Earth and Space 2016: Engineering for Extreme Environments

Following the discovery of the first young, still forming, partial zodiacal dust band, we have shown that partial bands retain significant information about both the size-frequency distribution and cross-sectional area of dust released in the disruption of their parent asteroids. The new observational constraints to our modeling work that are provided by the partial dust band allow us to begin to reconstruct the properties of the regolith on the surface of the parent asteroid before its collisional disruption, including the depth of the regolith and the size-distribution of the particles present. Using the constraints provided by modeling the partial dust band at 17°, we discuss the surface regolith of the parent asteroid to the Emilkowalski cluster and investigate the relationship between regolith depth and the size distribution of particles. By examining the available data for other asteroids, we determine a scaling relationship between depth of regolith and asteroid size.

Knowledge of the thermal conductivity of the regolith is required both for the design and the interpretation of in situ experiments in future missions to Moon and planets. A variety of available analogue soil material, intended to mimic extraterrestrial soils, have been considered in a series of laboratory experiments. They cover a broad range of finer grained silty sands to coarse sands. Thermal conductivity was determined by the standardized transient procedure using a needle probe at different porosities under ambient room temperature. A steady-state method based on the divided bar technique was used for verification purposes. The results show for all types of soil examined the expected reduction of the thermal conductivity with increasing porosity. Comparisons demonstrate that the use of solely the grain size distribution curve as the relevant characteristic to model the response of this type of granular media is not appropriate. A material-specific, linear variation of conductivity with porosity as derived from the test results is given in the paper.

Robotic missions could soon explore permanently shadowed craters on the lunar poles in order to characterize ice accumulation beneath the surface. However, the regolith in these craters is hypothesized to be very loose and could endanger a rover mission. This work analyzes the ability of thermal imaging to detect hazardous, low-density regolith in shadowed regions on the lunar poles. A series of simulations was conducted to estimate the surface temperature of lunar regolith as a function of density in polar craters. A generalized lunar crater model was used, and thermal properties of regolith were taken from experiments on Apollo samples. Results showed that in most situations there is a difference in temperature between nominal and loose regolith samples. This effect is most consistent at night in the absence of solar radiation and generally causes temperature differences between 2 K and 3 K. Based on comparisons to the capabilities of the DIVINER lunar radiometer, it is likely that regolith density differences would be detectable by a rover-mounted instrument.

Understanding granular materials on the surfaces of asteroids, known as regolith, has significance for science, exploration, and in situ resource utilization. A brief summary of the nature of asteroid regolith is presented. The discussion focuses on (1) observations from robotic spacecraft that have visited several asteroids and sent back a variety of data, (2) meteorites, which are samples of rock from the surfaces of asteroids, and (3) experiments performed on NASA’s microgravity aircraft facility. It is concluded that the regolith on asteroids behaves as a fluid, and many operations with such materials, the behavior will be counter-intuitive.

A regolith simulant test bin was constructed and completed in the Granular Mechanics and Regolith Operations (GMRO) Lab in 2013. This planetary regolith test bed (PRTB) is a 64 m² × 1 m deep test bin housed in a climate-controlled facility and contains 120 MT of lunar-regolith simulant, called Black Point-1 or BP-1, from Black Point, AZ. One of the current uses of the test bin is to study the effects of difficult lighting and dust conditions on telerobotic perception systems to better assess and refine regolith operations for asteroid, Mars, and polar lunar missions. Low illumination and low angle of incidence lighting pose significant problems to computer vision and human perception. Levitated dust on asteroids interferes with imaging and degrades depth perception. Dust storms on Mars pose a significant problem. Due to these factors, the likely performance of telerobotics is poorly understood for future missions. Current space telerobotic systems are only operated in bright lighting and dust-free conditions. This technology development testing will identify: (1) the impact of degraded lighting and environmental dust on computer vision and operator perception, (2) potential methods and procedures for mitigating these impacts, (3) requirements for telerobotic perception systems for asteroid capture, Mars dust storms, and lunar regolith ISRU missions.

We have developed an automated method to track particles in a quasi-2D tray. Here we apply this method to the data analysis of the NanoRocks experiment currently flying on the NanoRacks platform on the International Space Station. In the NanoRocks particle trays, we observe many low-velocity collisions between mm-scale particles of varying sizes and compositions. This experiment replicates the conditions in a protoplanetary disk, since many low-velocity collisions occur during the early stages of planet formation. We have developed a method to automatically detect and track these particles. We used the programming language IDL (Interactive Data Language) and the open source software package Fiji (based on ImageJ) in this tracking method. The data derived from this method match the data derived from other methods of analysis including manual tracking of individual particles and a statistical analysis. Using the particle tracks acquired by our method, we found that the peak speed of the particles is lower for particles coated in a layer of dust. We developed two methods to measure coefficient of restitution, finding that the mean coefficient of restitution, calculated using the particles’ mean free paths and average velocities, was lower in trays containing JSC-1, a lunar soil simulant. These results are significant for the early clustering of planetesimals and bodies in planetary rings. This paper will describe the development of this tracking method, its application to the NanoRocks experiment, and the results gained from this method.

Experiments were performed to study how rocket exhaust blows soil in lunar and Martian conditions. Jets of gas were blown downwardly at various granular materials while a camera recorded the formation of scour holes as the material was removed. The experiments were performed in a series of conditions ranging from ambient 101 kPa pressure down to 0.3 kPa. This includes the range that is relevant for lunar conditions, because it is not hard vacuum inside the rocket exhaust where soil is being eroded. Prior work in ambient conditions showed that erosion rate is proportional to the square of the densimetric Froude number. However, the prior work was not performed at low pressures. In the new work, preliminary results show that as the gas density is so low that gas flow around the sand grains is no longer in the continuum regime, then erosion rate is faster than predicted by the earlier results. The dependency of erosion rate on various parameters is determined, but it turns out to be more complex than expected so additional experimental work will be required to develop complete scaling relationships.

Exhaust-regolith interactions are a particular concern for any mission operating near a small body. Ejected soil can damage sensitive systems such as solar panels or cameras. We seek to quantify risk to the NASA’s Asteroid Redirect Mission (ARM) should thrusting near the target’s surface become necessary. We have developed a program to model gas diffusion into asteroid regolith and determine potential instability from resulting pressure gradients. This behavior is calculated using Darcy’s Law, which governs gas diffusion in a porous medium. Soil instability occurs when gas pressure gradients overcome weight and cohesive forces. We term the cohesion value necessary to maintain regolith stability critical cohesion. Due to uncertainty in asteroid properties, this value is calculated for a wide range of regolith parameters. For a nominal engine starting height of 7 meters, actual soil cohesion must be 0.4 Pa to prevent soil ejection. Since this value is two orders of magnitude below best estimates of actual regolith cohesion, we judge hazardous plume effects to be highly unlikely.

Planetary surface disturbances due to micrometeoroids or exploration activities can result in impacts between objects that occur at a range of velocities, including many events at very low velocities (<5 m/s). Continuous bombardment by micrometeoroids pulverizes the surfaces of airless bodies, breaking apart the rocky surfaces and generating the ubiquitous dusty regolith on these objects. While these impacts are typically high-velocity, lower-energy secondary impacts from cratering events redistributes regolith on the surfaces. Exploration activities on an asteroid or the Moon represent an additional low-energy impact process that can disturb the regolith in novel ways. To understand the response of regolith-covered surfaces to these impact processes, we must understand the granular mechanics in a range of conditions, as well as characterize the different mechanical properties of the regolith grains. Such knowledge is crucial in the design of exploration hardware and operations, in the mitigation of asteroid hazards, and in the design of space mission tests for asteroid deflection. Here, we present work that addresses these questions through a combination of experimental studies and numerical simulations that build from exploration of basic acrylic spheres to more complex compositions and particle shapes.

The dusty regolith covering the surfaces of planetary satellites and asteroids is subject to environmental conditions very different from what is found on Earth. The loose, unconsolidated regolith is produced by hypervelocity micrometeoroid impacts on asteroids and planetary satellites, leading to angular particles in a broad size distribution that is generally well-described by a power-law. In contrast, terrestrial soils are formed by erosional processes leading to more rounded particles that are sifted by aeolian and flow processes into narrow size distributions. The response of planetary regolith to low-velocity impacts, such as those that may accompany manned and unmanned exploration activities, may be completely different than what is encountered in terrestrial regolith. Further, the microgravity environment of small asteroids and moons and the absence of gravity can lead to new behaviors. Dust particles from regolith pose a hazard to equipment. The regolith itself is a possible resource for in situ processing of minerals and elements, and equipment may need to be anchored to the loose regolith. Experimental studies of the response of planetary regolith in the relevant environmental conditions are thus necessary to facilitate future exploration activities. We carried out a series of impact experiments into simulated planetary regolith in zero- and reduced-gravity conditions on parabolic airplane flights with the Physics of Regolith Impacts in Microgravity Experiment (PRIME) and measured rebound velocities, coefficients of restitution, ejecta production, and ejecta velocity distributions. Our results extend those of the first PRIME campaign (PRIME-1) reported in Colwell et al. (2008).

The first asteroid simulants workshop was held in late 2015. These materials are needed for tests of technologies and mission operational concepts, for training astronauts, for medical studies, and a variety of other purposes. The new program is based on lessons learned from the earlier lunar simulants program. It aims to deliver families of simulants for major spectral classes of asteroids both in cobble and regolith form, beginning with one type of carbonaceous chondrite and rapidly expanding to provide four to six more asteroid classes. These simulants will replicate a selected list of asteroid properties, but not all known properties, in order to serve the greatest number of users at an affordable price. They will be benchmarked by a variety of data sets including laboratory analysis of meteorites, observation of bolides, remote sensing of asteroids, data from asteroid missions, and scientific modeling. A variety of laboratory tests will verify the as-manufactured simulants are accurately and repeatedly providing the specified characteristics.

