Earth and Space 2012: Engineering, Science, Construction, and Operations in Challenging Environments

The surfaces of the Moon and Mars are covered with loose soil. In such conditions, planetary rovers can get stuck and even cause failure of an exploration mission. To avoid such problems, the wheels of planetary rovers typically have lugs (i.e., grousers) on their surface, which substantially improve their traveling performance. However, there exists no theoretical method to determine a suitable lug interval. In this study, we first modeled the linear traveling speed of a wheel with lugs and provided guidelines for determining a suitable lug interval, as well as the corresponding terramechanical stress models. Next, to verify the suitable interval for lugs, we performed traveling tests using a two-wheeled rover with wheels having different numbers of lugs of different heights. According to the experimental results, when a wheel has three lugs in a range where normal stress is generated beneath it, it can travel with constant speed while the traveling performance is substantially improved.

As NASA's exploration missions on planetary terrains become more aggressive, a focus on alternative modes of locomotion for rovers is necessary. In addition to climbing steep slopes, the terrain in these extreme environments is often unknown and can be extremely hard to traverse, increasing the likelihood of a vehicle or robot becoming damaged or immobilized. The conventional driving mode in which all wheels are either driven or free-rolling is very efficient on flat hard ground, but does not always provide enough traction to propel the vehicle through soft or steep terrain. This paper presents an alternative mode of travel and investigates the fundamental differences between these locomotion modes. The methods of "push-pull" locomotion discussed can be used with articulated wheeled vehicles and are identified as "walking" or "inching/inch-worming". In both cases, the braked non-rolling wheels provide increased thrust. An in-depth study of how soil reacts under a rolling wheel vs. a braked wheel was performed by visually observing the motion of particles beneath the surface. This novel technique consists of driving or dragging a wheel in a soil bin against a transparent wall while high resolution, high-rate photographs are taken. Optical flow software was then used to determine shearing patterns in the soil. Different failure modes were observed for the rolling and braked wheel cases. A quantitative comparison of inching vs. conventional driving was also performed on a full-scale vehicle through a series of drawbar pull tests in the Lunar terrain strength simulant, GRC-1. The effect of tire stiffness was also compared; typically compliant tires provide better traction when driving in soft soil, however it's been observed that rigid wheels may provide better thrust when non-rolling. Initial tests indicate up to a possible 40% increase in pull force capability at high slip when inching vs. rolling.

Soil mechanics study plays a key role in various engineering problems relating to future lunar/planetary surface explorations. In-situ measurement of regolith physical properties is of fundamental importance in developing a framework of lunar/planetary soil mechanics. An in-situ soil investigation package; LSM (lunar soil mechanics investigation system) is being developed as a moon utilization payload for Japan's Moon lander SELENE-2, which is planned as a follow-on program of Kaguya program (SELENE). This paper focuses on a soil testing tool, which is one of the subsystems of LSM, and describes a result of laboratory experiments using a prototype model. The equipment developed is a small-diameter tool with a paired-inflatable blade and is used in a pre-frilled borehole for performing two types of soil mechanics test; lateral loading test and direct shear test against the borehole sidewall. In this study, a series of shear tests were demonstrated with a Japanese lunar soil simulant (FJS-1) and the results were compared with results of a triaxial compression test and direct shear box test. The test results showed that the proposed method has a great potential to be a reliable tool that can provide strength parameters on the lunar surface. The characteristics and underlying limitations of the probe were also discussed for future improvements.

Reliable, robust methods for separation of granular materials that operate independent of gravity level would be useful for many applications in space exploration. Utilizing centrifugal force as the primary body-force, combined with shearing flow and vibratory motion the centrifugal-sieve separator can provide efficient gravity-level-independent size classification of granular feedstock like lunar regolith. A test apparatus has been built using a size-separating screen at the outside of the flow that will separate particles, with the fines passing through the outer wall screen, and the coarse material passing axially through the continuous feed system. The test apparatus is designed for semi-autonomous operation during reduced-gravity flights, and/or under vacuum conditions.

Impinging rocket plumes from spacecraft interact with the lunar regolith surface and release a high velocity particle-spray that is potentially hazardous to surrounding surface structures and surface architecture. Experiments performed at NASA-KSC and the University of Florida provide data on the cratering of a particle bed composed of lunar soil simulant JSC-1A by a turbulent subsonic jet of gas. Cratering experiments were also performed on beach sand, which has a narrower particle size distribution than JSC-1A. JSC-1A contains a wide particle size distribution with a high number of fine particles (20% by volume less than 35 μm). JSC-1A is highly compressible and contains much rougher and more angular particles than beach sand. The differences in the particle properties between JSC-1A and beach sand leads to stark differences in the cratering of the two materials. The cratering of beach sand results in a dual crater shape consisting of a conical outer crater and a paraboloid inner crater. While the jet is impinging on the sand, the crater grows logarithmically with time and the outer crater cycles between the angle of repose and angle of failure as particles are ejected from the inner crater onto the outer crater. The JSC-1A crater is similar to a scour hole in shape, which grows deeper over time, with large chunks of material being eroded by the jet. The growth rate of the crater of JSC-1A is highly dependent on the bulk bed density of the JSC-1A. For the same jet velocity the cratering rate of a bed of JSC-1A with a higher bulk density (more compact) was slower than a bed with a lower bulk density (less compact). Even for a lower jet velocity, the less compact bed can crater faster than the more compact bed. The cratering of a sieved fraction of JSC-1A in the absence of fine particles is studied by sieving to a particle size range of 150 to 425 μm. The cratering of sieved JSC-1A is more similar to the cratering of beach sand than to unsieved JSC-1A indicating that the presence of fine particles in unsieved JSC-1A is the cause for its atypical cratering behavior.

This paper presents the study of the influence of interparticle attractive forces on the stress-strain behaviour of a synthetic material made of elastic adhesive particles attributed with material properties typical of lunar soil. The aim is to address fundamental issues concerning the visible cohesion of lunar soil if compared to terrestrial materials of similar gradation. A micro-mechanical approach by means of the Discrete Element Method (DEM) is utilised to facilitate the reproduction of surface energy effects at the particulate level. Conventional triaxial compression tests are simulated for very dense samples and a wide range of confining pressures, up to 1kPa, typical of the lunar environment. Results show the influence of adhesion at the macroscopic level in terms of friction angle as well as cohesion. Physical explanations of these complex phenomena are advanced, and limitations of the current DEM model are highlighted.

An increasing number of activities require access to dedicated simulants to support the exploration of small bodies in the frame of the Human exploration program and the planetary science decadal survey 2013-2022. These activities include instrument design and testing, mission planning, sample curation, experimental research, etc. Targets of interest include comets, near Earth objects, Mars moons, and asteroids. We are working toward the development of a library of standard simulants that could support a variety of engineering and scientific needs. In this presentation we review the state of knowledge of small body materials and devise strategies for synthesizing low- and high-fidelity simulants. The production of high-fidelity simulants, especially of ice- and organic-rich materials, is challenging and requires dedicated facilities. This calls for a collaborative effort among relevant experimental facilities. We are planning to reach out to the community and get a better understanding of the high-priority needs that will help focus our efforts and identify potential collaborators.

Laboratory testing of equipment for lunar or Martian use is difficult due to the inability to accurately replicate the conditions in these environments (e.g. gravity). While it is important to do laboratory testing at times, modeling provides a low cost way to complete many tests in a repeatable soil bed. This work describes the development of a three dimensional discrete element method (DEM) simulation of a scoop (Surveyor Soil Mechanics Surface Sampler replica) in JSC-1a. The JSC-1a simulant is modeled using non-convex polyhedral grains. Both static and percussive digging tests are completed. Results of the DEM digging tests are compared with results of DEM scoop experiments and simulations reported by Lee et al. (2010).

Low-velocity impacts are common on regolith surfaces of planetary bodies. We have conducted a series of low-velocity impact experiments of various impactor types and energies into JSC-1 lunar regolith simulant in vacuo and in atmospheric pressure. Experiments done in the laboratory are limited to the velocities able to be achieved under 1 g of about 1 m/s. We found that ejecta mass production depends on the pressure of the environment, the energy of the impact, and the density of the target material. Ejecta mass velocity distributions fit a power-law or broken power-law distribution and, in some cases, exhibit a dependence on impact energy. Understanding the collisional outcomes of low-velocity impacts into regolith will help us understand the effect of manned and unmanned activity on the surface of the Moon and other regolith-covered bodies.

To reveal shallow subsurface structures as well as velocity distribution of the lunar regolith layer, we propose a survey of Reverse Vertical Seismic Profiling (RVSP) under a program of SELENE-2. In the RVSP experiment, seismic sources generated within the borehole are recorded by receivers deployed on the Moon surface. In Lunar Soil Mechanics (LSM) Investigation System, drilling operations and shear strength measurements (1 m in total depth) are planned for the regolith layer. We attach a vibrator at the shear experiment devices and generate an active source signal within the borehole. MEMS sensors are further attached at legs of the lander and record the wavefields derived from the vibrator within the borehole. Here we show the effectiveness of RVSP survey using the proposed simple (small-size) acquisition system from simulation study and laboratory experiments. First, we conducted simulation study for the designed survey geometry in order to determine the survey parameters (e.g., source signal). This simulation study demonstrates that the source signal should contain high-frequency components in order to resolve shallow velocity structure from short offset data (less than 3m). Since the high-frequency signal is much attenuated, we used a sweep waveform for the source signal. To examine the ability of the sweep waveform for the high-attenuation regolith layer, we conducted small-scale RVSP experiments in laboratory using lunar soil simulant. The laboratory experiments demonstrated that the seismic signal can be retrieved by cross-correlation between source (sweep) waveform and recorded waveform. From the direct P-waves and reflected waveforms observed on the processed gathers, P-wave velocity of the regolith was estimated as ~85m/s. This study shows that the proposed simple RVSP survey could reveal the shallow subsurface structures as well as velocity within the regolith layer.

Cleaning of lunar dust adhering to spacesuits is critical for long-term lunar exploration. Three different cleaning systems are being developed to address this issue. The first system employs an alternating electrostatic field; AC voltage is applied to parallel wires stitched into the insulating fabric to create an electrostatic field barrier on the fabric surface. It was demonstrated that more than 80% of the adhered dust particles are repelled from the fabric. The second system employs a combination of electrostatic separation and transport; a high voltage is applied between an Al coated Mylar sheet positioned under the surface fabric and the screen electrode of a cleaning device. The dust adhering to the fabric is captured by the screen electrode, and the captured dust is transported by a traveling wave to a collecting bag. The observed cleaning rate was higher than 80%. The third system employs electrostatic and magnetic forces, based on the fact that lunar dust is magnetic. The cleaning rate achieved was approximately 80%.

A unique shield system for lunar dust has been developed using electrostatic force to prevent dust from entering into bearings and mechanical seals of equipment used for lunar exploration. A single-phase rectangular voltage is applied to insulated parallel plate electrodes printed on the edges of the gap in the mechanical sealing part. It was demonstrated that more than 70% of the dust was repelled from the gap, and it was predicted by numerical calculations performed using the distinct element method that the shielding performance of the system would improve further in the low-gravity and vacuum environment of the Moon. This technology is expected to increase the reliability of equipment used in long-term manned and unmanned activities on the lunar surface.

Binary mixtures (granules of two different sizes) segregate when subjected to rotation in a tumbler. When large and small sized granules are mixed and rotated at moderate speed, segregation starts immediately with smaller sized granules concentrating at the center and larger ones on the periphery of the of the tumbler, which is known as radial segregation. After a few minutes, axial segregation (where bands of small and large-granules appear) begins.This paper presents experimental results relating granular segregation with power consumption using grains of rice and black beans as the binary mixture in a rotating drum. At constant voltage supply from a source, power consumption, expressed in terms of torque and rotational speed required to rotate a mixture of equal mass of rice and beans, decreases as axial bands form. Similar experiments using only rice or only black beans of the same mass show little or no decrease in power consumption. Rice (the smaller sized granules) consume larger and constant amount of power whereas black beans (larger sized granules) consumes smaller and constant amount of power consumption.

Space agencies and most recently private enterprises around the world plan to build structures for commercial operations on the Moon. However, we have no design experience or building standards that apply to this "extreme" environment. Understanding the behaviour of viable building materials under lunar conditions is one important step. This paper explores the characteristic of a waterless concrete utilizing of a lunar soil simulant "cemented" together by a polymer. Mixing polypropylene powder with the simulant created a dry mix that was filled into a steel form, compacted and slowly heated to melting temperature. Discussed are the formwork design and the innovative method used to produce a secondary compaction while the polymer liquidised. After each experiment, the density, compressive, and flexural strengths of the resulting hollow beams were measured and compared to assess their sensitivity to changes in mix-design, compaction, and heating temperature. The results indicate significant compressive and tensile strengths for the 10% polypropylene polymer samples. The unexpected lower tensile strength from 3-point beam bending test highlights the need for further improvements.

NASA has the plan for human exploration after the year 2020. This human exploration concept is based on ISRU (In Situ Resource Utilization). The concept of ISRU is reducing delivery cost supporting reasonable and efficient space exploration. And it plans to use the resources of the Moon and equipment at least. According to this human exploration plan, it mentioned how to make landing pad in the Moon such as soil compaction, dust and soft regolith replacement, and the bank construction around landing pad. But there is one problem with removing the dust that cannot be perfectly stabilized. Thus, this paper will present a new approach for landing pad construction in the Moon considering ISRU. First of all, this landing pad construction needs standardized building materials and methods suitable for lunar environment. Since Lunar Concrete using the lunar simulant called KOHLS-1(Korea-Hanyang Lunar Simulant- 1) has enough strength for compression, prototype is manufactured based on it. Then, landing pad is constructed in a similar way to lunar concrete manufacturing method. After making the landing pad, it is applied to feasibility study with SELENE-2 in JAXA, Astrobotic in Google X Prize and so on about compression strength. And the result has shown that it has enough strength which is suitable for other lading scenarios on the Moon.

The Apollo 12 lunar module (LM) landing near the Surveyor III spacecraft at the end of 1969 has remained the primary experimental verification of the predicted physics of plume ejecta effects from a rocket engine interacting with the surface of the moon. This was made possible by the return of the Surveyor III camera housing by the Apollo 12 astronauts, allowing detailed analysis of the composition of dust deposited by the LM plume. It was soon realized after the initial analysis of the camera housing that the LM plume tended to remove more dust than it had deposited. In the present study, coupons from the camera housing have been reexamined. In addition, plume effects recorded in landing videos from each Apollo mission have been studied for possible clues. Several likely scenarios are proposed to explain the Surveyor III dust observations. These include electrostatic levitation of the dust from the surface of the Moon as a result of periodic passing of the day-night terminator; dust blown by the Apollo 12 LM flyby while on its descent trajectory; dust ejected from the lunar surface due to gas forced into the soil by the Surveyor III rocket nozzle, based on Darcy's law; and mechanical movement of dust during the Surveyor landing. Even though an absolute answer may not be possible based on available data and theory, various computational models are employed to estimate the feasibility of each of these proposed mechanisms. Scenarios can then be tested which combine multiple mechanisms to produce results consistent with observations.

A technique is presented that evaluates the reliability of lunar rover wheel designs where data for operation in the lunar environment are not available for traditional reliability analysis. The visual inspection technique is described and an analysis of five historical wheels and four new wheels designed by McGill University is given. The wheel designs were visually analysed according to specific criteria with regard to potential failure under lunar conditions (temperature, vacuum, regolith) considering wear resistance, thermal compatibility, excess loading, torque, etc. Potential wheel performance was quantified using a numerical scale with regard to potential failure due to events, such as temperature fluctuation, wheel-rock impact, excess payload, abrasive wear, etc. The best designs were the Apollo 17 wire mesh wheel (historical) and the iRing wheel (McGill). A reliability checklist which can serve as a guideline to avoid unreliable design features is given.

Since lunar soil is a typical granular material and the microgravity environment can not be simulated easily in experiments on earth, the distinct element method (DEM) appears to be a very efficient method to analyze such problems. In this paper, first, a new contact model between particles for lunar soil is proposed, which takes into account particle rolling resistance and van der Waals forces between lunar soil particles, and then is implemented into DEM. By adjusting values of the parameters of the contact model, the basic mechanical characteristics of the DEM sample (e.g. the angle of internal friction, cohesion) can be numerically obtained which match the typical values of lunar regolith on the lunar surface. Second, the numerical simulation of tire-soil bin test was carried out and the interaction between the driving wheel of lunar rover and lunar soil was analyzed under lunar microgravity environment and terrestrial environment by DEM. The force and movement characteristics of the lugged rigid driving wheel, the stress and deformation of soil were analyzed. The results indicate that in lunar environment, the resistance of the wheels and the energy consumption will be less than that on earth but the slip ratio and settlement will be greater. So it will be more risky for lunar rover to travel on lunar surface than on earth.

This paper will discuss development of a tool that can be used as an attachment to existing rovers to gather local materials and build a landingpad. The landing pad must be able to withstand thruster heat, forces from the lander and prevent regolith from sandblasting everything in the surrounding area during landing. This paper focusses on Mars and the Moon as locations for this technology. Environmental conditions affecting the design is taken into account as well as the applicability of a variety of soil stabilization techniques. The evaluation process lead to the choice of using local gravel to build several zones with varying particle sizes in an analog application of a breakwater to prevent the exhaust gases from eroding the fine regolith dust while minimizing the amount of mass required to bring from Earth. Laboratory tests were run with a small rocket nozzle and compressed air to test the effectiveness of the layers of rocks and the size variation that was most effective. Once the effective size was determined, a tool was designed that would excavate the local regolith and sort out the rocks and sort them in different size fractions which then could be deposited in the optimal sequence to prevent regolith erosion and subsequent sandblasting of the surrounding area and assets. The prototype tool was then tested and proven to be able to sort the rocks of the required sizes.

