Earth and Space 2014: Engineering for Extreme Environments

Recent advances in the development of a subsurface characterization device that combines axial and torsional loadings are presented in this paper. The multi-sleeve penetration system uses interchangeable friction sleeves with a controlled surface roughness that provides unique information regarding geotechnical properties such as shear and interface behavior of granular media. Experimental laboratory tests performed in an axisymmetric device allow for both axial and torsional loading modes to be investigated without the disturbance effects of the penetration process. Studies of the global behavior in both axial and torsional shearing directions allow for direct comparison and fundamentally robust interpretation of the results. Furthermore, micro-scale studies provide useful information regarding the interface shear behavior of the granular media during testing. The results show the potential of the axial-torsional multi-sleeve device to provide information about soil and regolith properties such as shear strength, structure and state of stress as well as practical issues such as ease of excavation and mobility of vehicles. Discrete Element Method simulations provide further insight about the micro-mechanical processes involved in both axial and torsional shearing tests.

Know-how from terrestrial geotechnical engineering may be applied for a variety of space problems such as the prediction of the soil mechanical response of extra-terrestrial soils, the exploration of near-surface planetary soil, and the movement of vehicles. Penetration testing constitutes a well-established method for the back-calculation of the soil properties. In an initial study, indentation of a rod into granular material placed within a mold has been investigated for variable density states. Regolith simulants, natural soils, and glass have been considered. The test results are presented and key features are elucidated showing that the sole use of the grain size distribution curve as a prediction tool within each subgroup is not appropriate. The effects of the rigid base and the rigid walls are clearly revealed in the response.

People have been digging in dirt for hundreds of thousands of years, gaining much experience thereby. Yet we are always searching for more efficient, more effective methods. And when we begin digging on the surfaces of bodies other than Earth, such as the Moon and Mars, we must resort to a higher degree of automation and remote operation than many construction and mining engineers are comfortable with. This is made more difficult by the inherently uncertain and variable nature of dirt, soil, and regolith. This paper reports on the beginning of a sensitivity study of some of the important factors that control the excavatability of natural granular materials. Initial results reveal a complex interplay of behaviors affected by grain shape and compaction. These factors must eventually be understood more directly in space operations.

Tools and method to characterize the geotechnical properties of NEOs are needed to advance exploration, science, planetary defense planning, and resource exploitation of these bodies. We are evaluating several methods to characterize NEO geotechnical properties. In this paper we focus on a dart or kinetic impact approach. We have used empirical correlations developed to predict the depth of penetration of kinetic impactors into a variety of terrestrial surfaces, called the Young penetration equations. The Young equations predict penetration of a dynamic cone penetrometer reasonably well. The largest uncertainty in designing a NEO geotechnical evaluation tool is the lack of information on expected NEO geotechnical properties. In the approach presented here this translates to selecting an appropriate Penetrability (also known as Snumber) of the NEO surface. We evaluate the problem over the full range of Young penetration equation penetrability: equivalent to dense cemented sand to soft marine sediments. The utility of the Young penetration equations is that a large dart design parameter space can be explored that includes surface penetrability, penetrator diameter, penetrator cone angle, penetrator mass, and impact velocity. The paper discusses methods and instrumentation approaches for a NEO geotechnical evaluation dart and a 3U cubesat configuration.

When a binary mixture of two granules with different material properties is rotated in a horizontal rotating drum the granules often segregate. The smaller particles move towards the radial core within the first seconds. Depending on granular properties, drum speeds, and drum dimensions, axial segregation can follow. When axial segregation occurs, energy dissipation is observed. Contrary to previous research we show that axial segregation can occur with two granules with similar angles of repose and two granules with different angles of repose. When there is a substantial difference in density axial segregation does not occur. The size of the granules is also critical. Lastly granules “bounce” differently when they collide with different size granules. When a large granule falls onto smaller granules it tends to not move as much, but when a small granule falls onto bigger granules it moves much farther. This coefficient of restitution suggests that the smaller particles move farther and more freely in the drum. Physical models were created for six different types of granules, which varied in size, density, and angle of repose, and then experiments were performed to analyze each variable. Photographic images showing granular flows and patterns of each experiment were recorded and compared. The experimental results show that when axial segregation occurs, energy dissipation also occurs.

The success or failure of in-situ resource utilization for planetary surface exploration—whether for science, colonization, or commercialization—relies heavily on the design and implementation of systems that can effectively process planetary regolith and exploit its potential benefits. In most cases, this challenge necessarily includes the characterization of regolith properties at low temperatures (cryogenic). None of the nearby solar system destinations of interest, such as the moon, Mars and asteroids, possess a sufficient atmosphere to sustain the consistently "high" surface temperatures found on Earth. Therefore, they can experience permanent cryogenic temperatures or dramatic cyclical changes in surface temperature. Characterization of physical properties (e.g., specific heat, thermal and electrical conductivity) over the entire temperature profile is important when planning a mission to a planetary surface; however, the impact on mechanical properties due to the introduction of icy deposits must also be explored in order to devise effective and robust excavation technologies. The Granular Mechanics and Regolith Operations Laboratory and the Cryogenics Test Laboratory at NASA Kennedy Space Center are developing technologies and experimental methods to address these challenges and to aid in the characterization of the physical and mechanical properties of regolith at cryogenic temperatures. This paper will review the current state of knowledge concerning planetary regolith at low temperature, including that of icy regolith, and describe efforts to manipulate icy regolith through novel penetration and excavation techniques.

The modeling and simulation of lunar surface and sub-surface activities requires an understanding of the mechanical behavior of the regolith and of the terrestrial materials used to simulate its various components. The discrete element method is frequently applied to model regolith mechanics and this approach requires realistic contact models for the subject materials. In support of this approach, we have conducted grain-to-grain contact experiments on lunar materials and their simulants and herein report on several advancements in this effort. The paper describes a time-based, hereditary integral approach to model anelastic deformation, experimental evidence for nonlinear creep behavior in shear is examined and modeled, and the contact behavior of two lunar materials (plagioclase and pyroxene) are compared to that of their terrestrial simulants. Although as demonstrated in our previous work, space weathering substantially degrades the contact behavior (e.g., lower stiffness and increased frictional loss) of individual mineral grains, reasonably good agreement is found in the contact behavior of unweathered lunar materials and their simulants.

This paper presents some mechanical test results of a lunar soil simulant, FJS-1, to clarify the effect of grain size distribution on bulk mechanical properties of lunar surface soil under low confining pressure. The samples used are the original FJS-1 imitating an average grading of lunar soil, two sieved FJS-1 samples, whose grain sizes are less than 0.1 mm and from 0.1 to 0.4 mm, respectively. First, the maximum and minimum void ratio tests of those samples revealed both pore-filling effect and inter-granular adhesion effect of fines. Next, according to small-scale triaxial compression tests and self-standing height tests, the internal friction angle ranges from 30 to 50 degrees, and the bulk cohesion is about 0-175(Pa) depending on the void ratio, which are consistent with the previous estimation of typical lunar soil. Finally, based on the experimental results, we propose a simple micromechanics model that describes the experimental results in a consistent manner.

Martian regolith and rock may one day be used for building material to support long-term habitation on Mars. Despite several martian simulants being available, the capability of accurately matching a wide variety of reported grain size distributions coupled to the regolith’s chemical character for specific sites on Mars needs to be advanced before producing large quantities of material for material synthesis experimentation on Earth. Here, we use volcanic material (i.e. olivine basalt and basaltic glass) from Banks Peninsula, New Zealand, to demonstrate an applied approach to matching reported size distributions on Mars. The olivine basalt and basaltic glass were crushed, washed and combined to produce a particle size distribution representative of the Columbia Hills region of the Gusev Crater. As New Zealand has a wide variety of geologic material similar to Mars, we are in the process of acquiring rocks ranging from extrusive volcanics to serpentinites with the intent to provide ‘tailored’ simulant to aid in civil engineering applications.