The planetary science decadal survey for 2013–2022 has promoted mission concepts for sample acquisition from small solar system bodies. Numerous comet-sampling tools are in development to meet this standard. Manufactured porous ambient surface simulants (MPASS) materials provide an opportunity to simulate variable features at ambient temperatures and pressures to appropriately test potential sample acquisition systems for comets, asteroids, and planetary surfaces. The original “flavor” of MPASS materials is known as manufactured porous ambient comet simulants (MPACS), which was developed in parallel with the development of the biblade comet sampling system. The current suite of MPACS materials was developed through research of the physical and mechanical properties of comets from past comet missions results and modeling efforts, coordination with the science community at the Jet Propulsion Laboratory, and testing of a wide range of materials and formulations. These simulants were required to represent the physical and mechanical properties of cometary nuclei, based on the current understanding of the science community. Working with cryogenic simulants can be tedious and costly; thus, MPACS is a suite of ambient simulants that yields a brittle failure mode similar to that of cryogenic icy materials. Here, we describe our suite of comet simulants known as MPACS that will be used to test and validate the biblade comet sampling system.

One portion of our NASA contract “Task-Specific Asteroid Simulants for Ground Testing” was replicating the expected textures and morphology of asteroid materials. This paper reports preliminary results and procedures for the production of a prototype simulant. An asteroid analogue starts with an appropriate mixture of minerals. Our initial simulant was based upon the compositional analysis by Bland et al. (2004) of the Tagish Lake meteorite. These minerals were to be mixed and bound into the needed final form. The possible forms are those seen in the meteorite collection and photographic evidence from asteroid missions. These include (1) strongly consolidated cobbles or boulders; (2) weakly bound “dirt clod”-like structures; and (3) loose regolith soil with an appropriate particle size distribution. During the course of the project, we conducted a survey and an Asteroid Simulants Workshop to gather feedback from the simulants user community. One result of the survey and workshop was that our initial target meteorite type was changed to a CI chondrite, and specifically the Orgueil meteorite. We ground the source materials to particle sizes reported in meteorites and mixed them. At this stage, we had an acceptable “loose regolith” analog. Consolidation options included gentle consolidation to mimic a “dirt clod” hardness (perhaps 1 MPa). More strongly consolidated materials would mimic strong (compressive strengths >20 MPa) materials on asteroids. One challenge was in replicating the desiccation of millenia in space without over-heating the material and changing its chemistry; final drying included vacuum drying. Simulants were produced as loose regolith, small cobbles/boulders, or flat surfaces depending upon the simulant need. For some uses, a combination of the above was appropriate.

Recent advances have led to the development of a subsurface characterization device that combines axial and torsional loading capabilities. The multi-sleeve penetration device uses interchangeable friction sleeves with a controlled surface roughness that have proven to provide useful information regarding the geotechnical properties of soils such as their shear and interface behavior. This device can be mounted behind a conventional cone penetration testing (CPT) probe, further improving the efficiency and performance of this well-established in situ test. This paper extends previous findings by summarizing the results of a series axial and torsional interface shear laboratory experiments performed on lunar simulant GRC-3. The results obtained are compared with those obtained using sub-rounded and sub-angular terrestrial quartz sands. The results indicate that the axial and torsional test provide a direct measurement of the interface and internal strengths of the lunar simulant. Based on these studies, the interface behavior of the GRC-3 simulant and its implications on extraterrestrial structures and regolith characterization are discussed.

The liberation of particles induced by rocket plume flow from spacecraft landing on unprepared regolith of the Moon, Mars, and other destinations poses high mission risks for robotic and human exploration activities. Manipulation, fluidic transport, and processing of regolith materials for ISRU require a thorough understanding of the granular material response. These processes occur under a combination of “extreme environments” that combine low gravity, little or no atmosphere, with rocket exhaust gas flow that is supersonic and partially rarefied, and unusual geological and mechanical properties of highly irregular surface regolith. In particular, the extra-terrestrial granular regolith materials display granular stresses and fluidic behavior are dominated by their irregular particle shapes and poly-disperse mixture composition that defy any terrestrial experience and current modeling capabilities. An adaptive mesh gas-granular multi-phase flow computational framework has been developed to enable simulations of such granular flows. The flow solver implements a two-fluid model with flow equations for the gas phase and granular phase. Innovative granular phase constituent models have been developed and integrated that address the granular material mechanical stress complexities of irregular, jagged particle shapes and poly-disperse mixtures encountered in extra-terrestrial regolith. The capabilities of the solver are presented and key verification and validation results of the solver are demonstrated.

As a payload of NASA’s discovery mission InSight, DLR’s HP³-instrument is used to measure the internal heat flow of Mars. In order to reach the maximum penetration depth of 5 m HP³’s locomotion system, the self-impelling nail nicknamed “the Mole” will hammer itself into the Martian subsurface. In order to improve, optimize, and analyze the Mole’s dynamic behaviour and its interaction with the soil, several models were developed. In the article, the enhanced multi-body model of the mechanism will be presented in combination with two soil models used during the mission’s development phase. A highly precise particle model is used to analyze the dynamic interaction with the mechanism, as well as to enhance the simple but fast analytical soil model based on soil mechanics. Both techniques will be explained, and the transfer of effects from detailed models to simple models will be shown.

The European Space Agency (ESA) will launch the EXOMARS rover mission to Mars in 2018 which will operate a rover for subsurface soil sampling and analysis. Using several electro-mechanical systems within the rover, samples acquired will be mechanically processed and dispensed to instruments. For designing the grain-processing stations of spacecraft such as EXOMARS require reliable estimates on the internal and bulk flow characteristics of granular media under low gravitational environments. However, the micromechanical behaviour of granular materials under low-gravitational environments is still complex to understand. Experimental studies on the flow behaviour of grain under a low gravity, for example, using parabolic flight tests to simulate Martian gravity, are difficult to perform and expensive. Using computational modelling, here we present results on the flow behaviour of granular materials through flow channels under different gravity conditions including the low-gravity regime. For this, we use three approaches, viz., (i) one-dimensional discrete layer approach (DLA) based on hybrid-Lagrange continuum approach, (ii) three dimensional Kirya continuum model, and (iii) three dimensional discrete element modelling (DEM). Each model has its merits and limitations. Some qualitative comparisons are also made between the flow characteristics of grains observed from parabolic flight tests and DEM simulations.

To continue on a sustainable and flexible path, NASA needs to address the challenge of collecting and moving large amounts of regolith at the destination. Acquiring the water resources on Mars will require mining significant quantities of regolith, and this is not possible with the state-of-the-art low mass excavation systems. Low gravity environments (Mars = 3/8G) and launch mass restrictions limit the traction and the resulting reaction force of the vehicle, making current terrestrial techniques impractical. This project addressed this challenge by developing a completely new technology that can mine large quantities of regolith on Mars. Recent measurements by the “Curiosity” rover on Mars have found that the regolith contains ~2% water by weight globally, ~4% in Jezero Crater (Human Architecture Team’s reference landing site), and much more at the poles. RASSOR 2.0 is a planetary excavator, which has a mass of 66 kg, with a 0.38 kg vehicle mass per kilogram, per hour of excavation rate and power usage of 4 W per kg of regolith excavation rate. A single RASSOR 2.0 can excavate a minimum of 2.7 metric tons of regolith per day. This is accomplished by using counteracting excavation forces on two opposing digging implements called bucket drums and an autonomous mining control system. This work has addressed several major research areas outlined in the NASA Technology Area (TA) 04 Robotics and Autonomous Systems and TA 07 Human Destination Systems roadmaps. This project started at Technology Readiness Level (TRL) 4 as a low fidelity “proof of concept” prototype which has successfully demonstrated basic regolith simulant excavation functionality in a lab-scale gravity off load test. The foundational technology described here was awarded US patent number: US 9027265 for a “Zero horizontal reaction force excavator” on May 12, 2015.

This paper describes the effects of ultrasonically-assisted penetration of granular materials, in high gravity situations. The experimental rig, instrumented to obtain penetration force, rate, and power both with and without ultrasonic assistance, was used to drive a penetrator into a granular material inside the ESA Large Diameter Centrifuge at accelerations of up to 10 g during early September 2015. Ultrasonic penetration proved to be most beneficial at lower levels of accelerations, reducing the required overhead weight by 80% and the total power consumption by 27%.

We report on a wide range of tests that characterize the interaction of cohesive and water-rich soils with prototype Mars regolith sample handling systems. Lab and field tests designed to gain insight into the effect of moisture on sample collection and the effect of drilling on the sample are described. Our tests utilized cohesive and non-cohesive Mars simulants with a range of water contents, as well as samples from Mars analog field sites. Our intent is to help engineers qualify sampling operations expected at future Northern Mars landing sites through exposure to highly cohesive soils, demonstrating design margin for challenging operational scenarios. This work also provides instrument developers a set of data to help refine hardware used to prepare and transfer icy materials during instrumental analysis operations.