Magnesium is one of the most pervasive metals in lunar soil, and has many characteristics that make it applicable to in-situ refining and production. This somewhat overlooked alkaline earth metal is easily cast, utilized, and recycled, characteristics that are required in the Moon's harsh environment. Moreover, alloys of this element have several properties fine-tuned for building shelters in a lunar environment, including several advantages over aluminum alloys. Magnesium alloys may prove to be the optimal choices for reinforcing lunar structures or manufacturing components as needed on the Moon. As such, further research on the in-situ resource utilization (ISRU) of magnesium is imperative for the development of a self-sufficient lunar base. This paper brings together key properties of magnesium within the context of it being used as an in-situ resource once the Moon, again, becomes a goal for permanent habitation and we require the ability to live there in perpetuity.

NASA missions to Mars will need the utilization of local resources for the production of oxygen, fuel, and water. The extraction of these commodities from the Martian atmosphere will require the removal of dust particles smaller than 10 micrometers in diameter from the gas intakes feeding the processing chambers. An electrostatic precipitator is a widely used dust removal technology for dusty environments on Earth. However, the low pressure of the Martian atmosphere limits the electrostatic potentials normally needed for this technology. This low pressure also affects dust particle charging due to the much longer molecular mean free paths of the Martian atmosphere. In this paper, we report on our design for an electrostatic precipitator for the challenging Martian environment. We also show results on dust collecting efficiencies with an electrostatic precipitator prototype that could be effectively used on a future mission to Mars. All experiments were performed at 9 mbars with gases that approximate the Martian atmospheric composition.

As a lunar lander approaches the surface, the impinging exhaust gases entrain regolith into a high velocity spray. This two-phase spray can be damaging to nearby structures, such as a lunar outpost. One way of mitigating this damage is to use a berm or fence to shield nearby structures from the dust spray. In this work, we use a coupled continuum - DSMC (direct simulation Monte Carlo) solver to simulate the gas and dust flow fields. A continuum solver, DPLR, is used to model the internal nozzle flow from the nozzle throat out to the continuum regions of the underexpanded exhaust in the near vicinity of the engine. As the rocket exhaust expands further towards vacuum, continuum assumptions break down and kinetic equations are used. Additionally, a dust - gas collision model that conserves momentum and energy transfer between the gas and dust grains has been implemented into the kinetic solver. The distance of the deflection fence from the landing pad is studied parametrically and the corresponding gas and dust flow fields are analyzed. Additionally, the sensitivity of the model to the dust - fence coefficient of restitution is studied when the fence is located 15 m off axis.

The traditional methods of Lunar/Martian rocket plume-dust simulation lack essential physics and feasibility for realistic application. The challenges arise from plume impingement flow in extra-terrestrial environment and peculiar granular behavior of irregular regolith. This paper presents significant improvement in the physics of plume-surface interaction, soil erosion and debris release through Eulerian multiphase modeling. In this approach, the rocket exhaust gas and regolith phases are coupled with inter-phase momentum and energy exchanges. Appropriate new formulations of granular flow kinetics are developed for poly-dispersed, irregular particles. The surface stresses for plume scouring and regolith roughness are refined by appropriate turbulence modeling. The numerics are built upon high-performance, adaptive mesh refinement architectures. Validation studies and applications will include cratering experiments with sand, Moon/Mars regolith simulants, reduced gravity effects and various Moon/Mars landing scenarios. This tool will provide a basis for deeper understanding of extra-terrestrial debris impact and mitigation measures for future space exploration systems.

Lunar surface activities engage the mechanical properties of the regolith on a relatively small scale, and there is currently great interest in employing discrete element models to simulate such activities. The validity of this type of model depends critically on employing correct contact laws and particle descriptions (size, shape and surface roughness) for the materials of interest. This need has motivated us to conduct grain-scale experiments on Apollo soils, develop contact laws, and implement these laws in a discrete element model to simulate the engineering-scale behavior of the lunar regolith. The paper presents an overview of our findings with emphasis on the range of contact properties observed primarily for lunar plagioclase and pyroxene grains, with varying degrees of space weathering, and the implementation of the contact laws in a discrete element model of a standard geotechnical triaxial cell. We quantify grain size, aspect ratio, roundness, etc., and use these results to generate virtual particles with the desired population statistics. Carefully oriented SEM micrographs of each grain are used to determine the radius of curvature and surface roughness of the contact patches prior to and after mechanical testing. The paper presents normal and shear contact laws that quantify the elastic and inelastic (e.g., hysteretic) components of deformation. We observed space weathering to have a first-order effect on contact properties, reducing the effective elastic modulus of plagioclase grains by ~50% and increasing the hysteretic loss by a factor of 3-4. Implementation of the normal and shear contact models in a discrete element model is described, and the effects of the observed ranges in contact properties on the simulated triaxial behavior are demonstrated.

Disturbed lunar regolith has distinctly different photometric properties than undisturbed regolith. Properties such as composition, grain size and size distribution, grain shapes, glass and Fe₀ contents, and structure (fine-scale layering or "fairy-castle" forms) determine how light is reflected from the surface. Photometry can be used to extract this information from regions with different photometric behavior or to compare disturbed and undisturbed areas. Of interest here are regions around the Apollo landers that were disturbed during descent, which we refer to as blast zones. Lunar Reconnaissance Orbiter Camera (LROC) Narrow Angle Camera (NAC) images show that the blast zones are brighter and have distinctly different photometric properties than surrounding regolith, presumably owing to smoothing of the surface and/or removal/redistribution of fine particles. We use phase-ratio images for each landing site to determine the size of the blast zone around each lander and to quantify the differences in reflectance within the blast zones in comparison to nearby undisturbed regolith. Most of the blast zones are elliptical in shape, but some are irregular. The average area of regolith brightening from preliminary measurements for the blast zones is ~115,000 m2, with values ranging from as low as 75,000 m₂ for Apollo 15 (~150 m average diameter) to as high as 215,000 m₂ (~260 m average diameter) for Apollo 12, which has an enlarged disturbed region extending in the direction of Surveyor Crater. The average normalized reflectance is 0.0480 for the blast zone, 0.0400 for the area under the LM, and 0.0443 for areas outside the blast zone, indicating some process or combination of processes are causing differences in surface properties of the regolith. Whereas experimental work and dynamical modeling indicate that soil grains excavated from beneath the landers would have been transported and deposited many kilometers away, the images provide visible evidence for effects in close proximity to the landers. We are investigating what part of the excavated particle flow regime corresponds to these areas of visible alteration using Hapke modeling. Our working hypothesis is that surface brightening results from scouring and smoothing by exhaust gases, and exposure of fresh regolith material.

Uncertainty regarding the consequences of a rocket engine's plume interaction with a landing surface is a fundamental challenge posed by extraterrestrial vehicle landings. Prior research has established that a vehicle's landing thrusters can undermine the stability of the landing surface, putting the exploration vehicle at risk of an off-nominal landing or an altogether mission loss - this is known as "the plume problem." Analysis and experimentation have yielded several categories of design solutions to the plume problem through various treatments or configurations of the surface to create a landing pad using in situ materials. In support of research to enable missions to other celestial bodies, the authors have developed the Plume Impingement Test Bed (PITB) to provide a means of i) gathering data relating to plume effects upon prepared and unprepared soil media and ii) evaluating the effectiveness of design solutions to the plume problem. The PITB provides a terrestrial means of evaluating realistic plume effects by incorporating a flight-rated reusable launch vehicle (RLV), equipped with a liquid-propellant rocket engine. The PITB combines a Masten Space Systems, Inc. (Masten) vertical take-off and vertical landing (VTVL) RLV with a suite of instruments and a procedural framework to gather data and characterize the effects of a plume's interaction with a surface. The PITB is well-equipped to evaluate landing surfaces that have been prepared using robotic or other experimental methods to stabilize a surface for use as a landing pad. In operation, the instrumentation suite is deployed at a test site, calibrated and then the test surface is exposed to the VTVL RLV rocket plume. This paper will describe the design, operations and capabilities of the PITB.

Recent space missions to asteroids are providing new insights on regolith layers, which seem to be ubiquitous on their surfaces. They result from successive meteoritic impacts and present a huge variety of properties, corresponding to the huge variety in gravity, structure, composition and impact history on these atmosphere-less bodies. Complementary remote observations of the light scattering properties of numerous asteroids (which depend only upon the phase angle and the wavelength of observations, and upon the properties of their surface and sub-surface), give clues to regoliths' average composition and size through experimental simulations, including measurements on samples of selected powdered meteorites. The preparation of missions to near-Earth asteroids, together with experiments on board the ISS, should provide a better understanding in the coming years.

During lunar exploration, regolith is both the major available resource and a substantial obstacle in establishing a long term presence. The fine surface dust is highly abrasive and can both be a health hazard for the crew and the main contributor to equipment failure. On the other hand, regolith is the only material readily available to build protective shelters, stabilize slopes, form roads or engineer landing pads. To achieve this, methods had to be developed to convert regolith into a stable building material with minimal need for terrestrial supplies The approach described in this paper uses urethane resins to produce concrete-like materials on the lunar surface from minimal earth-supplied materials. The binder had to be capable of wetting regolith material both for optimal consolidation into bricks and to allow spray application for road formation. At the same time the resin had to have a very low vapor pressure to avoid contamination of the environment via outgassing. The program optimized a urethane formulation capable of penetrating and binding dense lunar surface particles under conditions consistent with the lunar surface. The urethane was capable of agglomerating lunar surface material into densely packed blocks capable of acting as a building material at a 20:1 regolith to binder ratio. The blocks were sufficiently strong to act as structural members of a habitat designed to shield inhabitants from dangerous solar radiation events. The blocks were tested for mechanical stress to ensure that their strength would not preclude their use in wall and habitat construction. Compression strength values of over 1000 psi were achieved. A prototype brickmaker to fabricate building blocks without exposure of personnel or moving parts to the mixed resin was designed and built, along with an automated spray system for surface stabilization.

In this work, we show how high resolution imaging coupled with a novel physics-based computational framework can provide a rich description of regolith-structure interactions, using the rover mobility in soft soil as a challenging canonical problem. The images of soil deformation under a rolling wheel were collected at 7 Hz resolution in time and 0.19 mm per pixel in space, with the camera approximately following the wheel motion. The soil under the wheel is a lunar simulant GRC-1. Image correlation (optical flow) was used to infer material velocities, i.e. regolith kinematics, at near-grain scale. From this data, strains can be calculated during post-processing, but stresses are beyond the reach of experimental measurements. Here we present a method to infer material stresses under the rolling wheel using a multiscale framework with a simple Drucker-Prager material description. From a purely computational standpoint, this mobility problem is extremely challenging involving wheel-regolith contact and interacting localization bands on the material scale, as indicated by the experiments. Capturing these features with the correct constitutive description is at the very cutting edge of computational research today. We bypass some of the aforementioned difficulties by inferring from experimental images a key plastic internal variable, the dilatancy, which is known to control strength and softening in dilative granular materials, and use its evolution directly in multi-scale computations. The method successfully marries experiments and computations in order to quantify material stresses under the wheel, which at present are beyond the reach of either method alone. From a practical standpoint, an understanding of the material stress state is helpful for several reasons, perhaps the chief of which is that stress distributions serve as input into reduced-order mobility models, e.g. Bekker-Wong terramechanics expressions.

Time and rate effects play an important role in processing of granular materials. It is a known phenomenon that granular soils (sand, gravel) subjected to dynamic in situ compaction exhibit a delayed increase in cone penetration resistance. A hypothesis is suggested that this time-dependent effect is caused by the stress corrosion cracking of the micro-morphologic features on grain surfaces at the contacts between the grains. Lunar regolith is likely to be strongly affected by this phenomenon, as regolith grains have rich surface morphology due to absence of water and atmosphere in lunar environment.

Granular media (GM) present locomotor challenges for terrestrial and extraterrestrial devices because they can flow and solidify in response to localized intrusion of wheels, limbs, and bodies. While the development of airplanes and submarines is aided by understanding of hydrodynamics, fundamental theory does not yet exist to describe the complex interactions of locomotors with GM. In this paper, we use experimental, computational, and theoretical approaches to develop a terramechanics for bio-inspired locomotion in granular environments. We use a fluidized bed to prepare GM with a desired global packing fraction, and use empirical force measurements and the Discrete Element Method (DEM) to elucidate interaction mechanics during locomotion-relevant intrusions in GM such as vertical penetration and horizontal drag. We develop a resistive force theory (RFT) to account for more complex intrusions. We use these force models to understand the locomotor performance of two bio-inspired robots moving on and within GM.

NASA is interested in designing a spacecraft capable of visiting a Near Earth Object (NEO), performing experiments, and then returning safely. Certain periods of this mission will require the spacecraft to remain stationary relative to the NEO. Due to the low gravity, such situations require an anchoring mechanism that is compact, easy to deploy and upon mission completion, easily removed. In the proposed approach, using Chrono::Engine (Tasora 2008; Negrut, Tasora et al. 2011; SBEL 2011), a simulation package capable of utilizing massively parallel GPU hardware, extensive validation experiments will first be performed. A set of parametric studies will concentrate on the simulation of the anchoring system. The outcome of this effort will be a systematic study that considers several different anchor designs, along with a recommendation on which anchor design is better suited to the task of anchoring. The anchors will be tested against a range of parameters relating to soil, environment and anchor penetration angles/velocities on a NEO to better understand their performance characteristics.

In the summer of 2011, we used three geotechnical instruments to assess the ground conditions in planetary analog sites on the Devon Island, Canadian High Arctic. The instruments included Percussive Cone Penetrometer (PCP) developed by Honeybee Robotics, and the two off the shelf instruments: Dynamic Cone Penetrometer (DCP), and the Static Cone Penetrometer (SCP). The three systems differed by the methods the rod was driven into the soil. SCP used a reaction force provided by the operator to drive the rod into the ground, the DCP used a drop hammer, and PCP used a high frequency hammer (percussive) system. The three instruments were evaluated based on their ability to be used by astronauts and be deployed autonomously on planetary robotic platforms (e.g. rovers, hoppers). The SCP, although simple to operate, was limited to soft soils and its data was unreliable. DCP required two people to operate, was heavy, and though the data was reliable, it took a few minutes to obtain it. The PCP has proven to be very reliable, fast, and the data was obtained and plotted in real time. Hence, PCP is recommended as the optimum geotechnical tool for planetary exploration for either a robotic system or an astronaut. The tests were performed at the Drill Hill site within the Haughton Crater. The site was covered by the polygonal features, the telltale signs of water activity (freeze-thaw cycle) beneath the surface. The measurements were taken at the polygons junctions, sides, and the center. It was found the polygon junctions are the weakest, followed by polygon sides, and finally polygon centers (the strongest). The depth to ground ice at these three locations was 65 cm in each case.

Outer space contains a vast amount of resources that offer virtually unlimited wealth to the humans that can access and use them for commercial purposes. One of the key technologies for harvesting these resources is robotic mining of regolith, minerals, ices and metals. The harsh environment and vast distances create challenges that are handled best by robotic machines working in collaboration with human explorers. Humans will benefit from the resources that will be mined by robots. They will visit outposts and mining camps as required for exploration, commerce and scientific research, but a continuous presence is most likely to be provided by robotic mining machines that are remotely controlled by humans. There have been a variety of extra-terrestrial robotic mining concepts proposed over the last 40 years and this paper will attempt to summarize and review concepts in the public domain (government, industry and academia) to serve as an informational resource for future mining robot developers and operators. The challenges associated with these concepts will be discussed and feasibility will be assessed. Future needs associated with commercial efforts will also be investigated.

In order to accurately model thermal distributions created during coring or drilling into rock or soil formations on solar system bodies, the roles of heat transfer via convection need to be investigated. An understanding of thermal distributions is necessary in order to protect the scientific content of samples, as well as to prevent sublimation of any ice present in the formation. Sublimated water may deposit ice onto cooler areas of the bit, causing the bit to become permanently stuck in its borehole. Three primary sources of convection are discussed herein, namely, increased heat transfer caused by drill-generated heat convecting from the surface of the formation, the "propeller" action of a bit's auger flutes drawing air into a permeable rock and out through the borehole, and pressure waves caused by any recoil of a percussive bit while sampling a permeable rock. An experiment was conducted to test the role of the rotating auger flutes in generating air currents. Surface convection was calculated to remove about 0.71% of heat generated by sample acquisition processes from the surface of a rock in fast wind gusts on Mars. The auger flutes were shown experimentally to be ineffective at driving convective currents because air flow in the borehole was found to be purely rotational with no axial component. At the borehole, even large bit recoils of 1.0 mm were calculated to drive flows of only 4.5 mm/s on Mars in permeable formations with large permeability of κ = 10^-10 m².