In this paper, the upgraded Anm model, which places multiple particles into a 3D unit cell, was used to study the microstructural properties of lunar soil simulant. A statistical analysis was performed to study the packing density and shape effects with a large number of modeled particles. The lunar soil simulant JSC-1a was developed to study simulant soil behaviors for large and medium scale engineering studies in support of future human activities on the Moon. Parameters such as particle size distribution, specific gravity, angle of internal friction, and cohesion have all been investigated. However, no research has been performed to explore the microstructural behaviors and their influences on the engineering properties as a whole. As such, Anm model can provide us a useful approach to investigate microstructural features of lunar simulant, e.g. charge contact, lofting, transport, stratification and adsorption. Thus the virtual JSC-1a microstructure can be used to study lunar soil handling, construction, excavation, and transportation. Furthermore, the uniform-thickness shell is a customized parameter to control the minimum inter-particle distances. Integrating this algorithm into individual particles packing, the Anm model can be used to create a virtual lunar regolith to investigate the particle contact charging properties at the individual particle scale. In general, this virtual lunar soil simulant model could provide a broad range of applications to lunar surface missions. It is a potential tool for modeling the behavior of the lunar soils, and accurately predicting the geotechnical properties of lunar soils for lunar base planning and construction.

Mechanical properties, such as strength and stiffness, of every Lunar or Martian soil simulant are greatly affected by Earth’s gravitational field. The stronger gravitational pull has made it difficult to simulate effectively high sinkage scenarios in any laboratory environment. Researchers at the NASA Glenn Research Center developed a large test bed called the “sink tank” specifically to test rovers in high sinkage/high slip situations. The material Fillite was chosen as the test bed material. Fillite exhibited the desired properties of being light weight, soil like in composition, and capable of being collected in mass quantities. The focus of this study was to determine index and mechanical properties of Fillite to aid in the analysis of rover testing. These properties were found to compare well with what is known about Martian and Lunar regoliths, and also matched closely with some frequently used Martian and Lunar simulants.

In future lunar exploration activity, ground excavation is required in construction of permanent lunar outpost and In-Situ Resource Utilization processes, which are important long-term goals of space program. In this paper, the Discrete Element Method (DEM) was employed to simulate horizontal lunar regolith excavation process. For this purpose, a high-efficient contact model was implemented into the DEM. The evolution of excavation resistance, slide surface and stress path are studied. Then the effects of excavation depth and rate, attack angle on the excavation re-sistance were analyzed under the terrestrial environment. The effects of gravity were also investi-gated. The simulation results show that the excavation resistance first increases rapidly to a peak and then drops to a stable value quickly. With further increase of the excavation zone, the excava-tion resistance again increases gradually mainly due to the accumulation of soil in front of the blade. The excavation resistance is greater under larger excavation depth, smaller attack angle, and greater excavation rate. The excavation resistance increases with the gravity level linearly. Since the excavation resistance needs to be balanced by the friction between the excavator and the ground, which is proportional to the weight of an excavator, the shallow, tilted and slow excava-tion is recommended based on the DEM simulation results. In this way, the mass of excavation equipment launched from the Earth can be greatly reduced in the early-stage of lunar base con-struction.

In situ resource utilization in space will add new manned and robotic exploration capabilities. Uncertainties exist regarding the interaction of exploration hardware with surfaces of airless bodies, particularly where volatile resources may be present such as asteroid surfaces, permanently shadowed craters on the Moon, and the martian moons Phobos and Deimos. We present a plan to study the interaction of idealized probes with analog regolith surfaces over a range of water ice content. The proposed tests are described as fundamental physical-sciences experiments that isolate a specific interaction of a technological component with the space environment. This work is in the beginning stages of the recently selected Institute for Modeling Plasma, Atmospheres, and Cosmic Dust, a member of the NASA Solar System Exploration Research Virtual Institute at the University of Colorado at Boulder, in which the authors at the Colorado School of Mines are co-investigators.

Long term settlement of lunar or Mars caves or subsurface features on planetary bod-ies where large pit openings exist provide an opportunity to substantially increase liv-able volume areas and allow inhabitants freedom from confines of living in modules or enclosed in a cave environment. Various studies centered on enclosing a lunar sky-light pit with a pressurized dome are under investigation by the authors. An intuitive approach of merely placing a dome cap over the skylight pit is fraught with a number of issues. Accomplishing this in a practical fashion without having the seal inde-pendent of the regolith surface is a challenge for understanding the porosity of the lunar regolith along the pit walls and outer rim of the pit. Not least among these is-sues is prevention of the regolith from consuming too much gas and never reaching an equilibrium pressure. Essentially, what happens to gas pumped into the dome? How much of it will simply pass into the surrounding desiccated regolith? How much of this valuable atmospheric resource will simply diffuse away into the skylight walls? Lunar regolith porosity studies investigate various challenges associated with pressurizing a large porous geologic feature.

Contamination of spacecraft components with planetary and foreign object debris is a growing concern. Face seals separating the spacecraft cabin from the debris filled environment are particularly susceptible; if the seal becomes contaminated there is potential for decreased performance, mission failure, or catastrophe. In this study, silicone elastomer O-rings were contaminated with JSC-1A lunar regolith and their leak rate performance was evaluated. The leak rate values of contaminated O-rings at four levels of seal compression were compared to those of as-received, uncontaminated, O-rings. The results showed a drastic increase in leak rate after contamination. JSC-1A contaminated O-rings lead to immeasurably high leak rate values for all levels of compression except complete closure. Additionally, a mechanical method of simulant removal was examined. In general, this method returned the leak rate to as-received values.

High-resolution Lunar Reconnaissance Orbiter (LRO) Narrow Angle Camera (NAC) images are used to study the effects of rocket exhaust on lunar soil reflectance properties at the Apollo, Luna, Surveyor, and Chang’e 3 landing sites. Areas disturbed by rocket exhaust appear as photometric anomalies in NAC images and are preserved owing to the lack of weathering processes on the Moon. Destruction of fine-scale surface structure, smoothing of the surface, and/or redistribution of fine particles created high-reflectance areas around the landers that we refer to as blast zones. Reflectance profile shapes are consistent across all landing sites and reflectance changes are similar in magnitude (12-16% increase) across all sites, indicating that these lunar surface features are not erased on the order of decades. Blast zone area scales exponentially with lander mass and thrust, although variations arise owing to differences in engine configuration and descent trajectories.

A method to estimate the optical extinction coefficient of dust above the lunar surface during Apollo lunar module (LM) landings is presented. This approach uses image frames acquired from the LM cockpit video camera. Previous methods relied on comparing specific features in clear versus dusty images which severely limited ability to analyze video frames. An improved method is constructed by defining an optical extinction model, using a dust thickness (extent along optical axis) model that is based on the tilt of the camera and height of the dust layer above the surface. The dust thickness model is used to account for the distance light travels through the dust for every image pixel. Dust can be artificially removed or added to images using the extinc-tion model. Then by comparing and matching image luminosity histograms of similar dusty im-ages to similar clear images, and by equating histograms mean and standard deviations, a histo-gram matching method (HMM) is able to estimate the extinction coefficient associated with the dust cloud.

The emerging interest in lunar mining poses a threat of contamination to pristine craters at the lunar poles, which act as “cold traps” for water and may harbor other valuable minerals. The KSC Granular Mechanics and Regolith Operations Lab tools have been expanded to address the probability for contamination of these pristine “cold trap” craters. Trajectory simulations of rocket plume ejecta have been mapped onto cold trap craters to predict deposition for expected lunar landings. The processes addressed are now expanded to address the migration of volatiles over the lunar surface, and deposition into cold traps assuming that the collection efficiency of the 40K cold trap surfaces is 100%. Landing nearby such a crater will result in the deposition of significant exhaust plume gas into the cold trap portion of the crater, and may also create an unnatural atmosphere over the volatile reservoirs that are to be studied.

Opportunity has been roving on the plains of Meridiani and the rim of Endeavour crater on Mars since January 2004. Curiosity has been roving across the plains on Gale Crater since August 2012. Realistic mechanical models have been generated for each rover, with classical terramechanics relationships included to simulate wheel sinkage and rover-based slippage, and simulated traverses have been conducted across terrain models with topography generated from rover-based stereo images and positionally dependent bedrock and soil properties. Modeling has been used, together with analysis of engineering telemetry and image data, to retrieve surface properties, and to understand the physics of interactions among the rovers, soils, and bedrock for situations in which mobility issues have been encountered. These include high wheel sinkage and rover-based slippage while traversing the uphill sides of wind-blown rip-ples, and wheel wear and tear for Curiosity while traversing sharply pointed and em-bedded rocks.