As NASA prepares to visit asteroids and other poorly-consolidated near-earth-objects (NEOs), it will be important to safely interact with the granular materials at the surface of these objects. A particular concern is the low elastic modulus of granular materials: rubble-pile asteroids are only held together by weak gravitational and van der Waals forces. This means that both the escape velocity and the sound velocity are low compared to their values on earth. To better predict the dynamics of the granular flows resulting from surface explorations such as digging, sample-collection, anchoring, or lift-off, we develop microgravity experiments which are able to predict the circumstances under which the NEO material will remain intact or become unstable. In our experiments, we insert a flexible probe into a granular material under simulated conditions of low gravity. We show that low-speed interactions reduce the effects of shock wave creation and observe that thinner diggers allow the grains to rearrange and minimize the possibility of ejecta.

In situ resource utilization (ISRU) will be a critical, game-changing technology needed for the enabling of long-term manned missions to Mars. In order for these missions to remain sustainable, critical resources must be obtainable in sufficient quantities from the regolith of Mars to sustain the technological and human needs of the mission. These goals are addressed in this simulation study by using a computational simulation of the most current design iteration of regolith advanced surface systems operations robot (RASSOR), an excavator for Mars regolith that uses counter-rotating bucket drum design for use in low-gravity environments. In this simulation, the following is performed: (1) the dynamics of the excavation and traction forces are modeled using the Bekker equations for traction and the Balovnev equations for bucket excavation, and (2) this simulation data is compared to empirical tests of draw-bar pull tests (for traction) and bucket drum rotation tests (for excavation) of test hardware in BP-1 regolith simulant.

A human exploration program of the Martian surface will require the optimal utilization of planetary resources. One of its more abundant resources is the Martian atmosphere that can be harvested through filtration and chemical processes that purify and separate it into its gaseous and elemental constituents. Effective filtration needs to be part of the suite of resource utilization technologies. A unique testing platform has been developed at the NASA Glenn Research Center which provides the relevant operational and instrumental capabilities to test articles under the proper simulated Martian conditions. A series of tests were conducted to assess the performance of filter media. Light sheet imaging of the particle flow provided a means of detecting and quantifying particle concentrations. The media’s efficiency was evaluated by gravimetric means through a two-ply filter media configuration. These tests will help to establish techniques and methods for measuring capturing efficiency and arrestance of conventional fibrous filter media for planetary surface operations. This paper will describe initial test results on different filter media.

Deep drilling using a rigid drillstring requires the assembly and disassembly of multiple drill pipes. The interfaces between these pipes provide a challenge for automation because they must transmit large drilling forces and movements while, at the same time, minimize the actions and forces that are needed to make or break the interface. A geometry which can address these requirements has been suggested by the authors. This approach would use a push-and-twist bayonet system to engage drill pipes, with torque transmission through the bayonet studs. A variety of L-shaped and T-shaped bayonet paths have been proposed to ensure that separation of specific drill pipes can be achieved through a combination of clockwise and counter-clockwise rotation and single-point clamping. Sustained drills into a variety of media are used to show that percussive impulses are transmitted across the interface, whilst ensuring that the drill interface is able to withstand the shock loading associated with hammer-drilling. These tests are repeated and contrasted to control experiments using a single-piece control drillstring, which allows the performance of the interface and any degradation over time to be quantified. Results suggest that the bayonet-style connection performs well with no significant performance losses encountered or structural degradation noted.

Recent exploration missions to celestial bodies have shown an increasing demand for surface based landers and rovers designed to perform experiments on the ground, rather than relying purely on traditional orbiting observatories. Many of the scientifically interesting locations have proven hazardous and difficult to reach and traverse, driving the need for different methods of locomotion. Some of these locations lie in deep, permanently shadowed craters or in rocky, highly uneven landscapes. Various wheeled, flying, jumping, and legged rovers have been proposed, some of which have been implemented with success and problems alike. The presented work focuses on a category of legged rovers intended to climb up steep slopes covered in soft soil or regolith, such as those found on crater walls on the Moon and Mars. The envisioned rover would utilized dynamic anchors on the feet of its legs to claw into the surface, engaging and disengaging with each step. This clawing effect can also be used to anchor a lander in near zero gravity on a comet or asteroid. A method for evaluating the performance of different dynamic anchors is proposed and implemented. Physical testing is performed by using a robotic arm to engage a series of anchors with a lunar regolith simulant while measuring the engagement, holding, and disengagement forces. A range of anchor geometries and engagement angles is evaluated and the results are analyzed to determine which parameters effect the holding force and in which way.

We report on the operational challenges of delivering drilled samples to companion payload instruments for a landed mission. Mixing and dilution effects on samples that reach instrument intakes are described. Mixing that can occur with particulates from other areas of the spacecraft is also of special interest to planetary protection efforts. Mixing between samples collected at different depths is of interest to instrument and mission developers. Laboratory and field experiments designed to examine contamination paths, mixing, and dilution of samples are described. Results presented in this paper provide mission planners with procedural tools for addressing challenges to sample delivery of drill cuttings.

Planetary exploration has been limited to surface and near surface terrains. To learn about planets’ histories and especially to find life, deep drilling is required. This paper presents the AMNH Planetary Deep Drill, designed for penetration to 100s of meters and kilometers into Mars’ ice caps and Europa’s ice sheets, respectively. The drill uses a wireline approach where the drill system is suspended on an umbilical; to drill deeper, more umbilical is paid out from a drum. This prototype drill weighs approximately 40 kg and is 4.5 m long. It has been field tested in a gypsum quarry and reached 10.5 meters in one hole and 13.5 meters in a second hole: 3x the drill’s length. The drill required no more than 250 Watt of power to penetrate at 50 cm/hr in this 38 MPa material, analog to ice at 240 K.

Accessing regions on planetary bodies that potentially preserved biosignatures or are presently habitable is vital to meeting NASA solar system “Search for Life” exploration objectives. To address these objectives, a wireline deep rotary-percussive corer called Auto-Gopher was developed. The percussive action provides effective material fracturing and the rotation provides effective cuttings removal. To increase the drill’s penetration rate, the percussive and rotary motions are operated simultaneously. Initially, the corer was designed as a percussive mechanism for sampling ice and was demonstrated in 2005 in Antarctica reaching about 2 m deep. The lessons learned suggested the need to use a combination of rotation and hammering to maximize the penetration rate. This lesson was implemented into the Auto-Gopher-I deep drill which was demonstrated to reach 3-meter deep in gypsum. The average drilling power that was used has been in the range of 100-150 Watt, while the penetration rate was approximately 2.4 m/hr. Recently, a task has started with the goal to develop Auto-Gopher-II that is equipped to execute all the necessary functions in a single drilling unit. These functions also include core breaking, retention, and ejection in addition drilling. In this manuscript, the Auto-Gopher-II, its predecessors and their capability are described and discussed.

Resource Prospector is a lunar mission to investigate “strategic knowledge gaps” (SKGs) for in situ resource utilization (ISRU). The mission is proposed to land at one of the two poles where there are indication of enhanced volatile (hydrogen) concentrations. The landing site will be determined by the RP site-analysis team with input from broader lunar exploration community as being near traversable landscape that has a high potential of containing elevated concentrations of volatiles such as water while maximizing mission duration. A rover will host the Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE) payload for resource mapping and processing. The instruments on the payload include a 1-meter drill, neutron spectrometer, a near infrared spectrometer, a drill operations camera, and a reactor with a gas chromatograph-mass spectrometer for volatile analysis. The concept of operations for the mission were tested during a field test in the fall of 2015. The path from the field test towards flight will be discussed as well as the current status of the instruments in the RESOLVE payload.

In 2014, Ontario Drive and Gear Ltd. (ODG), Canadensys Aerospace Corporation, and a number of partners began developing a pair of small to mid-size lunar rover prototypes funded by the Canadian Space Agency (CSA). Scheduled to be delivered in the first half of 2016, these lunar rover prototypes will demonstrate the compatibility of the 4-wheel rover mobility architecture developed by ODG over several years with higher technology readiness levels, with a target of achieving qualification to technology readiness level (TRL) 6. Additionally, ODG has developed a lunar wheel that is designed to remain compliant over a wide thermal range, thereby increasing tractive effort in both soft and rocky surfaces.

Over the past decade, there have been developments in one meter class rotary percussive drill systems designed for acquisition of volatile rich samples from up to 1 meter depth on the Moon and Mars. The technology readiness level or TRL slowly climbed through various drill iterations: CRUX (TRL3), IceBreaker (TRL4), and LITA (TRL5). The latest drill, called Resource Prospector Drill (RPD), is currently being developed with a goal of reaching TRL 6 in 2016. This paper describes past drill systems and lessons learned, as well as requirements for the new drill and a series of tests performed on LITA drill to reduce the design risk for the TRL6 RPD.

The National Aeronautics and Space Administration (NASA) resource prospector (RP) proposed mission rover prototype is being designed to carry the RESOLVE (regolith and environment science and oxygen and lunar volatile extraction) payload on a mission to the South Pole of Earth’s Moon to prospect for water ice and other volatiles believed to be trapped in the regolith. This is a joint project between Kennedy Space Center (KSC) Swamp Works and Johnson Space Center (JSC). JSC is building the resource prospector (RP) 2015 rover and KSC has designed and fabricated a launch-lock (LL) hold down mechanism prototype. The LL mechanism will attach and support the rover on a lunar lander during launch and transit to the Moon, then it will release the RP rover after touchdown on the lunar surface. This paper presents the design and development of the LL mechanism and its unique features which make it suitable for this lunar exploration mission. The LL is a critical part of the first mission to drill for water ice at the south pole of Earth’s Moon for in situ resource utilization (ISRU). An engineering development unit (EDU) prototype of the LL has been built and tested at KSC.