This is a part of a research program at McGill University, employing microwave assisted rock breaking system as an alternative to the explosive fragmentation. Given the fact that microwave radiation can reduce the strength of rock, a combination of microwave and mechanical rock breaking methods can potentially contribute in better and efficient mechanical breaking of hard rock. Microwave-assisted method can be used in mechanical breaking machinery such as full face tunnel boring machines and space excavators for rock sampling in space exploration missions. An experimental investigation of fracture toughness of basalt specimens under microwave illumination (BSUI) was carried out. Approximately 100 semi-circular basalt specimens with 50 mm diameter and 15 mm thickness were exposed to microwave radiations for 5 to 30 seconds at power level of 1000-5000 watts. Fracture toughness BSUIs were measured employing Semi-circular Bending Method (SCB) and compared with those of untreated samples. Note that terrestrial basalts have close chemical composition and physical property similarity to lunar and Martian rocks. Petrographic standard test has been employed to investigate the effect of micro-structural characteristics of BSUI on microwave susceptibility, thermo-mechanical cracks development in differential mineral phases. Such micro-structural characteristics include mineralogy proportion, grain size, pre-existing crack shapes, and pre-existing crack sizes. This study shows that although both power level and exposure duration lead to fracture toughness reduction and increase of fracture density; however, applying higher powers in shorter durations causes more fracture density and fracture toughness reduction. Given that heating rate of absorbent mineral dependent upon applied power and sudden expansion of neighbouring mineral due to the higher heating rate increases more grain bonds breaking and develops more micro crack in illuminated rock.

The multi-sleeve friction penetration system is an in-situ testing device that is derived from the well established cone penetration test. It incorporates a series of friction sleeves with varying surface texture in addition to the standard smooth friction sleeve located directly beneath the tip. The multiple measurements made with this device allow it to provide new insight into soil type and stratigraphic variations as well as in-situ shear strengths as a function of sleeve texture height. This paper describes a next generation version of this device that incorporates torsional load sensing capabilities in addition to the standard axial load sensing capabilities. In this manner, the effects of different vertical and horizontal stress states on measured sleeve stresses can be explored. This device offers significant benefits as an alternative to the portable bevameter, which was used in the past to measure the mechanical response of lunar soils under normal and shear loading conditions that were likely to be imposed by various wheel and track systems.

The idea of utilizing lunar lava tubes for habitation is not new. Most of the scientific and popular literature on the subject focuses on benefits of their extremely favorable environmental conditions, the savings of energy and mass in construction, and concepts for habitable structures and enabling habitation technologies if a base were to be located inside a lava tube. However, prior to any construction or emplacement of infrastructure, reconnaissance and site characterization must occur. Defining a mission planning architecture for exploration missions of robotic and/or human first contact with recently discovered entrances to potential lunar lava tubes is discussed. The paper presents a framework for developing reference mission architectures in order to assess candidate technology elements of reconnaissance missions to a lunar lava tube. The overall goal is to get some understanding of first robotic and human contact with a lunar lava tube for developing associated technologies needed to support these activities, including techniques of entering and examining them robotically and by astronauts. We investigate operational scenarios, technologies, and human and robotic performance feats associated with the first missions of planetary cave exploration.

The continued study of the history and expansion of the universe using radio telescopes has prompted a project to observe baryon acoustic oscillations by capturing neutral hydrogen gas as redshifted 21-cm radiation. This project, named Canadian Hydrogen Intensity Mapping Experiment (CHIME), will consist of 2500 radio antennas arranged in rows within cylindrical reflectors based out of Penticton, BC, Canada. To assist in the phase calibration of CHIME's instruments, the UBC ORBIT student club participating in the Geocentrix Technologies' first annual Canadian Satellite Design Challenge, has proposed a project which will send a repeatable set of up-chirped pulses (450-800MHz) from a specialized antenna that serves as the payload to a nano-satellite. Several mechanical, electrical and operational challenges exist due to critical dimension constraints of a three unit cube sat, low cost budget, low power requirements, low frequencies and large range of frequencies being emitted by the payload. This paper presents an effective design for a payload for the phase calibration of CHIME based double element Planar Inverted Cone (diPICA) with oval cut-outs. Details about Canada's first nano-satellite competition, the Canadian Satellite Design Challenge, will also be provided.

A semi-intelligent excavation mechanism was developed for use with the NASA-built Centaur 2 rover prototype. The excavator features a continuously rotatable large bucket supported between two parallel arms, both of which share a single pivot axis near the excavator base attached to the rover. The excavator is designed to simulate the collection of regolith, such as on the Moon, and to dump the collected soil into a hopper up to one meter tall for processing to extract oxygen. Because the vehicle can be autonomous and the terrain is generally unknown, there is risk of damaging equipment or using excessive power when attempting to extract soil from dense or rocky terrain. To minimize these risks, it is critical for the rover to sense the digging forces and adjust accordingly. It is also important to understand the digging capabilities and limitations of the excavator. This paper discusses the implementation of multiple strain gages as an embedded force measurement system in the excavator's arms. These strain gages can accurately measure and resolve multi-axial forces on the excavator. In order to validate these sensors and characterize the load capabilities, a series of controlled excavation tests were performed at Glenn Research Center with the excavator at various depths and cut angles while supported by a six axis load cell. The results of these tests are both compared to a force estimation model and used for calibration of the embedded strain gages. In addition, excavation forces generated using two different types of bucket edge (straight vs. with teeth) were compared.

NASA exploration missions are increasingly including sampling tasks but with the growth in engineering experience (particularly, Phoenix Scout and MSL) it is now very much recognized that planetary drilling poses many challenges. The difficulties grow significantly with the hardness of sampled material, the depth of drilling and the harshness of the environmental conditions. To address the requirements for samplers that could be operated at the conditions of the various bodies in the solar system, a number of piezoelectric actuated drills and corers were developed by the Advanced Technologies Group of JPL. The basic configuration that was conceived in 1998 is known as the Ultrasonic/Sonic Driller/Corer (USDC), and it operates as a percussive mechanism. This drill requires as low preload as 10N (important for operation at low gravity) allowing to operate with as low-mass device as 400g, use an average power as low as 2-3W and drill rocks as hard as basalt. A key feature of this drilling mechanism is the use of a free-mass to convert the ultrasonic vibrations generated by piezoelectric stack to sonic impacts on the bit. Using the versatile capabilities of the USDC led to the development of many configurations and device sizes. Significant improvement of the penetration rate was achieved by augmenting the hammering action by rotation and use of a fluted bit to remove cuttings. To reach meters deep in ice a wireline drill was developed called the Ultrasonic/Sonic Gopher and it was demonstrated in 2005 to penetrate about 2-m deep at Antarctica. Jointly with Honeybee Robotics, this mechanism is currently being modified to incorporate rotation and inchworm operation forming Auto-Gopher to reach meters deep in rocks. To take advantage of the ability of piezoelectric actuators to operate over a wide temperatures range, piezoelectric actuated drills were developed and demonstrated to operate at as cold as -200°C and as hot as 500°C. In this paper, the developed mechanisms will be reviewed and discussed including the configurations, capabilities, and challenges.

To realize reliable regolith sampling for autonomous operation in space, we are developing a new sampling system that employs electrostatic force. This system employs a combination of electrostatic capture and transport of particles. High voltage is applied between parallel screen electrodes of the sampling device. Owing to electrostatic force, particles are captured at the screen electrode of the device. The captured particles are then transported by an electrostatic traveling wave and transferred to a collection capsule. Because gravity is extremely low on small asteroids, the process of sampling particles on asteroids will be easier than that on the Earth. Particles of varying sizes will be transported by some transport conveyers with different pitches of the electrodes because the particle size that can be transported by this device depends on the pitch between the transport electrodes.

The quadrupole mass spectrometer (QMS) has over 30 years of spaceflight heritage in making important neutral gas and low energy ion observations. Given their geometrical constraints, these instruments are currently operated at the extreme limit of their capabilities. However, a technique called higher order auxiliary excitation provides a set of novel, robust, electronics-based solutions for improving the performance of these sensors. By driving the quadrupole rods with an additional frequency nearly twice that of the normal RF operating frequency, substantially increased abundance sensitivity, maximum attainable mass resolution, and peak stability can be achieved through operation of voltage scan lines through the center of formed upper stability islands. Such improvements are modeled using numerical simulations of ion trajectories in a quadrupole field with and without applied higher order auxiliary excitation. When compared to a traditional QMS with a mass range up to 500Da, sensors can be designed with the same precision electronics to have expected mass ranges beyond 1500Da with a power increase of less than twice that of its heritage implementations.

Impact-induced excavation is one of the few methods available that allows remote measurement of planetary subsurfaces. During a hypervelocity impact event on a planetary body, strong shockwaves and subsequent rarefaction waves set material in motion, excavating and ejecting a portion of the target up and out of the crater to expose fresh material from below. While fresh ejecta patterns and steep slopes of craters from natural impacts have long been used to infer properties of the subsurface, recent planned artificial impacts, such as the Deep Impact and LCROSS missions, have demonstrated the utility in observing and measuring the ejecta during the impact event. Measurements from instruments capturing the in-flight ejecta dynamics, such as cameras, spectrometers, and thermal radiometers, can expose volatiles hidden in the subsurface, characterize material properties, and constrain the provenance of the excavated material. In order to interpret the measurements, the mass-velocity distribution of ejected material must be understood. In this study, we present new experimental measurements of the ejecta distribution and crater growth from early- to main-stage flow for hypervelocity impacts at the NASA Ames Vertical Gun Range. These new data are used to estimate and compare the ejecta yield from LCROSS and a hypothetical cubesat impact mission, and demonstrate the ability to characterize the subsurface by analysis of the ejected material.

The maximal dependence on In-Situ lunar resources is essential for the establishing and sustaining a future lunar base. One key need of such an enterprise is a reliable source of energy to power the many needed equipment and devices. This paper presents an effort to study the effectiveness of lunar regolith as an ISRU medium to store thermal energy for use during the lunar night. The goal of the work was to compare the thermal properties of an Australian Lunar Simulant (ALS-1) with other materials and lunar regolith. For this, ALS-1 was sintered in an electric furnace to determine the Specific Heat Capacity (Cp) of the fused material. The resulting sample properties were evaluated with reference to thermal energy storage. The initial experimental results suggest that fusing the abundant fines of the basaltic lunar regolith creates a material that has an efficient capacity to store thermal energy. Factors that enhance its effectiveness are: a) vacuum (considered another ISRU), b) simplicity of installation and operation, and c) expandability of capacity.

The Mars Science Laboratory mission delivers the Curiosity rover to the surface of Mars in August 2012 to assess whether its Gale Crater field site ever was capable of supporting microbial life and preserving a record of life and past environmental conditions. The 150-km crater is one of many near Mars' dichotomy boundary in various states of exhumation as a result of massive regional deposition and erosion. The primary target for Curiosity is the 5-km high mound of stratified materials in the crater's center. Systematic variations in mineralogy and morphology through the section indicate that the sediments have witnessed major changes in regional, if not planetary processes. The Curiosity rover is designed to be robotic field geologist, as previous rovers, and a mobile geochemical laboratory. It is an integrated platform for exploration, monitoring, close inspection, and geochemical sample analysis. The latter capability drives the size and complexity of the rover by requiring a sample acquisition, processing, and analysis system consisting of a 2-m robot arm, rotary percussion drill, scoop, sieves and portioning tools, and the analytical instruments themselves. The rover will explore the region near Gale Crater for at least two Earth years, analyzing dozens of samples of Martian rock and soil.

Future exploration of Saturn's moon Titan can be carried out by airships. Several lighterthan- atmosphere gas airships and passive drifting heated-atmosphere balloon designs have been studied, but a heated-atmosphere airship could combine the best characteristics of both. This work analyses the thermal design of such a heated-atmosphere vehicle, and compares the result with a lighter-than-atmosphere (hydrogen) airship design. A design tool was created to enable iteration through different design parameters of a heatedatmosphere airship (diameter, number of layers, and insulating gas pocket thicknesses) and evaluate the feasibility of the resulting airship. A baseline heated-atmosphere airship was designed to have a diameter of 6 m (outer diameter of 6.2 m), 3 layers of material, and an insulating gas pocket thickness of 0.05 m between each layer. The heatedatmosphere airship has a mass of 161.9 kg. A similar mission making use of a hydrogenfilled airship would require a diameter of 4.3 m and a mass of about 200 kg. For a longduration mission, the heated-atmosphere airship appears better suited. However, for a mission lifetime under 180 days, the less complex hydrogen airship would likely be a better option.

During the 2011 summer field campaign of the NASA Haughton-Mars Project at the Haughton impact crater site on Devon Island in the high Arctic, field tests were conducted of the use of a robotic arm system integrated to Humvees serving as analog pressurized vehicles for the human exploration of near-Earth asteroids, the Moon, and Mars. The goal of these field tests was to begin assessing how field geology, including sample acquisition, might in some cases be conducted effectively from the confines of a pressurized vehicle (in intra-vehicular or IVA mode) without the crew having to always go out on EVA. Preliminary findings suggest that, particularly at sites where rocks and soils available for sampling occur mostly as loose rubble or "float" (as with planetary regoliths), the use of a robotic arm can allow efficient collection and characterization of high quality samples. An important implication of the finding for future space exploration architecture development, if confirmed through further field tests, is that the number and frequency of EVAs needed for sample acquisition during planetary vehicular traverses might be reduced from current assumptions. Wear and tear on EVA suit and suit-port systems, mission operations complexity, crew exposure to space radiation, and planetary protection concerns, might all be significantly reduced if robotic-arm assisted sample acquisition in IVA mode became available as an effective option for science operations.

We have tested a portable mass spectrometer (MS) system, the Mini 10.5, for in situ applications, including the analysis of volatile organic hydrocarbons (VOC's) and water soluble organic components extracted from solid material using an wet-chemistry automated sample processing system (WASP). By doing so, we intend to demonstrate the utility of in situ analysis compared to sample acquisition and return for analysis on future robotic space missions.

Incorporation of In-Situ Resource Utilization (ISRU) and the production of mission critical consumables for 9 propulsion, power, and life support into mission architectures can greatly reduce the mass, cost, and risk of missions 10 leading to a sustainable and affordable approach to human exploration beyond Earth. ISRU and its products can 11 also greatly affect how other exploration systems are developed, including determining which technologies are 12 important or enabling. While the concept of lunar ISRU has existed for over 40 years, the technologies and systems 13 had not progressed much past simple laboratory proof-of-concept tests. With the release of the Vision for Space 14 Exploration in 2004 with the goal of harnessing the Moon's resources, NASA initiated the ISRU Project in the 15 Exploration Technology Development Program (ETDP) to develop the technologies and systems needed to meet 16 this goal. In the five years of work in the ISRU Project, significant advancements and accomplishments occurred in 17 several important areas of lunar ISRU. Also, two analog field tests held in Hawaii in 2008 and 2010 demonstrated 18 all the steps in ISRU capabilities required along with the integration of ISRU products and hardware with 19 propulsion, power, and cryogenic storage systems. This paper will review the scope of the ISRU Project in the 20 ETDP, ISRU incorporation and development strategies utilized by the ISRU Project, and ISRU development and 21 test accomplishments over the five years of funded project activity.

Volatile solids occur naturally on most planetary bodies including the Moon, Mars, asteroids and comets. Carbon dioxide and water ices have been detected remotely at the poles or in permanently shadowed craters on Mars and on the Moon. Comets consist mostly of ice (>85% of mass), and some asteroids also contain solid ices in various amounts. In the outer Solar System, moons of the giant planets host the same resources; Ganymede, Europa and Callisto are composed of silicate rock and water ice to varying degrees, and the Cassini-Huygens probe has revealed methane snow and water ice crusts on Titan. We investigate the concept of sublimating these ices and minerals to form gases where favorable environmental conditions prevail on many bodies in the Solar System. The applications offered by this resource sublimation concept range from powering surface systems during planetary missions to deflecting Near Earth Objects (NEO) threatening our planet by in-space propulsion.

One of the recent issues for lunar exploration is finding a spot which has abundant amount of Moon ice and characterizing it. This is essential for future lunar outpost site selection. Orbital remote sensing is one way for prospecting Moon ice, this could provide variable information of global location. However, there is a limit of remote sensing as it cannot perform subsurface investigation and we cannot know which is actually over there before we touch it or feel it. Thus, developing a rover which could explore inside the crater is required for the Moon ice prospecting inside the Permanent Shadow Region (PSR). This paper presents the new approach to travel steep slopes through lunar anchoring supported rover tested on lunar similar environment. These are preliminary work in designing and testing a locomotion system offering high agility and tractions for the Extreme Rough Terrain Exploration Rover (ERTER). Results of the first locomotion tests will be presented during the Earth & Space 2012 conference.

A novel experimentation and analysis technique has been developed to enable detailed investigation of robot interactions with granular regolith. This technique, the Shear Interface Imaging Analysis Tool, provides visualization and analysis capability of soil shearing and flow as it is influenced by a wheel or excavation tool. The method places an implement (wheel, excavation bucket, etc.) in granular soil up against a transparent sidewall. During controlled motion of the implement, images are taken of the sub-surface soil, and are processed with optical flow software. Analysis of the resulting displacement field identifies clusters of soil motion and shear interfaces. The Shear Interface Imaging Analysis Tool enables analysis of robot-soil interactions in richer detail than possible before. Prior art relied on long-exposure images that provided only qualitative insight, while the new processing technique identifies sub-millimeter gradations in motion and can do so even for high frequency changes in motion (several Hz). Results are presented for various wheel types and locomotion modes: small/large diameter, rigid/compliant, with/without grousers, and rolling/inching. Results are also presented for an excavation bucket horizontally cutting granular soil.