Orbital data over Gale Crater are used for selecting traverses that visit scientifically interesting locations while maintaining rover safety. Here we focus on predictions for Curiosity’s traverse to Mt. Sharp using along-track oversampled (ATO) Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) datasets. The high spectral and spatial resolution of these datasets provides important information about terrain physical properties and surface composition. Spectral variability along the traverse is dominated by variations in the flux of dark sand versus bright dust, and spectral differences among aeolian material are likely due to variations in dust cover on darker aeolian material. We focus our investigation of CRISM data over the smallscale aeolian features along Curiosity’s traverse, and we couple this analysis with in situ data gathered during drives to determine the degree to which the variations in compositions and physical properties of aeolian materials influence the degree of rover slip and wheel sinkage when crossing these bedforms.

Mars Exploration Rovers (MERs) experienced mobility challenges when crossing wind-blown ripples and deformable sands while exploring Martian terrain. Analysis of MER wheel mobility using a 3D discrete element method (DEM) model indicate three stages of mobility: (1) low slip (< 30% slip) defined by soil strength, (2) intermediate slip (30-60% slip) defined by residual soil strength and (3) high slip > 60% slip) defined by residual soil strength and depth of wheel sinkage. MER wheel sinkage and drawbar pull increased then decreased during contact between soil and the wheel tie-down patch, compared to wheel cleats, in high slip conditions, but had little affect on overall wheel mobility. DEM simulations well describe intermediate and high slip average wheel sinkage and replicate the signature of drawbar pull and sinkage for the tie-down patch, but not its magnitude. Improved DEM simulation accuracy can be achieved by using smaller polyhedral particles to represent soil.

Exploring the soil information of an unknown terrain on the extraterrestrial is one of the major missions of space exploitation and human colonization. Using the autonomous vehicle to facilitate the soils sampling process is an emerging technology; it has been applied many times in the previous missions of Moon and Mars. This paper takes advantage of the nature of soil-zonality to propose a novel algorithm to traverse an area to save time and energy of the autonomous vehicle. Three searching tactics to suggest the vehicle to move next location, including: (1) fundamental—based on the patterns of soil map; (2) density—based on the higher scale first principle; and (3) statistical—based on the soil information gathered from the previous scan. This paper also argues using the statistical analysis as the soil properties sample comparison tool will be less cost from present practice—visually remote controlled and grabbing the samples back for later analysis.

There are at least two approaches in searching for water-ice in lunar regolith: indirect and direct. In the indirect method, neutron spectrometer can be used to capture epithermal and thermal neutrons—signature of Hydrogen and hence possibly water. If a neutron spectrometer is integrated inside a drill string, as the drill penetrates subsurface it can determine water concentration at different layers. In the direct method, a sample is captured at depth and transferred to a Gas Chromatograph Mass Spectrometer (GCMS) for analysis. The indirect method is simpler as it does not require sample transfer, however the direct method provides higher fidelity data. This paper focuses on the direct method. The Lunar Prospecting Drill (LPD) has been tested in frozen NU-LHT-2M with 5wt% water and in dry NU-LHT-3M. The drill captured sample in 10 cm intervals, called bites. The mass of each bite varied from 20-40 grams for 5wt% simulant and from 10-20 grams for dry simulant. The drill will next be tested at lunar-like conditions of low temperature and vacuum at NASA GRC.

Exploring and interrogating the shallow subsurface of Mars from the surface will require some form of excavation and penetration, with drilling being the most mature approach. The latest LITA drill, designed for use at the Atacama Desert Chilean analog site, was recently tested at the same Arctic site (Haughton Crater) as have a series of past NASA drill prototypes since 2004. Unlike previous tested prototypes, the smaller LITA did not demonstrate a capability of penetrating hard rock or ice-consolidated material at the Drill Hill test site.

A drilling system that is a rotary hammering mechanism called the Auto-Gopher was developed to establish the capability to reach below the surface of Mars, a surface that is unprotected from cosmic ray (predominately protons and atomic neculi) and solar (predominately UV) radiation. The hammering mechanism is driven by piezoelectric stack while the rotation is actuated by an electromagnetic motor. In order to meet this need, the drilling operation parameters were optimized with a labversion of Auto-Gopher system by varying the duty cycle, weight-on-bit, and power of the percussive mechanism. A full wireline Auto-Gopher system was then designed and fabricated, and the drilling performance was investigated by drilling in gypsum and limestone substrates, reaching a depth of 3 meters, which is 1.5x drill’s length. The results demonstrate the potential capability to reach many meters deep without considerable increase in the drill mass, size or power. The average drilling power that was used has been in the range of 100-150 Watt, and the penetration rate has reached 15-30 mm/min when operated as a rotary-percussive drill.

In this paper the design of the ultralight mobile drilling system (UMDS) dedicated for planetary environment is presented. The main features of the system are connected with its mobility by integration with a rover, and the special design of support module which take advantage of tubular booms to guide the drilling subsystem. The latter is designed to reduce the path for cuttings and to be applicable for operation in vacuum conditions. At the system level, UMDS was designed to reduce the mass and power consumption in each operational phase. Special care was applied to minimize the cross contamination of the gathered core by volatiles as well as to reduce the influence of heat dissipation during the drilling process. The system is also considered for terrestrial applications and testing with UAV helicopter is foreseen.

Exploration of the Moon is considered a high priority in the overall strategy of the European Space Agency (ESA), together with activities in Low Earth Orbit and missions to Mars. The Lunar South Polar region presents key opportunities for scientific discovery and advancement of exploration capabilities, but is also a uniquely challenging operational environment for robotic missions and for human explorers. ESA has placed accessing this environment and the surface material found there as a high priority. In this context ESA is discussing with international partners, in particular with ROSCOSMOS, how these ambitions might be realized in cooperation. To support this work ESA is engaged in a range of mission level activities with ROSCOSMOS on the Luna-27/Luna-Resurs Lander mission as well as Lunar Polar Sample Return (LPSR). In addition to this ESA is undertaking, with European institutes and industries, a set of specific development activities which seek to address the challenges of operating in the challenging environment of the Lunar South Pole.

To realize reliable and autonomous sampling of regolith on the Moon and Mars, the authors have developed a unique sampling system that employs electrostatic cap-ture and mechanical vibration transport of particles. A high ac voltage is applied be-tween parallel screen electrodes mounted at the end of the sampling tube. Regolith particles on the surface are captured after they are passed through the openings in the screen electrodes by means of an electrostatic force. The captured particles are then transported through a tube against gravity and transferred to a capsule utilizing me-chanical vibration. Experiments demonstrated that some amount of regolith is sam-pled for a short period, even in the 1-G environment on the Earth if the end of the screen electrode is in contact with the regolith layer. Because the gravities on the Moon and Mars are one-sixth and three-eighths, respectively, of that on the Earth, the process of sampling particles on the Moon and Mars will be easier than on the Earth. Not only simulant particles but also crushed ice can be sampled using this system.

The paradigm for space exploration is changing. Large and expensive missions are very rare and the space community is turning to smaller, lighter, and less expensive missions that could still perform great exploration. These missions are also within reach of commercial companies such as the Google Lunar X Prize teams that develop small scale lunar missions. Recent commercial endeavors such as “Planet Labs inc.” and Sky Box Imaging, inc. show that there are new benefits and business models associated with miniaturization of space hardware. The MicroDrill is part of the ongoing effort to develop “Micro Sampling” systems for deployment by these small spacecrafts with limited payload capacities. The ideal applications include prospecting missions to the Moon and Asteroids. This paper describes development and testing of the “MicroDrill” system. The MicroDrill is a rotary-percussive coring drill that captures cores 7 mm in diameter and up to 2 cm long. The drill weighs approximately 1 kg and can capture a core from a 40 MPa strength rock within a few minutes, with less than 10 Watt power and less than 10 Newton of preload.