3D printing presents a new and exceptionally versatile class of construction tasks for robots to undertake using granular materials found in planetary terrains. For space applications, a printing head on a mobile robotic platform could free 3D printing from the constraints of a printer’s workspace, enabling arbitrarily large structures and objects to be built with small robots. Mobile 3D printing consists of building compound parts by looping over 3 high-level steps: (1) printing directly onto the ground surface (and directly onto pre-existing segments as well); (2) relocating from one static build location to the next; (3) accurately and precisely establishing the location of the relevant interface on a pre-existing segment of the printed object, relative to the current position of the robot after relocation. This work presents an approach to mobile 3D printing that addresses these required steps in significantly greater detail than the current literature. A Rostock Delta 3D printer configuration with fused filament extrusion printing is selected to enable direct printing onto the ground surface. Printing directly onto pre-existing segments is demonstrated with a series of thermoplastic parts. Preliminary experimental stress analysis does not reveal any obvious weaknesses at the seam of a compound part, when compared to a monolithic part. Localization techniques are proposed that utilize structured light surface sensing combined with laser range-finder triangulation to precisely measure the robot’s relative translations and rotations, respectively, between build locations.

The NASA Centennial Challenges Program (CCP) uses incentivized prize competitions to push the boundaries of human potential and generate solutions to problems of interest to NASA and the nation. One of the latest NASA challenges is the 3D-Printed Habitat Challenge, designed to advance the fundamental technologies necessary to manufacture off-world habitats reusing, repurposing, and/or recycling available materials and planetary indigenous materials. The vision is that autonomous habitat manufacturing machines will someday be deployed to the Moon or Mars to construct shelters for human habitation. It is expected that advancing the additive construction technology needed to create sustainable housing solutions for Mars and beyond will also help make life better on Earth. NASA has partnered with the National Additive Manufacturing Innovation Institute, also known as “America Makes,” to hold the $2.25 million prize competition.

We present a conceptual construction process for an inhabitable outpost on Mars, using an autonomous multi-robot swarm approach to additively sinter layers of regolith into a protective shield over an inflatable pressurised module. The guiding design hypothesis investigated is that physically distributing risk across multiple simpler units working in parallel can improve chances of success, rather than the traditional consolidation into a single complex unit. This approach is fundamentally enabled by the decreasing size and cost of hardware. Larger numbers of more intelligent robots offers the possibility of emergent behaviour as the collective action of a complex group can be greater than that of individual independent units. In the paper, we consider the general benefits of distributed redundancy, its implications for a robotic construction process using microwave power to selectively sinter layers of regolith in situ, a subsequent habitat design with regolith shield, and a roadmap for a future technology demonstration.

Using automated additive construction (AAC), low-fidelity large-scale compressive structures can be produced out of a wide variety of materials found in the environment. Compression-intensive structures need not utilize materials that have tight specifications for internal force management, meaning that the production of the building materials do not require costly methods for their preparation. Where a certain degree of surface roughness can be tolerated, lower-fidelity numerical control of deposited materials can provide a low-cost means for automating building processes, which can be utilized in remote or extreme environments on Earth or in space. For space missions where every kilogram of mass must be lifted out of Earth’s gravity well, the promise of using in situ materials for the construction of outposts, facilities, and installations could prove to be enabling if significant reduction of payload mass can be achieved. In a 2015 workshop sponsored by the Keck Institute for Space Studies, on the topic of three dimensional (3D) additive construction for space using in situ resources, was conducted with additive construction experts from around the globe in attendance. The workshop explored disparate efforts, methods, and technologies and established a proposed framework for the field of additive construction using in situ resources. This paper defines the field of automated additive construction using in situ resources, describes the state-of-the-art for various methods, establishes a vision for future efforts, identifies gaps in current technologies, explores investment opportunities, and proposes potential technology demonstration missions for terrestrial, International Space Station (ISS), lunar, deep space zero-gravity, and Mars environments.

In situ resource utilization (ISRU) or “living off the land” relies on exploiting local resources and in turn reducing burden of transporting supplies. In a more conventional ISRU approach, feedstock is mined and transported to a processing plant. In this paper, we present alternative design that combines mining and extraction into one and eliminates transport step. We investigated three planetary volatiles extraction (PVEx) methods: “sniffer,” mobile in situ water extraction (MISWE), and corer. All three approaches are drill based, which helps with material penetration and capture of volatiles. It was determined that the sniffer approach does not work very well, because volatiles tend to escape up the soil and into the vacuum above. The MISWE came second in terms of water extraction efficiency and energy conversion efficiency. The corer turned out to be the best approach. It also required less energy to drill than MISWE, rendering it a more efficient approach in terms of drilling.

Research is ongoing to develop a laboratory volatiles extraction system that can demonstrate a heating process for releasing helium-3 (³He) and other important lunar volatiles from lunar regolith. Beyond the Apollo and Luna lunar soil samples, there is no regolith or regolith simulant implanted with solar wind volatiles that is available. An implantation device is being developed to implant helium into batches of JSC-1A simulant. The device, named the solar wind implanter (SWIM), uses a voltage difference between planar electrodes to accelerate ions at solar-wind speeds into a thin, falling sheet of regolith simulant. The SWIM device has been assembled and initial implantation tests have been conducted. Updates to the system are being developed to allow SWIM to produce simulant with the desired amount of embedded helium.

Ascending steep slopes is often a very difficult challenge for off-road vehicles, whether on Earth or on extraterrestrial bodies. This challenge is even greater if the surface consists of loose granular soil that does not provide much shear strength. This study investigated how the path at which a vehicle traverses a slope, specifically the angle that it is commanded to drive relative to the base of the hill (the angle of attack), can affect its performance. A vehicle was driven in loose sand at slope angles up to 15 degrees and angles of attack ranging from 10 to 90 degrees. A novel photogrammetry technique was implemented to both track vehicle motion and create a three dimensional profile of the terrain. This allowed for true wheel sinkage measurements. The study showed that though low angles of attack result in lower wheel slip and sinkage, the efficiency of the vehicle’s uphill motion increased at higher angles of attack. For slopes up to 15 degrees, a 90 degree angle of attack provided the greatest likelihood of successful ascent.

Regolith is present on most planetary surfaces such as Earth’s moon, Mars, and asteroids. If human crews and robotic machinery are to operate on these regolith covered surfaces, then they must face the consequences of interacting with regolith fines which consist of particles below 100 microns in diameter down to as small as sub-micron scale particles. Such fine dust will intrude into mechanism and interfaces causing a variety of problems such as contamination of clean fluid lines, jamming of mechanisms, and damaging connector seals and couplings. Since multiple elements must be assembled in space for system level functionality, then it will be inevitable that interfaces will be necessary for connections to pass commodities such as cryogenic liquid propellants, purge and buffer gases, water, breathing air, pressurizing gases, heat exchange fluids, power, and data. Dust tolerant automated umbilical (DTAU) systems which can operate in dusty planetary surfaces have been under development at NASA’s Kennedy Space Center (KSC) for a number of years. Engineering development unit (EDU) prototypes of a DTAU have been built and tested. The design and operation of these prototypes are explained and discussed in this paper.

To date, concepts for establishing long-term habitats for a human crew on Mars have revolved around the periodic delivery of wholesale systems built fully on Earth, which then dock together in a similar fashion to the International Space Station. While initial missions will require such rigorously-tested systems, this ‘plug-and-play’ method of pre-built systems from Earth becomes unfeasibly costly over time due to the high launch mass. In situ resource utilization (ISRU) provides a cost-effective, sustainable means of expansion and maintenance of a human habitat on Mars. In this paper, we propose a design for a Martian human habitat for a crew of four constructed exclusively with in situ resources, using existing technologies in robotics, materials processing, and additive construction. We further draw attention to livability and architectural considerations in the design which operate in tandem with engineering ones, as they are critical to long-term human habitation.

A long-term base on Mars, at the center of an “Exploration Zone,” would require substantial quantities of in situ resources. Although water is not the only resource on Mars of potential interest, it stands out as the one that most dominates long-lead strategic planning. It is needed for multiple aspects of various human activities (including our own survival), and in significant quantities. The absence of a viable deposits could make a surface “field station” logistically unsustainable. Therefore, identification of deposits, and development of the technology needed to make use of these deposits, are an important priority in the period leading up to a human mission to Mars. Given our present understanding of Mars, ice and hydrated minerals appear to be the best potential sources for the quantity of water expected to be needed. The methods for their extraction would be different for these two classes of deposits, and at the present time, it is unknown which would ultimately be an optimal solution. The deposits themselves would ultimately have to be judged by an economic assessment that takes into account information about geologic and engineering attributes and the “cost” of obtaining this information. Ultimately, much of this information would need to come from precursor missions, which would be essential if utilization of Martian in situ water resources is to become a part of human exploration of Mars.

The atmosphere of Mars, which is ~95% carbon dioxide (CO₂), is a rich resource for the human exploration of the red planet, primarily by the production of rocket propellants for Mars ascent vehicles and oxygen for life support. Three recent projects led by NASA’s Kennedy Space Center (KSC) have been investigating the processing of CO₂. The first project successfully demonstrated the Mars Atmospheric Processing Module (APM), which freezes CO₂ with cryocoolers and combines sublimated CO₂ with hydrogen to make methane and water. The second project absorbs CO₂ with ionic liquids and electrolyzes it with water to make methane and oxygen, but with limited success so far. The goal of the third project is to recover up to 100% of the oxygen in spacecraft respiratory CO₂. A combination of the reverse water gas shift reaction and the Boudouard reaction eventually fill the reactor up with carbon, stopping the process. A system to continuously remove and collect carbon is showing promise.