Excavation in low gravity environments produces a problematic force imbalance between soil shear strength and excavator body loads. The same body forces which normally overcome a soil's shear strength are insufficient in low gravity. Consequently, percussion is being researched as a means of reducing a soil's in situ shear strength. By applying percussion to the soil-tool interface during excavation the interlocking particle forces, soil dilatancy, within a dry granular soil are mitigated. As applied percussive frequency is increased there is an exponential decay in the excavation baseline draft force. In addition, the continuity of shear plane formation increases inhibiting a soil's ability to strain-harden. Given these outcomes, it is concluded that the effect of a soil's in situ relative density, in the context of dilatancy, is nullified.

We present details of a Precision Subsampling System (PSS) developed for surface exploration of Mars and other planetary bodies. The PSS combines a fine-scale solid powder extraction tool with sample collection, manipulation, and instrument analysis subsystems in a highly compact package. The system offers future landed missions the ability to selectively analyze heterogeneous surface sample composition on millimeter scales. Analysis of subsamples by mass spectrometry and other tools would then permit characterization of highly-localized chemical and mineralogical phases that could be key indicators of past or present habitability on Mars. Systematic measurements along a finely laminated sedimentary sequence would also lead to a greater understanding of surface formation processes. Following subsystem design and test, our breadboard PSS will undergo full end-to-end characterization at Mars ambient pressures using analog rock samples and integrated prototype spaceflight analytical instruments.

In this paper we will discuss a new mass-efficient and innovative way of protecting high-mass spacecraft during planetary Entry, Descent & Landing (EDL). Heat shields fabricated in situ can provide a thermal-protection system (TPS) for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from regolith materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Three regolith processing and manufacturing methods will be discussed: 1) oxygen & metal extraction ISRU processes produce glassy melts enriched in alumina and titania, processed to obtain variable density, high melting point and heat-resistance; 2) compression and sintering of the regolith yield low density materials; 3) in-situ derived high-temperature polymers created to bind regolith particles together, with a lower energy budget.

As part of a potential Mars Sample Return campaign NASA is studying a sample caching mission to Mars, with a possible 2018 launch opportunity. As such, a Sample Acquisition Tool (SAT) has been developed in support of the Integrated Mars Sample Acquisition and Handling (IMSAH) architecture as it relates to the proposed Mars Sample Return (MSR) campaign. The tool allows for core generation and capture directly into a sample tube. In doing so, the sample tube becomes the fundamental handling element within the IMSAH sample chain reducing the risk associated with sample contamination as well as the need to handle a sample of unknown geometry. The tool's functionality was verified utilizing a proposed rock test suite that encompasses a series of rock types that have been utilized in the past to qualify Martian surface sampling hardware. The corresponding results have shown the tool can effectively generate, fracture, and capture rock cores while maintaining torque margins of no less than 50% with an average power consumption of no greater than 90W and a tool mass of less than 6kg.

Rock and soil core samples are typically extracted using a rotary drill and a hollow coring bit. A core sample encapsulation technology was developed which uses a cylindrical sample sleeve made from heat shrink tubing material. The sleeve is placed into a coring bit which has film heaters and temperature sensors mounted on the inside wall. The device can be activated while the drill bit is still in the drill hole, thus preserving sample integrity before the core is even extracted. The cores would be further preserved by the addition of a heat shrink cap. A hermetic seal is created by heat welding the cap to the sleeve with a thin heating wire. Furthermore, with heaters and thermocouples inside a coring tool there is the opportunity to do significant in-situ science like the measurement of thermal diffusivity of rocks and soil. The feasibility of this technology was demonstrated through a trade study, thermal analysis and the fabrication of prototype hardware.

A rotary-sonic drilling system was designed, built, and tested at Earth and Martian atmospheric pressures and the performance was compared against that of rotary and rotary-percussive drills. The sonic drilling technique uses vibrations to create resonance in the drill string to improve drilling performance and assist with cuttings removal. Tests were performed using a full-faced drill bit to a depth of 1 meter. Data from these tests demonstrated improved drilling performance of rotary-sonic over rotary drilling. However, for these set of tests, the rotary-percussive drill out performed the rotary-sonic drilling technique. Future testing should be done to evaluate and compare the sonic drilling method to other methods for capturing cores and for reaching depths in the 10 meter range.

Harold Rosen, the decades-long technical leader of Hughes Space & Communications and pioneer of spinning satellite technology, has applied core architectural features of "dual-spin" satellites pioneered by him and his Hughes team in the 1960s to enable a novel spinning lander concept—a new spacecraft system architecture first presented to the solar-system exploration technical community at the 9th Low Cost Planetary Missions (LCPM) Conference in summer 2011. Properly scaled, his novel architecture can be applied to landing missions on virtually any hard body in the solar system, including Earth or even large human-made objects in space. This ASCE paper updates the earlier LCPM paper, providing further insight into how the mass-efficient, cost-effective spinning lander system designs can, for relatively low total mission costs, address mission objectives for planetary exploration, resource utilization and commercialization at various solar system destinations. Four separate U.S.-based mission study teams are currently assessing the applicability of this concept to various exploration, technology-demonstration and commercial program objectives, leading perhaps to one or more proposals in 2012 for mission-development funding.

This paper discusses results of finite element investigation of two different mechanisms to drive a drilling instrument designed for lunar exploration. The instrument consists of a hollow tubular rod, one end of which rests upon the substrate to be drilled and the other end is actuated upon by a powered mechanism. Two different mechanisms of driving the drill have been considered - (1) Impact hammer which can rebound after contact, and (2) Attached hammer which is actuated by, for example, piezoelectric mechanism, and there is no rebound of hammer. Deformable three dimensional finite element models were prepared in ABAQUS to investigate the above two cases. Three different models were studied, with two of them simulating a rebounding hammer while the third simulating an attached hammer. An initial velocity was assigned to the hammer for both cases to simulate impact. Propagation of axial stress and displacement waves resulting from the impact as well as their time histories were studied. It was observed that no rebound case has a higher stress magnitude as well as a larger frequency of stress fluctuation, which might translate to a higher drilling efficiency.

In recent years, unmanned planetary explorations have received a lot of attention in the world. Direct exploration missions to land softly and traverse on the surface of the moon or other planets have been studied and planned in the world. Japan has earnestly studied lunar lander-rover missions. In these missions, it is required to conduct in-situ analysis of geological samples and deploy devices for measurement and observation. Recently deep drillers or penetrating systems have been required to obtain deep data for subsurface exploration. In lunar or planetary missions, it is needed to excavate the regolith layer, which covers the lunar surface, in depth of several meters. This paper, describes lunar or planetary mission scenarios and scientific requirements. A detailed surface and subsurface exploration by a mobile explorer is presented. Then this paper proposes a worm-typed drilling robot which is maneuverable in regolith by peristaltic crawling and the developed earth auger. A new mechanism to move forward in the soil is described. A propulsion unit using dual pantographs with a large area of an expansion plate is developed. The drilling function is studied by analyses and some experiments. The experimental results show the feasibility of the proposed robot.

The MOSBE Team has developed a terrestrial field campaign to explore subsurface biological habitats under the Mojave Desert. This field campaign will not only help us understand terrestrial desert biology, but also will develop methodologies and strategies for future Mars missions that seek to find traces of life in the Martian subsurface. We have proposed to the ASTEP program to integrate a suite of field demonstrated instruments with a 20 m subsurface drill as a coherent unit, the Mojave Subsurface Bio-geochemistry Explorer. The ATK Space Modular Planetary Drill System (MPDS) requires no drilling fluid, which allows aseptic sampling, can penetrate lithic ground up to 20 meters of depth, and utilizes less than 100 W throughout the entire depth. The drill has been developed and demonstrated in field testing to a depth of 10 meters in Arizona, December 2002. In addition to caching a continuous core throughout the drilling depth, it also generates and caches cuttings and fines that are stratagraphically correlated with the core. As a core segment is brought to the surface, it will be analyzed for texture and structure by a color microscopic imager and for relevant chemistry and mineralogy with a UV fluorescence/Raman spectrometer (Bhartia et al., 2011). Organic and soluble ionic species will be identified through two instruments: a microcapillary electrophoresis, and a ion trap mass spectrometer that have been developed under PIDDP, ASTID and MIDP funding (Beegle et al. 2011).

This paper describes the results of a recent (July-August 2010 and July 2011) planetary surface traverse planning experiment. The purpose of this experiment was to gather data relevant to robotically repositioning surface assets used for planetary surface exploration. This is a scenario currently being considered for future human exploration missions to the Moon and Mars. The specific scenario selected was a robotic traverse on the lunar surface from an outpost at Shackleton Crater to the Malapert Massif. As these are exploration scenarios, the route will not have been previously traversed and the only pre-traverse data sets available will be remote (orbital) observations. Devon Island was selected as an analog location where a traverse route of significant length could be planned and then traveled. During the first half of 2010, a team of engineers and scientists who had never been to Devon Island used remote sensing data comparable to that which is likely to be available for the Malapert region (eg., 2-meter/pixel imagery, 10-meter interval topographic maps and associated digital elevation models, etc.) to plan a 17-kilometer (km) traverse. Surface-level imagery data was then gathered on-site that was provided to the planning team. This team then assessed whether the route was actually traversable or not. Lessons learned during the 2010 experiment were then used in a second experiment in 2011 for which a much longer traverse (85 km) was planned and additional surface-level imagery different from that gathered in 2010 was obtained for a comparative analysis. This paper will describe the route planning techniques used, the data sets available to the route planners and the lessons learned from the two traverses planned and carried out on Devon Island.

A novel small time scale model is proposed in this paper for the creep fatigue crack growth analysis. The proposed model is time-based formulation and does not need to transform the realistic loading history to cycles for fatigue analysis. The key idea is to formulate the instantaneous crack growth kinetics with respect to the crack tip opening displacement (CTOD). Creep deformation is included in the CTOD calculation and the effect of frequency/ hold time is intrinsicaly included in the proposed formulation. Crack growth under mechanical and thermal loadings can be directly calculated by the time domain integration according to the specified mechanical and thermal loading history. Various experimental data from the open literature for metals are used to validate the proposed method and a satisfactory agreement is observed.

Subway station in modern city is a densely populated area, and there is a great amount of population movement. Once an internal explosion happened in the subway station, it will result in a huge number of casualties. A finite element model of Shenyang single arch subway station with LS-DYNA software was set up in this paper to analyze personnel injuries of an internal explosion by numerical simulation method. The overpressure peak of different reference points from the source for an explosion shock wave had been analyzed, compared with the allowable criteria for personnel protection given in the USA DoD manual and the NATO standard, and the situation of personnel injuries had been obtained. In addition, the impact of the station entrance and staircase to personnel injuries were also considered in this paper. The numerical results in this paper can provide a reference for the casualties' assessment of blasting in subway station in the future.

In this paper, a shear connection bolt loosening damage detection technique for a steel-concrete composite girder based on the electromechanical impedance (EMI) measurement of piezoceramic sensors was proposed. A number of piezoelectric Lead Zirconate Titanate (PZT) patches were surface-bonded on the upper flange of the steel girder and the concrete slab and the corresponding EMI was measured by an impedance analyzer before and after the loosening of the connection bolts. Based on the impedance measurement, several overall statistics damage metrics including the root mean square deviation (RMSD), the mean absolute percentage deviation (MAPD) and the correlation coefficients deviation (CCD) were employed to compare the impedance spectra and to assess the presence of connection bolts. Results showed the impedance based damage metrics can be employed to detect the existence of bolt loosening of the concrete-steel composite girder. The proposed approaches have great potential to be applied in practice for the inaccessible interface performance monitoring of composite structures.

In this research, the self-healing phenomenon of cracked High Performance Fiber Reinforced Cementitious Composites [HPFRCC] with two types of deformed high strength steel fibers was investigated under various environmental conditions such as water submersion, sea water and oil water. HPFRCC for the verification of selfhealing capability were prepared following tensile test. Crack width was controlled by tensile test and then some specimens were fully pulled out in order to survey interfacial matrix damage. Morphology and the shape and size of precipitated particles in the cracks were examined by Digital 3D microscopy, SEM-EDS and TGDTA. 3D X-ray microtomography (Micro CT) has been also used for the healing process after put-out test. The results show that most of the cracks (below 50 μm) were fully filled by newly-formed hydration products in short term period when recured in water after cracking. And then, self-healing capability of HPFRCC was largely dependent on the crack width. From these results, it is considered that HPFRCC also has a high potential for self-healing capability in some underwater structures.

Bi-axial strength of woven composites is particularly important due to the use of such materials in pressure vessels. Pressure vessels typically have interconnecting fixtures, which often are secured by bolted connections. In this research, two cruciform bi-axial test specimens were developed with the aide of Finite Element Analysis (FEA) and tested in the tri-axial test facility located at the Air Force Research Lab (AFRL) Space Vehicles Directorate Kirtland Air Force Base, Albuquerque, NM. Tests results were then compared to specimens with a central hole to study the decrease in strength due to stress concentration at bolted connections. Two hole diameters were drilled into each of the two cruciform types; 6.33mm (0.25") and 3.175mm (0.125"). All specimens are thick cross-ply and quasi-isotropic, [(0/90)₄]_s and [(0/90)₄(45/-45)₄]_s, IM7/UF3352 woven carbon fiber specimens. Analysis of stress concentration and test results will be provided, that are not currently available in the literature.

In this article, total shrinkages of early-age concrete specimens, which formed by controlled permeability formwork (CPF) liner and normal formwork, were obtained by non-contact contractometer test, and the results show that shrinkage amounts before initial setting and swelling amounts can be distinguished. Compared with ordinary specimens whose water-binder ratio dosage varied from 0.50 to 0.35, total shrinkage of specimens poured by CPF liner reduced from 76 percent to 87 percent. The study also demonstrated that evident differences on shrinkage-reducing depend on water retention of CPF liner, which can contribute researchers to understand the shrinkage-reducing working mechanism and improve of CPF liner properties.

The buckling behavior has an important effect on the performance of a dome structure. The computational time for the buckling problem will significantly rise, if a complex structure with considerable nodes and elements is concerned. This study develops an efficient method for the elastic stability for dome structures having high-order symmetry properties. Based on group theory, the elastic stiffness matrix and the geometric stiffness matrix are expressed in symmetry-adapted coordinate systems and decomposed into many sub-matrices. Then the eigenvalue buckling problem associated with the matrices is decomposed into many independent problems with smaller dimensions. To describe the general procedure for the proposed technique using the symmetry method, analyses on the stability of several highly symmetric dome structures are carried out. The results are compared to the corresponding ones obtained by the conventional numerical methods and using ABAQUS, to validate the computational accuracy. We will also prove the proposed method is efficient, by comparing the computational efforts with those cost by the other methods.

Interface debonding can grow slowly within the FRP-to-concrete interface in aggressive environments, even though the energy release rate at the crack tip is only a fraction of the critical energy release rate of the interface. This slow debonding process is called environment-assisted subcritical debonding, which may be a dominant mechanism for the failure of the FRP-to-concrete interface under service loads in aggressive environments. By using wedge-driven testing, this study shows that aggressive environments can substantially increase the debonding growth rate along the epoxy-concrete interface. Fracture surface analysis suggests that the debonding mode can change from the cohesive failure within the concrete in critical debonding to the adhesive failure along the epoxy-concrete interface in subcritical debonding.

This study presents a combined experimental and finite element analysis of composite wood I-joists under torsion, cantilever buckling, and four-point bending. Wood I-joists are long, slender structural members designed for long-span joist and rafter applications. Theses members are composed of thin-walled webs with relatively low stiffness and relatively thick flanges. Due to the nature of the web, these beams will likely fail in buckling before ultimate load is reached. Recently at West Virginia University, a new structural wood composite panel has been developed using discarded veneer-mill residues (McGraw 2009). This unidirectional composite panel was manufactured with two specific geometries, a flat and a sinusoidal configuration with equivalent volumes, to be used as web material in prefabricated wood I-joists. The web panels were joined in length using a finger joining technique and a tongue-and-groove joint was used connect the web to the laminated veneer lumber (LVL) flanges. These beams were evaluated at two different depths, each with flat and sinusoidal webs. Three tests were performed to evaluate specific properties of these joists. First, these beams were tested in torsion to evaluate their stiffness and torsional response, following the procedure outlined in Davalos et al. (2009). An evaluation of the flexural-torsional buckling response was performed using a cantilever test as presented in Qiao et al. (2003). Finally, a four-point bending test was performed to determine the elastic moduli of the beams. A finite element analysis was performed for each of the different tests, showing good correlations.

Due to the efficiencies and lightweight, wood I-beams have been extensively used for long-span applications in civil engineering. Buckling is the most likely mode of failure before material failure. This paper presents an analytical approach based on energy method to characterize flexural-torsional (lateral) buckling of cantilever composite wood I-beams with sinusoidal web geometry. The accuracy of this analytical model is verified through good correlations with existing Finite Element and testing results for I-beams with flat and sinusoidal webs.

In order to investigate workability of fresh concrete quantitatively, a newly device for test online was invented to measure rheolgical parameters of concrete. The device consists of temperature measurement system, torque measurement system, driving system and human-computer interaction system. The working principle of this device is to adopt single-chip microcomputer auto-control system driving cross axis torquemeter operation by stepping motor and, total 6 classes different speeds of the corresponding rotating torque are obtained to calculate the rheological parameters of fresh concrete. Results of verifying test continuously with the device indicated that rheological characteristic of fresh concrete is similar to Bingham models and yield stress reduces linearly with increase of slumps, but relation between plastic viscosity and slumps is inexplicit. The device can be used to measure continuous rheological parameters for situ-pouring concrete expediently.

