature. Both methods consistently show that hydrating cement pastes have water contained in two principal and distinct components in their pore size distribution, capillary and gel water. Measurements have been made of the water consumption, the total specific surface area, and pore size distribution as a function of hydration times ranging from 2.5 hours to 6 months. The amount of evaporable water in the pore space can be determined from the magnitude of the NMR signal. The NMR relaxation times provide a measure of the characteristic pore sizes. Their interpretation is made in the context of a fast exchange model for which strong support can be obtained from systematic measurements with samples partially filled with water. The drying studies have been performed to determine the surface spin-spin relaxation time, which can be related to the pore structure. These experiments support a model of capillary and gel pores in the cement paste and provide strong evidence of a stable dense-gel structure. Supercooling and freezing point depression of confined water has been studied systematically. The depression of the freezing point of liquid water confined within a pore was found to be dependent on the pore size with capillary pore water freezing at 240 K and the remaining gel pore water freezing at temperatures near 160 K. Comparison with neutron scattering experiments is made on samples prepared with heavy water. Application of these non-destructive methods can be helpful to further understanding of cement hydration in extreme harsh conditions such as in the lunar environment. Under these circumstances the effects of drying and freeze-thaw cycles on microstructural stability must be determined. The NMR methods we have developed can provide useful tools to characterize cement pastes in simulated lunar conditions. The experimental results should allow us to make quantitative estimates and establish models of water loss during freezing at cryogenic temperatures taking into account transport through the complex structure of frozen capillary water and mobile gel water.

The effects of vacuum and microgravity on the hydration of cement are primary concerns regarding casting concrete both on the moon and in space. Previous studies by others have focused on the behavior and mechanical properties of concrete cast in a vacuum without addressing the microstructural characteristics of the paste. More recently, an experiment was carried out onboard a space shuttle to investigate the effect of microgravity on cement hydration. In the present study, mortars hardened in a vacuum for 4 to 12 hours and control mortars not exposed to a vacuum were studied by light microscopy and scanning electron microscopy in order to examine differences in microstructural and microchemical characteristics. The principal findings, that rapid loss of water from the fresh mortar leads to frothy texture, poor cement hydration and paste development, and low compressive strength, appears to preclude casting water-rich mortar or concrete in a vacuum.

The objective of this research program was to study the feasibility of making quality concrete with soils for regions where construction sand and aggregates are in short supply, for example, lunar construction. Mitchell et al., reported that lunar soil had substantial variability in type and properties. Hence five different soil types were used in this study. A control concrete mixture with standard sand and eleven other mixes with soil were prepared. A cement, sand or soil, and coarse aggregate ratio of 1:1.5:1.5 by weight was used. The sand replacement was either 100% or 50%. The variation of density and strength of soil concrete with water content was investigated to obtain suitable water cement ratios for soil concrete. The test results showed that the variation of density with water content was as that for compacted soils. With the increase of water content the density of soil concrete increased. Then it decreased beyond an optimum water content value. The experimental results showed various optimum soil cement ratios with maximum soil concrete densities for different soil types. Soil concretes produced at its optimum water cement ratio had the highest compressive strengths. These optimum water content values were used in a detailed study of the pozzolanic reaction in soil concrete. The test results showed that except for the two clays all other mixtures developed had more than 50% of the 28 day strength after seven days of curing. However, the one day strength varied from 15% to 33% of the 28 day strength. Therefore, it may be concluded that there is a delay in pozzolanic reaction due to soil in concrete, and soil concrete needs more than seven days to gain substantial strength. The compressive strength test results show that all soils mixes produced concrete with compressive strengths higher than 17237 kPa (2500 psi) except for the mix having 100% of clay. Therefore, all the soil types except clays may be used to make concrete. The durability test showed that all soil concrete types continued pozzolanic reaction beyond the 28 days.

This paper presents general information regarding lunar materials and Hokkaido anorthite and the basic concept of lunar cement formulation. Hokkaido anorthite consists of 16 wt.% of calcium oxide and is considered a candidate material for the proposed lunar cement production study. An electric furnace capable of generating heat up to 1600 C was used to conduct several bench burns using Hokkaido anorthite as simulant. The sintering temperature and duration were 1450 C and one hour, respectively. Two types of lunar cements with fineness ranging from 2670 to 5000 Blaine were made. The conventional wet mix procedure and the Dry-Mix/Steam-Injection (DMSI) method developed by T.D. Lin were applied to make a series of 4 cm mortar cubes for compression tests. The wet-mix cubes developed 2.9 N/mm² after 7 days of curing in a moist room while the DMSI cubes developed 21.9 N/mm² after 24 hours of steaming at 170 C. Scanning Electronic Microscopic analyses and X-Ray Diffraction analyses were performed to determine the morphology and chemical compositions of the obtained hydrates. This paper also discusses Japan's current interest and initiatives in the space technology development. This project was carried out with a support from Hokkaido Space Technology Consultative Association. It is hoped that the results of this test program will be a contribution to the international community on lunar concrete and space development.

The Lunar regolith has two potential uses; the first as a building material in its native state and the second as feedstock for industrial processes, including that of the creation of manufactured building materials. For the purposes of this effort it is assumed that the early uses of lunar regolith will be used in the first sense, in its native state. Used in this manner it can provide shielding for personnel and equipment spaces, shielding from meteorites, thermal extremes, radiation, both natural and man-made, and the blast effects of rocket landings and takeoffs. The regolith is also the most probable foundation for structures. (The moon is mostly covered with regolith; there comparatively little exposed rock.) This paper is, therefore, devoted to an examination of regolith used in its natural state. However, the issues of handling the regolith are also valid for regolith used as feedstock. Uninhabited structures such as antennae, solar power arrays, nuclear power sources, and scientific apparatus can be made to sit upon and/or be anchored to the regolith. As the size and sophistication of lunar structures increase so will the knowledge of the lunar environment that will engender their design and construction. Enough is known about the general mechanics of the regolith to use it as a building material. However the issues of excavatablity and material handling are yet to be resolved. Much of the information required for a particular installation will be site-specific. Therefore the level of knowledge required may be quite limited but the ingenuity to obtain reliable and usable information at this level may well prove to be quite complicated. As each of the issues is discussed "data needs" are identified.

The surface of the moon is a dirty place. Unlike free flying orbital and deep space craft, the surface of the moon presents all the environmental extremes of space and adds to that the lunar regolith. The lunar regolith consists of shattered basaltic rocks with most of the material a fine grit. The other significant fractions of the fines are basaltic glasses and metallic dust, mostly iron. This is a mix that has proven to be extremely harsh on equipment in a terrestrial environment. The lack of the lubricating effect, minor as it may be, of air and moisture in the vacuum of the lunar surface compounds the abrasive qualities of the regolith. This paper is an examination of this harsh environment upon such equipment as excavators, transporters, hoisting machinery, antenna aiming mechanisms, air locks, and similar moving equipment. The goal is to define what additional data must be gathered to design reliable and effective equipment to survive the lunar surface environment.

Despite the knowledge gained in over 30 years of crewed space flight, continuing uncertainties lead to conservative measures which constrain additional exploration. Greater understanding in many areas, including space and lunar radiation protection, will reduce the cost and risk of near term missions and permit the development of future missions now deemed not feasible. Additional research is necessary in the composition and variability of solar and cosmic radiation, the shielding characteristics of man-made and native lunar materials, and the health effects of residual and secondary radiation within a protected habitat. Present cross section measurements and transport code information for homogenous materials need to be supplemented with further studies of low molecular weight materials, mixed matrix exposures, time varying characteristics, and geometry effects. Composite shielding materials also merit further study to identify optimal combinations and quantities. Dependance upon regolith shielding must be considered with respect to transportation and emplacement logistics. Additional experimental work needs to be performed both on Earth and in the actual lunar radiation environment.

The goal of this paper is to provide a predictive model for lunar meteoroid impact for the assessment of impact risk to equipment and structures. We demonstrate that the meteoroid flux varies with respect to the inclination of the ecliptic and is non-constant due to the significant flux of meteoroid streams. The foregoing is combined with the normal component of the impact velocity having the principal effect on the mechanics of impact to explicitly demonstrate that there is a risk reduction for equipment and structures located near the lunar poles. It is also implicit that when an installation is active can be important as well as the duration of the activity. The first section of the paper is devoted to defining the velocity parameters of the lunar meteoroid environment. The second section addresses the mechanics of impact. The third section examines various protection strategies and defines some the relevant parameters. The last section offers some thoughts on risk analysis for lunar installations exposed to the meteoroid bombardment. There are gaps in the data needed to refine the model: Identifying the areas in which there needs to be more research, is as much an object of this paper as the basic model presented herein.

On earth, the potable water industry has evolved to meet the needs of a sophisticated customer — the general public. These needs are for water that is safe to drink (lifetime ingestion), water that tastes good (palatable) and water that is in sufficient supply. In space (including the moon) as long as man's presence develops beyond basic survival, so will the desire for water that meets the needs of a sophisticated customer. On earth, another industry, the wastewater treatment industry, has evolved to meet the needs of another sophisticated customer — the regulatory agency, which is influenced indirectly by the general public. The general public on earth shows far more concern about the water they drink than about the water they "waste". However, in the close confines of space, the sophisticated customer will almost certainly show equal concern for wastewater treatment as the wastewater may be the source of their drinking water. In this paper, we explore the perceptions, psychology and actual measurements of the man/water interface. We further discuss how the water needs of space may be met by the technologies developed on earth for the water industry and ultimately the implications of human water-borne biology on earth and in space.

One aspect of an American Society of Engineers (ASCE) /NASA study investigating data needs for lunar construction of a permanent lunar base is the interaction and protection from and of the lunar environment. Activities associated with the permanent colonization of the moon will interact with the lunar environment in two ways. Humans, equipment, and, the associated biological systems will require protection from the extreme lunar environment. Likewise, the lunar environment will require protection from human activities as we have seen on earth. This paper discusses the complex interaction of a permanent lunar base and its associated with a pristine lunar environment. Experience from the Apollo and Lunar Missions indicate that lunar dust, radiation, meteors and meteorites, and the complete absence of water are four major considerations in this interaction.