Modeling is developed for a thermal water propulsion system for small spacecraft such as CubeSats and for larger spacecraft acting as their mother ship. Water is chosen as the propellant because it is easily mined on many planetary surfaces so that the spacecraft can refuel and continue their mission as long as they have an energy source. The propulsion system works by heating the water tank to high temperature and pressure, then venting the water vapor through a converging-diverging nozzle into vacuum. Modeling needed to account for the non-ideal gas behavior of steam while in saturated conditions of the tank and while expanding through the nozzle into space. The results show that a specific impulse of about 160 sec is possible, and that hopping distances for such spacecraft are in the range of multiple kilometers to tens of kilometers, depending on spacecraft mass, water tank size, and planetary gravity.

A decade of evolutionary development of integrated automated drilling and sample handling at analog sites and in test chambers has made it possible to go 1 m through hard rocks and ice layers on Mars. The latest Icebreaker-3 drill has been field tested in 2014 at the Haughton Crater Mars-analog site in the Arctic and in 2015 with a Mars lander mockup in Rio Tinto, Spain (with sample transfer arm and with a prototype life-detection instrument). Tests in Rio Tinto in 2015 successfully demonstrated that the drill sample (cuttings) was handed-off from the drill to the sample transfer arm and thence to the on-deck instrument inlet where it was taken in and analyzed (“dirt-to-data”).

This paper documents the development of an autonomous health monitoring system for an interplanetary drill using structural health monitoring (SHM) techniques. Given the desire to search for extinct and extant life on other planets, it becomes necessary to develop a deep penetrating system to obtain samples for analysis. This system may drill into icy soils, which can cause the drill to become irrecoverably stuck if preemptive measures are not taken. There is also the added lightspeed and buffering communications delay, which makes manual human operation impossible. For these reasons, it is important for the drill to recover from faults completely autonomously.

Optical mining is an approach to simultaneously excavate carbonaceous chondrite asteroid surfaces and drive water and other volatiles out of the excavated material. Optical mining is part of an in situ resource utilization (ISRU) propellant and mission consumable mission architecture called Apis (asteroid provided in situ systems). The asteroid is captured in an inflatable bag without the need for complex robotics. Highly concentrated sunlight is delivered to the surface of the asteroid using reflective non-imaging optics. Concentrated sun light ablates the surface, continually exposing new material and forcing water and other volatiles out of the ablated material. This paper presents results of an experimental program to support optical mining. We show evidence that when exposed to intense light asteroid simulants spall and surfaces disaggregate.

Optical Mining is an approach to excavate volatile rich asteroids; drive water and other valuable volatile materials from the excavated material; and collect the volatiles for use as propellants and feedstocks for mission consumables. Optical Mining is part of an in situ resource utilization (ISRU) mission architecture called Apis (Asteroid Provided In Situ Systems) which includes Honey Bee mining vehicles and Worker Bee space tugs. In the Honey Bee mining vehicles, the asteroid or large boulder is enclosed in a thin-film bag to minimize the need for complex robotic material handling and excavation equipment. Highly concentrated sunlight is delivered to the surface of the asteroid using non-imaging optics and lightweight, thin-film deployable reflectors. The concentrated sunlight spalls the surface, continually exposing new material while heating the spall particles to extreme temperatures, thereby releasing the volatiles. Released volatiles are subsequently thermally separated and collected in geometrically large but lightweight thin-film cold traps at temperatures controlled to sort specific molecular species into specific containers, each held at the correct temperature to store the collected material as a solid. This paper summarizes results of a coordinated experimental and analytical program to develop Optical Mining and enable the Apis architecture. Efforts described in this paper include subscale tests and demonstrations of the Optical Mining process on 2 to 5 cm diameter samples of meteorites and asteroid simulants; developmental work on a solar thermal oven simulator to conduct fundamental and applied work on kilogram sized samples; an engineering demonstration of Optical Mining of a kilogram sized sample of asteroid simulant; analytical modeling of optical excavation; and analytical work assessing the magnitude of resources available and discoverable in highly Earth-like heliocentric orbits.

Near-earth asteroids (NEAs) are key resources for the cost-effective exploration and eventual settlement of space. However, the microgravity environment results in several challenges for asteroid exploitation, including the difficulty of processes—such as digging—that we take for granted on the Earth’s surface. The electromagnetic asteroid regolith excavator (EARE) is a method of excavation (including drilling) that circumvents some of these challenges using travelling waves of magnetism to draw magnetic materials into and through a tube and then to direct their movement into a collection bag. It takes advantage of the magnetic nature of most chondrite asteroids (whether in nickel-iron grains or in ferromagnetic minerals such as magnetite) to rapidly move large volumes of material. Non-magnetic materials are carried along with the magnetic portion, thanks to friction, inertia, and the careful timing of magnetic pulses. No hard asteroid anchoring is required—the forces pulling the asteroid regolith up and into the EARE provide more than enough force to keep it in contact with the asteroid. This paper reports preliminary results from a terrestrial prototype that necessarily uses magnetic fields several orders of magnitude stronger than would be required on an asteroid, using NWA ordinary chondrites and carbonaceous chondrite simulants prepared as loose regolith.

The Mars 2020 and Mars Sample Return missions expected to fly to Mars within the next ten years will each include an in situ resource utilization (ISRU) system. They convert carbon dioxide in the Martian atmosphere into consumable oxygen at 1% and 20% of the rate required by a full scale human exploration Mars mission, respectively. The ISRU systems will need to draw in the surrounding atmosphere at a rate of 110 L/min and 550 L/min, respectively, in order to meet their oxygen production goals. Over the duration of each respective mission, a total atmospheric dust mass of 4.86 g and 243 g will be drawn into each system, respectively. Ingestion of large quantities of dust may interfere with ISRU operations, so a dust mitigation device will be required. The atmospheric volume and dust mass flow rates above will be utilized to simulate Martian environmental conditions in a laboratory electrostatic precipitator being developed to provide active dust mitigation support for atmospheric ISRU systems such as these.

Dust mitigation technology has been highlighted by NASA and the International Space Exploration Coordination Group (ISECG) as a global exploration roadmap (GER) critical technology need in order to reduce life cycle cost and risk, and increase the probability of mission success. The Electrostatics and Surface Physics Lab in Swamp Works at the Kennedy Space Center has developed an electrodynamic dust shield (EDS) to remove dust from multiple surfaces, including glass shields and thermal radiators. Further development is underway to improve the operation and reliability of the EDS as well as to perform material and component testing outside of the International Space Station (ISS) on the materials on international space station experiment (MISSE). This experiment is designed to verify that the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the Moon.

This paper has two main objectives: to review the current knowledge of the Moon’s environmental conditions, and to derive from them, the top-level requirements for the assembly, integration, and testing (AIT) of lunar systems and structures. The lunar environmental conditions include temperature variation, radiation aspects, atmosphere and pressure, meteoroid impacts, the lunar gravitational field (including anomalies), lunar regolith (dust), moonquakes, and other lunar geophysical features depending on the location of the lunar scientific station and their impact on any lunar system or structure operating on the lunar surface for the required time range. This lunar system or structure must first be developed on Earth and then brought to the pre-selected lunar destination. Afterwards, the top-level AIT requirements for surface lunar systems/structures are derived and presented based on the current knowledge of lunar environmental conditions. Special attention is given to requirements associated with the thermal, atmosphere, radiation, micrometeoroid, and dust environments. This paper also includes conclusions and recommendations from a Canadian perspective.

The all-terrain hex-limbed extra-terrestrial explorer (ATHLETE) robotic mobility platform can provide precision positioning and mobility for site preparation and regolith construction needs. ATHLETE is a multi-use platform designed to use swap-out tools and implements that can be applied to any number of tasks that need precision limb manipulation or mobility. Major capabilities include off-loading habitats, transporting surface assets, robotically assembling outposts from multiple mission manifests, and supporting science and technology objectives. This paper describes conceptual approaches for supporting NASA regolith construction research, such as additive construction, modular brick and panel factory, and mobile ISRU platform.

In support of an ESA-funded concept study considering a sample return mission, a simulant of the Martian moon Phobos was needed. There are no samples of the Phobos regolith, therefore none of the four characteristics normally used to design a simulant are explicitly known for Phobos. Because of this, specifications for a Phobos simulant were based on spectroscopy, other remote measurements, and judgment. A composition based on the Tagish Lake meteorite was assumed. The requirement that sterility be achieved, especially given the required organic content, was unusual and problematic. The final design mixed JSC-1A, antigorite, pseudo-agglutinates and gilsonite. Sterility was achieved by radiation in a commercial facility.

Anchoring, drilling, extraction, storage, and transfer of regolith under micro-gravity while avoiding loss of volatiles, exposure to space environment, or dilution of in situ volatiles with ‘working gasses’ presents numerous challenges for future missions to small bodies and especially for prospecting and ISRU operations. A specialized flexible micro-gravity drilling and regolith extraction system under development can selectively extract subsurface regolith fines from depths between 1m and 3m below the surface through a small (~3cm diameter) entrance drill hole. Such a system could selectively extract just the fine-fraction of regolith from depths which have not been exposed to significant space-weathering (e.g. by utilizing its unique oversize-particle-rejecting drill-head feeder). The flexible drill system could also be utilized to create horizontal wells for direct in situ extraction of volatiles on the moon, for instance, without removing the bulk of the regolith. Microgravity capable storage and transfer vessels and conveying lines could be utilized to store, dispense, or transfer the material in continuous or batch modes to other equipment for processing (i.e., the microgravity storage vessels could act as a buffer volume to provide a uniform rate of delivery for a continuous process, or they could dispense material in batches, as needed). The entire regolith extraction systems being developed can be enclosed to minimize loss of volatiles, and the systems produce no extraneous debris after initiation of the drill-hole.