Tensile strain softening curve is very important in crack analysis for concrete structures. It can be obtained from direct axial test, but the test machine should have enough stiffness. Recently, inverse analysis approach is often used to evaluate softening characteristic parameters of concrete from bending test. It needs the shape assumption of the softening curve and the experimental value of crack tip opening displacement. Up to now, the curve of displacement with load including softening by tests is the basis to determine the parameters of concrete tensile strain for any method. There are three kinds of tests to determine concrete tensile strength. They are direct axial tension, bending tension and splitting tension. Because of the different stress distribution and the concrete softening behavior, the tensile strengths from the three kinds of test are significantly different. By assuming the softening curve to be linear or bilinear, a new method to determine the characteristic parameters is presented from a series of FEM analysis. Only two tensile strengths are required in this method, and no test including the softening behavior is needed. It is verified from the existing tests of literature.

The ability to fold and unfold large sensor structures in space using hinges is important for space-based sensor technology. Tape spring hinges have become common in deployable space structures due to their simplicity, repeatability and unique folding properties. The mechanical response of these hinges (i.e., momen-tcurvature, energy stored) is important for deployment accuracy, safety and low cost of the structure. Finite element software, Abaqus_TM, was employed to analyze the folding and unfolding properties of a hinge using multidirectional bending. Uniform tape springs require a higher moment to overcome the curvature of the cross section when they are folded. In order to flatten the moment-curvature response of tape springs, a length of the middle segment of the hinge was first flattened, thereby removing the initial curvature about the long axis of the hinge. With the middle segment flattened, the hinge was subjected to opposite-sense bending about the hinge's short axis (axis perpendicular to the length of the tape spring). In addition to providing the means to determine stress (and potential damage) during folding and unfolding, the study determined the optimum method of hinge folding.

Rehabilitating and retrofitting concrete structural members using externally bonded Fiber Reinforced Polymer (FRP) strips has been gaining steadily use in recent years because of its many advantages. An important design issue with significant performance and safety implications is the debonding of externally bonded FRP strips in flexural members, where the delamination is primarily due to Mode-II facture. Although extensive research has been conducted on Mode II fracture of CFRP-concrete interface, only limited studies are available on durability. This paper explores the long-term behavior of FRP-concrete interface under Mode II loading condition through a combined accelerated ageing test and a prediction model based on Arrhenius relation. Mode-II single shear test was adopted in the accelerated ageing test, where specimens were subjected simultaneously to two environmental conditioning effects: (1) immersed in deionized water varying from 0 to 13 weeks; and (2) controlled temperatures varying from 25°C to 60°C (77°F to 140°F) of samples while immersed in water. The Energy Release Rate (ERR) determined before and after conditioning was considered a measure of the durability performance of the specimens. Based on the short-term data from the accelerated aging test, a detailed procedure is developed using Arrhenius relation to predict the long-term performance of the CFRP-concrete interface. It can be concluded that the accelerated ageing test and the prediction procedure used in this study can be a useful tool to evaluate the durability of the CFRP-concrete interface.

Partial replacement of Portland cement by industrial by-products such as fly ash and silica fume (collectively known as mineral admixtures) in the normal concrete diverts the deposition of those by-products from landfills, reduces CO2 emissions, and produces durable and sustainable concrete. Shrinkage strain is a major parameter for concrete durability. No systematic data are available to predict the shrinkage of concrete containing mineral admixtures from paste properties to coupon level. In this study, composite modeling was developed from paste level to coupon level for 10 concrete mixtures containing fly ash, and, silica fume, individually as well as in combination, at two different w/cm ratios. Then a two-step composite model was used; firstly to find the shrinkage of mortar from the paste and then the range of the concrete shrinkages was determined using the shrinkage of the mortar and the Hashin-Shtrikman bounds (1963) with the corresponding elastic modulus. The prediction model agreed well with experimental data. The predicted shrinkages from the ACI 209R and CEB M90-99 were computed and the predicted model was found to be in close agreement with the experimental results.

This study presents a novel technique to grown CNTs on microfibers/fabrics, PopTube approach. In this technique, only a single chemical is used to provide both the carbon source and catalyst. Microwave is used to heat a conducting polymer to provide fast and energy-efficient heating source for CNTs' growth. It takes only 15-30 seconds to grow CNTs under the the microwave irradiation at room temperature in the air, with no need of any inert gas protection, and additional feed stock gases, typically required in chemical vapor deposition (CVD) approach. To the best of our knowledge, this is the fastest CNT growth, and probably the only approach that can be done in ambient condition. The PopTube approach requires very simple equipment, can be easily scaled up for large-scale manufacture, and is highly energy-efficient and cost-effective.

Bond behaviors of magnesium and potassium phosphate cement (MKPC) matrix with glass fiber bundle (GFB) were investigated through measuring pullout forces of GFB. Test results showed that, the self-made inorganic adhesive could permeate into glass fibrils well and rectified damage weakness possessed by fiber, pullout force of GFB which was dipped self-made inorganic adhesive added in some magnesium oxide (MgO) powders was greatly improved due to chemical reaction between MgO powders and phosphate in MKPC matrix. Fluidity of MKPC paste mixed proper water glass would be improved, and compressive strength of MKPC paste added in some fly ash would be reinforced, amorphous hydrates would increase in both of the concretion, the microstructure would be more compact and the pullout force of GFB was greatly improved as well. Minimum embedded length of GFB existed achieved its maximum pullout force which could guarantee the tension strength of GFB bonding with MKPC matrix reached maximum.

A preliminary analytical study was conducted to investigate the effects of cruciform test specimen geometries on strain distribution uniformity in the central gage section under biaxial loads. Three distinct specimen geometries were considered while varying the applied displacements in the two orthogonal directions. Two sets of woven fabric material properties found in literature were used to quantify the influence of specimen geometries on the resulting strain distributions. The uniformity of the strain distribution is quantified by taking the ratio between the two orthogonal strain components and characterizing its gradient across the central area of the gage section. The analysis results show that increasing the specimen's length relative to its width promotes a more uniform strain distribution in the central section of the cruciform test specimen under equibiaxial enforced tensile displacements. However, for the two sets of material properties used in this study, this trend did not necessary hold, when the enforced tensile displacements in the two orthogonal directions were not equal. Therefore, based on the current study, a tail length that is 1.5 times that of the tail width is recommended to be the baseline/initial specimen design.

In this study, a novel three-parameter viscoelastic foundation model has been developed to predict the long-term behaviors of FRP-strengthened reinforced concrete beams. Both the FRP plate and the RC beam are modeled as Timoshenko's beams connected through the adhesive layer, which is modeled as a three-parameter viscoelastic foundation using Standard Linear Solid model. Closed-form expressions of the time-dependent interface stresses and deflection of the beam are obtained using Laplace transform. The validation of this viscoelastic solution is verified by finite element analysis using a subroutine UMAT based on the Standard Linear Solid model.

The mechanical property of rock discontinuities is one of controlling factors of deformation, strength and stability of rock mass. Due to the limitation of available constitutive models for rock discontinuities within the framework of classical continuum mechanics, a new constitutive model for rock discontinuities is presented by taking use of the direct methodology based on the strength and deformation behaviors of rock discontinuities. In the presented model, the tangential stress and deformation curve and dilation curve are divided into linear part before peak point, nonlinear part before peak point, and softening part after peak point, and the mathematical models which can accurately characterize the major mechanical behaviors of rock dis-continuities are given. Based on the above-mentioned, the incremental constitutive model for rock discontinuities is developed. Then, a classical direct shear test of rock discontinuities are simulated by the developed model in this paper and the Plesha's model which is used widely, and the results show that the major mechanical behaviors of rock discontinuities can be reasonably described by the presented model, and the simulation ability of the presented model is better than the Plesha's model. In the last, through the combination of the proposed model and the joint element method, a new joint element is developed by using the user element subroutine interface UEL in ABAQUS. The correctness of the development of the subroutine is validated by a numerical test.

To reasonably evaluate the seismic safety of concrete dams,by introducing the ageing degradation function into dynamic damage constitutive model, a method which is used to evaluate the seismic safety of long-term operating concrete dams is proposed,the method can consider the effect of ageing of concrete on the safety assessment of the dam under earthquake load.The ageing damage model also is adopted to evaluate the 1ife of concrete dam.In order to illustrate the application of the model, examplification is given according to the model at the end of the paper.The results show that the effects of ageing damage on the dynamic response of the dam are significant under earthquake load. The nvestigations, in this paper, are not only important improvement for seismic safety evaluation method of oncrete dam, but also the solid foundations for further study on the seismic safety of inservice concrete dams.

A one-dimensional advective-dispersive equation is analytically solved to predict patterns of contaminant concentration distribution in a homogeneous and finite aquifer. The dispersion of solute along and against transient groundwater flow is considered. Initially the aquifer is assumed to be not clean, which means that some initial background concentration exists and it is represented by uniform concentration. A pulse-type exponentially decreasing temporally dependent source concentration is considered in the intermediate portion of the aquifer and at other end, the concentration gradient is supposed to be zero. The Laplace Transform Technique (LTT) is used to obtain the solution of the problem of contaminant distribution in two different domains. In fact, in one domain the distribution pattern is depicted along groundwater flow and in other domain, it is depicted against groundwater flow. This represents a realistic situation of the contaminant concentration distribution pattern in an aquifer in the presence or absence of temporally dependent source concentration. The time-varying velocity expressions are considered. The dispersion is directly proportional to the seepage velocity used in which the effect of molecular diffusion is not taken into account because the value of molecular diffusion does not vary significantly for different soil and contaminant behaviors. Results of the obtained analytical solution may form useful complements to benchmark numerical models or for their verification. The long-term vertical transport of solute during transient saturated groundwater flow can be described correctly with appropriate analytical models. It may also be used as a preliminary predictive tool for groundwater resource management to estimate transport parameters.

Considering the heavy rain conditions, the saturated - unsaturated flow field of Xin'an river dam's right bank after blocking is analyzed and foundation's uplift pressure of he right shoulder of the dam and variation of rock's water table are studied here to evaluate the practical effect of blocking the platform based on three-dimensional saturated-unsaturated seepage theory and its anti-analysis theory. The calculation and analysis results show that after the platform blocked, it effectively blocked surface infiltration of rainfall in this area and reduced the lateral supply from rainfall infiltration to the around rock and as well as improved the movement state of groundwater at right abutment slope which to a certain extent helped to reduce the dam foundation's uplift pressure. Therefore the conclusion can be drawn that the blocking of the platform has a positive effect on the dam's safety.

Regarding the different characteristics of the normal and the tangential of the construction interface, based on the material damage and the mechanical parameters, damage evolution equation is estabished by taking elastic modulus as damage variable on the normal direction. Further more, according to the creep process and properties on the tangential direction of the RCC, a tangential creep damage analysis model is selected and established, based on which, expression for the damage variable on the tangential direction of the RCC construction interface is proposed, thus the damage state of the construction interface can be determined. The example shows that these proposed models can simulate the creep damage characteristics of RCCD.

Due to the effect of extreme environments, concrete dams face emerging challenges. Effect of two typical extreme environments, earthquake and climate fluctuation, on concrete dam was studied. Analysis on the effect of earthquake on concrete dam, dealt mainly with seismic damage of Shapai and Tongkou hydropower stations to obtain characteristics of seismic damages, thereby, to propose measures for project rehabilitation. It is to increase our knowledge of objective laws for effect of earthquake on concrete dam and enhance capability against seismic risk. Taking the low temperature event of Xixi reservoir dam due to climate anomaly for example, the effect of climate anomaly on concrete dam was systematically studied. Through analyzing observational data of uplift pressure of the dam foundation, the conclusion that low temperature and increase of reservoir water level leaded to the increase in uplift pressure is drawled qualitatively. To further analysis of the relationship between uplift pressure coefficients and the changes of temperature or water level, the statistical regression model of uplift pressure coefficient was established. Then, the effect of low temperature and reservoir water level on the dam safety was analyzed qualitatively. The results show that in high water level conditions, extreme low temperatures resulting in a larger temperature difference will affect the safety operation of concrete dam.

Three reservoir models and the numerical schemes are given for the dynamic characteristic and response analysis of high arch dams. Combining with engineering practice, the effects of different reservoir models on dynamic characteristic of high arch dams are studied. The results show that both the dynamic response and the dynamic characteristics, such as natural frequency, mode and mode shapes, obtained from different reservoir models are quite different. From the view point of physics, the effects of reservoir on dynamic characteristic of high arch dams can be included well by the compressible model since the model reflects the actual performance of the water. Moreover, there is no much increase of calculation amount in computing following the proposed method. The compressible model is recommended for the dynamic characteristic analysis of high arch dams.

The rough set theory is applied to evaluate water conservancy project modernization. Rough sets theory is used to analyze the raw data. Based on discretization of the measured data, the significance of attributes among rough sets is estimated instead of weight determination, and a relation data model about water conservancy project modernization assessment is established. A knowledge system is built through making attribute value into eigenvalue. The weight of a water conservancy project modernization assessment model is computed by analyzing the information and significance of forecasting method for the predicted object. The proposed approach overcomes the subjectivity of traditional evaluating method, and improves the precision of assessment for water conservancy project modernization. At last, an example is given to show the effectivitv and rationality of this new method

Face slab dispatch often occurs when concrete faced rock-fill dam (CFRD) has undergone a large earthquake, such as the Wen Chuan earthquake in China. In this paper, an approach for face slab dispatch detection of CFRD based on measured nature frequency of face slab under varying water level is proposed. The principal component analysis (PCA) method is used to eliminate the effect of water level changes. The advantage of this method is that the actual relation between water level and nature frequency is not need to understand and only reference data of measured frequencies from face slab without dispatch and monitoring data of measured frequencies from face slab maybe with dispatch is necessary. Through PCA on the reference data, the number of principle component and a linear subspace in which environment variable (water level) effects lie is identified. Then the monitoring data from face slab maybe with dispatch is project to the linear subspace identified above and the residual error of this projection is calculated. By performing kernel density estimation (KDE) on the residual error of PCA, the upper control limits of it is calculated to judge whether dispatch occurred. In order to verify the feasibility of this method, the FEM of a face slab is made and the dispatch between face slab and cushion of a CFRD was stimulated by removing some springs between them. The impact of water level on nature frequency is simulated by some theoretical and empirical formulas. Three sets of computer-simulated data of nature frequencies are studied and the dispatch identification result shows the good performance of this method. Since the identification of nature frequency is more convenient and accurate than other modal parameters, this method has a good prospect to apply to practical engineering.

This paper presents a complete finite-element treatment for the coupled heat-fluid transfer problem with phase change in frozen soil. This paper applies the staggered solution to solve these nonlinear problems. Moreover, some improved methods are presented to overcome the spurious oscillations, misconvergence, and low convergence rates of the solutions. Numerical freezing simulations of the horizontal and vertical soil column are conducted, with experiments at sub-zero temperature to validate the numerical methods. Predicted values of temperature and total water content were close to the measured values. The methods presented here can effectively solve the spurious oscillations and misconvergence induced by the abrupt change of ice content and heat flux at the interface. The accelerated iterative method used here considerably reduces the iterated counts per time step.

Pairs of contact points were set along the possible developing path of the crack. The Mixed Freedom Finite Element Method proposed for contact problems was extended to implement the mechanics of concrete fracture numerical simulation by the Fictitious Crack Model. The system of forces acting on the structure was divided into two parts: external forces and contact forces. The displacement of structure was chosen as the basic variable and the nodal contact force in possible contact region under local coordinate system was chosen as the iterate variable, so that the nonlinear iteration process was only limited in the possible contact surface and much more economical. Firstly, the basic idea of the Mixed Freedom Finite Element Method was presented. And then, the softening constitutive relation for the concrete was introduced to the method. At last, the validity and accuracy of the proposed procedure was demonstrated by a numerical example.

Support vector machine (SVM) is an identification method using the largest classification margin between classes of the training samples as its classification criteria. The final value of decision function of general classified SVM only depends on the inner product in Hibert space after transformation of input parameters into higher dimensional space. In this paper, the decision function of SVM is used as the synthetic affect factor on slope stability, and the regression equation of the decision function and safety factor of the training samples is proposed to be utilized to predict the slope safety factor.

Through the presentation of Fujian Mianhuatan Dam safety monitoring system development principles, the independent program model like statistical model, not sure model and monitoring index which are similar with DLL format files were introduced. Then introduced the three principles of the development of independent program modules are described. By setting in the modules, data analysis and monitor index development of the measuring points to the dam monitoring system were achieved, it provides a basis for further analysis and diagnosis of the dam. At last, the module calculated results and the prediction accuracy were verified with different point monitoring data of Mianhuatan Gravity Dam in this article, and then provided a theoretical basis and experience for reference.

Local Scour is one of the key challenges for construction of bridge in deep water, especially, for bridge at the estuary of Yangtze River. The flow condition here is really complex due to rugged topography and evident tide influence. Local scour might deteriorate for the disturbance during construction of pile group and bearing platform. Thus, stability of riverbed becomes the most fundamental for the safety of pier foundation, including construction of temporary construction platform and installation of pile group. So, protection of riverbed soil is usually started before foundation of bridge. To study the real result, multi-beam echo sounder using ultrasonic is often adopted to periodically measure and mapping riverbed topography. But due to the effect of foundation, blind area often exists around the pier. At Sutong Bridge, vibrating wire piezometers using to continually monitoring local scour happened within and around pile group. Multi-beam Echo Sounder is using for the large-scale detection progress during and after construction, and the vibrating wire piezometers is using for the small-scale detection within and around the pier foundation soil. Special protection applied for the vibrating wire piezometers and its cable to avoid harm from torrent. The result shows: 1) Different scale detection systems, using vibrating wire piezometers and multi-beam echo sounder separately, can get enough and better information for the monitoring of local scour occur around pier. As an example, monitoring of riverbed protection at Sutong Bridge lead out the conclusion that protection does effect on riverbed and weaken the scour around pile group. 2) Special protection for the Vibrating Wire Piezometers and its cable is really needed.