REGA, the Regolith Evolved Gas Analyzer, is a flight instrument under development at the Johnson Space Center. REGA is designed to measure volatiles and their interactions with the regolith on a variety of solar system bodies. The instrument consists of a small programmable furnace, a supply of reactant gas, and a quadrupole trap mass spectrometer. REGA will provide quantitative data on implanted, adsorbed, and chemically bound volatiles in many different types of regolith. It will measure the reactivity of regolith with gases such as hydrogen, oxygen, or water vapor. Finally, it will provide quantitative measurements of a planet or satellite's ambient atmosphere and indigenous gas release.

This paper describes the engineering properties of JSC-1, which is a lunar regolith simulant developed by NASA, Johnson Space Center. Simulants of this type are an essential tool for modeling and anticipating the behavior of the lunar soils, and accurate prediction of the geotechnical properties of lunar soils is of particular importance to lunar habitat planning and construction. The authors have studied the mechanical properties of JSC-1 by conducting an extensive suite of experiments. These studies were performed at a variety of effective stress levels and material densities. Both shear and isotropic compression tests were performed, and precise measurements of the stress-strain, dilatancy and strength behavior of the material were made. Measured values of various geotechnical properties of JSC-1 are presented and compared to values for both actual lunar soils and other simulants, as presented by other investigators.

A study of the influence of surface cleanliness on the geotechnical properties of lunar regolith was undertaken. Surface cleanliness and its effect on soil shear strength were evaluated by applying a recently developed model. Results indicate that a significant portion of lunar soil shear strength is induced by the surface cleanliness. Surface cleanliness considerations for lunar base design are discussed.

When we return to the moon we will likely do so on limited budgets that will necessitate small, low-cost missions. Since the cost of transportation to moon consumes upwards of 50% of the cost of an entire mission, one way to reduce mission cost is to use lunar resources to the greatest extent practical. This will reduce the amount of material transported to the moon, translating directly and linearly into cost savings. The most obvious lunar resource is the lunar regolith. With the lunar regolith we can build blast barriers, provide radiation and micro-meteorite protection for habitats, and provide feed stock for oxygen production processes. Excavation technology for the lunar environment is an important element that will enable these uses of lunar regolith and one that requires further investigation. The objective of this paper is to summarize the research efforts of the authors including recent results of excavating force measurements in one-sixth Earth's gravity. It is concluded that more research is required to establish force prediction equations for the simple case of a flat blade drawn through lunar soil simulant. The simple case of flat blades can then serve as a base line of comparison for other methods such as curved blades or scoops, vibrating blades or scoops, and rotating brush techniques. Once these methods are also investigated, lunar excavator design parameters and functional requirements can be established and prototypes designed, fabricated, and tested.

This paper reports on the construction and operation of a brassboard end-to-end system capable of manufacturing rocket propellant primarily out of indigenous materials freely available on the surface of the planet Mars. The constructed system consists of a two-chamber zeolite sorption pump for CO2 acquisition out of a simulated Martian atmosphere, a Sabatier reactor for reacting the CO2 with hydrogen to produce methane and water, a condenser to separate the methane and water produced by the Sabatier reactor, and electrolysis unit to separate the water into hydrogen, which is recycled back to the Sabatier reactor, and oxygen, which is sent to the dewar, and a refrigerator and dewar system for liquefying and storing the oxygen product. The system runs at a production rate of 0.75 kg of propellant per day (0.5 kg oxygen and 0.25 kg methane), approximately the rate required for a Mars Sample Return mission. Total power required by the system is 300 W; the total mass of all the working components of the system is about 21 kg; and the unit operates at 96% efficiency in converting input CO2 and hydrogen into methane and water. The complete system has been operated 8 hours a day for several days and is considered a complete success.

Recent studies of human missions to Mars clearly reveal that utilizing indigenous resources at Mars to reduce the quantities of propellants, life support gases, and other materials that would otherwise be transported to Mars can dramatically reduce the total mission cost. An investigation was undertaken by a team of engineers and scientists at the NASA Johnson Space Center to determine whether similar benefits could be realized for a small, robotic Mars Sample Return mission that produced some or all of its Mars-ascent and Earth-return propellants using Mars materials as feedstock. Our design is called the MARS ISRU SAMPLE RETURN (MISR) mission. Once landed on Mars, a surface stay time of 580 days is needed to allow Mars and Earth to re-align for the voyage home. During this period, an automated production plant operates to slowly manufacture propellant. Though several attractive chemistry options exist and are being investigated, the MISR Team has chosen to manufacture and store oxygen from the principal constituent of the Martian atmosphere — carbon dioxide. Seventy-five percent of the mass of the propellants needed to lift off Mars and return to Earth will be oxygen produced in-situ. The fuel will be propane, which has high performance and is both easy to transport from Earth and to store on Mars. While on the surface, MISR will collect 2.5 kilograms of Martian rock, soil, and atmosphere samples using a microrover that is teleoperated by scientists on Earth. The samples will be placed in separate, sealed containers within a Sample Return Capsule. It is a mission constraint that no Martian materials come in contact with the Earth's biosphere. Once the MISR Sample Return Capsule is on its way home, a combination of a protective bio-bag and a pyrotechnic outer skin layer will ensure that no extraneous Martian materials are attached to the outside of the capsule.

This paper analyzes the three major approaches to the Mars Sample Return mission; direct return using propellants transported from Earth, Mars orbit or interplanetary rendezvous with all propellants transported from Earth, and direct return from the Martian surface using in-situ propellants. It is found that the direct. return with terrestrial propellant fails on the basis of cost, while the orbital rendezvous approaches fail on the basis of risk. In contrast, the approach employing direct return utilizing indigenous propellants appears to be attractive on both a cost and risk basis. In addition, the in-situ propellant technology is found to offer maximum benefits for follow-on missions, including robotic Mars hopper science missions and human exploration missions.

The method described here involved the reduction of iron oxides in lunar simulants MLS-1 and JSC-1 using carbon in the form of graphite as the reducing agent. In an effort to optimize efficiency, reduction conditions were studied. The best results were obtained when the simulants were mixed thoroughly with finely powdered graphite and heated to 1200°C. Elemental iron was produced, as evidenced by its magnetic properties and by X-ray diffraction analysis. Gases produced during reduction were analyzed by gas chromatography. Calculations of the amount of carbon monoxide produced indicated that, under optimum conditions, all the oxygen had been released from the iron oxides.

Selection of a site on the lunar surface for a soft lander, perhaps with a rover, possibly with astronauts, should be led by a strategic purpose or vision which considers (1) scientific objectives, both on the Moon, as well as from the Moon (e.g., astronomy), (2) resource utilization, and (3) operational considerations, both orbital and surface. Some of the relationships between these factors were explored during workshops convened at Johnson Space Center by NASA in April and August, 1990. However, the reports from these workshops are buried in the `gray literature;' they are not even official, catalogued NASA publications. With any plans for a return to the Moon, it is paramount to consider thoroughly the rationale for site selection. The three factors mentioned above are complex and strongly inter-connected. For example, if astronauts are involved, operations are paramount, and safety is the prime consideration. In an emergency situation with the rescue spacecraft in a polar orbit, this vehicle is overhead to receive a rendezvous vehicle from the lunar surface only once every 14 days. Safety also mandates a location on the lunar frontside so that constant communications can be maintained with the astronauts. These two factors alone dictate near-equatorial sites on the frontside, with the spacecraft in an equatorial orbit. About 50 potential sites for both robotic landings and manned lunar outposts were considered. In a simulation of the site-selection process, six locales were evaluated in detail: Mare Tranquillitatis; Mare Ingenii; Riccioli; Amundsen; Aristarchus; and Mare Smythii. The merits of each of these sites were discussed in terms of lunar geoscience, geophysics, space physics, astronomy, and lunar resources, as well as operational constraints. These "strawman" considerations and recommendations of the NASA Site Selection Committee provide the basis for a realistic site selection for a human presence at a base on the lunar surface.

We have conducted experiments on 17 lunar soils to characterize oxygen release. The soils span the range in composition of the Apollo samples. All were reduced in flowing hydrogen for 3 hours at 1050°C. Most oxygen release occurred within the first hour. Oxygen yield is strongly correlated to initial Fe abundance, in the relationship: Yield (wt%) = 0.21 Fe (wt%) + 0.45 (wt%). The potential of any lunar soil as an oxygen ore can be assessed from lunar orbit by means of gamma ray spectrometry or multispectral imaging. Iron-rich volcanic glass may be the optimum lunar oxygen ore. An oxygen plant utilizing such a feedstock could be operated efficiently at a temperature of 1050°C with a cycle time of 1–3 hours and produce 4–5 wt% oxygen. Volcanic glass deposits can be delineated using orbital multispectral images. Within such deposits, regions with high purity, hence high oxygen yields, can be identified.

A detailed trade-off and comparative evaluation of lunar oxygen production processes was carried out, resulting in the selection of the technique of vapour pyrolysis as the preferred production process concept on which to base the design of a pilot lunar oxygen production plant. A description is given of the design of the lunar regolith pyrolyser which is central to the production plant, together with the supporting pilot plant infrastructure.

Fluidized beds are key hardware items for lunar oxygen production processes using hydrogen as a reducing agent. A Plexiglas two-dimensional bed was constructed to measure bubble sizes at lunar gravity on NASA's KC-135 aircraft to develop fluidized bed reactor design criteria. Four lunar simulants were filmed while fluidized at lunar gravity for digital analysis of the video data. Analysis revealed that a linear relationship clearly exists between bubble size and vertical bed position. A key observation was the size of the bubbles is inversely proportional to the particle density of the test solids. Solids with low particle density such as glass beads form larger bubbles than the more dense MLS-1 and Florida ilmenite fractions. Also, a theoretical correlation relating bubble rise velocity as a function of bubble diameter and gravity was verified by these tests. A comprehensive data set now exists making it possible to predict the bubble size and rise velocity of numerous lunar starting materials for fluidized bed lunar oxygen processes.