To achieve reliable and autonomous regolith sampling on asteroids, we have developed a unique sampling system that utilizes electrostatic force. When a rectangular high voltage is applied between parallel screen electrodes, the resultant Coulomb force and dielectrophoresis force act on particles in the vicinity of the electrodes, and some particles are captured passing through the openings of the screen electrodes. The sampling system is simple, has low power consumption, and has no mechanical moving parts. It was demonstrated that a lunar regolith simulant can be captured in a zero-G environment reproduced by the parabolic flight of an aircraft. As predicted by a numerical calculation utilizing a hard sphere model of the three-dimensional Distinct Element Method, a large amount of lunar regolith simulant, approximately 900 mg, was successfully sampled. The captured regolith particles contained not only small particles but also large particles more than 0.5 mm in diameter. Moreover, it was predicted by the numerical calculation that the sampling system would perform much better in a vacuum than in air.

This paper describes a method of manufacturing concrete under vacuum conditions, based on an enhancement of the Dry-Mix/Steam-Injection method (DMSI) by T. D. LIN. The aim is the production of concrete elements for the construction of modular protective structures on the moon. Due to the vacuum, manufacturing by wet mixing of cement, aggregate and water is not possible, because the unbound water would quickly evaporate. In initial experiments it was shown that the water demand for concrete mixtures with a high content of fine particles can be greatly reduced with the help of the DMSI method leading to nearly equal compressive strength in shorter hardening time.

The present study concerns a production of lunar concrete using the artificial lunar soil and thermoplastic polymeric material as binder. The lunar soil was cast with the polymer in a cubic mould (50×50×50 mm) in a lunar environment-mimic chamber. Prior to solidification of the lunar soil mixture, the chamber was evacuated by a vacuum pump to 0.1-0.2 torr, followed by preheating by an electric heater placed inner wall of the chamber to sustain the internal room temperature at 123°C. Then, a heat plate, of which the surface temperature accounts for 230°C, was attached in one dimension for 5.0 hours on the top of the specimen in the mould to melt the polymer embedded in the mixture then to bind artificial lunar soil. Simultaneously, a specimen was in the equated condition except for the preheating process; the room temperature was about 15°C at the onset of plate-heating and instead the heating duration lasted 24 hours to compensate for preheating benefit. As a result it was found that the specimen subjected to preheating was mostly solidified, of which solidified depth accounted for about 49.2 mm, whilst non-preheated specimen was only partially solidified in the vicinity of the top, where the heat plate was directly attached. It implies that preheating of the mixture would be more effective in melting the polymer and thus binding lunar soil then to form a solid body, even in a shorter heating duration. Without preheating, the melting efficiency of the polymer was marginal to solidify the lunar soil in a relatively long heating (i.e. 24 hours).

Identified as critical to lunar or Martian exploration, stabilized regolith can be used as a foundational construction material for key infrastructure systems. These infrastructure systems include stabilized landing pads, pavements, and protective structures that can shield humans from exposure to high energy radiation. Current approaches to regolith stabilization, however, require large amounts of energy or binder mass, and thus require significant upstream infrastructure to produce the stabilized regolith. This paper presents a novel approach to the production of stabilized regolith by binding regolith within a protein matrix. The constituent materials, processing techniques, and experimental mechanical performance of Regolith Biocomposite (RBC) material are described. Further, the mechanical performance, material requirements, and energy requirements for in situ fabrication of RBC are compared to other regolith stabilization methods found in literature. Results indicate that RBC material properties are on par with the other techniques, and that energy and binder requirements for in situ fabrication are lower than other regolith-based materials.

Using modular construction equipment and additive manufacturing (3D printing) techniques for binding, mission support structures could be prepared on remote planetary surfaces using native regolith. Material mass contributes significantly toward the cost of deep space missions, whether human or robotic, due to the resources needed to lift each kilogram of equipment out of Earth’s gravity well. Proposing the modular Freeform Additive Construction System (FACS) concept, using the reconfigurable All-Terrain Hex-Limbed Extra-Terrestrial Explorer (ATHLETE) robotic mobility platform, a variety of walls, berms, vaults, domes, paving, and thick radiation shielding could be prepared in advance of crews and mission assets to help reduce the material needed to be brought from Earth. This paper discusses the current ATHLETE technology, and describes how flexible mission elements could be derived using a combination of three dimensional additive construction and in-situ manufacturing technologies using native regolith.

A discussion of the concepts that civil engineers and planners can bring to the table in the development of a Mars built environment, this paper focuses on the civil engineering challenges and differences of Mars and presents recommendations for the planning and engineering of a Mars colony. The basics of terrestrial civil engineering for undeveloped areas are discussed from an American perspective. A contrast is shown between the anticipated conditions on Mars and those on Earth. Attention is drawn to the assumptions of modern infrastructure development, based on millennia of human history and Earth conditions and which could or should be modified for Martian environmental challenges. A concept is discussed for mimicking the development and civilization of terrestrial life for a Martian settlement, taking into account these environmental challenges, differences in basic design assumptions and correction of existing development patterns which are inefficient and unnecessary on Mars.

All space development efforts are hindered by the cost of placing payloads in orbit. Reducing launch costs allows more mass to be placed into orbit for a given budget. Most of the weight (mass) in any rocket is used to launch the fuel and not the payload. Electromagnetic (EM) railguns or mass drivers would avoid that problem. A major assumption made in the paper is that construction materials including solar panels do not have the same accelerations limits as humans.

Regolith is present on most planetary surfaces such as Earth’s moon, Mars, and Asteroids. If human crews and robotic machinery are to operate on these regolith covered surfaces, they must face the consequences of interacting with regolith fines which consist of particles below 100 microns in diameter down to as small as sub-micron scale particles. Such fine dust will intrude into mechanisms and interfaces causing a variety of problems such as contamination of clean fluid lines, jamming of mechanisms and damaging connector seals and couplings. Since multiple elements must be assembled in space for system level functionality, it will be inevitable that interfaces will be necessary for structural connections, and to pass commodities such as cryogenic liquid propellants, purge and buffer gases, water, breathing air, pressurizing gases, heat exchange fluids, power and data. When fine regolith dust is present in the environment it can be lofted into interfaces where it can compromise the utility of the interface by preventing the connections from being successfully mated, or by inducing fluid leaks or degradation of power and data transmission. A dust tolerant, hand held “quick-disconnect” cryogenic fluids connector housing has been developed at NASA KSC which can be used by astronaut crews to connect flex lines that will transfer propellants and other useful fluids to the end user. In addition, a dust tolerant, automated, cryogenic fluid, multiple connector, power and data interface mechanism prototype has been developed, fabricated and demonstrated by NASA at Kennedy Space Center (KSC). The design and operation of these prototypes are explained and discussed.

For the US and Western Civilization to return to space there has to be a number of driving factors other than just national pride re first to the Moon. In addition the Federal government has become so large and so risk adverse that it has become almost incapable of executing a large, multi-year program successfully. Furthermore the divisive nature of congress, if you are for it then I’m against it, and special interests fighting for fewer and fewer Federal dollars preclude almost any Federal support for a new major space initiative. The thesis presented in this paper is that: a) blending US and European energy tax policies to create a level competitive field it would be economically feasible to produce liquid synthetic fuels from sunlight, water, and air, a modern version of the philosopher’s stone; b) space based solar arrays using wireless power transmission can provide base load electricity without the environmental issues associated with other forms of electrical generation; c) designing, fabricating, and constructing space based solar arrays provide the basis for the re-industrialization of the United States; and d) a strong economy based on producing the high tech products needed to industrialize space is a better long term strategic defense strategy than funding capital consuming defense programs that the government can’t manage in the first place. We evolve complex systems. It is only after we have learned from evolution can we begin to attempt to design similar systems of equal complexity or create simpler systems that accomplish the same thing. The space program is a classic example moving from Goddard’s work in the early 20’s to the German V-2’s of WW II and then to the Saturn V and the Space Shuttle. Now we have private launch systems that, while complex, have shed the layers of bureaucracy that suppress creativity and result in cost overruns. The evolutions of the oil and air transport industries are other examples of us evolving complex industries and systems from simple beginnings. The concepts in this paper are presented as an evolutionary path: a) the creation of a semi-automated construction system that allows for the very economical construction of large terrestrial solar arrays; b) the integration of the SPS rectenna with the terrestrial array; c) using array power to synthesize liquid fuels thus providing a transition path to a hydrogen economy, d) providing a market for competitively priced synthetic fuels; and e) an economic analysis of both power from space and synthetic fuels using energy from space. .Finally, a top level economic and environmental comparison of alternatives is made with the conclusions being drawn that there are no easy choices left and that it is up to us. “We must provide a Great Age or see the collapse of the upward striving of the human race” - Alfred North Whitehead