Taking measured data of some reservoir rainfall Caused by typical Typhoon and environment variables of typical typhoon as a sample, the nonlinear analysis method is adopted to analyze the relationship between environmental factors of typhoon (including wind speed, wind power, wind circle radius of 7 level and 10 level, central pressure, the distance between typhoon center and the reservoir area, etc.) and reservoir rainfall. Then the form of mathematical representation of typhoon environmental factors and their effects are reduced and optimized. On this basis, the nonlinear analysis model of reservoir rainfall caused by typhoon is made up. Example analysis showed that the model reflects the nonlinear relationship between typhoon environment and reservoir rainfall caused by typhoon to certain extent, and has good fitting results.

A numerical model to simulate the distributions of the voltage, deformation, and hydraulic head in a laboratory electro-osmosis test was developed. The governing equations are derived based on the principles of charge and mass conservations, equation of momentum equilibrium, the Darcy's law and the Ohm's law. An electro-osmotic test combined with vacuum drainage was conducted on the marine sediment in laboratory. The test was simulated with the numerical model, in which the nonlinearity caused by soil-water characteristic and mechanical constitutive was taken into account. The calculated distributions of voltage, current, settlement, pore water pressure, and drainage rate were consistent with the measured ones obtained from the test, illustrating the good performance of the proposed numerical model. The experimental and the numerical results also indicate the effectiveness of the electro-osmotic treatment for weak clays.

The sluices play an important role in engineering, agriculture and social economic development and also occupy an important position in the river basins or city flood control and drought work. In combination with the characteristics of sluices in plain area, the influence on water discharge through sluice and discharge way of sluices were analyed in this article. An integrated operation control model for Sluice was established. Then the criterions including the water level up and down the sluice, the open orders of sluices and the number of open holes and open height of sluices were determined in the article. Their evaluation indexes are determined by the principle of which degree comes close and judged by experts. Finally the prediction results were came up through the fuzzy comprehensive evaluation and compared with the indexes of the safty degrees and the conclusion of operation control could be made by this method.

The importance of the selection of strength to concrete dam safety evaluation is first presented. We can get different results of safety evaluation according to different strength criterion. Stress analysis methods of concrete dam are briefly introduced. Concrete strength theory including uniaxial strength, biaxial strength and triaxial strength is summerized. According to different versions of concrete arch dam design standard, uniaxial strength, biaxial strength and triaxial strength criterion are applied to Xiluodu Arch Dam safety evaluation with subentry coefficient method and safety factor method. The results that have been analysed show that different strength criterion would give different safety degree. Compared with safety degree from multiaxial strength, safety degree from uniaxial strength is lower than multiaxial compressive stress states while higher than multiaxial tensile-compressive stress states. Besides, there is some differences between the safety degree in biaxial strength and triaxial strength. Furthermore, the results from subentry coefficient method and safety factor method are different because of different impacting factors considered. The necessity and recommendations of selecting reasonable strength on concrete dam safety evaluation are presented.

By the static strength reduction method, time history analysis method, dynamic strength reduction method based on numerical calculation, the static and dynamic stability of 2# potential sliding block in natural state and the reinforcement effect are researched, which is located at the left bank of Baihetan Hydropower Station in western China. As the static and dynamic stability of the block in natural state can not meet the requirement of design specification, two concrete replacement holes are arranged in the bottom sliding surface for reinforcement. Two simulation methods for concrete replacement holes are used for the research of reinforcement effect, i.e. equivalent area simulation and detail simulation. Mohr-Coulomb failure criterion is taken in the elastic-plastic calculation, and the static and dynamic safety factors after reinforcement are calculated. The results show that the static stability safety factor obtained by equivalent simulation is less than that by detail simulation, and the dynamic stability safety factor is slightly greater than that by detail simulation, and the safety factors by the two simulation method are overall similar with each other. According to the research results, the static and dynamic stability of 2# block after reinforcement can satisfy the requirement of the design specification, and it can be considered that the reinforcement plan is reasonable.

The Zhangkeng Reservoir is an earth dam with height of 26m, which has been reinforced for several times during the running period of about 50 years. Based on the field safety check and analysis of seepage observation data, the seepage field of the dam is inversed under the running water level by the finite element method (FEM), and the comprehensive seepage parameter of the dam material is obtained. By use of the finite element model adjusted by back analysis, the seepage fields under the normal water level, design flood water level and check flood water level are obtained by the steady seepage theory, and the distribution of piezometric head and penetration gradient of dam and its foundation are analyzed. It is shown that the maximum penetration gradient of dam body and its foundation are larger than their allowable penetration gradient. It is suggested that the anti-seepage system of the dam be reinforced for improving the seepage behavior of the dam.

Reverse-arch base slab, a particular kind of structure, was applied on several medium and large shiplocks during the 70s in the last century. The reverse-arch base slab can strikingly reduce investment outlay, however cracks can appear easily due to slab's bad adaptation to foundation's differential settlement. In order to assess the safety of Taiping Shiplock and provide technical support on reinforcement project, with non-linear finite element theory, recomputation of displacement and stress of Taiping Shiplock's reverse-arch base slabs under different conditions is done, and the cause of crack is analyzed.

A new algorithm for abutment safety analysis-dynamic contact strength reduction method is proposed for nonlinear dynamic contact problems considering the interaction between arch dam body and the abutment. Based on the traditional Finite Element time-schedule Strength Reduction Method, the abutment sliding bodies, foundation, arch dam body and reservoir water is taken as one system, which can be more accurate. According to the characteristics of local nonlinearity for this problem, the system of forces acting on the contactor is divided into two parts: external and contact. The displacements of contactor are chosen as the basic variable and the nodal contact forces in possible contact region are chosen as the iterate variable, so that the nonlinear iteration process is only limited in the possible contact surface. In this way, the sophisticated contact nonlinearity is shown by the variety of the contact forces, thus make the iteration easy and feasible.

Wuyue pumped storage power station will be built in Guangshan county, Henan province of China. The upper reservoir dam of the power station is a concrete face rockfill dam, which is more than 130m high. With complex arrangement, the axis of dam consists several straight lines and arc lines. Moreover, the geological condition of the foundation is very poor, and the topographic relief is terrible and irregular. With consideration of the engineering characteristics and geological conditions, the 3-D finite element model is built, including the dam body, the dam foundation and the backfill area of the reservoir. The dam filling and water storage process are simulated, and the stress and deformation analysis of the dam and the backfill area of the reservoir are taken both after the completion and during the operating period. Furthermore, the stress deformation distribution of the concrete face is studied in details, as well as the deformation distribution of the slab joints and peripheral joints. What's more, the rationality of the dam partition and the design parameters of the dam materials are demonstrated, and the optimization methods of the dam partition and connection slab are thus put forwards.

The method of adding a flexible anti-seepage layer is a way to solve the problem of cracks in upstream surfaces of arch dams. Spraying polyurea as anti-seepage layer has been used in several projects for the crack repairing in china. But there is no technique standard for checking the construction quality in using sprayed polyurea, such as requirements of thickness, material tensile strength, bonding strength, anti-seepage and wear resistance. Taking Xiluodu arch dam as an example, the test in-situ is done to check whether the main requirements for material behavior are reasonable and economic..

When the pseudo-static method is used to analyze the seismic stability of homogeneous soil slope, the earthquake load is computed on the basis of seismic coefficient figure of earth-rock dams according to Chinese standard for engineering slopes in water resources and hydropower projects. With a single free surface, the dynamic characteristic of a rock slope is significantly different from that of a shear wedge which is taken as the basis of earth-rock dams. With a great deal of FEM analysis by time-history method with viscoelastic artificial boundaries, the distribution law of seismic coefficients and its influence on the slope height, rock DEM, slope angle and foundation range in rock slope are concluded. The results are valuable on evaluation of slope stability, and can provide important reference in the pseudo-static method.

The stability safety factor against sliding at deep layer foundation of one gravity dam is analyzed by using the FEM Strengthen Reduction Method (Dawson, E. M., 1999). An evaluating criterion for both single and overall dam is established based on the intensity index of the foundation and weak structural surfaces whose material parameters are reduced through analyzing. For a single dam, the significant displacement change of the feature point at the dam crest is taken as the criterion to define the safety while its corresponding reduction factor regarded as the safety factor (Zhou Guiyun, 2006). Meanwhile, for the overall dam, its evaluating criterion is to find out the plastic zone that is about to run through the foundation (Luan Maotian, 2003), and the safety factor is the corresponding reduction factor of run-through state. The results indicate that the dam is safe under natural condition and safer under the reinforced condition.

The increasing number of super-high arch dam being built around the world demands accurate methodologies for the realistic evaluations of the working performance and dam safety. A regression model of dam horizontal displacements during construction and first impounding process is given. It takes into account relevant factors such as construction process, water level, temperature change and time component. Elastic modulus of concrete and rock materials are feedback based on the displacement caused by water level. The process of dam construction and first impounding is simulated based on feedback elastic modulus with the finite element method. Then the dam performance and safety are predicted and evaluated according to the simulation results. Xiaowan arch dam is studied as an example. The feedback elastic moduli are bigger than the design values. Radial displacement is mainly determined by water level and affected significantly by temperature change and time component. Results from the regression analysis and the simulation method are consistent well with monitoring data. Thus the performance of Xiaowan arch dam mainly including displacements, stresses, and safety in near future can be predicted with the proposed method.

To build a numerical model for simulation of crack propagation in concrete structure is of theoretical and practical significance. In this paper, theories of three dimensional (3D) Radial Point Interpolation Meshfree method (RPIM) are introduced. The method of coupling linear elastic fracture and discrete crack model with RPIM is studied in details. Then crack propagation in concrete is analyzed by this coupling method. Some typical problems in programming are studied. The result is testified by a three-point bending beam example.

In recent years, several concrete dams try a fast pouring method. To achieve the fast construction aim, thicker pouring layer or shorter interval is adopted. The fast pouring idea is introduced and then the layer thickness and pouring interval are analyzed. To reveal the temperature and stress safety of the fast pouring dam, numerical simulation is applied in a high roller compacted concrete dam. The layer of 3m, 4.5m and 6m are simulated and analyzed separately. The main disadvantage of thicker layer is more temperature difference between concrete inner and surface which will cause more surface tensile stress in early age. But the shortcoming can be overcome by reasonable combination of pouring temperature, pipe cooling and surface insulation. The temperature control measure and the corresponding norm have been applied in the actual construction. In the construction of past 2 years, nearly no crack appeared in the fast pouring concrete dam.

After operation of the reservoir some time, the sediment such as sand or soil will be deposited before the dam in the reservoir. It is important effect of the sediment on dynamic water pressure on the dam face and the response of concrete dam under earthquake. In the past, the absorption coefficient is employed to simulate the effect of the sediment by some researches. Moreover, the sediment is analyzed with elastic two-phase porous media by some authors. In the fact, the nonlinear of the sediment can be show under the seismic. In this paper, the system of the dam-foundation-water-sediment is built. In this system, the sediment is analyzed with the fluid-solid two-phase porous media and simulated with the nonlinear Pastor-Zienkiewicz model which is established on the general plastic theory, the water as compressible fluid, the dam and the foundation as elastic solid, the interaction between the different media is also considered. With this analyzing model, the effect of the nonlinear of the sediment on the concrete dam is researched. The result shows that the pore pressure in sediment is increased and the effective stress in sediment is reduced during earthquake and the liquefaction can be shown at the surface layer of sediment.

The crack of concrete structure is commonly aroused by temperature action during construction period. The base slab of the water gate is the important structure, and in this paper, non-steady temperature field and temperature creep stress field are researched. Temperature creep stress field has the influence on the strained condition of the base slab, and a conclusion is draw: temperature stress has certain influence on the base slab of the water gate. The temperature stress of the base slab is improved to a certain extent, if the concrete has additive.

To avoid the through cracks in the upper part of the gravity dam near the geometrical change of the downstream slope because of the whiplash effect, the high-position seismic isolation is proposed to reduce the dynamic response of dam head in this paper. The characteristics and principles of the high-position seismic isolation are introduced. Koyna Dam is taken as a test case and the dam-reservoir-foundation-seismic isolation cushion interaction model is established. The nonlinear time history analysis of the dam, with or without the isolation, is performed using ADINA program to compare the effect of the seismic isolation. The research result provides a new idea with the aseismic design of gravity dam.

Due to the 50km₂ wide one-time reclamation which has not yet occurred worldwidely, closing the closure gap became a key technology of constructing the Qing Cao Sha reservoir. Based on a large amount of scientific experiments, the design scheme is proposed and the key control process during construction organization as well, namely the site selection of closure gap, the technical routine of hydraulic design of 800m long single closure gap scheme, the innovation of protection structure, the closure scheme using section-steel frame cage for the first time, the hydraulic monitor during closing and the key technology during construction. And the success of such reclamation in deepwater would provide positive reference for other similar ultra-large closure gaps.

With the development of hydropower resources in water-rich karst areas in southwest of China, the success or failure of the construction of underground works will matters lots about the results of the entire process, and the key problems of the construction of underground projects is the water problems. In this paper, a depth analysis of the main problems on water of deep underground projects in Water-rich area has been done in conjunction with the situation of the Jinping grade II Hydropower Station under construction in China. Besides, the influence of water problems on the constructions of the projects has been simply analyzed and evaluated. The water management principle that "water blockage combined with water drainage, comprehensive treatment by Local conditions" has been proposed. Some treatments such as consolidation grouting of high confining pressure rock, underground water blockage etc. have been adopted to ensure the stability and security of the surrounding rock and the lining support structure, and effective control of water inflow combined with the use of grouting surrounding rock and tunnel lining joint bearing support functions. Theoretical basis and good engineering practice are provided for the construction of such project.

When the large width closure gap need to be completed under the condition of rapid flow and limited construction period, gap closure work becomes one of the most difficult construction part of all the whole Qingcaosha reservoir dike project. Considering the huge engineering quantity and complex hydrology of such engineering during construction phase, the real-time monitor, analysis and prediction of the hydrology are implemented. With numerical analysis of the closure gap under the design tide process, the model results show that the rising flow of the closure gap is more rapid than the ebb flow, and the maximum current speed caused by water level difference between the internal and external is mostly located at top slope corners of the gap protection layer. From the result of observation and calculation, the local maximum current speed was about 4.0m/s and experienced a short time due to small tidal range, which is suitable for construction. To sum up, it is feasible and helpful to combine the real-time observation with numerical analysis to ensure the safety in construction during the closing of the closure gap. Keywords: Closure gap, Tide range,Water level, Current speed

A new principle of seismic refraction imaging was introduced to obtain successfully accurate high definition ground model. Through secondary development, ground imaging system was established and applied in dam cross-section and culvert through the dam imaging. The status of the dam structure and the location and severity of hidden danger of dam structure were showed identify quickly and efficiently. Results from two field applications are presented showing the benefit of assessing seismic refraction data using the three-dimensional ground imaging system.

This paper describes the introduction of two new courses in the area of the project management and ethics used by both Computer and Electronics Engineering Technology programs at Texas Southern University. These introductory courses are offered in the first and second semesters for both programs as part of continuous improvement and curriculum modification. The rationale for creating these courses was to provide students with a better overview of both respective subjects. The main emphasis of this paper is devoted to the process of assessment and curriculum development. It also shows how assessment data were obtained and analyzed. Finally, it demonstrates how the feedbacks from analyzed data were utilized to enhance or modify either course or program's educational objectives and outcomes. In order to establish an efficient assessment method, a two-tier process was developed. The first tier was course-embedded, while the second tier was implemented at the curriculum level. The two-tier process provided a system of on-going evaluation and continuous improvement of the program. Furthermore, a set of assessments instruments were developed to evaluate and modify the program's educational objectives and outcomes on a continuous basis to ensure that students achieved the desired program outcomes. This includes various survey instruments, an outcome-based exit exam, students' works, and the feedback from Program's Industry Advisory Board Committee members. Finally, the curriculum and planning committee, which consists of the faculty members in the program, analyze the data and subsequently made recommendations for course and/or program improvement. These changes were presented to the Industry Advisory Board for concurrence, and thereafter, submitted to the Texas Higher Education Coordinating Board through the University's Registrar for final approvals.

Emerging wireless technologies have the promise of improving the centralized cable-based Structural Health Monitoring (SHM) system performances. Recently, a smart sensor based on the Berkeley mote platform was introduced, and application to the next generation of SHM and control was proposed. In this study, the performance of the latest version of the "mote", called IRIS mote, is experimentally investigated through dynamic tests of an in-house cable-stayed bridge model. This paper focuses on the verification of wireless sensor network integration technologies and their application on determination of structural dynamic properties. Six IRIS wireless sensors were installed on the center and quarter span of the bridge model to measure acceleration signals. The dedicated sensor network platform includes the multi-functional wireless nodes, base station, data acquisition software, and computer is designed for experiment evaluation. The results of dynamical tests using the wireless monitoring system are compared with those using wired instrumentations. A finite element model was also developed to investigate the dynamical properties of the bridge model. The experiment results, combined with the FE analysis results, demonstrate the IRIS mote as a wireless smart sensor has sufficient performance for the intended purpose.