The hydrogen reduction of lunar ilmenite oxygen production technique has been researched in many different aspects since 1985. One of the objectives during this time has been the understanding of standpipe behavior in fluidized beds at lunar gravity and to provide solids friction factors at 1/6-g for predictive design. A total of six flights have been conducted aboard NASA's KC-135 variable gravity aircraft to aid in the understanding of this behavior. A variety of materials were tested during these flights including glass beads with air, Florida ilmenite with helium, and JSC-1 lunar soil simulant with helium. The flights proved to be very successful and the information obtained was used to improve the test hardware and procedures for successive flights. An empirical formula for solids velocity versus friction factor was determined for the glass beads and air, f_s = 66.5u_s^(–2.34). Since the necessary equations contain the gravity term explicitly, this relationship can be combined with existing 1-g data to properly size standpipes for a lunar multi-stage fluidized bed reactor system. Further research is planned for both 1-g and 1/6-g experiments to verify these results.

This paper discusses results of our work on development of the Optical Waveguide (OW) Solar Energy System for Lunar Materials Processing. In the OW system, solar radiation is collected by the concentrator which transfers the concentrated solar radiation to the OW transmission line consisting of low-loss optical fibers. The OW line transmits the solar radiation to the thermal reactor of the lunar materials processing plant. The features of the OW system are: (1) Highly concentrated solar radiation (up to 10⁴ suns) can be transmitted via flexible OW lines directly into the thermal reactor for materials processing, (2) Solar radiation intensity or spectra can be tailored to specific materials processing steps, (3) Provide solar energy to locations or inside of enclosures that would not otherwise have an access to solar energy, and (4) The system can be modularized and can be easily transported to and deployed at the lunar base.

Analysis of the data gathered during the Comet Halley encounter during 1987 resulted in a body of literature asserting that all comets contain substantial percentages of hydrocarbon solids. These solids appear to have a strong similarity to petrochemicals. Arguments are made that the amount of hydrocarbon material in the accessible comets of the inner Solar System can substantially exceed the known reserves of hydrocarbons on Earth. An example is given of at least one conceptually simple method to use comet material as feedstock for space transportation schemes that can move masses through the solar system comparable to the mass carried by oil supertankers. The presentation concludes we need to send prospecting and assay probes to a sampling of the accessible comets to determine the amount of hydrocarbons and the form and location of materials needed for space transportation systems.

This paper will explore potential cooperative efforts between industry and government for commercial development of the Moon. Incentives for mining industry involvement will be suggested, and a phased program will be suggested which would maximize leverage from initial public funding toward rapid evolution of an early lunar base into commercial self-sufficiency. Roadblocks to industry participation in space mining are identified, and potential solutions are recommended. The goal of this paper is to lay the foundation for support of future space mining entrepreneurs. The fundamental stages of a successful public-private lunar mining venture are cost sharing for establishing the initial infrastructure and the creation of opportunity for economic returns. A vision of an early lunar mining partnership includes the mining of regolith to produce lunar liquid Oxygen (LLOX) as the first commercial product, to be sponsored by the government agency or international cooperative who builds and operates the first lunar outpost. A private industry entity with both mining and aerospace experience would be selected as a contractor and operator, with the government agency serving as both the transportation provider and initial customer. Incentives for productivity beyond a given baseline would be in place to create an atmosphere of innovation and rapid improvement. Additional processing circuits for the production of other materials (i.e. metals, ceramics, solar-wind gases, Helium-3, etc.) would be encouraged through discounted transportation and construction costs, and would form the basis for profitability of the mine as the customer base is developed. Part of this customer base would be private industrial entities, which would be attracted by favorable raw-material pricing. As additional lunar outposts are created, their mining needs should be provided by separate mining contractors to help create a competitive environment that stimulates innovation and the expansion of a new industry.

Every type of industry in the world is constantly searching for something to supply it with a competitive advantage. The mining industry is no exception. For the mining industry, a number of factors are converging to force mine operators to develop and adopt dramatic technological changes in both the underground and surface mining sectors. These factors include the decreasing ability for some mining companies to compete successfully in world markets, the problem of keeping productivity at a pace that, at least matches inflation and the ever increasing need to mine from deeper deposits as near surface deposits are depleted. To survive in the mining business, operators need to develop better designed mining machines and to improve mining methodology. Some of the newly developed mining technologies like the use of electricity at high voltage to break hard rock formations can have very interesting applications in space mining. This paper examines some of the more dramatic technological developments in the mining industry over the last two decades and will explores the possibilities for applications in other fields of human endeavor.

A method of lunar drilling using a fluid-based cooling and cuttings removal system will be described. The proposed system would be composed of a non-reactive fluid (gas or liquid) source, insulated fluid transfer lines, and drilling technology based on terrestrial experience. The amount of drilling fluid required to move lunar soil will be estimated. Solutions provided by fluid usage may enable lunar mining in situations where it may other wise be more difficult. It is expected that partial recycling of drilling fluids will be possible during the mining and processing phase. An experimental program to determine both bailing and cooling rates for candidate fluids will be suggested. Advantages in the productivity of fluidized drilling are expected to outweigh additional system mass and associated cost factors.

In the next century Mankind may have to choose from two options for our supply and usage of some nonrenewable natural resources, such as gold, platinum metals, and fossil fuels: learn to live with diminishing supplies of these materials obtained at ever increasing economic and environmental cost, or reach into difficult places and develop new technologies to give us what we need to sustain economic growth. Either prospect faces formidable technological and economic challenges. Exploitation of asteroids for precious and strategic metals is a possible environmentally friendly remedy for impending shortages of some resources. Certain types of asteroids could completely replace terrestrial sources of platinum metals. Asteroid metal mining may become a 21st-century industry worth ten to fifty billion dollars annually (1995 dollars). Asteroids could make the United States and other countries self sufficient in many strategic metals, and it could usher new technologies and increase our applications of existing technologies that depend on these metals.

Under lunar conditions, the most accessible raw material is the regolith and its components. Solar energy is the most accessible power-generating source. Hence, the offered mining and building technologies at the initial development stages should be oriented on use of these sources. One of the first mining technologies on the Moon could be the method using a three drum rope scraper. The main advantage of this design is the low weight of its main components — bucket, ropes, winches, rear racks. The suggested mining plan consists of triangular sectors with the point of regolith collection in center, formed as sectors connect. For these outlines, the use of two rear support drum racks is characteristic, with the distance between them defining the angle of the mineable sector.

The ability of small, solar powered, electrically propelled spacecraft to obtain samples of near earth asteroids and return them to low earth orbit (LEO) was analyzed. Vehicles of up to 10 kW were examined for five cases of varying difficulty. If launched with a Delta II 7925 rocket, more than 600 kg can returned in the best case. No return ability was found in the toughest cases without trajectory tricks. A 5 kw vehicle, which can return 300 kg for several cases, was defined and costed. As a standard vehicle, its cost would be comparable to aeroentry systems which return less than a kilogram. The small electric sample return mission appears feasible, flexible and economical.

The regulatory aspects of spectrum coordination are described. The definition of the shielded zone of the moon as a radio quiet zone is explained. The roles of the international Space Frequency Coordination Group and its Lunar and Planetary Exploration Intersessional Working Group are explained. Existing plans for lunar missions are reviewed, and the known radio frequency spectrum requirements are summarized. Implications and limitations to communication systems required to protect radio astronomy observations in the shielded zone of the moon are discussed.

Radio astronomy observations are routinely undertaken in all portions of the radio spectrum except the region of the spectrum which is greatly effected by the propagation of waves through the ionosphere. The HF (high frequency) portion of the radio spectrum (0.3 to 30 MHz) is the area that is impacted by poor propagation conditions. It is especially difficult to make high resolution observations (∼one arc second) because the extremely long baseline between the antennas required for high resolution implies that the propagation conditions will be very different for the signals received by each antenna. The signal amplitude, due to propagation, can fluctuate by many dB and the phase can be irretrievably corrupted which makes it essentially impossible to do aperture synthesis in a feasible manner. These propagation difficulties can be completely alleviated by putting the radio telescope array above the ionosphere. The most widely consider methods for doing this are to put the array into Earth orbit, lunar orbit, or on the lunar surface. The most practical place to put it is in Earth orbit. Unfortunately, with this location, the ionosphere still cannot be ignored. While the ionosphere can grossly distort HF signals, it frequently allows them to pass through. Thus, numerous communication signals from the Earth can reach the low-directivity antennas in orbit and considerably raise the radio telescopes' noise level. The purpose of our project is to characterize the interference phenomena as it would be observed by an Earth orbiting radio telescope. Somewhat recent reviews of the radio frequency interference environment around the Earth in the HF portion of the spectrum are given by Erickson and by Desch. Weiler et al. have proposed an Earth orbiting low-frequency radio telescope, LFSA (Low Frequency Space Array), consisting of four to eight antennas forming a coherent interferometer. The antenna on each spacecraft is a pair of mutually orthogonal dipoles with very little directivity. This avoids the necessity of steering antennas mechanically, but the telescope has no tolerance for interference. A table of harmful interference levels for the LFSA is shown using a criterion that harmful interference is introduced when the interference level is 10% of the system noise (includes the Galactic background).

This investigation shows that a lunar-based Fabry-Perot gravitational wave antenna would provide a valuable complement to Earth-based systems, both for conclusive, first detection of astrophysical events as well as for new opportunities which afford themselves on the Moon. Due to the unique features of the lunar environment, the possibility of probing the early Universe by detecting relic gravitational waves left over from the Big Bang is discussed.

Observations from the Moon and the Earth-Moon system in the next century will improve our knowledge of the Universe and probably open several new windows to the very early period of its formation. Measurements of gravitational waves from the threshold of classical cosmology, low-energy neutrinos from the end of the lepton era, primordial magnetic fields, and young galaxy formation at high redshift will help us probe the post-recombination era. This, in turn, can extend and refine our picture of the origin of the Universe, a prospect particularly suited for the vantage point of the Moon as a scientific laboratory.