It is well-understood that natural resources are scarce and that the world’s population is predicted to climb exponentially. As the global population continues to grow, demand for consumer goods including food, hygiene, and technology will increase accordingly. Part of this problem is that mineral resources are becoming increasingly difficult to find and extract profitably. The necessity to consider the feasibility of resource extraction in new locations is paramount to our continued prosperity. Although mining in outer space is not considered a conventional solution to the growing mineral shortage, extraterrestrial environments are becoming particularly attractive due to increasing rates of mineral depletion, government regulations, and capital costs here on earth. Successful mine designs in space must address a wide array of challenges including mineral exploration, determining economic recovery rates, safety practices, equipment maintenance, materials handling and transportation, and mineral processing. There is not a cut and dry approach to mine design because a variety of methods exist for specific conditions. The product of this research study will lend to the future development of a reasonable, economic and safe platform on which extraterrestrial mining can be considered. The physical environmental conditions in extraterrestrial mining are in many ways similar to those on earth, however, there are significant differences. On earth, gravitational force assists the excavation and materials handling processes. In space, the lack of gravity impedes both these tasks. Moreover, moons, asteroids, and small planets can be buffeted by micro-asteroid storms, requiring a unique layer of protection not necessary on Earth. The unfiltered radiation and electromagnetic interference from the sun can pose hazards to human health and to electrical systems in the space. As with any new mining environment, extraterrestrial locations present distinct challenges. By consolidating and expanding upon current knowledge pertaining to extraterrestrial mining, this study focuses and directs efforts towards solving resource scarcity through the successful exploitation of natural resources in outer space.

The Solar System has vast resources that have the potential to greatly benefit humanity. But developing those resources presents major challenges ranging from the limitations of human physiology to the lack of celestial bodies suitable for human habitation. The Habitat Automatous Locomotive Expandable (HALE) is offered as one solution to these challenges. Built initially at the Earth-Moon Lagrange Points, the HALE will be capable of reaching the most remote reaches of the Solar System where it will supply stable and safe habitation and major capabilities, for both scientific research and resource development.

This research introduces novel experimentation that for the first time subjects excavators to gravity offload (a cable pulls up on the robot with 5/6 its weight, to simulate lunar gravity) while they dig. Excavating with gravity offload underestimates the detrimental effects of gravity on traction, but overestimates the detrimental effects on excavation resistance. Though not ideal, this is a more balanced test than excavating in Earth gravity, which underestimates detrimental effects on both traction and resistance. A 300 kg excavator offloaded to 1/6 g successfully collects 0.5 kg/s using a bucket-wheel, with no discernable effect on mobility. For a discrete excavator of the same weight, production rapidly declines from the initial rate of 0.5 kg/s as rising excavation resistance stalls the robot. The experiments presented in this work demonstrate that continuous excavation fares better than discrete excavation when subjected to comparable reduced gravity circumstances. In Earth gravity, on the other hand, both the continuous and discrete configurations operated successfully. Excavation tests done exclusively in Earth gravity may thus misleadingly predict better excavation performance than is actually achievable in reduced gravity, and should be interpreted with caution.

Planetary surfaces are often covered in regolith (crushed rock), whose geologic origin is largely basalt. The lunar surface is made of small-particulate regolith and areas of boulders located in the vicinity of craters. Regolith composition also varies with location, reflecting the local bedrock geology and the nature and efficiency of the micrometeorite-impact processes. In the lowland mare areas (suitable for habitation), the regolith is composed of small granules (20–100 microns average size) of mare basalt and volcanic glass. Impacting micrometeorites may cause local melting, and the formation of larger glassy particles, and this regolith may contain 10–80% glass. Studies of lunar regolith are traditionally conducted with lunar regolith simulant (reconstructed soil with compositions patterned after the lunar samples returned by Apollo). The NASA Kennedy Space Center (KSC) Granular Mechanics & Regolith Operations (GMRO) lab has identified a low fidelity but economical geo-technical simulant designated as Black Point-1 (BP-1). It was found at the site of the Arizona Desert Research and Technology Studies (RATS) analog field test site at the Black Point lava flow in adjacent basalt quarry spoil mounds. This paper summarizes activities at KSC regarding the utilization of BP-1 basalt regolith and comparative work with lunar basalt simulant JSC-1A as a building material for robotic additive construction of large structures. In an effort to reduce the import or in-situ fabrication of binder additives, we focused this work on in-situ processing of regolith for construction in a single-step process after its excavation. High-temperature melting of regolith involves techniques used in glassmaking and casting (with melts of lower density and higher viscosity than those of metals), producing basaltic glass with high durability and low abrasive wear. Most Lunar simulants melt at temperatures above 1100°C, although melt processing of terrestrial regolith at 1500°C is not uncommon. These temperatures are achievable by laser heating or by using solar concentrators. Similar to volcanic magma, the cooling rate determines the crystallite size—slower cooling develops larger crystals, and rapid quenching can result in fully amorphous glass.

Special percussive mechanisms, e.g. Auto Gopher and Ultra Sonic/Sonic Driller/Corer (USDC) have been developed by NASA Jet Propulsion Laboratory and Honeybee Robotics Spacecraft Mechanisms Corporation to explore the Lunar, Martian, and other planetary subsurface and extract soil (regolith)/rock samples for further study. The percussive mechanism consists of an ultrasonic horn, a free mass (hammer) and the drill rod. This paper presents an analytical methodology to analyze the dynamic and contact analysis of the longitudinal impact of the free mass and the drill rod including the effects of structural vibration. The contact force due to impact is obtained using Hertz force-indentation relation coupled with the structural vibration obtained using mode superposition method. Numerical solution, with equilibrium iterations, of the equations of motion is implemented. The contact force was observed to follow a sinusoidal like shape, consistent with results available in literature for similar problems.

With the new advancements in space technology and also involvement of private sectors in space programs, space mining became an attractive subject either in In-Situ Recourse Utilization (ISRU) on the moon or mineral extraction from an asteroid. One can imagine that excavation and break-age technique that will be used will mainly be affected by the terrestrial methods which has been tested, tried and proved reliable. Drilling rocks is the first stage in order to extract the resources. It mainly relies on the mass of the drill and the reactive force that comes from the gravity. On the moon or an asteroid, where the gravitational force is one sixth or negligible, the drilling perfor-mance would not be equivalent to that on the earth. In this study, employment of microwave as a mean to reduce strength of the rocks before drilling is investigated. A magnetron can be installed on the drill and emit microwaves on the rock sur-face. Microwave penetrates into the rock and creates macro/micro fractures on the surface of the rocks due to thermal expansion ratio within grains, consequently easing the breakage process. Tests were performed on basalt, a common hard rock sample, when exposed to 3 kW electro-magnetic waves at 2.54 GHz in a 60×60×60 cm confined oven. Temperature was measured at different depth of the rock as its distance varied from the waveguide. Numerical modeling was also carried on to study the power dissipation inside the load and electric filed distribution inside the oven. Experimental experiences show, when exposed to microwaves, the micro-cracks density inside the rock increases which will result in less breakage energy requirement during drilling or crushing. Employing Microwave assisted drilling in space drilling or crushing applications may improve the drilling equipment performance; even though the gravitational forces are very low. Furthermore, microwave assisting drills will weight lighter compare to a conventional drilling rig. This reduces significantly the transportation costs the outer space.

This study evaluated the effect of water saturation on the behavior of porous rock during mechanical excavation, such as drilling. Such understanding will increase the ability to design robust and flexible tools for drilling in liquid-water aquifers in the martian shallow crust. This capability will be crucial to sustaining the exploration of Mars, and ultimately of other places where liquid water occurs near the surface. The experiment controlled speed of indentation of the rock (by an indenter of a typical shape for drill bits), and the state of saturation of the rock samples. The indentation speeds were expected to bracket the threshold between drained and undrained conditions. Specific energy of indentation increased with saturation during high-speed indentation, but no other experimental parameters gave clear results. Further tests are needed.