The vast majority of the world's wind turbine blades are used of composite materials, and crack damage is common failure mode of wind turbine blade. Therefore, a reliable nondestructive testing (NDT) method is required to detect the crack damage. In this paper, the crack damage for a composite plate which is part of the wind turbine blade is experimentally researched by using piezoelectric ceramic to determine the damage location and level. A group of piezoelectric ceramics is pasted on the surface of the composite plates with the artificial crack damage. One PZT patch is applied as an actuator, the others as sensors. An experiment for the crack damage detection is performed by using sine sweep wave generated by actuating PZT patch. Based on the Fourier spectra analysis on the received signals, the artificially mimicked crack area has been successfully detected and the defined damage index is used to judge the crack damage level.

An innovative optimal design method based on H∞ norm is presented for the seismic response control of eccentric building structures using liquid dampers. The H∞ norm of the transfer function from the ground motion to the structural response is selected as the optimal objective. A numerical optional procedure is carried out by using Genetic Algorithms (GAs) in order to reach an optimal solution. The solving of equation of motion for the control system is unnecessary in the optimal design process and the obtained optimal parameters of dampers are not dependent on the ground motion records. A 12-story eccentric structure is selected as an example. The results showed that the liquid dampers with optimal parameters acquired through the proposed method can effectively reduce the structural response in different site conditions.

With the strong support from Federal Highway Administration (FHWA), Texas Southern University (TSU) hosts a National Summer Transportation Institute (NSTI) since 2001 to education high school students for earlier preparations in engineering. Among the fantastic activities that STI prepares, the course "Intersection Signal Timing" is one of the representatives that are designed to illustrate that Engineering is all about creating, building, and making things better for our lives. An intersection within the campus is selected for students to collect traffic data, and a workable Excel spreadsheet together with the theoretical formulations embedded is distributed to students for their practices. Through the hand by hand instructions, the students are able to calculate timing parameters for intersections and present their recommendations in class. They are aware that becoming an engineer requires hard work and good educations.

Labs-to-go is an innovative take-home laboratory system suitable for a variety of undergraduate laboratory experiments in civil, mechanical, and computer engineering. Conventional labs are expensive in terms of hardware, lab space, and support staff. Furthermore, for urban universities, the majority of students commute. The labs-to-go project can reduce the pressure on limited lab resources and required commuting via take-home kits which provide a learning experience equivalent to traditional labs. The apparatus consists of a set of smart beam elements, each comprised of an aluminum plate, a piezoelectric actuator, a piezoelectric bending sensor, and mounting hardware, with display and control provided using a personal computer with a digital signal processing interface subsystem. The students assemble (with extensive online teaching assistant support) a specified configuration and then measure and control its behavior using algorithms they develop as part of the assignment. The laboratory experiments fall into two general classes: measurement and control. This paper describes the measurement experiments, in which students use the apparatus to determine the dynamics of the structures and to develop experience with sensing, signal conditioning, and identification. The assessment results confirm that the labs-to- go concept is viable and offer insight into improvements which can enhance the learning outcomes.

The safety of a pipeline structure, as a very important means of transport, becomes very important under explosion load when explosion is now becoming more common event. To evaluate the effects of a possible ground explosion on buried pipeline, this paper attempted to analyze the dynamic responses of the pipeline in soft soil by using a widely applied explicit dynamic nonlinear finite element software ANSYS/LS-DYNA through selecting proper material constitutive relation and using nonlinear dynamics theory and arbitrary Lagrangian-Eularian (ALE) algorism. The paper also considered fluid and solid coupling such as soil and pipeline, and pipeline and liquid in it under the explosion load. Two research paths were selected to analyze the dynamic responses of the pipeline. The path 1 was along the transverse direction of the pipeline, and 5 typical points were selected around the cross-section; and the path 2 was along the longitudinal direction and the horizontal distance from the explosion center ranged from 0 to 2 m. The numerical results indicated that using numerical simulation method to study the explosion ground shock effect on buried pipeline was feasible, and the upper part of the pipeline cross-section with directions ranging from 0 to 45° and horizontal distances of 0 to 1m away from the explosive center was the vulnerable areas.

One way in which robotic systems can be integrated into industrial operations is as part of ground surveys for environmental monitoring. In mining and other industrial plants that entail soil disturbance, methods are required to perform accurate and low-risk terrain characterization of what can be highly uncertain terrain, such as partially reclaimed oilsands tailings deposits. With good geotechnical characterization, earthmoving activities to place final reclamation material can be done with lower risk to people and equipment. The design and development of a robotic system capable of terrain characterization through sampling and mapping of unknown regions is presented. Two soil parameters, cohesion stress and internal friction angle, have been estimated based on a slip-based terramechanics model used for planetary exploration. The shear strength of the terrain can be calculated from these parameters in order to determine the trafficability of the terrain. The results from outdoor experiments show the feasibility of conducting ground surveys with robotic systems on soft ground.

This paper is a summary of recent research efforts of the author's group on intelligent structural health monitoring (SHM) systems, including both system integration technologies and engineering applications. A key design feature of intelligent SHM system is the collocation of different types of sensors and the tight integration of multi-functional subsystems to provide the opportunity to self-interrogate measurement data. In particular, there is strong interest in using various sensing units to build SHM systems that interrogate structural data for signs of damage or danger. The paper has reviewed the design of a number of different intelligent SHM systems prototypes that have been designed explicitly for real SHM applications. These practical projects include the Shenzhen Civic Center (the first health monitoring system on a large space structure in China), the Nation Aquatic Center, also known as the "Water Cubic" (the Natatorium of the Beijing 2008 Olympic Games), the Shenzhen Vanke Center of a cable truss structure, and the Shenzhen Bay Stadium (the opening ceremony and main stadium of the 2011 Summer Universiade). Real applications on these large space structures showcase the accuracy and reliability of the proposed intelligent SHM systems installed.

The paper combines grey forecasting model and support vector machine together to predict the ultimate bearing capacity of single static pressure pipe pile based on their respective advantages. New model adopts the advantage of "accumulated generating", which is in grey forecasting method, to deal with the sample and reduce the influence of random disturbance factors in original sequence. It is more regular and also avoids theoretical defect, which is existed both in the grey forecasting method and the model. Choose appropriate kernel function and establish the grey support vector machine forecasting model for ultimate bearing capacity of static pressure pipe pile. The results show that the model referred in the paper has a better forecast accuracy and a good applicability, so it develops a newly approach for the theoretical analysis of vertical bearing behavior of static pressure pile, besides it provides reference and guidance for the research of related problems in the future.

In this study, wind vibration coefficient and the most unfavorable part of wind-induced vibration of a long-span thin shell dome structure are investigated, by using the finite element method to analysis three dimensional wind vibration in time domain. And wind load is simulated by harmonic superposition method combined with self-programmed MATLAB, based upon which fluctuating wind speed curve and fluctuating wind pressure curve are obtained. The influences of dome's thickness are considered in the analyses of the change of vibration coefficient. The results show that, Long-span dome structure's wind coefficient increase with the decrease of thickness and its central part is the most unfavorable part of wind-induced vibration. Moreover, harmonic superposition method is an effective way to simulate fluctuating wind in time-history analysis. Finally, it provides a reference and analytic procedure for long-span dome structures in wind-resistant design.

With human on energy demand is growing, fossil energy is reducing day by day, and the requirements quality of human survival environment is growing, the new type of green energy called Hot Dry Rock(HDR) have developed rapidly in developed countries. The technology for development and utilization of the dry-heat rock in China is still in the initial stages, on the other hand, heating supply is an eternal demand in the cold areas of China, in order to meet the demand of heating, This paper puts forward a system to develop the HDR energy for heating, based on the analysis of the geological conditions in the north of Shenyang, feasibility analysis of using HDR heating system in Shenyang area; the same time it will solve analysis the key technology of this heating supply system, the thermal conductivity of rock under high temperature and high pressure and the heat transfer ability between rock and water as well as pipe material and insulation technology, all of which will realize the key technology about the dry-heat rock heating. In conclusion, if the key technology on heated system would be settled, it will bring breakthrough about using the hot dry rock on heated supply in cold areas.

Virtual and Remote Laboratory (VR-Lab) is an inevitable necessity for Internet enabled education in Engineering Technology and other STEM fields due to the effectiveness, flexibility and cost-saving. The VR-Lab research at Texas Southern University (TSU) is to develop a software and hardware framework that allows users to simulate the experiments virtually and control physical instruments remotely via the Internet with minimal to zero-installation beyond a typical web browser. Currently, multiple web based experiments for Data Communication, DC circuit, Active Vibration Control and Digital Signal Processing (DSP) subjects are available for experimentation and coursework integration. To allow rapid development, National Instruments (NI) software and hardware is used for the programming, data acquisition, and interaction with remote devices. The programming of virtual experiments is primarily done with NI LabVIEW v8.6 as well as Java. To reduce or eliminate the need for browser plug-ins or third party software in order to operate, the VR-Lab framework uses Web 2.0 technology. The goal of the VR-Lab framework is to provide cross-browser and client-side plug-in free experiment environment for engineering and technology education. A remote Smart Vibration Platform experiment which is good for teaching active vibration control is used to demonstrate how to integrate a remote experiment into the VR-Lab framework.

A hybrid analysis method, entitled Combined Meso-Macroscale finite element analysis approach, that combines the currently existing macroscale and mesoscale approaches for modeling the braided composite materials has been developed in this study. The method fully utilizes the advantage of both the macro-level and the meso-level approaches, with the mesoscale model using the embedded unit cell with damage and delamination to describe the details of local deformation and the macro-scale model capturing the global response feature of the entire structure. The approach is verified with a coupon plate, and may be extended to large systems like jet engine containment. Two different methods are used to connect the macro-level modeled region and the meso-level modeled region: the direct coupling method and the submodeling method. The former couples the different meshes and material properties across the interface with mathematical interpolation while the latter uses submodeling technique to map the solution on the connecting interface of the global model onto the boundary of the meso-modeled portion - the submodel. Comparisons are preformed between the two methods with the baseline in their efficiency and accuracy. The Combined Mecro-Macroscale analysis method presented here captures the response feature of triaxially braided composite structure under impact accurately with a much lower computational expense, making it feasible to analyze this type of analyses efficiently.

Ceramic matrix composites in advanced gas-turbine engines must have predictable toughness under impact from foreign objects. A damage evolution based multi-scale progressive failure analysis (MS-PFA) was performed using in-situ fiber/matrix/interphase properties. The MS-PFA code augments commercial explicit FE codes for impact and implicit code for post impact analysis including the effect of impact residual stress and damage. The physics coupling the micro and macro scale boundaries are used by MS-PFA. The root cause of translaminar damage advancement (delamination between fiber and matrix, fiber-breakage/micro-crack density and matrix residual stiffness) at the micromechanical level is used to: a) to understand the damage tolerance of structures; b) produce probabilistic sensitivities of contributing parameters (i.e., strain rate, interphase, fiber and matrix properties) to damage size foot print. Steel projectiles (diameter=1.59mm) were used to impact a SiC/SiC: 2D 5 Harnes Satin Woven Sylramic iBN MI SiC at speeds from 100-400m/s (Mach:0.3-1.2). Literature data of impact tests were simulated in this work from various sources. The paper will discuss the foreign object damage (FOD) test and simulation comparisons for variables such as energy vs. time, damage foot print, % damage volume vs. time.

An experimental program is underway to develop a consistent set of material property and impact test data, and failure analysis, for a variety of materials that can be used to develop improved impact failure and deformation models. Unique features of this set of data are that all material property information and impact test results are obtained using identical materials, the test methods and procedures are extensively documented and all of the raw data is available. This report describes ballistic impact testing which has been conducted on Aluminum (Al) 2024 and Titanium (Ti) 6Al-4Vanadium (V) sheet and plate samples of different thicknesses and with different types of projectiles, one a regular cylinder and one with a more complex geometry incorporating features representative of a jet engine fan blade.

In order to design impact resistant aerospace components made of triaxially braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to features such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat coupons have been examined to alleviate difficulties observed with standard test methods. The results from the coupon level tests have been used to characterize and validate a macro level finite element based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid architecture is simulated by using four parallel shell elements, each of which is modeled as a laminated composite. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the coupon level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.

The microcrack distribution and mass change in PR520/T700s and 3502/T700s carbon/epoxy braided composites exposed to thermal cycling was evaluated experimentally. Acoustic emission was utilized to record the crack initiation and propagation under cyclic thermal loading between -55°C and 120°C. Transverse microcrack morphology was investigated by using X-ray Computed Tomography. Different performance of two kinds of composites was discovered and analyzed. Based on the observations of microcrack formation, a meso-mechanical finite element model was developed to obtain the resultant mechanical properties. The simulation results exhibited a decrease in strength and stiffness with increasing crack density. Strength and stiffness reduction versus crack densities in different orientations were compared. The changes of global mechanical behavior in both axial and transverse loading conditions were studied.

This paper focuses on improvements to modeling dry fabric-based systems widely used in propulsion engine containment systems. Simulations of fabrics under impact using finite elements provide valuable insight into the mechanics of fabric behavior and its energy absorption. In our model, the fabric is treated as an equivalent continuum model composed of thin shell elements. The fabric of choice is Kevlar 49 whose behavior is characterized using uniaxial quasi-static and high strain rate tension tests, picture frame tests and friction tests. test results are used determine the material properties and to build the material and finite element models. The constitutive model is programmed as a user-defined material model in LS-DYNA. Simulations of a suite of ballistic impact tests are models using both deterministic and probabilistic (based on the Weibull distribution of strength) approaches and the results are compared against experimental results.

Polymer matrix composite materials are utilized for a variety of aerospace applications because of their reduced weight, and versatile material properties. Composite structures may undergo a variety of loading conditions during service life. In order to be used as protective structures, composites are required to resist ballistic impact loading. For these types of applications, it is necessary to have a model that accurately simulates not only the ballistic limit and damage patterns in an impact region, but also the effect of barely visible impact damage (BVID). BVID plays an important role in the design process of many composite structures. In an impact event, a projectile may not penetrate through the composite material, but there may still be a significant decrease in the load carrying capacity of the structure. It is important to be able to simulate the breakpoints in energy when BVID starts to occur, when BVID becomes significant, and when BVID should be considered catastrophic for a given structure. These points will depend on the material and the purpose of the structure. The BVID mechanisms are highly dependent on the material constituents, the structure's layup, the textile architecture, and the shape of the projectile. Specifically, in a braided composite, numerous micromechanical phenomena occur contributing to the ballistic limit, the damage patterns, and BVID.

Although the Orion Multi-Purpose Crew Vehicle (MPCV) is being designed primarily for water landings, a further investigation of launch abort scenarios reveals the possibility of an onshore landing at Kennedy Space Center (KSC). To gather data for correlation against simulations of beach landing impacts, a series of sand impact tests were conducted at NASA Langley Research Center (LaRC). Both vertical drop tests and swing tests with combined vertical and horizontal velocity were performed onto beds of common construction-grade sand using a geometrically scaled crew module boilerplate test article. The tests were simulated using the explicit, nonlinear, transient dynamic finite element code LS-DYNA. The material models for the sand utilized in the simulations were based on tests of sand specimens. Although the LS-DYNA models provided reasonable predictions for peak accelerations, they were not always able to track the response through the duration of the impact. Further improvements to the material model used for the sand were identified based on results from the sand specimen tests.

This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar® honeycomb to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed until needed for deployment. Experimental evaluation of the DEA included dynamic crush tests of multi-cell components and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto multi-terrain. Finite element models of the test articles were developed and simulations were performed using the transient dynamic code, LSDYNA ®. In each simulation, the DEA was represented using shell elements assigned two different material properties: Mat 24, an isotropic piecewise linear plasticity model, and Mat 58, a continuum damage mechanics model used to represent laminated composite fabrics. DEA model development and test-analysis comparisons are presented.

NASA has sponsored research to evaluate an externally deployable composite honeycomb designed to attenuate loads in the event of a helicopter crash. The concept, designated the Deployable Energy Absorber (DEA), is an expandable Kevlar® honeycomb. The DEA has a flexible hinge that allows the honeycomb to be stowed collapsed until needed during an emergency. Evaluation of the DEA began with material characterization of the Kevlar®-129 fabric/epoxy, and ended with a full-scale crash test of a retrofitted MD-500 helicopter. During each evaluation phase, finite element models of the test articles were developed and simulations were performed using the dynamic finite element code, LS-DYNA®. The paper will focus on simulations of two full-scale impact tests involving the DEA, a mass-simulator and a full-scale crash of an instrumented MD-500 helicopter. Isotropic (MAT24) and composite (MAT58) material models, which were assigned to DEA shell elements, were compared. Based on simulations results, the MAT58 model showed better agreement with test.