The Moon is an excellent site for astronomy. It lacks an appreciable atmosphere, has no wind, snow or rain, and rotates slowly. It is a stable platform with a very small amount of ground motion unlike the active geology of the Earth, and it is also very quiet on the farside away from the radio frequency background noises emitted from the Earth. Its 1/6th g gravity enables large lightweight structures to be built. It is still a very hostile place with high vacuum, thermal extremes, radiation, micrometeorites, and dust. This paper discusses the architectural considerations, namely, structural design, construction sequence and human factors, for various classes of astronomical structures which were evolved through several workshops and studies performed for NASA. These structures include the 100 m diameter radio-telescope, a large 16 m aperture infrared telescope and a Lunar Optical/Ultraviolet/Infrared Synthesis Array (LOUISA). Earlier instruments (e.g. for all-sky surveys in the ultra violet) which will be landed on the Moon to serve as test beds for the later larger telescopes are also discussed.

The construction of a Lunar Base is seen as achievable. The paper provides a useful summary of challenges facing pioneers of lunar base construction. It highlights important aspects of the location and use of the facility, the local environment, the human physiological adaptation process, and a principal concern for the construction industry—construction materials and methods required to erect the facility. Specific emphasis is placed on the latter two major issues. The authors believe that a lunar base will be built, operated and maintained by humans. It may be the next generation that carry out these dreams, but it is research of the type reported in this paper that will make these dreams a reality.

The shield structure is critical for a manned lunar base. The reinforced earth method, with geotextile used in shield walls, which we call "the Lunar Textile Method," has been proposed. Construction robot are used by tele-operation or automatic maneuvering in the Lunar Textile Method. The advantages of Lunar Textile Method are construction by a robot, reduction in EVA time for construction, and using light weight geotextiles transported from earth. For developing the robot for the Lunar Textile Method, the following items should be considered. (1) The robot has many different functions, and its mechanism and material must be resistant to the lunar environment and (2) The robot, which is divided into several parts, should be small and have light weight.

Many authors have proposed methods to excavate lunar material and to construct lunar habitats. The purpose of this paper is to illustrate the overwhelming degree of difficulty in preparing for and performing a lunar excavation. The authors identify typical procedures and problems faced by contractors while performing routine excavations on Earth and then suggest excavation techniques and equipment required to perform the same excavation under extremely adverse conditions on Earth. The incremental difficulty identified to perform excavation activities under adverse Earth conditions offers a means to realistically assess additional difficulty to be encountered on the Moon. Finally, the authors suggest practical considerations for excavation procedures and equipment for excavation within the lunar environment.

This paper describes the results of research on the use of vibratory tools for lunar regolith moving, cutting and penetration. It has been shown that the effort required to accomplish these tasks can be significantly decreased by forced vibration. The purpose of this research is to study the various issues through model tests, including centrifuge modeling. It has been demonstrated that vibrating the blade of a model bulldozer significantly reduces the force needed to dig into and break up dense relatively unconfined soils. Depending on the boundary conditions even relatively dense soils tend to density further when subjected to certain forms of vibration. Test results obtained on model bulldozer systems, involving excavation of dense lunar simulants, are presented. It has also been demonstrated that penetration of the lunar surface can be accomplished more efficiently using vibratory tools. Research is currently being conducted in the area of screw-in plates, which might be used as anchors or supports for equipment, scientific instruments or foundation elements. Preliminary results of experiments performed using a model screw plate are presented. All of these effects give rise to the possibility of smaller, more efficient machines for lunar activities.

Exploration of the Moon is the first critical step in the human expansion into the vast reaches of space. Human capabilities to survive, function, expand and settle into the space environment should be defined on the Moon which represents the most nearby ideal testbed. Scientific studies and utilization of space resources should culminate in the establishment of a nearly self-sufficient permanently human-tended lunar base sometime in the 21st century. An evolutionary process for development of the infrastructure for a lunar base consisting of four stages is suggested. These four development stages are: (1) exploratory, (2) pioneering, (3) outpost, and (4) mature base. Overall goals, specific objectives, functional requirements, construction conditions and life support systems requirements needed in each stage are identified and summarized.

To establish, in a small lunar crater, a permanent domed oasis which optimizes human factors, a satellite first performs global mapping prior to site selection. It will transfer to lunar-stationary orbit transmitting power to the base via laser beam to drive equipment and illumine the long lunar night. Tele-robotic operations minimize risk during heavy construction prior to occupancy. Habitats within the crater wall provide an elevated outlook towards the interior ground plane. Plant growth trials are conducted prior to the introduction of other life forms.

Many previous concepts for manned Mars surface facilities have not been developed fully because of attempting to integrate the Mars habitat and the trans-planetary spacecraft. The design emphasis stagnated upon trans-Mars spacecraft. NASA has started to look at the decomposition of the Mars mission into two activity categories "Getting There" and "Being There". Focusing on the part called "Being There" enables separating some of traditional space vehicle construction constraints from the definition of Mars mission habitat requirements. This approach will be demonstrated and clarified with a set of First Mars Outpost [FMO] elements and assumptions. Those design guidelines will provide the objectives to be explored and evaluated as architectural design issues, and may actuate the Mars mission strategy and generates requirements for necessary technology development as well. Beside the technology development, the syntax of design philosophy will lead to architectural insights: man-machine interface, human factors, and space ergonomics. Simultaneously, implications of the FMO will expose architectural ideologies; robotic construction applied for site preparation, such as building automation, robotic served self-building assembly system, such as kinetic architecture, and autonomous architecture with utilization systems for in-situ resources, consist in condensing the working-living human complex in space.

The Moon is an ideal site for conducting astronomy and other scientific studies, and the lunar regolith contains abundant materials that can be used for the construction of scientific laboratories and supporting infrastructure. The paper proposes a concept for establishing a permanent circumferential lunar utilities system that would provide a continuous and reliable source of solar electric power and other utilities in support of mining, manufacturing, and scientific activities on the Moon. The South Pole of the Moon is proposed as the initial site for the utilities system, which could be expanded to encompass all other areas of scientific interest on the Moon.

This paper announces the Lunar Settlement Foundation (LSF). Its goal is to establish a permanent, private, lunar settlement within the next 25 years. The purpose is to provide people the opportunity to live on the Earth's moon. Lunar base studies from von Braun's lunar exploration mission through on-going First Lunar Outpost (FLO) studies at NASA'a Johnson Space Center are referenced. Permanent lunar base functional capabilities are identified to meet the primary goal of survival. Concepts for habitation modules and landers are identified. Population size is addressed. Lunar transit missions are parametrically described. An Internet Home Page is announced.

To enhance the scientific benefits of a near-term return to the Moon, a concept for a reusable, unmanned spacecraft, the Sub-Orbital Lunar Explorer (SOLE), is proposed. Such a spacecraft would provide the lunar explorers with greater access to the lunar surface and make accessible areas that are difficult to traverse on foot or by surface craft. The propulsion system consists of a pressure-fed engine utilizing silane (LSiH₄) and oxygen (LOX) as propellants. The reference SOLE spacecraft has a nominal range of 400 km with a 150 kg payload. Estimates for range and time of flight, based on a range of initial impulsive velocity maneuvers, for round trip missions are presented. Two mission scenarios are discussed to illustrate the operational capability of the SOLE spacecraft.

The rationale for organizing an Earth-Moon Test Range as an early part of any return-to-the-Moon program is explained. Separate requirements developed by different scientific and engineering interests for information from the Moon are reviewed. Problems of site selection for lunar equipment are considered relative to these differing interests and to the Moon's environment, its rotational and orbital cycles, terrain, soil characteristics and gravitational field. Automated facilities for both the terrestrial and lunar terminals of the Range are outlined. Operational considerations which typically dominate during installation and maintenance of remote instrumented stations are brought out, and related to the advantages of a Range organization for servicing instrumented lunar facilities.

Dense lunar soil simulants have been shown to possess secant friction angles in excess of 50°, while exhibiting a significant decrease in the secant friction angle with increasing mean normal effective stress. These characteristics lead to questions regarding the suitability of existing conventional stability solutions used to predict lunar facility performance. The particular problem of bearing capacity has been examined by performing centrifuge model experiments using two lunar soil simulants (MLS-1 and JSC-1). Results from these experiments are presented in light of a solution approach which accounts for the scale effects due to material non-linearity and progressive failure.

Near-term, low-cost space fission power systems can enhance the feasibility and utility of lunar and planetary bases. One such system, the Heatpipe Power System (HPS), is described in this paper. The HPS draws on 40 yr of United States and international experience to enable a system that can be developed in <5 yr at a cost of <$100M. Total HPS mass is <600 kg at 5 kWe and <2000 kg at 50 kWe, assuming that thermoelectric power conversion is used. More advanced power conversion systems could reduce system mass significantly. System mass for planetary surface systems also may be reduced (1) if indigenous material is used for radiation shielding and (2) because of the positive effect of the gravitational field on vertical heatpipe operation. The HPS is virtually non-radioactive at launch and is passively subcritical during all credible launch accidents. Full-system electrically heated testing is possible, and a ground nuclear power test is not needed for flight qualification. Fuel burnup limits are not reached for several decades, thus giving the system long-life potential.