Exploring and mining on the Moon is dependent on the availability of sufficient power to drive essential equipment and tools. One sustainable source of direct energy is the sun during a lunar day. However, energy required for manufacturing during the lunar night, lasting 17 Earth days, will require a means of storing this daytime energy. The focus of this thesis is to compare the thermal energy storage capabilities of sulphur concrete, polymer concrete and sintered Australian Lunar Regolith Simulant (ALRS-1). Experimental procedures were developed that allowed the calculation of heat loss in hollow cylinders made of predefined; sulphur, polymer and sintered ALRS-1 material recipes. The velocity of the heated air as well as the changing temperatures inside and around the sample was measured, this data was then used to determine the thermal energy storage properties of each sample. Four sulphur concrete samples were cast with inner pipe diameters of 2.5 cm and 3.5 cm, and sulphur contents of 45% and 55% respectively. One sample of polymer mix and one sintered lunar soil sample were used for comparison. The results showed that the highest specific heat capacity was 1.63 kJ/kgK for the sintered lunar soil simulant, followed by 0.93 kJ/kgK for the polymer concrete, then 0.61 kJ/kgK for the 45% sulphur concrete and finally 0.55 kJ/kgK for the 55% sulphur concrete. Analysis of the test results determined that sulphur concrete, polymer concrete and sintered lunar soil simulant (all ISRUs) are viable options for thermal energy storage on the both the Earth and the Moon.

The multi-NASA center Mars Atmosphere and Regolith COllector/PrOcessor for Lander Operations (MARCO POLO) project was established to build and demonstrate a methane/oxygen propellant production system in a Mars analog environment. Work at the Kennedy Space Center (KSC) has focused on the Atmospheric Processing Module (APM). The purpose of the APM is to freeze carbon dioxide from a simulated Martian atmosphere at Martian pressures (∼8 torr) by using dual cryocoolers. The resulting pressurized CO₂ and hydrogen are fed to a Sabatier subsystem to make methane and water vapor. This paper covers (1) the design and selection of major hardware items, such as the cryocoolers, pumps, tanks, chillers, and membrane separators, (2) the determination of the optimal cold head design and flow rates needed to meet the collection requirement of 88 g CO₂/hr for 14 hr, (3) the testing of the CO₂ freezer subsystem, and (4) testing of the Sabatier subsystem.

This paper describes a proposed method for extracting frozen volatiles from subsurface (especially lunar) regolith and outlines steps that can be taken to evaluate the feasibility of the method, along with appropriate enhancements to simulation models, and terrestrial studies that could assist in optimization of the process. The basic premise of this concept is that after a well bore is drilled, a heat source and an extraction tube could be inserted into the bore hole to the depth of the desired resource; and a seal achieved around the extraction tube near the entrance (e.g., with an inflatable bladder or grout). Heat introduced in the well-bore would radiate/conduct into the surrounding material and vaporize the frost closest to the bore-hole. As the frost heats and sublimes, the pressure in the production region would increase and the vapor would flow to a lower pressure region (hopefully/presumably) into the open well-bore leading to the collection tube near the well entrance. The scenario just described sets up a flow pattern where there is radial outward heat flow, but radial inward gas flow surrounding the heated cylindrical well bore—a non-ideal configuration. Alternate configurations and the potential benefits of this general approach for extracting subsurface volatiles, as well as some of the challenges to overcome, are discussed.

Several asteroids are the targets of international robotic space missions currently manifested or in the planning stage. This global interest reflects a need to study these celestial bodies for the scientific information they provide about our solar system, and to better understand how to mitigate the collision threats some of them pose to Earth. Another important objective of these missions is providing assessments of the potential resources that asteroids could provide to future space architectures. In this paper, we examine a series of possible mission operations focused on advancing both our knowledge of the types of asteroids suited for different forms of resource extraction, and the capabilities required to extract those resources for mission enhancing and enabling uses such as radiation protection, propulsion, life support, shelter and manufacturing. An evolutionary development and demonstration approach is recommended within the framework of a larger campaign that prepares for the first landings of humans on Mars. As is the case for terrestrial mining, the development and demonstration approach progresses from resource prospecting (understanding the resource, and mapping the ‘ore body’), mining/extraction feasibility and product assessment, pilot operations, to full in-situ resource utilization (ISRU). Opportunities to gather specific knowledge for ISRU via resource prospecting during science missions to asteroids are also examined to maximize the pace of development of needed ISRU capabilities and technologies for deep space missions.

Asteroid deflection through explosive blasting provides an avenue to achieve significant changes in velocity for a given explosive yield, enabling deflection of bodies on a collision course with Earth much closer to time of impact. In this analysis, a number of computational numerical methods have been applied to outstanding problems of determining the change of velocity induced to an asteroid, the uncertainty distribution within the model, and the impact deflection that a modeled change in velocity would induce in a hypothetical test case. The results from this modeling support the utility of further research and small-scale testing, and suggest that blasting has the capacity to redirect asteroids less than a year before the time of impact in many cases. Filling this capacity is essential, considering the potentially short detection interval compared to the times necessary for many other deflection strategies.

The force required to pull 7 t and 40 t polyhedral boulders from the surface of an asteroid is simulated using the discrete element method considering the effects of microgravity, regolith cohesion and boulder acceleration. The connection between particle surface energy and regolith cohesion is estimated by simulating a cohesion sample tearing test. An optimal constant acceleration is found where the peak net force from inertia and cohesion is a minimum. Peak pulling forces can be further reduced by using linear and quadratic acceleration functions with up to a 40% reduction in force for quadratic acceleration.

The bending ability of an optical fiber is determined by the inherent micro-structural properties of the fiber. The major differences between the properties of an amorphous glass and a glass containing small amounts of microcrystals is that these inherent flaws play a strong role in the handling and bending ability of optical fibers, particularly in ZBLAN fibers. ZBLAN, a formulation from the ZrF4-BaF2-LaF3-AlF3-NaF system is the most stable glass for mid-infrared (IR) optical fiber applications, such as application in mid-IR sensors, radiometry, and laser power delivery. However, microcrystals formed during the fiber drawing process make this fiber a difficult material to handle and often fails when collected around the take-up reel. This study analyzes the bending ability of ZBLAN optical fibers by subjecting samples to heat-treatments and incremental bending radii of curvature. The results show that a fiber drawing take-up reel needs to be at least 15.24 cm (6.0 in.) in order to prevent breakage while drawing.

A finite element analysis (FEA) based mesomechanical modeling approach suitable for two-dimensional triaxially braided composite (TDTBC) materials and structures under high speed impact was developed. This new modeling approach is capable of considering the braiding geometry and architecture as well as the mechanical behavior of fiber tows, matrix, and the fiber tow interface, making it feasible to study the details of localized behavior and global response that happen in the complex constituents. Additionally, it is capable of simulating inter-laminar and intra-laminar damage and delamination of braided composites subjected to dynamic loading. With high fidelity in both TDTBC architecture and mechanical properties, it is well suited to analyze high speed impact events with improved simulation capability in both accuracy and efficiency. Special attention was paid to the applicability of the method to relatively large scale components or structures.

The effects of oxidation on mechanical behavior of a cone sample of ZrB₂-SiC ceramic under arc-jet test conditions is studied by a finite element (FE) model. First a steady-state heat transfer FE method was employed to conduct the thermal analysis and obtain the temperature distribution in the inner body of the cone. Then, resulting temperature distribution is applied to the thermomechanical finite element analysis to calculate the thermal stress distribution in the cone body. Due to the mismatch of material properties between the bulk ZrB₂-SiC and its new products after oxidation, the outer oxide layers constrain the thermal deformation of the inner bulk ZrB₂-SiC thereby putting it in compression and outside oxide layers in tension. The stress concentrations occur at the pore tips in the pore area due to the geometric heterogeneity.