This paper presents preliminary results towards the development of a new set of systems and technologies that support in situ resource utilization (ISRU) for future space exploration missions to near-earth objects (NEO). In situ resource utilization has called the attention of researchers since it would greatly facilitate planetary exploration by drawing needed resources from the local environment, reducing costs of operation and making more feasible long term space exploration missions. Due to the nature of these extreme environments, this requires the development of novel technologies and advanced unmanned space systems integrated with sample-capture devices designed to prospect the desired resources. In particular, this research effort is focused on the development of advanced flight control systems, vision-aided navigation algorithms, and design and implementation of micro sampling system devices to be implemented in a marsupial free-flyer prospector vehicle. The preliminary results presented in this paper show favorable and feasible results in order to use some of these technologies to advance future space exploration missions.

Asteroids with high concentrations of volatiles and organics have high potential for in situ resource utilization (ISRU) and may be a key resource for future exploration architectures for near earth objects (NEOs) and the moons of Mars. Samples of this asteroidal material are available for analysis in the form of the volatile-rich carbonaceous chondrite meteorites. The organic component of these meteorites are rich in polycyclic aromatic hydrocarbons (PAHs) which can be either toxic or carcinogenic or both. To pave the way for the success of potential missions and ISRU applications, there is a need to conduct detailed studies of meteoritic PAHs that will provide the parameters necessary for developing handling protocols, design of ISRU systems, and the qualification of engineering designs.

This paper discusses the laser-induced remote analyzer (LIRA) LIBS engineering breadboard, relevant verifications, and its potential application to future lunar and asteroid missions to assist the exploration and mapping of mineralogy and in situ resources. LIRA consists of a laser-induced breakdown spectrometer and imaging system that provides elemental data and context imaging for stand-off investigations of targets on planetary surfaces.

This objective of this project was to propose the fabrication of porous construction materials from lunar, Mars, or terrestrial basalt regolith to help address the technology needs for safe and efficient space exploration identified in NASA Space Technology Roadmap (TA-12), Materials, Structures, Mechanical Systems and Manufacturing. The proposed technology also addresses in situ resource utilization and construction and assembly found in the roadmap (TA-7), Human Exploration Destination Systems. This technology combines an innovative regolith processing method, using supercritical fluids, with extrusion and injection molding, which are used to produce useful shapes. The innovation differs from existing technologies in that the low density allows for faster processing time and lower power requirements, while producing complex shapes allowed by injection molding. In this paper, we have summarized the results of a new and innovative method for terrestrial and in-space production of materials/systems for use in exploration activities such as roads, habitats, radiation shielding, launch/landing pads, and ejecta mitigation: the supercritical processing of basalt materials.

For repeated missions to develop infrastructure on the Moon and Mars, repeated visits to the same location will be required and landing pads will be a necessity. On the Moon these landing pads would prevent the regolith dust from sandblasting other infrastructure at 3 km/s and spreading dust all over the Moon and even into lunar orbit. On Mars the landing pads would prevent the lander exhaust plume from excavating a large hole under the lander, melting possible ice and possibly tipping the lander on its side resulting in damaging the lander. These landing pads would have to be built by robotic means before the human sized missions would arrive. To design these robots, it is necessary to determine what the landing pad could be made of and how they could be constructed. Various ISRU approaches have been suggested and studied for the center zone of the landing pad where the hot hyper velocity exhaust gases would contact the landing pad directly. A landing pad would provide a stable landing zone for touchdown of the lander and effective deflection of the exhaust plume without excavating a hole under the lander. This deflected (now horizontal flowing) plume would still scour the immediate area (secondary zone) next to the central landing zone and pick up the dust particles there. The secondary zone has a much larger surface area that needs to be stabilized and thus it would be beneficial to use in situ materials. Various options can be considered such as sintering, tiles, rock cover, and others. This paper will focus on tests performed on rock stabilized zones and their layering and on a method to model the in situ collected and constructed rock cover needed to lock in the regolith dust. The test setup, several tests and the results will be discussed. In addition, a first order model will be discussed to determine the maximum size rock needed to lock underlying layers in place during landing and take-off rocket exhaust plume loading cases.

Recently, NASA Headquarters invited the pacific international space center for exploration systems (PISCES) to become a strategic partner in a new project called “additive construction with mobile emplacement (ACME)”. The goal of this project is to investigate technologies and methodologies for constructing facilities and surface systems infrastructure on the Moon and Mars using planetary basalt and other in situ materials. The first phase of this project was to robotically-build a 20 meter (66-ft) diameter vertical takeoff, vertical landing (VTVL) prototype pad out of local basalt material on the Big Island of Hawaii. This VTVL pad is a technology “proof of concept” demonstration project to show how a robotic precursor mission could viably construct a VTVL pad on a planetary surface. Such VTVL pads can mitigate the effects of a lander rocket engine exhaust plume impinging on the regolith surface, which can cause cratering and high speed ejecta. In March 2015 a “lunar sidewalk” construction was first completed in Hilo, Hawaii, which proved that raw crushed Hawaiian basalt could be sintered into modular paver elements. The Hawaiian basalt is very similar to granular materials found on Mars and the Moon. Subsequently, PISCES and the NASA Kennedy space center (KSC) Swamp Works team completed the basalt construction of a tele-operated, robotically-built basalt VTVL pad. Construction was started in October 2015 and successfully completed by the end of December 2015. PISCES and NASA KSC assessed various in situ construction methodologies for the 2015 VTVL pad deployment demonstration using additive construction with Hawaiian basalt regolith. Using the PISCES robotic rover (named “Helelani”) as the central platform for construction, the team evaluated a variety of technologies for stabilizing the basalt surface, and then selected a sintered inter-locking paver system to meet the requirements. New methods for sintered basalt regolith paver production were developed and a tele-operated paver deployment mechanism (PDM) was developed and installed on the PISCES rover to simulate VTVL pad construction operations during an actual space mission. The rover was tele-operated locally in Hilo, Hawaii, and also from NASA KSC in Florida, which created valuable lessons learned for future space missions requiring a VTVL pad capability.

Increasing human demands on the Earth’s limited resources has generated a need for the development of new technologies that are more environmentally sustainable. Since space settlements must, because of their isolation from Earth, be designed from the start to be mostly self-sufficient, it follows that the technology needed for space settlement will also produce major benefits in the advance of environmentally sustainable technology for communities on Earth. This paper explores the potential synergy between space settlement research and research on environmentally sustainable technologies in water recycling and vertical farming systems. It then outlines a research agenda for space settlements that could provide near-term benefits to the technological base for developing more self-sufficient communities on Earth.

In this paper, we demonstrate that a simple robotic swarm can use a genetic algorithm (GA) to achieve autonomous navigation in highly cluttered environments. We also show the GA can evolve effective strategies for coping with random obstacle placements using a central place foraging algorithm (CPFA). The CPFA combines stochastic movements, insect-inspired obstacle avoidance, and simple communication among robots. We modify the CPFA by allowing simulated robots to communicate with stygmergic trails in CPFA-trails (CPFAT). Both the CPFA and CPFAT can evolve foraging strategies to collect resources in the presence of a high density of randomly placed obstacles. CPFAT additionally succeeds against a classic bug trap, where the CPFA fails. These methods are simple to implement, run in real-time, and need no global knowledge of the environment.

Long-term autonomous operation of a robotic swarm in harsh or inaccessible locations will require the ability of the swarm to manage operational details such as battery charging without human intervention. Small robots may not be able to manage their own power internally, via solar cells or fuel cells, but may be dependent on external means to recharge batteries. In this paper we will demonstrate the ability of a simple robotic swarm to use a genetic algorithm (GA) to evolve optimized, behavioral parameters including the ability to determine battery charging behavior. We introduce two new battery parameters to the robots’ central place foraging algorithm (CPFA) and allow the GA to optimize the behaviors such that, on average, no robots are left “dead” due to inadequate battery charge. We also demonstrate that the GA can evolve a successful resource collection strategy while minimizing the number of robot casualties. The additional parameters and behaviors do not alter the original algorithm’s simplicity, ability to run in real-time, and requirement of using only local knowledge.

High-mass planetary surface access is one of NASA’s technical challenges involving entry, descent, and landing (EDL). During the entry and descent phase, frictional interaction with the planetary atmosphere causes a heat build-up to occur on the spacecraft, which will rapidly destroy it if a heat shield is not used. However, the heat shield incurs a mass penalty because it must be launched from Earth with the spacecraft, thus consuming a lot of precious propellant. This NASA innovative advanced concept (NIAC) phase I project investigated an approach to provide heat shield protection to spacecraft after launch and prior to each EDL thus potentially realizing significant launch mass savings. Heat shields fabricated in situ can provide a thermal-protection system for spacecraft that routinely enter a planetary atmosphere. By fabricating the heat shield with space resources from materials available on moons and asteroids, it is possible to avoid launching the heat-shield mass from Earth. Regolith has extremely good insulating properties and the silicates it contains can be used in the fabrication and molding of thermal-protection materials. In this paper, we will report on the findings of the NIAC phase I study.

The ultimate product from extraterrestrial in-situ resource utilization is a self-replicating machine by virtue of its ability to exponentially expand productive capacity. Self-replication is a byproduct of the universal constructor and we propose that 3D printing technology constitutes a universal construction mechanism. Universal construction is based on the manufacture of robotic mechanisms that are the core to any motorized kinematic machine. All robotic mechanisms are mechatronic systems comprising motors, sensors and control system. We present preliminary work to demonstrate that electric motors and electronics (as the medium of control) can be 3D printed. We also impose the constraint that our self-replicating machine be constructed entirely from lunar-derived materials. The acquisition of these materials is emphasized. The existence of self-replication capacity on the Moon would revolutionise space exploration and introduce the possibility of robust space-based solutions to our current global environmental problems at low cost.

