Journal of Aerospace Engineering

Many of the launch systems that are used by the United States to send payloads to orbit trace their heritage to military systems of the 1950s and 1960s. Even with launch systems built on more recent technology, the cost of placing a payload in orbit is thousands of dollars per pound. To develop new customers with heretofore only dreamed-of missions—tourism in space, power from the moon, etc.—the cost of placing a payload in orbit must be reduced by an order of magnitude or more. Since the propulsion system is the cornerstone of a space transportation system, it has a major impact on the acquisition and operations costs. Improvements in materials and in manufacturing technology are needed to develop lightweight, high-strength materials for efficient and economic structures, thermal protection systems, tanks, etc. Operational considerations, such as fewer vehicle elements to check out and to integrate, have a significant impact on lowering launch costs and should be given strong consideration in the choice of materials and propulsion systems. Achievement of a substantially more maintainable and capable launch system is feasible. Benefits will be well worth the cost and risk.

The corporate vision of a proposed Interlune-Intermars Initiative encompasses commercial enterprises related to resources from space that support the preservation of the human species and our home planet. Within this vision, the major mission objectives of the Initiative are to provide investors with a competitive rate of return; protect the Earth's environment and expand the well-being of its inhabitants by using energy from space, particularly lunar ³He, as a major alternative to fossil and fission fuels; develop resources from space that will support future near-Earth and deep-space activities and human settlement; and develop reliable and robust capabilities to launch payloads from Earth to deep space at a cost of $1,000/kg or less (1996 dollars). Attaining a level of sustaining operations for the core fusion power and lunar resource business of the Initiative requires about 15 years and 10–$15 billion of private investment capital as well as the successful marketing and profitable sales of a variety of applied fusion technologies.

The establishment of a lunar base with a permanent human presence is on the horizon. The scientific importance of the Moon and the potential use of local resources at a lunar base provide valuable concepts to consider. Importantly, there are significant ideas, concepts, and reports from the past, the products of a wealth of “mental calorie” inputs, which should be reconsidered; herein, many of these are placed within an historical perspective, in hopes that we may learn by our past experiences. The 1994 Clementine mission, its instrumentation and returned data, provides the first global coverage of the composition, structure, and topography of the Moon. The planned 1997 Lunar Prospector will add significantly to this database. These new global data are requisite for the selection of a lunar base. It is paramount to consider thoroughly the rationale for site selection, and much of the groundwork for this rationale has already been performed. The selection process should be led by a strategic purpose or vision that 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. Many of the relationships between these factors were explored during workshops convened at Johnson Space Center by the National Aeronautics and Space Administration (NASA) in April and August 1990. However, these workshops have not resulted in official, catalogued NASA publications. The merits of numerous potential sites were analyzed in terms of lunar geoscience, geophysics, space physics, astronomy, and lunar resources, as well as operational constraints. The considerations and recommendations of the NASA Site Selection Committee should provide the basis for a realistic site selection for a human presence at an outpost on the lunar surface.

A steady-state model for first-order magnitude estimates of lunar base masses is presented. The main focus of the model is the derivation of initial and annual resupply mass estimates for a lunar base at certain development stages. These estimates are not only a function of several thousand input parameters and boundary conditions such as crew size; lunar base location; and environmental conditions, but also specific system masses; specific power requirements; and specific thermal loads. This integrated lunar base model indicates which systems and subsystems have the greatest mass impact on the overall base. Also, brief overviews of possible activities at a lunar base and of lunar development strategies are given.

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 U.S. portion of the ISS. The EVA hardware 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 and the uses of the hardware are described. In addition, a brief overview of the Russian ISS EVA capability is provided along with plans for interoperability between U.S. and Russian EVA.

In recent years the possibility of developing a space tourism industry has received growing attention since it has the potential to generate a commercial launch market of tens of launches per day—enough to justify investment in developing reusable launch vehicles capable of airline operations. The provision of accommodation in orbit will be an important part of this activity, since it will enable guests to enjoy a wider variety of entertainments in Earth's orbit, and so will help expand the market. Once orbiting hotels are put into operation, competition will drive them to become more sophisticated, and progressively more advanced facilities will be developed. One direction of such development will be to include increasingly larger rooms for guests to exercise and participate in sports in weightlessness, or “zero gravity” as it is popularly known. This paper considers the case of a small gymnasium that might be the first sports facility to be used as part of an orbital hotel. The engineering design is considered, together with its assembly, costs, and commercial potential. Overall, once launch costs fall sufficiently for space tourism to become commercially feasible, such sports facilities appear likely to become attractive commercial investments.

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 the 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 micrometeorite 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 present the results of experiments that provide bounds to the problem. These bounds may be used for the design and construction of a realistic prototype for further testing and development.

The National Aeronautics and Space Administration (NASA) has been studying (as of 1996) a possibility to return to the Moon in 2001 or 2002. The mission will involve many lunar surface activities and may include a concrete production experiment. This paper presents a conceptual approach utilizing the newly developed dry-mix/steam-injection (DMSI) procedure to make three 50-mm concrete cubes (cement and water from Earth and aggregate from the Moon). Astronauts will deliver the test equipment to the Moon only. The test procedure shall be carried out through a remote-control semiautonomous manipulation system with a human supervisor unit stationed on Earth. A solar thermal concentrator will be manufactured to provide heat to generate steam for the DMSI process. The proposed program shall be carried out collectively by three technical groups and will proceed in three successive phases: I, design/manufacture of a prototype steam generator/chamber system (the first writer's group); II, design/manufacture of robotic system (the second writer's group), solar thermal concentrator system (the third writer's group), and mock-up tests of the complete test system; and III, the full experiment on the Moon. A duration of 3.5 years is anticipated to complete all three phases. At the completion of the lunar experiment, only concrete cubes will be returned to Earth for further tests. The test results should demonstrate the validity of the concept of concrete lunar bases that NASA hopes to pursue in the 21st century.