The polyurea aerogels (PUA) were created by reacting triisocyanate Desmodur N3300a and water using triethylamine as a catalyst in a solution of acetone. Three PUA with densities 0.12 g/cm³, 0.17 g/cm³ and 0.33 g/cm³ were fabricated tested and used in model simulation. Quasi-static testing was conducted for mechanical strength in tension, compression, and shear. Testing was also conducted in dynamic tension and bending. Simulations were performed to develop a better understanding of structure-property response of PUA. Micro-scale effects such as particle stiffness, bond strength, and particle frictional coefficients were incorporated into the macro-scale structure-property relationship for the prediction of the Young’s modulus. The results indicate that polyurea aerogels are not particularly sensitive to various mid-range frequencies. The change in storage modulus across the tested range was minimal. The 0.17 g/cm³ damped the oscillatory motion more effectively in tension than the other two densities. Compression simulations using PFC3D were completed using the PUA model. Simulations showed that the shear and normal stiffness of the particles were equivalent rather than a ratio as suggested by literature.

At present, light steel structures for residential buildings are widely constructed. Light steel columns used as important supporting members are often applied in practical engineering. These columns are very sensitive to blast and fire which may occur together. The bottom column failure may lead to progressive collapse of the structure under fire and explosion. In this paper, light steel columns with different sections of H-type, rectangle and round are numerically analyzed to clarify influences of different temperatures and blast loading on the dynamic responses and failure modes. The element model of light steel columns considering high temperature thermal and high strain rate coupling effects is established by finite element software ANSYS/LS-DYNA. Dynamic responses and failure modes of light steel columns are numerically analyzed to develop mechanical behaviors and failure mechanisms. The results show that the light steel column with rectangle section has better capacity under fire and explosion than that of others, and the light steel column with H-section is the weakest among them. The failure modes of light steel columns may be summarized as three types of bending failure, direct shear failure and bending shear combination failure. The relevant research will establish a firm foundation for the analysis method of light steel columns under fire and explosion.

Bridge damage due to impact loads from over-height vehicle collisions is a major issue occurring throughout the transportation network. In this study, the numerical finite element modeling of reinforced concrete (RC) beams protected with and without honeycomb sandwich panels is conducted to simulate the over-height vehicle impact, and the numerical results are com-pared with the available experimental data. The experimentally-correlated numerical models can be used to perform virtual simulations of different over-height vehicle collisions, and they shed light on the behavior of honeycomb sandwich collision protection systems for RC beams.

Taken gravity dam deformation as random variables, multi-scale manifestation has been taken on deformation to build multi-scale statistical model based on multi-scale system theory. Then dam monitoring system has been transformed to integrate deformation monitoring information in the multi-scale domain. Furthermore, the multi scale information fusion estimation model has been established. At last, the predicating model of gravity dam deformation has been built with EWKHEFA algorithm using standardized Kalman filter. These methods have been applied into an actual project and the result shows that the model can be used into gravity dam deformation prediction effectively.

Subjected to construction situations, engineers of some lock head projects do not perform adiabatic temperature rising test to determine thermal parameters of concrete. To solve this problem, this paper proposed an inverse analysis method of lock head thermal parameters based on BP neural networks. Firstly, combinations of concrete thermal parameters were constructed based on uniform design theory and FEM(finite element method) analyses of temperature field using these parameters were performed to generate a series of samples. Then a BP neural network was trained by these samples. After entering the measured temperature, the neural network would output the result of inverse analysis. The future temperature curve was obtained using the inverse result and was compared to the measured temperature. The result showed the reasonability and efficiency of this method, and the rate of convergence of the BP neural network was improved by uniform design, and the accuracy of this method can meet engineering requirements.

Multi-layer and multi-strand energy dissipation by hydraulic jump was adopt to discharge flood by one giant hydropower station to avoid the atomization effect. The safety of the stilling basin structure was critical for whole project, therefore, the flow-induced vibration characteristics of the stilling basin was studied by the combined method including model test, numerical prediction and field monitoring in this paper. Pulsation pressure characteristics on the discharge chute, bottom plate and guide wall was obtained from model test. In the frequent flood condition, the main pulsation pressure was located at the end of the chute, while that of the bottom plate and guide wall was slightly smaller and reducing along the stilling basin. The main frequency of the pulsation pressure was 1.5∼3.5 Hz. Based on the pulsation pressure from the model test, stilling basin structure vibration responses were predicted numerically, and different vibration characteristics were shown among the chute wall, guide wall and bottom plate. When the project was running, vibration field monitoring on the guide wall and bottom gallery of the stilling basin. It was found that guide wall vibration decreased linearly in the flow direction and the vibration response of field monitoring was consistent with the prediction value.

Hydraulic model test is a very important method for research on large hydraulic structure under complex and extreme environments such as floods. To measure the topography around hydraulic structure model, a non-contact measurement method with laser and ultrasonic has been developed. Besides little disturbance to flow and river bed, this method makes it possible to simultaneously and quickly measure the land topography and underwater topography. The measurement system is composed of plane positioning mechanism, measuring devices with laser and ultrasonic, system of control and data acquisition. The measurement accuracy of the system is ±1 mm, which was tested by experiments with different water depth and sediment concentration. The measurement system was well applied to measure the variation of topography around a bridge at the downstream of a sluice.

Knowledge gained from frozen ground real-time monitoring is crucial in understanding the freeze/thaw status of the ground, which is important for applications such as construction and agriculture. The traditional monitoring of frozen ground is based on temperature measurement using thermocouples or other commercial tools. However, the inhomogeneous composition of the ground can cause uneven freezing and thawing across the field. In this paper, an active-sensing method was applied to quantitatively evaluate the soil freeze-thaw degree using piezoceramic based smart aggregate (SA) transducers. A pair of SAs with a pre-determined distance apart were embedded the soil specimen. One SA was used as an actuator to generate stress wave and the other one was used as a sensor to detect the propagated stress wave. The change of the mechanical properties of the soil greatly affected the SA-generated stress wave propagation through the soil during the freeze-thaw process. To quantitatively identify the soil freeze-thaw condition, a wavelet packet-based ground freeze-thaw indicator was applied to extract the degree of soil freeze-thaw condition.

Based on image processing technology, a laser spot identification method of bridge displacement monitoring was proposed. A laser device is affixed on the monitored object and projects a laser spot onto a projection panel. When the object moves, the laser device and the laser spot move along with it. The motion trail of the laser spot on the projection panel is recorded by a webcam. The displacement of the object is obtained by analyzing the motion trail of the laser spot. Many experiments had been conducted; the results show that this method has high accuracy. We hope to find a low-cost and high accuracy method for bridge displacement monitoring by means of these preliminary efforts.

Many kinds of uncertainties exist in in-situ structure performance assessment and damage detection in structure health monitoring (SHM). At present, most research in SHM field focuses on statistical analysis, data acquisition, feature extraction and data reduction. A method is introduced in the paper to improve pattern recognition and damage detection by supplementing intelligent structure health monitoring (ISHM) with fuzzy sets. Based on the developed method, a multi-class fuzzy comprehensive evaluation method (MFCEM) is used to identify the damage status of piezoelectric concrete frame structure during the service. First, a multi-level fuzzy comprehensive evaluation model and index system of the reinforced concrete frame structure is established according to the fuzzy evaluation theory. Second, the fuzzy evaluation matrix of the target system is obtained and the weight coefficient of index is reasonably determined. In the end, the evaluation result of each layer for the system is calculated by the fuzzy theory. In order to validate the proposed method, a two story reinforced concrete frame structure is built for the experimental research. Several pairs of smart aggregates (SA) used as transducers are embedded into the concrete frame structure. By analyzing the signal and combining with the developed MFCEM, the damage state of the structure can be classified. The results show that the theoretical analysis matches well with the test results. Therefore, the proposed method used for damage evaluation of reinforced concrete structure is feasible and effective.

Many kinds of uncertainties exist in in-situ structure performance assessment and damage detection in structure health monitoring (SHM). At present, most research in SHM field focuses on statistical analysis, data acquisition, feature extraction and data reduction. A method is introduced in the paper to improve pattern recognition and damage detection by supplementing intelligent structure health monitoring (ISHM) with fuzzy sets. Based on the developed method, a multi-class fuzzy comprehensive evaluation method (MFCEM) is used to identify the damage status of piezoelectric concrete frame structure during the service. First, a multi-level fuzzy comprehensive evaluation model and index system of the reinforced concrete frame structure is established according to the fuzzy evaluation theory. Second, the fuzzy evaluation matrix of the target system is obtained and the weight coefficient of index is reasonably determined. In the end, the evaluation result of each layer for the system is calculated by the fuzzy theory. In order to validate the proposed method, a two story reinforced concrete frame structure is built for the experimental research. Several pairs of smart aggregates (SA) used as transducers are embedded into the concrete frame structure. By analyzing the signal and combining with the developed MFCEM, the damage state of the structure can be classified. The results show that the theoretical analysis matches well with the test results. Therefore, the proposed method used for damage evaluation of reinforced concrete structure is feasible and effective.