A new plasma drilling system is under development by the Zaptec, Inc. company that will enable deep subsurface access on asteroids, Mars and its moons for in situ science investigation, sampling and exploration. The current project's purpose is to develop prototypes and field-test robotic plasma drilling technologies for missions to the Moon, asteroids, and Mars in the 2021-2025 time frame. Zaptec has developed a powerful electronic micro-transformer that enables transformation of high voltages and high currents into very compact and small devices for space applications. The core application is a new standard for safety, light-weight and energy efficient power distribution for space systems.

The ultrasonic/sonic driller/corer (USDC) and Auto-Gopher drills were developed by NASA Jet Propulsion Laboratory Honeybee Robotics Spacecraft Mechanisms Corporation and NASA Jet Propulsion Laboratory to overcome the limitations of current drilling devices for planetary exploration. The percussive mechanism of these drills is comprised of the ultrasonic horn, free mass, and drill rod. This paper presents a detailed model of the interaction between the free mass (striker) and the drill rod, and between free mass and the ultrasonic horn. The contact interaction between the components is obtained using Hertz theory coupled with the vibration of the drill rod and the motion of the ultrasonic horn. The average duration of impact, average maximum contact force, and average frequency of oscillation of the free mass was obtained. It was observed that the frequency of oscillation of the free mass is lower than that of the ultrasonic horn.

An ideal candidate to accomplish the reinforcement of the matrix and interphase zones of fiber reinforced composites (FRPs) is carbon nanotubes (CNTs). Because of their superior mechanical performance along with their excellent thermal and electrical properties, CNTs have been studied extensively as potential enhancements to traditional composite materials. CNTs are commonly grown in bulk and subsequently dispersed directly into the matrix material for composite material production. However, this approach has proven to be very difficult to implement in practice. A more effective approach is to grow CNTs directly on the reinforcing material, thereby avoiding the issue of CNT dispersion while also placing the CNTs precisely in the interphase zone. To these ends, a novel process – the PopTube Approach – has been developed that uses microwave irradiation to grow CNTs on carbon fibers in 15-30s in air. One concern with this technique is that the axial properties of composites can be adversely affected due to damage induced in the fibers by microwave irradiation. The objective of this study is to examine the effects of PopTube Approach treatment on one important axial property of composites: low-speed impact resistance. To this end, CNT-reinforced woven composites were produced using this novel method and tested for low-speed impact resistance using the Izod impact test. Two composites processing techniques/material systems were considered: wet layup vacuum bagging (with a room temperature-cure epoxy resin) and prepregging/press curing (with an elevated temperature cure polybenzoxazine resin). With each processing technique/material system, an untreated group was tested along with a treated group. Izod impact resistance testing showed that with wet layup vacuum bagging, the PopTube Approach-treated group exhibited a sizable decrease in Izod impact strength relative to the untreated group, whereas with press curing, the treated group exhibited a moderate increase in Izod impact strength relative to the untreated group. Following mechanical testing, scanning electron microscopy (SEM) was used to characterize fracture processes in the woven composites. This experimental program serves to not only provide insight into the low speed impact resistance of CNT-reinforced composite materials produced via the PopTube Approach, but also to characterize the effectiveness of processing techniques with regard to the implementation of reinforcing fabrics processed by this novel method.

It is shown that force-induced-dimple (FID), initial geometric imperfection leads to a far worse deterioration of buckling strength (for up to four times) than currently used modulated eigenshape(s) or lower bound increased-radius shape deviations from perfect geometry. The FID approach provides not only safer estimates of buckling resistance, but also it is efficient in terms of computing time. The physics behind the FID-concept is closer to reality than in the other two approaches.

The need for accurate material models to simulate the deformation, damage, and failure of polymer matrix composites under impact conditions is becoming critical as these materials are gaining increased usage in the aerospace and automotive communities. In order to address a series of issues identified by the aerospace community as being desirable to include in a next generation composite impact model, an orthotropic, macroscopic constitutive model incorporating both plasticity and damage suitable for implementation within the commercial LS-DYNA computer code is being developed. The plasticity model is based on extending the Tsai-Wu composite failure model into a strain hardening-based orthotropic plasticity model with a non-associative flow rule. The evolution of the yield surface is determined based on tabulated stress-strain curves in the various normal and shear directions and is tracked using the effective plastic strain. To compute the evolution of damage, a strain equivalent semi-coupled formulation is used in which a load in one direction results in a stiffness reduction in multiple material coordinate directions. A detailed analysis is carried out to ensure that the strain equivalence assumption is appropriate for the derived plasticity and damage formulations that are employed in the current model. Procedures to develop the appropriate input curves for the damage model are presented and the process required to develop an appropriate characterization test matrix is discussed.

This work focuses on a novel class of composites that can be produced extraterrestrially, or in situ, by desiccating a mixture of soil, water, and protein binder to create a strong, versatile material. To date, experimental tests of mechanical properties have shown significant variability among samples. For this paper, the focus is on the framework for the creation of statistically equivalent periodic unit cells (SEPUC) to stochastically model protein-bound composites for the purpose of creating finite element models that provide insights into experimental results. Model inputs include the soil granulometry and volume fractions of the phases. After a virtual image is created, it is then statistically compared to real images obtained through micro-CT scanning and a simple genetic algorithm is used to minimize the statistical difference between the virtual model and the real image.

This paper studies the coupled mechanical and electrical behaviors of carbon fiber-based structural electric capacitors (CSEC) materials, in particular the effects of interlaminar damage on both mechanical and electrical performances of the material. CSEC specimens with three different dielectric materials (i.e., trilayer PP-PET-PP, PETE, and LTX films) and four layup configurations were fabricated and tested to failure. The mechanical and electrical properties of material were measured concurrently and the results were compared to conventional carbon fiber reinforced polymer (CFRP) composites. It was found that the load bearing capacity of CSEC materials is, in general, lower than their CFRP counterparts, and it varies as a function of the dielectric material type. The lower load bearing capacity of CSEC is mainly due to interlaminar damage, which also leads to capacitance deterioration as mechanical load. The interlaminar damage initiates at early-stage of loading (i..e, 30-40% of the peak stresses), accompanied by capacitance decay. Both the mechanical and electrical properties of CSEC are functions of the dielectric material type and layup configuration. In general, thinner dielectric films will lead to higher nominal stiffness/strength and higher initial capacitance. On the other hand, the materials’ ability to retain electrical capacitance under mechanical loading is primarily related to the interfacial fracture toughness, G_Ic, between dielectric materials and the matrix polymer.

In the exploration of planetary materials using robotic probes, one of the key priorities is to establish fundamental level understandings on the mechanical response of materials under different levels of loading. In this context, though a number of strength characterisation tools are applied in the space industry, whole-field visualization of stress and temperature distribution on rock samples and their potential relevance to fracture under external loading is not yet well exploited. In this work, we apply two types of tomography namely (i) IR tomography and (ii) PSAT tomography to understand the variation of temperature and shear stress distribution respectively anywhere on the samples at point scale. Sandstone is used as a simulant material here. Potential links between the tomography measures and the fracture strength of the sandstone are revealed in this work.

A concrete face rockfill dam has been running for 8 years since the construction completed. Aiming at the crack problem of the left dam abutment in the dam site inspection, firstly, according to the data analysis of dam displacement monitoring data, the displacement of the left dam abutment is determined. Secondly, in order to analyze the cause of the cracks in the left dam abutment, considering the characteristics of the project, the construction scheme, and the filling material, the three-dimensional finite element model is established, thus the left dam abutment of dam crack irregular deformation is calculated under the influence factors such as the slope gradient, dam filling materials, and dam filling sequence. Finally, based on the research, it is shown that it should make much account of the slope gradient, dam filling materials, and dam filling sequence in order that the irregular dam deformation could be avoided for the concrete face rockfill dam.

The Zhen’an pumped-storage power station is located at a gradient valley in Shanxi Province, China. Its concrete face rock-fill dam of the upper reservoir is about 125.9m in height. The seismic response characteristics of dam body under design earthquake condition are calculated by using the three-dimensional nonlinear finite element method and the Hardin-Dernevich model. Specifically, the acceleration response, the displacement response, and the stress response of rock-fill dam body, and face slab, the permanent deformation, and the maximum shear stress of dam, etc. are all obtained. Moreover, the earthquake-resistance safety of dam is evaluated, and the ultimate aseismatic capacity of dam under checking earthquake is predicted using overloading method. Results show that the distribution laws of displacements and stresses of dam is consistent with the general rule, but the sloping valley terrain impacts the local deformation and stress of dam significantly. Under normal water level and design earthquake condition with peak acceleration 186.00cm/s², the maximum acceleration response along the upstream-downstream direction is 8.70m/s² at downstream of dam crest; the maximum displacement response is 94.5mm; the maximum shear stress of dam body is 337kPa and the permanent settlement is 56.7cm. Additionally, the ultimate aseismatic capacity calculated by overload method is about 760gal, which indicates that the seismic safety of dam body meets requirement.