This essay attempts to clear up a persistent confusion about the character of planetary surface exploration habitats and what they have and do not have in common with interplanetary vehicles. This essay argues that a Trans Mars Injection Vehicle (TMIV) or Trans Earth Injection Vehicle (TEIV) and a Mars Surface Habitat are so fundamentally different in functional and architectural character that no single design can serve both purposes. This confusion between interplanetary vehicles and surface habitats probably springs from the romantic sources of science fiction in which the Buck Rogers type pilot lands his space ship on the surface of the planet. The intrepid explorer descends a ladder in a pressure suit, and proceeds forthwith to the business of exploring. A recent incarnation of this tradition appears in Weaver & Duke's Mars Exploration Strategies, which describes a NASA "1993 Reference Mission" that depends extensively upon "commonality" between the TMIV habitat and the Mars surface habitat. In Weaver & Duke's vision, the crew launches direct to Mars à la Robert Zubrin's Mars Direct concept in a habitat and then "fly it down" to the Mars surface. The romantic paradigm of exploration from the landed spaceship—surface base carries many unexamined assumptions with it that appear even today in serious proposals for planetary exploration. Chief among these assumptions are: 1) that it makes sense to design a living environment that serves equally well in zero gravity and in a gravity field, 2) that it is economical and sensible to drag the mass of radiation shielding and zero-G countermeasures down to the surface after having paid a high price to place it in Low Earth Orbit and given it sufficient Δν to reach Mars, and 3) that the extravehicular exploration systems, including pressure suits, airlocks, and rovers require no design features specialized for the planetary surface and that they are essentially similar to zero-gravity EVA systems. Beyond these assumptions are a number of misunderstandings of the specific characteristics of an interplanetary vehicle. TABLE 1 summarizes these characteristics, showing the corresponding design solutions for both interplanetary vehicles and surface habitats. The Apollo Lunar Module (LM) had all the characteristics of an ascent/descent vehicle ensemble, but it also served as the surface habitat while the crew was on the lunar surface. The Apollo paradigm sometimes serves as an example of combining the lander with the surface habitat but it is an incorrect example because of the tremendous differences in surface stay times, as well as the transit times. Apollo astronauts typically spent less than 48 hours on the moon, with the total trip time less than a week. A First Mars Outpost crew will spend about 500 to 600 days on the surface, with a total trip time of 1000 to 1200 days. This much greater timeline creates not only a quantitative difference, but also a qualitative difference. There was no way that the LM could support the crew for even a few weeks, let alone nearly two years on the surface An expedition of almost two years requires a specialized habitat to support the crew in their necessary living and working activities. A generic or general purpose habitat will not serve this purpose on the surface nor on the interplanetary vehicle. The LM was a specialized vehicle, not intended to support a crew between the earth and the Moon. It's success during Apollo 13 was the exception that proves the rule. NASA needed to improvise several extraordinary procedures to enable the LM to serve as an interplanetary rescue vehicle. The Mars transit vehicle and the Mars surface habitat should be separate systems, optimized to their primary functions. This essay questions whether habitat commonality as a key to cost and risk reduction is really possible. It questions how the 1993 NASA Reference Mission and other variations of "Mars Direct" trade this reduction of potential risk for acceptance of known, actual and quantifiable danger, particularly in terms of radiation exposure on the Mars and Earth legs. Nor does the 1993 NASA Reference Mission provide for effective counter-measures against the debilitating effects of prolonged exposure to weightlessness. Yet, at the same time, they propose to bring down to the Mars surface all the accommodations within the habitat that presumably should provide protections from the interplanetary environment.

Polar expeditions and extended space flight and surface missions require a relatively small group of individuals to work together in a hostile and isolated environment. Safety and mission success are dependent on optimal functioning of each team member. Monotony and loneliness become problematic as missions increase in duration; task performance and interpersonal processes become even more complex in the case of international teams. Psychological, group process, and task performance characteristics were evaluated in four different polar expedition teams varying in national and gender composition. North American members were more highly focused on achievement strivings, Soviets on avoidance of failure. These motivational differences had an influence on task performance and group relationships. Perceptions of the appropriateness of assigning particular tasks to women also differed by national group. Gender differences in behavior were evident, related to a greater likelihood for men to share emotional problems with women than men team members, and to feel a lesser need for competitiveness in a mixed gender group. The all women's team demonstrated a high level of cooperativeness and social support of other team members. However, concerns about the welfare of other group members added to the personal stress experienced. Across teams, anxiety, tension, and health concerns increased in early stages of the expedition and decreased significantly at later stages. Unrealistically high self-perceptions of personality and performance ability were associated with relatively poorer actual performance. Leaders played a crucial role in promoting strong group cohesiveness and morale through the perceived quality of their decision making and clarity of designating task responsibilities. These findings indicate the need to focus on the interaction of personality, cultural, gender, and task performance demands in personnel selection and during long duration missions. There are also implications for the structure of a Mars habitat, including optimal design of modules for privacy and psychophysiological equipment for relaxation needs.

Avoiding large-scale environmental extremes is a primary medical and technological policy for enhancing crew protection during the Mars mission. However, to help maintain normal physiological functioning of all body systems, physical and mental health, and optimal work performance, it is important to create a range of intermittent environmental and emotional contrasts onboard and in the Mars habitat that simulate variations in earth conditions. Developing an adequate battery of methods for health monitoring has been a serious issue since the first space flight, and remains a major problem. Health changes associated with zero gravity have very serious consequences in terms of productivity, reliability, safety and capability for sustained individual and group performance. With regard to suit design, the thermal protection of astronauts on the Mars surface requires not only the use of an EVA suit with a cooling system for removing heat, but also a warming system. During EVA, heat generated by intensive physical labor, and low temperature conditions promoting cold sometimes occur simultaneously or sequentially. Therefore, a cooling/warming system must operate by local and whole body principals of thermoregulation. Adequate feedback for monitoring the level of heat exchange and controlling core body temperature also are highly important. Particular challenges to adequate monitoring occur when there are different temperatures on different parts of the body, rapidly changing surroundings, or various kinds of emergencies. Maintaining normal temperature topography during these situations is a key suit design problem for astronaut survival.

The NASA NSCORT Center for Space Environmental Health (CSEH) has adapted the research paradigm for Risk Assessment and Management put forth by the National Research Council (NRC) for investigating Space Habitat Environmental Health. This paradigm covers five sequentially related areas: Hazard Identification, Dose-Response Assessment, Exposure Assessment, Risk Characterization, and Risk Management. Using this research paradigm, a current area of focus within CSEH is Exposure Assessment; specifically, the selection of the sensors to monitor contaminants aboard the space habitat. A methodology has been developed to design an array of sensors to monitor contaminants in a space habitat, with the goal of maximizing crew health while. The design of the sensor array specifies the type, number, and placement of sensors in the space habitat. As an example environmental health threat, we are postulating three contaminants, each with a specified probability of occurring within a simplified space habitat. The objective is to maximize the amount of healthy time for the crew, and thereby maximize the performance of the crew, given the probabilities of contamination occurring, the probabilities of that contamination being detected by selected types and numbers of sensors, subject to various resource constraints in choosing the sensors.

This paper proposes a Surface Dwelling System for support of initial Mars exploration. It is designed to function as an Earth/Mars transit system and reconfigure, upon arrival at Mars, to function as a surface referential shelter/lab for long term occupation. The system is composed of self-contained modular units that may be transported individually to low Earth orbit by a Shuttle or Buran type system, or launched as an assembled unit in an Energiya class HLV.

Students in a unique, graduate seminar program at the University of New Mexico that explored the role of architects in understanding and planning for the needs of humans in extreme environments present initial results of an engineering test case that pursed development of an international lunar space station housing 30 persons over a two-year period. Seminar participants, challenged with balancing both people and engineering factors, propose establishing a science station featuring modular neighborhoods of three 10-person groups sited under a radiation shielding dome in a near-side crater with Earth views. Central to the crater-based neighborhood design is an architectural and engineering philiosophy that incorporates creating familiar sights, sounds, and a shirt-sleeve lifestyle to enrich the crews' lunar experience as missions in astronomy, extravehicular research, geology, and pre-Mars base habitation are conducted. The neighborhood concept is essential in achieving the multiple goals of safe, cost effective, and rewarding exploration, while maintaining healthy and creative social and cultural interactions among multi-national and skill-diverse crews. Spaces for bathing, recreation, crew-arrival celebrations, and problem solving are desired while the introduction of a new culture to the Moon occurs concurrently with human adaptation to a foreign environment. "Neighborhooding" features regular events — such as meals, seminars, and a gathering place for descision-making — as required rituals. To address population spread, architectural eco-care considerations were viewed as critical. Engineering and construction objectives comprise eco-considerations to protect the lunar environment through techniques that maximize in-situ vitrification and dust mitigation building technologies, as well as air-, heat-, water-, plant-, and waste-matter recycling. Power needs are met by a combination of solar arrays and a stand-alone, inherently safe nuclear unit. Additional out-of-crater electrical needs, primarily for science experiments, are met via radio isotopic thermoelectric generator technology. Station access for crew rotations and resupply is available via a nearby landing site, and such events are celebrated. Emerging areas of concern remain, however, as this academic program, now in its second year, applies terrestrial, architectural and engineering principles and experience as an analog to the lunar environment. This one-of-its-kind seminar program is performed under the auspices of the University's School of Architecture and Planning. Active involvement of astronauts, architects, engineers, scientists, and space pioneers from U.S. industry, the national laboratory system, NASA, and academia has proven invaluable to this applied academic program. Students from ten countries attended, with significant Pacific Rim participation. Academic disciplines ranging from engineering to philosophy were represented, as were multi-national and multi-gender perspectives, and that of the physically challenged. The program's test-case application could serve as a template for future courses, encouraging a multi-disciplinary approach to science projects. Program results could have applications to architecture in extreme space and Earth environments, in multi-national and multi-cultural urban settings, and to sub-surface defense, intelligence, and science posts.

Today the trend of Space policy is based on designing low-cost missions. Especially thinking to Moon and Mars Missions, this approach seems to be mandatory. Two principal aspects affect the mission's costs: the launches' number, the astronauts' work hours necessary for building and assembling space infrastructures and operations/maintenance time. It is possible to reduce the number of flights for a given mission if we, as designers, approach the space habitat design and construction with a different way of thinking.

The process of designing a lunar base involves architecture in a pure sense, with detailed programming, design and arrangement of peoples' living spaces and working interactions rigidly defined by programmatic function and site location, and coordinated closely with multiform complex feats of engineering. L-bAS (Lunar-based Astronomy Station) is a hypothetical test-case facility that must comfortably accommodate 30 people on the moon for a period of 24 months. Its crew is the critical human element in a masterplan for the operation or various types of astronomical observatories, remote sensing stations and other robotic scientific installations which will eventually be deployed on the lunar surface. As an exercise in creative thinking, the purpose of the design has been to explore, define and demonstrate the importance of humanist architectural design philosophy in the development of facilities engineered for long-duration missions in harsh extraterrestrial environments.