Tidal bore loads are the main control loads for Sluice gate of Cao’e River dam. Tidal bore loads are complex and influenced by many random factors, thus the Monte Carlo method is adopted to conduct a stochastic simulation analysis on such loads. Firstly, the procedure of Monte Carlo stochastic simulation analysis on structural reliability is studied, and the random variable sampling method with improved Two-Dimensional Logistic Map is introduced in our study. Then, random analysis are made for the selected typical tidal bore parameters based on field observed data, including tidal bore height, velocity and flow direction. Our random analysis results indicate that the tidal bore height and velocity follow normal distribution, and the flow direction obeys uniform probability distribution. In the end, the tidal bore loads are simulated using Monte Carlo method based on our rapids vibration test data, hence allowing the impact loads of the sluice gate to be investigated. The reliability assessment of the sluice gate is conducted finally base on sampling analysis results.

This paper identifies near-fault pulse and non-pulse like ground motions based on the relative energy of velocity pulse and the peak velocity of pulse. An ANOVA analysis is performed to distinguish between main characteristics of pulse and non-pulse like ground motions, suggesting that the PGV-to-PGA ratio, energy, and peak displacement of pulse like ground motions are greater than that of non-pulse like ground motions. This paper also investigates the response of a three-span continuous reinforced concrete bridgesupported by pile foundationsunder near-fault pulse andnon-pulse likeground motions. Numerical resultsindicate that near-fault pulselikeground motions generate stronger responsethan do near-fault non-pulse like ground motions.In addition, this paper finds that scour depth have great influence onthe response of the structure. Finally, based on statistical analysis, this paper proposes anefficientparameter which performs better in reflecting the structural response to near faultpulse like ground motions.

Based on the shortcoming of the passive friction damper that the friction force cannot be adjusted during working, a new type of piezoelectric variable friction damper that the friction force can be adjusted by piezoelectric actuator was developed. The energy dissipation capacity of the damper under cyclic loading was investigated by Material Testing System. The energy dissipation performance of the damper was also analyzed by the preload, loading frequency and displacement amplitude. The experimental results indicate that the proposed piezoelectric variable friction damper has both stable hysteretic performance and good energy dissipation capacity. The energy performance of the damper varies with preload and excitation amplitude. The excitation frequency has little effect on the energy dissipation of the proposed piezoelectric variable friction damper.

Labs-to-Go (LTG) is an inexpensive dynamics and control experiment toolkit suitable for take-home laboratory projects, in-class work, demonstration in lectures, and outreach to K-12 and the general public. The LTG kits consist of a set of smart beam elements, assembly hardware, interface circuitry, a digital signal processing subsystem, and support software. The LTG kits enable take-home labs which reduce the need for our students to commute to campus for labs (40% of UH students commute more than 30 minutes one-way). This paper extends previous work on LTG take-home experiments and introduces the active control experiments. We also describe use of the kits to support other academic disciplines, introductory engineering courses, and outreach.

In this study, the potential of using nonlinear oscillators with asymmetrical potential wells to scavenge mechanical energy from ambient vibrations is investigated. Mechanical energy of ambient vibrations is normally distributed in a spectrum of frequencies. To scavenge such energy, methods using linear and nonlinear oscillators have been proposed. In these existing methods, however, the potential wells of the oscillators are symmetrical with only one frequency dominating in the free-vibration response. Such dominance of a single frequency indicates that in the zone of resonance, the response of the oscillator will likely be dominated by a single frequency. Thus, such oscillators do not perform well if there are multiple dominating frequencies in the vibration. To overcome such limitation, a method based on nonlinear oscillator with asymmetrical potential well is proposed. An asymmetrical potential well supports multiple frequencies in the response, as demonstrated by the multiple-frequency dominance in the free-vibration response. As a result, it is more effective in scavenging energy from vibrations of multi-frequency content. In this study, the potential benefits of the system with asymmetrical potential well are numerically studied. The results confirm the effectiveness and improved performance of the proposed method.

The extreme hot and cold temperatures present on the surface of the Moon bring about one of the most important design challenges when considering a lunar habitat for use in a long-term colonization mission. Within this paper, the analytical determination of the lunar surface temperature within a one-meter regolith shield is presented. It was found that the surface temperature on the structure built at the lunar Equatorial surface could reach temperatures as high as 457 K (183.85°C) during the day while dropping to 183 K (-90.15°C) at night. Secondly, the initial static analysis, including the determination of both member stresses and nodal deflections due to the applied internal pressure and the aforementioned temperature profile, is presented. The added mass of the regolith shield helped to reduce both the stress and deflection magnitudes throughout the structure. The high daytime temperatures resulted in increased nodal deflections due to thermal expansion, while the cold nighttime temperatures had an inverse effect. This same design process can also be used to consider other locations on the surface of the Moon or for different habitat structural concepts.

Extreme environments on Earth share similar facilities and operations, design and planning challenges. Each environment presents special lessons regarding housing design, crew/staff operations and training, and equipment and logistical requirements for human activities. The paper discusses these challenges and lessons. Recurrent and specific to environment and conditions events are outlined and categorized based on case studies reviews and literature summary. Understanding of relationships and influences between different facets of human society and architecture can help to find a design approach which would optimize needs and requirements for various types of people living in different environments, societies and cultures. Environmental conditions affecting architectural requirements include form developing factors, site orientation and circulation, and budget considerations. They have to be addressed at the programming design stage in order to avoid costly adjustments at later development stages. It is even more critical in case of designing for challenging environments.

Five full-scale specimens of the Ganhaizi long-span bridge, which is concrete-filled steel tube (CFST) truss structure, were fabricated to simulate the potential defects, such as debonding, void, mortar, etc. The specimens were tested using the ultrasonic wave based method. The relevant regularity and evaluation standards for identification of defects were obtained from the test results. The ultrasonic wave based method was also applied to Ganhaizi long-span bridge for checking the pouring quality of CFST structure. The measured data not only demonstrated the accuracy of the relevant evaluation standards, but also proved that the ultrasonic wave based method researched in this paper is an effective method to detect the compactness of CFST structures.

Time-varying environmental and operational conditions such as temperature and external loading may produce an adverse effect on damage detection with the structure exposed to these changes. In fact, these effects can often mask more subtle structural changes caused by damage. Therefore, in order to achieve successful structural health monitoring goal, a new data normalization technique based on the improved restoring force model (IRFM) is proposed in this paper to distinguish the effect of damage from those caused by environmental and operational variations. Firstly, a special training data set, whose IRFM coefficients are closest to the IRFM coefficients from the testing data, is determined and selected by a Euclidean distance measure. The IRFM coefficients of this training data are then applied to calculate the residual errors of this special training data and the testing data for the respective IRFM approximations to these measured time histories. Finally, the ratio of the variance of the residual errors is defined as the damage-sensitive feature and used in the outlier detection process. The usefulness of the proposed approach is demonstrated using an experimental study tested at Los Alamos National Laboratory.

The development of efficient ice monitoring methodologies is critical for the ex-ploitation of wind energy in cold regions. In this study, an icing monitoring approach for a wind turbine model blade using active piezoelectric lead zirconate titanate (PZT) patches acting as actuator and sensors is proposed. Experimental study on a model blade covered with different thickness of ice is carried out and the correspond-ing responses of different sensors are recorded when a certain designated actuator was excited with sweep sinusoidal signals. The wavelet packet analysis on the meas-urement and the corresponding wavelet packet energy (WPE) of the measurement is determined. Results show that the WPE of the measurement of the same PZT patch is related to the increase of ice thickness. The proposed method based on the WPE can monitor the icing conditions of the tested specimen and has the potential application in practice for the ice monitoring for wind turbine blades operating in cold regions.