In this paper a new approach to tracking control problems for nonlinear uncertain systems is proposed. Real-life complex multi-body systems are usually uncertain, the uncertainties arising from the lack of precise knowledge in modeling the systems. These uncertainties, which we assume to be time varying and unknown yet bounded, are considered in this paper. The uncertainties being unknown, what is available in hand is therefore just the so-called ‘nominal system,' which is simply our best assessment and description of the actual real-life situation. The aim in this paper is to develop a general control methodology that when applied to an actual real-life uncertain system, causes this system to track a desired reference trajectory that is pre-specified for the nominal system to follow. Our control methodology is developed in two steps. First, we utilize the fundamental equation that provides a nonlinear optimal controller for the nonlinear nominal system so that the reference trajectory is exactly tracked. No approximations/linearizations are done related to the nonlinear nature of the system. In the next step, we ensure that the unknown, uncertain system tracks this reference trajectory by augmenting an additional controller—based on the idea of sliding mode control—to the fundamental equation, providing a general approach for obtaining the equations of motion for a nonlinear uncertain constrained mechanical system. While based on the idea of a sliding surface, the approach permits the use of a large class of control laws that can be adapted to the specific real-life practical limitations of a given, particular controller being used. Thus, in sum, a methodology is developed to obtain a set of closed-form controllers for nonlinear uncertain multi-body systems that can track a desired reference trajectory that the nominal system is required to follow. The set of controllers shows good transient behavior and is robust with respect to the uncertainties involved in the description of the real-life system.

A set of ‘n' gyroscopes are coupled together to form a system of ‘slave' gyroscopes. A simple approach is developed for synchronizing the motion of these slave gyroscopes, whose individual motion may be regular or chaotic, with the motion of an independent ‘master' gyroscope, irrespective of the chaotic or regular motion exhibited by the master. The problem of synchronization of these multiple gyroscopes is approached from a constrained motion perspective through the application of the Udwadia-Kalaba equation. The approach yields explicit, closed form expressions for the control torques that are required to be applied to each of the coupled slave gyroscopes and achieves 'exact' synchronization with the master's motion. The effect of the ‘no-sleeping' condition on the synchronization of the gyros is discussed. An incidence matrix is also introduced to describe the coupling interaction between individual slave gyros.

In this paper, a unified methodology for modeling and control of complex multi-scale mechanical systems is presented. The method utilizes recent results in analytical dynamics adapted to general complex multibody systems. The term multi-scale is employed to denote those mechanical systems whose equations of motion are highly nonlinear, non-autonomous, and can yield motions at multiple time and distance scales. These types of problems can easily become difficult to model and control and the complexity of the equations of motion grows rapidly as the number of component bodies in the system increases. The approach considered herein opens up new routes for modeling and control of general multibody systems by explicitly developing closed form expressions in terms of any desirable number of generalized coordinates that may appropriately describe the configuration of the multi-scale system. The approach is simple in implementation and it poses no restrictions on the total number and nature of modeling constraints to construct the explicit equations of motion of the system. Likewise, no restrictions are placed on the nature and number of the feasible tracking control requirements to obtain explicit expressions for the requisite generalized control forces. Conceptually, the method relies on a simple six-step procedure. It utilizes in a pivotal manner the the explicit equations of motion for constrained mechanical systems with singular mass matrices. The simplicity of the unified method is highlighted by illustrating its use in the modeling and control of a dumbbell made of two unequal masses which is required to be controlled so that one of the masses follows a prescribed time-varying trajectory.

The debonding between the steel tube and the concrete core of Concrete-Filled Steel Tube (CFST) member can weaken the confinement effect of steel tube on core concrete and may lead to the decrease in load-carrying capacity and in ductility. In this paper, a kind of multi-functional smart aggregate (SA) which is based on piezoelectric Lead Zirconate Titanate (PZT) is employed to detect the predesigned interfacial debonding damage in a CFST column specimen. Three SAs are embedded into the concrete of the specimen as actuators and a number of PZT patches are bonded on designed locations of the outside surface of the steel tube as sensors. Laboratory tests are performed on the CFST column. The responses of all the employed PZT sensors are measured when one of the SAs is excited with sweep sinusoidal signals. Based on the analysis on the power spectral density (PSD) of the employed PZT sensor measurements, the artificially mimicked debonding areas are detected successfully.

Unmanned aircraft systems (UAS) provide an ideal platform for remote sensing, monitoring and data collection. Small scale, field portable systems are particularly useful in remote environments, where a lack of infrastructure dramatically increases the cost of remote sensing operations. A low-cost, portable remote sensing system is under development for industrial and research monitoring and data gathering. The UAP1 research platform has been assembled from commercially available components, using open-source software. Commissioning and testing of the airframe is discussed. Challenges encountered during testing, such as engine vibration, and their solutions, are presented within. A detailed vibration analysis is prevented, showing the benefit of isolating the inertial measurement unit (IMU) from the airframe. Additionally, autopilot tuning information is provided. Finally, current and future work on the research platform, such as image postprocessing and payload solutions.

The principle of fiber Bragg grating (FBG) sensors for monitoring cracks in concrete structures is analyzed, and the distributed crack monitoring technique based FBG sensing is studied. To verify the feasibility of FBG crack sensing, an experiment was conducted using a concrete beam. The test results show that the FBG sensors can accurately monitor crack initiation and propagation as well as the quantitative rule of crack propagation, which can reflect the failure mode of concrete. Multiple FBG sensors in one single fiber possess distributed sensing capability, and can monitor crack initiation and propagation without knowledge of crack locations a priori.

The ambient environmental factors present on the lunar surface pose the most difficult challenges for long term human settlement of the Moon. Aside from the dangerous radiation levels and the lack of atmosphere, the temperature on the surface can range from very cold during the night (-233°C) to very hot during the daytime (134°C) posing a variety of complications including the alteration of the structural response of the habitat due to thermal expansion and contraction. This paper presents the study of the membrane attachment and variation of both surface temperature and internal pressure and their effects on the frequency response of a lunar habitat made of an aluminum frame with a Kevlar membrane attached to contain the internal air pressurization. The frame-membrane structure was considered pinned at bottom periphery of the structure. For the frame alone without the membrane attached, the hot external temperatures increased deflections and decreased frequencies slightly while the cold temperatures had the opposite effect of increasing the natural frequency of vibration by a small amount. When the membrane was attached, the initial modes were dominated by local membrane vibrations with lower frequencies when no internal pressure was applied. The internal pressure and high daytime external temperatures were observed to increase the frequency of the structure further when considering global vibrations and the low nighttime temperature was found to enhance local membrane vibrations and decrease the natural frequency of vibration throughout all of the first twenty-five modes.

We describe a method to accurately calibrate indicated airspeed for an electronic flight instrument system (EFIS) which records key parameters for offline analysis. The technique is based on estimating airspeed error, heading error, and wind vector. Examples are provided for two popular experimental aircraft EFISs.

This paper provides a new, exact controller for formation-keeping in the presence of attitude tracking requirements. Both orbital and attitude dynamics are simultaneously considered and continuous thrust propulsion systems are assumed. A leader satellite is assumed to be in a given Keplerian orbit around a central body and each follower satellite is required to stay in a prescribed, desired orbit with respect to the leader satellite, and at the same time, to exactly point to a specific spot in inertial space that may be fixed or time varying. The satellites are considered as rigid-bodies and for attitude dynamics quaternions are used to realize arbitrary orientations and avoid singularities. Unlike most studies, no linearizations and/or approximations are made in dynamics or the controllers. It is hoped that the novel controller provides a remarkable improvement over the current state-of-the-art in that the control force and torque to satisfy the given orbital and/or attitude constraints are obtained in completely closed form. This new, analytical solution can be easily used for on-orbit, real-time control with low computational burden. Furthermore, it is useful in estimating the magnitude of the required control inputs and results in some interesting consequences, including the separation principle, which describes when the orbital control can be completely decoupled from the attitudinal control required to be applied to the follower satellite. Extensive computational simulations are performed to demonstrate the simplicity of implementation and accuracy of the control method developed herein.

Intersections account for more than two million crashes in the United States every year. Besides good geometric designs, an even more efficient and powerful way is to design a smart guide signing system to accurately and timely provide drivers with proper control and regulation information (e.g., STOP and YIELD signs, speed limit), which are however normally blocked by roadside trees and parking vehicles. The Radio Frequency Identification (RFID) technology, which is ideal in providing short range "infrastructure (i.e., the roadways) to vehicle" communications, is one of the good tools to implement such smart guide system. In this paper, a pilot test using RFID as an intelligent sensor is presented, including the selection of proper RFID emitters and receivers, the testing design, data collection from the tests and performance analysis, computer programming, simulation of in-vehicle display system to broadcast the received information, etc. Besides, the possible impacts of RFID based smart guide system to transportation safety, environment, and efficiency are also provided.

The Virtual Autonomous Navigation Environment (VANE) is a modeling and simulation tool that is being developed by the US Army Engineer Research and Development Center (ERDC) to support the design, development, and testing of autonomy algorithms for intelligent ground vehicles. The VANE is an open architecture, modular simulation that is compatible with desktop and parallel computing. It consists of a set of independent models for sensors, vehicle dynamics, and terramechanics. The VANE uses high-fidelity environment geometry and ray-tracing to simulate GPS, Light Detection and Ranging (LIDAR), and camera sensors. Inertial sensors are simulated using the dynamics engine, which also interfaces with the Vehicle Terrain Interaction (VTI). The VTI is a validated mobility model that gives performance predictions for both hard and soft soils for tracked and wheeled vehicles. These models interact through a run time interface in a high performance distributed computing environment and can be used to simulate environmental effects on sensors and mobility.

The permanent settlement of the Moon will begin with a single human habitation, one that is designed to be both sustainable and expandable. But in order for it to be both sustainable and expandable it will be necessary to consider the economic, organizational, and legal requirements as well the technology of its design from the beginning. This paper will examine those factors and how they will impact the basic "design" of this facility. A key argument is that the facility should not be "over-designed" and that the usual "aerospace approach" to design will be counter-productive when applied to the design of a facility with mixed uses and multiple stakeholders, in a fixed location. The second theme is that we are far more likely to succeed on the Moon if we adopt an evolutionary, not a programmatic strategy towards the first settlements, and that the first facilities built, in particular, must be designed to evolve and adapt to the changing needs of the first settlement. This "design to evolve" approach will need to consider details such as: the ownership structure, facility management, and operational control. Especially important will be how users will be able to "buy in", and also how to fund infrastructure expansion as the settlement grows. The focus of the paper is on the interaction of the business model for a lunar settlement and the technical requirements for building a sustainable settlement on the Moon. Analogies with remote industrial facilities on Earth are also discussed.

Several unique systems including the Lunar Electric Rover, the unpressurized Chariot rover, the versatile light-weight crane and Athlete cargo transporter as well as the habitat module mockups and a new generation of spacesuits are undergoing coordinated tests at NASA's facility for Desert Research and Test Studies (D-RATS). A synergetic plan is proposed for utilizing these maturing systems coupled with a fabrication technology called Contour Crafting, tailored for swift and reliable lunar infrastructure development. The intent is to increase astronaut safety, improve buildup performance, ameliorate lunar dust interference and concerns, and reduce time-to-commission, all in an economic manner.

Future human space exploration will require large amounts of resources for shielding and building materials, propellants, and consumables. A space-based resource economy could produce, transport, and store resource at distributed locations such as the lunar surface, stable orbits, or Lagrange points to avoid Earth's deep gravity well. Design challenges include decentralized operation and management and socio-technical complexities not commonly addressed by modeling and simulation methods. This paper seeks to tackle these challenges by applying aspects of military wargaming to promote effective communication between decision-makers. A software architecture for federated simulation based on IEEE-1516 (HLA-Evolved) is presented in the context of multiple lunar in-situ resource production processes, resource depots, and intermediate transportation. The federation-level framework identifies interfaces between simulation models (federates), focusing on persistent assets (elements) and resources exchanged. Future work will develop the federated resource economy model and evaluate with decision-makers playing the roles of competing and collaborating players.

Space Mining for resources such as water ice, and regolith, which contain many elements in the form of metals, minerals, volatiles and other compounds, is a necessary step in Space Resource Utilization. One of the primary goals is to extract propellants from the regolith such as oxygen and hydrogen which could then be used for in-space transportation. In addition, the space mining system can be used for various construction tasks that can benefit human and robotic exploration as well as scientific investigations based on the exposed topography. The National Aeronautics & Space Administration (NASA) Lunabotics Mining Competition is a university-level competition designed to engage and retain students in science, technology, engineering and mathematics (STEM). NASA will directly benefit from the competition by encouraging the development of innovative lunar excavation concepts from universities which may result in clever ideas and solutions which could be applied to an actual lunar excavation device or payload. The challenge is for students to design and build a remote controlled or autonomous excavator, called a lunabot, that can collect and deposit a minimum of 10 kilograms of lunar simulant within 15 minutes. The complexities of the challenge include the abrasive characteristics of the lunar simulant, the weight and size limitations of the lunabot, and the ability to control the lunabot from a remote control center or operate autonomously. This paper will present an update of the results and lessons learned during the first and second annual Lunabotics Mining Competitions held in May 2010 and May 2011. It will also preview the 2012 competition with a review of the revised rules. In 2010, 22 United States (US) universities competed, and in May 2011 the competition was opened to international participation. In 2011, 36 teams actually competed from 26 USA states and 4 foreign countries (India, Bangladesh, Colombia and Canada). This combined total directly inspired an estimated 653 university students. In 2012 more students and the public will be engaged via internet broadcasting and social networking media. The various designs will be cataloged and categorized to provide information to future Lunabotics mining robot designers and competitors. It is also expected to be of value for actual future space missions, as knowledge is gained from testing many innovative prototypes in simulated lunar regolith.

What seems to be almost sure is the solutions to space travel and living in space will be found when the possibility of profit from development of technologies in and for space is seen as immediately at hand. In other words when the people see opportunity to profit from space, solutions will come quickly. Using analogues of how cities on Earth have evolved because of the creation of new technologies and markets, the paper discusses how the future settlement and development of a lunar habitation can be predicted. The goal of this study will be to see through the habitation process from a real estate developer's perspective and demonstrate how to attract interest from the public, as well as potential investors. The report will utilize SICSA's design of a self-sustainable lunar habitat, for the Houston Museum of Natural Science, to illustrate the project's feasibility and room for expansion.

This paper describes NASA's current plans for the exploration of Mars by human crews within NASA's Capability-Driven Framework (CDF). The CDF describes an approach for progressively extending human explorers farther into the Solar System for longer periods of time as allowed by developments in technology and spacecraft systems. Within this framework, Mars defines the most challenging objective currently envisioned for human spaceflight. The paper first describes the CDF and potential destinations being considered within this framework. For destinations relevant to the exploration of Mars, this includes both the Martian surface and the two moons of Mars. This is followed by a brief review of our evolving understanding of Mars to provide the context for the specific objectives set for human exploration crews. This includes results from robotic missions and goals set for future Martian exploration by NASA's community-based forum, the Mars Exploration Program Analysis Group (MEPAG) and the MEPAG-sponsored Human Exploration of Mars - Science Analysis Group (HEM-SAG). The paper then reviews options available for human crews to reach Mars and return to Earth. This includes a discussion of the rationale used to select from among these options for envisioned Mars exploration missions. The paper then concludes with a description of technological and operational challenges that still face NASA in order to be able to achieve the exploration goals for Mars within the CDF.

The Cis-Lunar Destination Team of NASA's Human Spaceflight Architecture Team (HAT) has been performing analyses of a number of cis-lunar locations to inform architecture development, transportation and destination elements definition, and operations. The cis-lunar domain is defined as that area of deep space under the gravitation influence of the earth-moon system, including a set of orbital locations (low earth orbit [LEO], geosynchronous earth orbit [GEO], highly elliptical orbits [HEO]); earth-moon libration or "Lagrange" points (EML1 through EML5, and in particular, EML1 and EML2), and low lunar orbit (LLO). We developed a set of cislunar mission concepts defined by mission duration, pre-deployment, type of mission, and location, to develop mission concepts and the associated activities, capabilities, and architecture implications. To date, we have produced two destination operations concepts based on present human space exploration architectural considerations. We have recently begun defining mission activities that could be conducted within an EM L1 or EM L2 facility. This paper will review details of this work.

NASA's Human Spaceflight Architecture Team (HAT) Lunar Destination Team has been developing a number of "Design Reference Missions" (DRM) to inform exploration architecture development, transportation approaches, and destination elements and operations. There are four destinations being considered in the HAT studies: Cis-Lunar, Lunar, Near Earth Asteroids and Mars. The lunar destination includes all activities that occur on the moon itself, but not low lunar orbit operations or Earth Moon LaGrange points which are the responsibility of the HAT Cis-Lunar Team. This paper will review the various surface DRMs developed as representative scenarios that could occur in a human lunar return. The approaches have been divided into two broad categories: a seven day short stay mission with global capabilities and a longer extended duration stay of 28 days which is limited to the lunar poles as a landing zone. The surface elements, trade studies, traverses, concept of operations and other relevant issues and methodologies will be presented and discussed in the context and framework of the HAT ground rules and assumptions which are constrained by NASA's available transportation systems. An international collaborative effort based on the 2011 Global Exploration Roadmap (GER) will also be examined and evaluated.

Near-Earth Asteroids (NEAs) provide an intermediate destination for human missions between the Moon and Mars that, among other benefits, can reduce the risks for all deep space exploration. NEA missions can provide important scientific discoveries about the solar system, vital operational experience for Mars missions and beyond, assist in the development of planetary defense approaches, and foster the future utilization of space resources. This paper summarizes the different NEA Design Reference Missions currently used by NASA's Human Spaceflight Architecture Team, the operational challenges that these missions present, and approaches that can overcome these challenges. Other aspects of NEA missions, such as payload delivery needs, sample collection techniques and requirements for sample return, current strategic knowledge gaps, and operational experience gained during the missions applicable to future Mars missions are also discussed.