Inflatable structures have wide applications in space, ranging from large low pressure satellite balloons to human occupied structures on extraterrestial surfaces. Among their desirable attributes are their lightweight nature, small stowage volumes, easy deployability, and efficiency as pressure vessels. Inflated membranes are load adaptive structures which generally display a nonlinear response resulting from possible large movements upon loading. The shape of an inflatable structure is key to its feasibility and efficiency. The general structural behavior of inflated membrane structures, methods for controlling their shape, and other design considerations for inflatable structures utilized in space are described.

Unexpected punctures or leaks can he catastrophic for inflatable membrane structures placed in the harsh lunar environment. Drake and Richter proposed that an inflatable membrane structure be used for a Lunar Assembly Building (LAB) in the development of a lunar base. In these investigations, inflatable membrane structures of non-circular cross section were developed to provide large open work areas. Matsumoto, Pazargadi, and Richter evaluated six different configurations of inflatable membrane structures for LAB applications. Their results indicate that numerous, non-circular membrane configurations are possible with proper placement and combinations of cables and rigid members. Schroeder and Richter developed a plausible option incorporating such cables and rigid members. They concluded that future studies should investigate potential failure mechanisms and behavior at large deflections of the LAB. This paper summarizes the results of additional investigations of typical LAB structures. Two design approaches are proposed to prevent catastrophic structural failure. In the first approach, a flexible membrane shell incorporating secondary rigid elements is examined. In the second, a semi-rigid, composite membrane utilizing a vacuum cured resin system is examined. These two design approaches are evaluated for constructability and analyzed for structural integrity in response to inflating, operating and accidental pressure loss conditions. They are evaluated using finite element analyses. Advantages and disadvantages of both systems are identified.

The Mars Pathfinder lander uses a novel airbag impact attenuation system to perform its landing on Mars. Full scale testing under Mars like atmospheric pressure conditions was performed to obtaining accurate loading conditions on the airbags during impacts on a rocky terrain. The objective was to minimize the total mass of the airbags while maximizing their performance. This paper will discuss the design of the airbags, the testing techniques used and the lessons learned from the tests. The final design of the airbag subsystem incorporates a 5 layer Vectran fabric construction with solid propellant gas generators and has a mass of 99 kg.

An analysis of the framing system for an inflatable structure to be used in a lunar/Martian base has been conducted. The framing system consists of cylindrical arches and columns, all of the same diameter. Three options for the framing system were evaluated: (1) rigidized foam encased in membrane sleeves, (2) rigid thin-walled tubes, and (3) pressurized membrane tubes. The results of this evaluation indicate that the pressurized membrane framing tube system offers the optimum combination of minimum weight and meeting the structural requirements.

This paper describes part of NASA's ongoing effort to study inflatable habitats for use as habitat facilities in such missions as the Human Lunar Return (HLR) Mission. The habitat described in this paper is a horizontal cylindrical sectioned foam inflated and rigidized structural envelope. This inflatable habitat will provide a living and working environment for a crew of two for a surface stay of three to six days. It is 2.5-m diameter by 4.0-m long cylinder containing 14.5³ meters of volume. The outfitted inflatable habitat has an estimated mass of 1200 kg. This habitat is delivered and predeployed on the lunar surface by the same open cockpit lander the crew uses for descent and ascent.

Long-term human missions in space, establishment of a human-tended lunar base and of a Martian base require autonomous life support system. A Lunar/Martian-Engineered Closed/Controlled EcoSystem (L/M-ECCES) can provide autonomy by integrating a human module with support plant and animal modules and waste treatment subsystems. Integration of physical/chemical and biological waste treatment subsystems can lead to a viable and operational bioregenerative system through minimizing resupply requirements from Earth. Life support requirements of the human module drive the design and operation of a L/M-ECCES. A top-level diagram for a L/M-ECCES was developed based on the human module requirements. The proposed top-level diagram is presented and its components are briefly discussed.

Higher plants will be an important component of regenerative life support systems using biological and physicochemical elements. As part of NASA's Advanced Life Support Program, the Johnson Space Center (JSC) is conducting plant growth experiments and building facilities to demonstrate life support technologies. A synthetic soil developed at JSC, termed zeoponics, and two facilities, the Early Human Testing Initiative (EHTI) Facility and the Human-Rated Test Facility (HRTF) will provide valuable data in the ultimate design of life support systems for the Moon and Mars.

BioServe Space Technologies (a NASA Center for the Commercial Development of Space) is committed to identifying the mechanisms by which plants sense gravity and control the directional growth of their root structure to seek soil, nutrients and water. Part of this work involves the use of "Identification Theory" to infer the order, transfer function and feedback in the control system that governs gravity-dependent plant growth. When a vertical root is placed on its side (a gravity stimulus of 90°) altered growth redirects the root in the new downward direction. This process, called gravitropism, may be quantified by measuring the curvature responses of roots to given gravitational stimulation. Plant sensitivity to gravity is dependent on species, specific hormone and metabolic pathways and also on the nature of the gravitational input. By varying the inputs which are known to affect gravitropism and observing the gravity-response of seedling roots we are developing a mathematical model of the control system that governs gravity-dependent plant growth. Because the ability of plants to sense and respond to gravity is essential for their survival, the control model developed here will aid both scientists and engineers in creating better plant biotechnology experiments and bioregenerative life support systems. Here on Earth, even at the earliest stages of seed germination, plants must expend valuable energy reserves to direct emerging shoots upward and emerging roots downward. By understanding plant gravitropic controls we may also take steps to maximize Earth-bound crop production by minimizing plant energy expenditure on gravitropic growth. This work was supported jointly by NASA:NAGW-1197 and the Coalition to Increase Minority Degrees #F95UR064.

The symbolic manipulator Mathematica is used to derive and solve the equations of equilibrium of a composite plate with in-plane fiber waviness. The plate is assumed to be in cylindrical bending and the resulting eigenvalue problem is governed by an ordinary differential equation with variable coefficient. The eigenvalue problem is solved using a combination of the shooting algorithm and the secant method. A numerical example of a plate with sinusoidal fiber waviness shows that, for all studied cases, the waviness reduces the buckling load and thus has a detrimental effect of the static stability of the plate. Moreover, for the studied cases, the buckling load is more sensitive to variations in the frequency of the waviness for small frequencies.

A total Lagrangian finite element scheme for arbitrarily large displacements and rotations is applied to a section of an isotropic circular toroidal shell and an aircraft tire. The scheme decomposes the motion into stretches and rigid-body rotations, describing the deformed state in terms of local engineering measures: the Jaumann stresses and strains. Local and layer-wise thickness stretching and shear warping functions are used to model the three-dimensional behavior of the shells. The finite element model successfully models the bi-curved shell as well as the complex geometry of the aircraft tire under inflation and contact loads.

The symbolic manipulator Mathematica is used to analyze the nonlinearity associated with the free vibration of a simply-supported orthotropic shell. This expands upon earlier analyses conducted by Rivieccio and Nayfeh on the nonlinear free vibration of an orthotropic shell. The nonlinear equation of motion is derived using the time-averaged Lagrangian analysis technique. The effects of various initial amplitudes on the nonlinear natural frequencies are evaluated. The effects of the different shell geometries on the nonlinearity are investigated. The nonlinearity is found to decrease with increasing radius of curvature, opening angle, and length.

This paper addresses the requirements (codes and softwares) for building a composite (fiber/matrix) pedestrian bridge, that is being planned for the campus of the university of New Mexico, Albuquerque, NM. The bridge is comprised of pultruded beams as the main span members. An `isogrid" deck integrated with the pultruded beams will support the pedestrian load. The governing design codes were first explored and the requirements were implemented in a spreadsheet software. Materials and component fabrication is based on experience gathered from the personnel at the Air Force Phillips laboratory, Albuquerque, NM. A commercial finite element code was used to analyze the isogrid structure to help design the deck in accordance with code requirements. Components were tested to determine their mechanical properties. The elastic modulus of pultruded members was also determined independently from ultrasonic inspection to address the feasibility of using this method for in-service monitoring.

This paper discusses ongoing work to develop structural health monitoring techniques for composite aerospace structures such as aircraft control surfaces, fuselage sections or repairs, and reusable launch vehicle fuel tanks. The overall project is divided into four tasks: operational evaluation, diagnostic measurements, information condensation, and damage detection. Five composite plates were constructed to study delaminations, disbonds, and fluid retention issues as the initial step in creating an operational system. These two foot by two foot plates were graphite-epoxy with nomex honeycomb cores. The diagnostic measurements are composed of modal tests with a scanning laser vibrometer at over 500 scan points per plate covering the frequency range up to 2000 Hz. This data has been reduced into experimental dynamic-response matrices using a generic software package developed at the University of Colorado at Boulder. The continuing effort will entail performing a series of damage identification studies to detect, localize, and determine the extent of the damage. This work is providing understanding and algorithm development for a global NDE technique for composite aerospace structures.

Spacecraft have been troubled by thermally induced vibrations of deployable appendages for over 25 years. Thermally induced vibrations are an oscillatory structural response resulting from rapid uneven solar heating. These structural disturbances reduce the pointing accuracy of a spacecraft and in extreme cases may affect the stability of the entire vehicle. Examples of recent spacecraft whose performance has been degraded by thermally induced structural disturbances are the Hubble Space Telescope (HST), the Upper Atmosphere Research Satellite (UARS), and the Ulysses spacecraft. Current investigations of this potentially debilitating phenomena involve analytical, computational, and experimental research focused on non-spinning and spinning spacecraft booms and deployable solar array structures.

A three-dimensional scale model of a hexagonal boom truss of the then space station Freedom was built and tested in the laboratory. The purpose of the tests was to extract complete quality data of the vibrational characteristics of the structure, before and after damage, for use with damage detection/evaluation theories, that could eventually be implemented in a space environment. The vibration tests consisted of experimental modal analysis before and after the infliction of artificial damage. The structure was subjected to 18 different damage scenarios, the damage consisted of partial and complete damage at single and multiple locations. This paper describes the details of the structure, the construction procedure, the testing procedure and the test results. The test results consist of the vibrational signatures due to different damage scenarios on the structure. The results will be used to implement global damage detection/evaluation theories based on modal strain energy distribution and Artificial Neural Networks.

A finite element model for aeroelasticity analysis of hypersonic panels, using a 9 degree-of-freedom Discrete Kirchhoff Theory (DKT) triangular element along with the 6 d.o.f. in-plane membrane element, had been developed in Authors' previous work, where the Von Karmam's large deflection plate theory was used to account for the geometric nonlinearity, the first-order unsteady piston aerodynamic theory was applied for computation of the aerodynamic pressure, and the temperature effect was also included. This paper applies the model to the determination of flutter boundary of hypersonic panels. The stability boundary for a simply supported rectangular panel with dimensions a/b=1.0 under a uniform temperature distribution ΔT/ΔT_cr has been found. The results computed are compared with those reported in Dowell's work. A very good agreement has been achieved.

In this paper, a self deployable large disk antenna is proposed for power transmission between locations in space. Its mechanism of self deployment is examined through a geometrical study. This antenna is discussed for use in a power transmitting test using an S-520 sounding rocket in a few years time.

Under this research, a single degree-of-freedom hinge has been developed that facilitates the unassisted deployment of a solar array using Shape Memory Alloy (SMA) components. The hinge is a marriage of two concepts, one providing exaggerated excitation and the other providing bearing-free rotational mobility. The first concept translates the relatively small motion achievable with SMAs into a large rotation using appropriate rolling contact surfaces. The second concept comprises a hinge equipped with conical inserts that when activated allow free rotational movement about the hinge's axis but otherwise pre-load the hinge. The features of the aforementioned concepts are combined to create a low cost versatile hinge that provides actuation, is highly reliable and predictable.

Previous studies of self-assembly techniques applying Lyapunov's theorem have utilised elements with the ability to manoeuvre simultaneously with an assembly vehicle for each element. However, this Parallel implementation would be impractical for large extended structures. Therefore, this paper examines the possibility of a Serial implementation with a greater number of elements than controlling assembly vehicles. To do so, the method demands the use of Virtual Elements to replace the uncontrolled elements within a Global Potential Function.

One of the most severe environment that a satellite will be subjected to during its lifetime will occur during qualification testing and launch. This paper summarizes the results and status of research efforts in the area of satellite isolation from the launch environment. The objective of this effort was to reduce the launch induced-dynamic acceleration of the satellite by insertion of a passive isolator. Isolation issues involving the use of passive elements and launch vehicle system-level requirements will be discussed.

Locations and compositions of Near Earth Objects (NEO's) could be discovered by simple, inexpensive, kinetic energy projectiles launched by the thousands, provided they contain a minimum amount of propellent for course correction and a control system. The largest problem with these projectiles is incorporating enough advanced control capability on-board. The solution is the use of a compact, single chip, neural network control system. Our objective is to achieve more rapid and accurate tracking, coupled with better disturbance rejection, when compared to other controllers. The procedure was to classify a minimum list of cause and effect variables and train a recurrent neural network to mimic the dynamics of kinetic energy projectiles. We then incorporated the neural network into a model predictive control strategy, and computationally evaluated response times, tracking errors, and other performance indices. The results were excellent. Furthermore, because a neural network is inherently non-linear, it could be expanded to respond to non-linear effects not included in our simplified considerations. The neural network could also be trained in-flight. Our results were supported by on-line experimental results in a mining environment not directly related to kinetic energy projectiles. We concluded that a neural network architecture could provide optimal on-board control for propellant containing, kinetic energy projectiles, reducing the amount of control action taken, and minimizing the propellant required for course corrections.

This paper presents a study of the dynamic effects of the Space Shuttle launches on the ground support structures at Launch Pad 39A at the NASA-Kennedy Space Center. Pressure and structural acceleration data recently recorded at the Kennedy Space Center in support of a 1990-1992 study were reviewed and incorporated with additional recordings of similar data at other locations, and with the measurement of ground accelerations. The combined effects of excitation pressure and ground acceleration on the launch pad support structures are significant.

The Mobile Service Tower (MST) is a lightweight movable, steel-braced-frame structure, approximately 230 feet (23 stories) tall and 87 feet (26 m) by 54 feet (16 m) in plan. It provides protection for and access to the Atlas/Centaur space booster and satellite payload during integration and assembly, prior to launch. The tower is enclosed by metal siding and large environmental doors. The tower contains movable platforms for access to the launch vehicle and payload. It also houses service cranes and mechanical, electrical, and control systems used in support of the flight vehicle integration and assembly. The tower is mounted on drive trucks supported on two sets of railroad tracks spaced 67 feet (20 m) apart. After the flight vehicle is assembled and prior to launch, the tower is moved approximately 250 feet (76 m) from the service to the park position. The MST is anchored by a removable, tie-down system in the service and park positions. The MST was designed and constructed using a state-of-the-art 3-D model system.

This paper presents an alternative method for the "minimum-time" design for a slewing flexible beam. The two-point boundary problem involved, which incorporates nonlinearity of the rigid slew manoeuvre coupled with flexibility of the beam, is linearized and then decoupled using a mode shape based transformation. The rigid mode, which dominates the slew manoeuvre of the beam, is used to minimise the time of operation from an initial state to final desired state subject to the constrained input. A quadratic control input is suggested for the remaining flexible modes. It follows a combination of "bang-bang" and quadratic feedback control for the beam. The dynamic behaviour of the beam is handled by using a high precision integration finite element method. Numerical results show the high performance with respect to position and also the general applicability of the method.

This paper presents a new algorithm for solving general inequality/equality constrained minimum time problems. The algorithm's solution time is linear in the number of Runge-Kutta steps and the number of parameters used to discretize the control input history, with no a priori initial guess needed. At the core of the algorithm is a method for finding and re-solving for a fixed-time feasible solution to the full nonlinear problem. The fixed time solver/re-solver uses a new method of finding a near-minimum-2-norm solution to a set of linear equations and inequalities. This near-minimum-2-norm subproblem solution achieves quadratic convergence to a feasible solution of the full nonlinear problem. The algorithm solves for a feasible solution for large trajectory execution time t_f and then reduces t_f by a small amount and re-solves. The re-solve routine is called repeatedly, giving a sequence of feasible solutions, with smaller and smaller time t_f, until convergence is obtained. The method is being applied to a three link redundant robotic arm with torque bounds, joint angle bounds, and a specified tip path. Our experience with the minimum time program is that it solves case after case within a graphical user interface in which the user chooses the initial joint angles and the tip path with a mouse. Solve times are from 30 to 120 seconds on a hewlett packard 175-125 workstation, for 90 control variables and widely different initial arm positions and tip paths all of which require large angle motions of the arm. A zero torque history is always used in the initial guess (invisibly to the user) and the algorithm has never crashed, indicating its robustness. A representative numerical example is presented in which the solve time was 82 seconds with 150 control variables, and 153 seconds for 300 control variables.

This paper will discuss the design of an input shaped open-loop control for a single flexible robot link. The authors develop the equations of motion, including the first flexible mode shape and the actuator dynamics. Additional content includes the hardware system identification iterative runs used to update the model. Optimized input shaped commands for the flexible robot link to produce a rest-to-rest, residual vibration-free, 90 degree maneuver are developed. Correlation between both experimental and analytical results of the 90 degree slew, using two different identification models, are reviewed.

This paper describes an approach for designing a control system based on the linear quadratic Gaussian (LQG) for suppressing vibrations in structures. The LQG is modified by placing bounds on the control forces to simulate real actuators. The control system is designed through two optimization problems. The first problem is one of designing the LQG control system. The gain matrices obtained form the LQG problem are the basis for finding the transient response of the system, but the actual forces used in calculating the transient response are modified so that they do not exceed the specified bounds. These bounds are the design variables of the second optimzation problem which sizes the actuators for minimum weight. The bounds are assumed to be proportional to the weight of the actuators. A constraint on the time to reduce the energy of the vibration is used to determine a state of rest. As an example to illustrate an application of the approach, a wing box idealized by rod elements is used.

This paper presents a Newmark-based predictor-corrector (NPC) method for the solution of constrained structures characterized by differential and algebraic equations (DAE's). The feature of this method is the formulation and solution of the generalized displacements of the structure incorporating Lagrangian multipliers in the mixed DAE's separately using a predictor-corrector-like procedure. By giving predictions of the generalized displacements, the Lagrangian multipliers are evaluated from their governing equation, and then the generalized displacements are corrected based on the evaluated Lagrangian multipliers. A rigorous proof of the unconditional stability of the integration scheme for linear DAE's is derived. To demonstrate the effectiveness of the proposed method, a 14-bar truss structure with circular slot constraints is solved.

An analysis of wind conditions and the aerodynamic design for the rooftop helideck of the Fairview Medical Center (FMC), Minneapolis, is presented, based on an extensive literature search and the examination of current Federal Aviation Administration (FAA) and United Kingdom Civil Aviation Authority (CAA) guidelines. The following points are examined: pilot comments; the advisability of a model study; the need for field measurements; the configuration of the helideck, including its location on the rooftop, dimensions, and the size of the air gap under it; and the effects of rotor downwash and temperature on helicopter power and lift. Recommendations for site measurement of wind characteristics and future work are given.

An energy-bound convex model is used to estimate the maximum structural response of single-degree-of-freedom and multiple-degree-of-freedom structural systems which are subjected to arbitrarily time-varying forces. Convex models specify uncertainties in the absence of detailed probabilistic information about the variables of interest. The concept of convex models provides an alternative way of analysis when a limited amount of information about the excitation is available. The subjective decisions which result when using convex models to incorporate uncertainty do not involve the element of chance. In general, convex models yield estimates of the maximum response that are conservative. In the present paper, equations for reduction factors are given for arbitrary time-varying forces of unknown shape. The reduction factors are independent of the value of the energy bound. The resulting predictions obtained by the reduced convex model estimates are within reasonable agreement to the maximum response obtained by time-history analysis of the arbitrarily time-varying forces.

Throughout the course of history, man's ability to view earth as a planet has dramatically changed. With the aid of satellites, he has been able to see earth as a whole rather than in disjointed pieces. The study of the ozone layer, in particular, has benefitted from this broader view of the earth. Through special sensors attached to spacecraft, experiments that were impossible before satellite technology are now a routine and essential part of ozone studies. The Nimbus-7 satellite provided maps of ozone layer depletion using a especial instrument on board. Another of NASA's missions involved the Upper Atmosphere Research Satellite (UARS) which carried a Microwave Limb Sounder. Using microwave spectral regions, this sensor conducted experiments to measure reactants which break down the ozone layer.

The effects of zero gravity on human bones remains a serious problem facing our astronauts. Zero gravity puts our astronaut's skeletal system at risk. Bone mass loss may greatly increase the potential for a serious fracture. It is necessary to defy the negative effects of weightlessness before we attempt to cross the galaxies. In other words, before we go exploring the far reaches of the universe we must first be able to withstand the negative effects that zero gravity has on our bones.

In this day of failing interest and budget levels for the space program a change in direction is needed. What is needed is an approach to the space program that can be beneficial to a wider scope of society. One way society benefits from the space program is the use of technological advances originally used for the space program that are found to have important uses on Earth. The dual-use of space technology is commonly known as technology transfer. NASA realized this and is reshaping the tech-transfer program to involve the commercial market at every step. NASA will now do business more like the private sector, making NASA profit oriented. The tech-transfer program now goes two ways; besides the commercial market using NASA technology, NASA will use technology developed from commercial applications. Also, NASA and the private sector are working together in the development of new technologies. Defense programs are also involved in this process. New technology will have wide spread effects on both the commercial market and the space program. The new technologies will create many new products and jobs, thus improving the economy. Examples of such technologies include autonomous robots, microtechnology, and satellite control systems that have applications in electromagnetic engines. The technology currently being developed and will revolutionize both the space program and the commercial market.

Space debris, a long-term threat for future space activities, is a rapidly growing problem that needs to be solved. Space debris is the accumulation of artificial objects in earth's orbit that serves no useful function. Many questions arise on this subject including: how did it get there, what are its dangers, how can we reduce it, and finally how to protect from it. All of these will be briefly addressed in this paper.

The tragedy of the Space Shuttle Challenger could have been avoided. Errors, both human and mechanical, resulted in the space shuttle disaster. Feeling pressure from the public and Congress, NASA rushed the launch and circumvented safety procedures. Steps have been taken to reduce the possibility of such a disaster happening again.

The probability of an asteroid or a comet hitting the earth is about as great as one in a million per year. The damage that an asteroid or comet could create, though, is extreme. Asteroids and comets provide a threat to earth. Earth is helpless without some kind of real protection. The problem is how to detect, destroy or deflect the earth-bound object if it is headed toward earth. Thomas Gehrels, a University of Arizona astronomer, has come up with the idea of Spacewatch. Spacewatch is a system that would detect an asteroid or a comet so that it could be destroyed or deflected before it reached earth.

With the twenty-first century approaching, the entire world faces the crucial dilemma of constant need for clean energy in order to prevent an economic and environmental disaster from happening. Not only is the earth's fuel supply dropping rapidly, hut it is also unfortunate that some of these fossil fuels such as petroleum are polluting the earth's atmosphere. A solar power satellite will collect energy while orbiting around the earth, with a large panel containing millions of solar cells and then transport clean energy back to receptors on earth. It may seem as though a solar power satellite might fulfill the idea that Energy-rich societies flourish; energy-poor societies flounder. There are also many constraints which have prevented the National Aeronautics Space Administration(NASA) from constructing a solar power satellite. Some of these are cost, construction, and launching methods. Overall the idea of a solar power satellite is a possible solution to the need of clean, abundant energy.

Space shuttles are part of our newest technology, but there are still problems that occur. One of the major problems is hydrogen leakage. Hydrogen is dangerous because it ignites spontaneously with oxygen. Actions have been taken to protect against hydrogen. A hydrogen sensor is being used to help solve the problem, but it has many faults. Sandia National Labs is creating a new hydrogen sensor. Hydrogen is currently sensed by pumping air from space shuttle cavities to an external mass spectrometer type sensor. The Sandia Robust Wide-Range Hydrogen Sensor is a semiconductor microsensor. This microsensor has significant advantages in size, weight, and performance. The microsensor is also much easier to use. The Robust Wide-Range Hydrogen Sensor should be used in place of the current external sensing method.

Space debris continues to be a growing environmental problem. Accumulation of objects in Earth orbit has been increasing steadily since 1957 and threatens space systems through the possibility of collisions. Research studies at NASA, United States Space Command and the Air Force Phillips Laboratory have resulted in better ways to detect and catalog space debris. Initial results of these studies indicate specific hazards to spacecraft created by man-made debris remain relatively low. However, these hazards are growing and require international action to deal with this threatening reality of space debris. This paper will begin with what space debris is, giving an overview of the amount and type of debris there is currently in orbit. From this, a discussion of the evolving space debris threat, indicating the increasing danger since that first Russian launch. Finally, a look at what current studies have recommended be done in dealing with this threat. Since the inception of space flight and travel, we have been leaving behind a trail of debris. Now, as Space Shuttle missions become more frequent and construction of the Space Station begins, debris will continue to increase. Implementation of global action plans must start now before the loss of critical space systems occurs, but more importantly, before the loss of human life results from this debris.

Many incurable diseases such as cancer and HIV face the world. With intensified research in the field of microgravity crystal growth these diseases could be cured. Experiments have shown that protein crystals can be grown larger with better quality due to the lack of gravity. Protein crystals are of great importance in understanding life at the molecular level. Since larger crystals can be grown in space, scientists can examine crystals more easily by means of atomic force microscopy or by X-ray diffraction. Plans for continuing research into protein crystal growth are being made and crystals could be grown on the space station Freedom when it is built. Continual research is being done in the field of crystallography with applications to cancer and HIV research.

Each morning millions of people get out of bed and never once consider the gravitational force that is necessary to their lives. Jogging, walking, swimming, and driving to work are all examples of every day activities which do not exist without gravity. Physical excercise is extremely difficult to perform in a "near weightless" environment. Without excercise the body cannot function properly, and the bones, blood circulation, and muscular system are negatively affected. Muscle strength determines the ability of the body to perform simple actions. To maintain a strong, healthy body, an artificial gravity environment will have to be maintained for long term space travel or in space colonies.

As humankind strives to learn more about our universe, the efficiency of crew members on space flights is very critical. A problem that poses a threat to efficiency is the space adaptation, syndrome, commonly known as space sickness. Most researchers believe that the vestibular system is what mainly causes the space sickness. The sickness may result from the lack of gravity-s pull on the otolith crystals in the inner ear. Scientists are not able to predict who is susceptible to space sickness because most experiments conducted on Earth do not tell the researchers who is prone to getting sick. This is because sometimes those that get sick during the experiments seem fine in microgravity, whereas others that are fine on Earth seem to get very sick in space. So far, scientists have no way of stopping space sickness, but they do have drugs that can alleviate the symptoms. However, most of these drugs have negative side effects. Once scientists can stop space sickness, space crews will work more efficiently during a flight, and space technology will advance faster.

Energy is the most crucial problem as we near the next century. Collecting solar power in space and beaming it to earth could possibly be much more efficient than collecting solar energy on earth. An SPS (solar power satellite) would be expensive to build but would then provide cheap energy. There are three possible ways of beaming energy from a satellite to a collector in a remote area — microwaves, lasers, and concentrated light — but they all have drawbacks. Since solar power satellites were last seriously studied in the U. S. in 1979, the Japanese and Soviets have made advances in SPS technology. There are many possible steps to take to build an SPS. A lunar base and "power tower" would provide materials to build an SPS. Although a solar power satellite is many years away and would take much effort to build, it would provide much needed clean efficient energy.

Our population is growing very rapidly and we may need, very soon, a whole other planet to live on. We need to explore other planets in order to find one to inhabit. One ideal planet for us to try to inhabit is Mars. Mars is very much like Earth in ways such as having frozen water and an atmosphere that like may already exist. One setback about inhabiting Mars is that the atmosphere is not quite ready for humans. With a little work we may be able to accomplish the task of preparing the atmosphere ourselves, but we must be careful not to destroy Mars like we are destroying Earth.

Due to the extended exposure of astronauts to microgravity, serious health problems have occurred which inhibit further exploration of space. The most efficient solution to this problem appears to be simulating gravity by radial acceleration. Radial acceleration can be used in the form of centrifugal force by causing a spacecraft to spin around an axis. There are already several different designs for this, and overall, creating artificial gravity seems quite possible.

This paper is a summary of guidelines and specific rules for high school students submitting papers for publication with the Space Conferences and Exposition on Engineering, Construction and Operations in Space. It explains the reason for formatting choices and compares the rules which govern technical papers with those given in non-technical writing. The paper includes recommendations on choosing a topic, as well as ideas for organization of the paper and specific formatting rules required by the publisher. This paper is written by a teacher and sponsor of student participants for the high school session sponsored by the American Society of Civil Engineers in Albuquerque, New Mexico.

The Educational Ozone Researcher (EOR) is a small scientific spacecraft designed by students of the Colorado Space Grant College (CSGC) at the University of Colorado at Boulder. EOR was a finalist in the Universities Space Research Association (USRA) Student Explorer Demonstration Initiative (STEDI) program and received Phase I funding in the amount of $160K during late 1994 and early 1995. This paper provides a description of the scientific objectives and the design of the EOR mission.

An alternative design for a particulate sampler will be presented. Two major distinctions separate this design from previous particulate samplers. First, a single body would be used rather than separate compartments for each sample. This has been proposed in order to reduce weight. The second distinction would be the abandoning of a motor in favor of a spring in order to provide the motive force of the device. It is hoped that this will again reduce weight and reduce complications in control. These changes from the standard design present other obstacles which must, in turn, be overcome. This paper is meant to evaluate the relative advantages and disadvantages of this design when compared to other, more standard, designs.