Discontinuities are ubiquitous in rock masses, such as faults, joints, and fractures. The localized stability around underground openings in discontinuous rock masses depends on geometry, geology, and properties of discontinuities between rock masses. Understanding the failure mechanism of discontinuous rock masses around an underground structure is important. In this paper, multibody finite element method (MFEM) was proposed for analysis of discontinuous deformation problems of underground opening with faults. Using this method, discontinuous deformation problem is transformed to contact problems between blocks to be simulated and solved. Detailed theoretical basis of MFEM were given. The localized stability around underground openings in discontinuous rock masses under different fault dips and lateral pressure coefficient are analyzed and presented. This numerical investigation revealed that both fault dips and lateral pressure coefficient have significant impact on the underground cavern stability. The distribution of displacement and plastic zone was graphically presented, and the mechanisms were discussed. These results offer a guideline in support design.

Calculations of thermal stress and nonlinear soil behavior for mass concrete are separately dealt in traditional methods. Thus, the combined influences cannot be considered simultaneously, and the calculation accuracy is significantly affected, especially when structures are built on soft foundation which has obviously consolidation behavior. This paper presents a new method for calculating displacement and stress distribution of mass concrete during construction on soft foundation with consideration of thermal stress and soil consolidation. The necessity of consideration of “consolidation” is proved using simple 2D cases. A real lock floor program is conducted, and comparisons between with and without consolidation are made. The results show that calculation with consolidation is more realistic. The new method used in this paper is valuable for similar engineering cases for more reasonable design.

An aluminum/high-density polyethylene (HDPE) functionally graded material (FGM) has been fabricated as a key component of a multifunctional building envelope for high performance of energy efficiency and sustainability. The FGM layer gradually transits material phases from the well-conductive side (dominated with aluminum) to another highly insulated side (dominated with HDPE). The heat in the PV cells can be easily transferred into the conductive side of the FGM and then collected by the water flow in the embedded tubes. Therefore, the operational temperature of the PV cells can be significantly lowered down, which recovers the PV efficiency at high temperatures and at the mean while collect hot water for residential usages. Because of the gradual phase change of aluminum and HDPE across the thickness direction, after cooled down and removed from the mold, considerable curving deformation was found in the final product of the designed FGM panel. Such curving deformation causes quite challenges in assembling the FGM panel into a flat multifunctional roofing panel and bring forth serious impact on the structural integrity. To overcome such a problem, the thermal and mechanical behaviors of the FGM panel have to be well predicted. For this purpose, a closed-form solution based on a refined plate theory is presented in this study for a FGM circular plate subjected to thermo-mechanical loading. Corresponding experimental tests have been conducted to verify the present theoretical solutions. It was found that the presented theoretical model is able to accurately predict the thermo-mechanical behavior of the developed FGM panel.

Fiber-reinforced polymer (FRP) is made of high-strength fibers embedded in resins, which can provide high-strength and durability. In the last two decades, general attention has been significantly increased towards the use of FRP in various structural types in civil engineering. However, the low fire endurance remains a major obstacle. A literature review shows that a fair amount of research has used insulation as an effective way to achieve the required fire performance, which is costly. A more cost-effective way to enhance the fire resistance of FRP is to add fire-retardant filler, such as alumina tri-hydrate (ATH), to the resin. Extensive research has been conducted in this area, including the author’s research group, mainly focused on experimental investigations. The objective of this paper is to develop a numerical model to predict mechanical properties of FRP with different ATH ratios based on a composite micromechanical model. The accuracy of this model is validated against existing experimental data. Discussions and recommendations for further research are provided.

Clean, plentiful, and easy-to-harvest solar energy is the ultimate renewable energy. It is becoming more important as the world begins to take notice of the burgeoning carbon emission problems that come with burning fossil fuels. Thin-film solar cells have been increasingly used for energy harvesting. This paper studies the strain effect on their performances under compression and tension. To this end, compression and tension tests were conducted using an MTS machine. Since the solar cells are flexible, they were bonded to fiber-reinforced polymer (FRP) plates. A projector was used to illuminate the cells during the tests to simulate 100% sun. J-V characteristic curves were measured at different strains until the samples failed. It can be concluded that there are strain thresholds for both compression and tension. Solar cells worked properly below the threshold but degraded rapidly once the threshold was passed.

Thin oxide and metal films deposited on polymer substrates are emerging technologies for advanced reflectors for concentrated solar power applications, due to their unique combination of light weight, flexibility, and inexpensive manufacture. Thus far, there is little knowledge on the mechanical integrity or structural persistence of such multi-layer thin film systems under long-term environmental aging. In this paper, the cracking of a brittle titanium dioxide layer deposited onto elasto-plastic poly(ethylene terephthalate) (PET) substrate is studied through a combination of experiment and modeling. In situ fragmentation tests have been conducted to monitor the onset and evolution of cracks both on pristine and on samples aged with ultraviolet (UV) light. An analytical model is presented to simulate the cracking behavior and to predict the effects of UV aging. Based on preliminary experimental observation, the effect of aging is divided into three aspects and analyzed independently: mechanical property degradation of the polymer substrate; degradation of the interlayer between substrate and oxide coating; and internal stress-induced cracks on the oxide coating.

Based on the Galerkin method, a semi-analytical solution for the buckling and post-buckling of composite laminated plates with all four edges elastically-restrained against rotation is presented. The considered laminated plates are symmetric, and they are loaded in pure in-plane shear or combined in-plane shear and compression. The deformation shape function of the restrained plates is obtained through a linear combination of vibration eigenfunctions of simply supported and clamped beams along either the longitudinal or transverse direction of plates. The validity study shows that the presented method is effective for performing the buckling and nonlinear post-buckling analysis of laminates with all four edges elastically-restrained against rotation.

A new damage detection technique of comparing the pitch-catch Lamb wave response signals from a piezoelectric transducer (PZT) network in a set of regular hexagons of sensor arrays is proposed for delamination identification in composite laminated plates. The proposed damage detection technique is capable of detecting the delamination in the cases of unknown material properties as well as without any direct comparisons with previously obtained baseline data. The sensors, either surface-mounted or embedded in structures, are arranged in the network of a set of regular hexagons. Both the numerical simulation and experimental testing are conducted to illustrate the validity of the proposed delamination detection method.

The development of sulfur-based waterless concrete, also sometimes referred to as lunar concrete (lunar-crete), dates back to the 1980’s and the concept is centered on the approach to using the moons natural resources to develop a colony on the lunar surface. The majority of the research initiatives with regard to the use of lunar-crete have focused on mixture designs and strength properties to ensure structural integrity. The majority of research performed to date have involved the study of strength, density, resistance to radiation, sublimation, and impact resistance. This research investigates the role of permeability as a main transport mechanism in concrete in lunar-crete and other porous materials and are used to determine the rate at which gasses and liquids migrate through semi-permeable materials such as Portland cement concrete or lunar-crete. The investigation of the permeability of lunar-crete is important because it has the potential of affecting the design parameters of lunar structures. Specifically, the thickness of the walls and the transport properties of lunar-crete are especially important when taking into consideration material properties and NASA placement techniques.

The rheological properties of fresh concrete as mixed materials are affected by multiple factors and internal movement of each phase is difficult to be observed due to invisibility. For those reasons, this paper focused on an alternative transparent material with similar rheological properties of fresh concrete to verify their equivalent consistency. Moreover, the aggregate motion was simulated by PFC^2D (Particle Flow Code) software and compared with experiment results based on principle of KL (Kullback-Leibler) divergence. Research results showed that rheological parameters of carbopol gel have good correlation with that of true mortar when choosing appropriate carbopol solution concentration according to statistical analysis. Besides, the aggregates settling characteristics during vibration can be observed intuitively and the KL divergence value could assess aggregate distribution distinction between experiment and simulation quantifiably. In all, the method using carbopol gel as an alternative of raw material to achieve test visualization proves to be feasible, it will provide a new approach for the experimental research on constitutive model of fresh concrete.

Based on the compressible packing model (CPM), a new method of optimizing particle grading on manufactured sand is proposed and the workability and mechanical properties of the mortar prepared by them are experimentally compared with those by natural gradation. Furthermore, internal force transfer and crack propagation of mortar during the load process are simulated by the PFC^2D (Two-Dimension Particle Flow Code). Experimental results show that the maximum packing density of optimized gradation manufactured sand can be obtained by the CPM. It demonstrated that mortar mixed by the optimized gradation manufactured sand obtains better fluidity than that by natural gradation manufactured sand, uniaxial compressive strength, and flexural strength of optimized gradation manufactured sand mortar are higher than that by natural gradation manufactured sand. The simulation results of mechanical properties by PFC^2D agree well with test results, which account for the optimized gradation manufactured sand mortar generates partial micro cracks due to good particle embedding each other and continuity in gradation. The method of optimizing particle grading is proved to be used to guide manufactured sand in cement based materials design.

Arc dam deformation is one of the main monitoring programs which reflect the structural performance of arc dam. Traditional regression monitoring model has been used in arc dam deformation, in which reservoir water level component, temperature component, and timeliness component are used. However, due to the influence of complex environmental factors on arc dam deformation, there exists the under fitting problem in traditional monitoring model. Thus, the temperature component is improved to improve the model precision. Meanwhile, to reflect the integral deformation of arc dam, spatial coordinate vector is adopted and the 3D geospatial function monitoring model based on the improvement of temperature component is established. Considering dozens of factors in the established monitoring model, quantum genetic algorithm, and stepwise regression method are adopted to obtain prominently factors and exclude indistinctively factors. Then, both 3D geospatial function monitoring model and traditional monitoring model are used to the deformation analysis of one concrete arc dam. The results show that 3D geospatial function monitoring model has a better precision, which provides important basis for the analysis of arc dam deformation.

Due to a variety of complex dynamic loads, pumping station suffers some problems such as strong noise and abnormal vibrations during the operation, which will pose adverse effects for the normal operation and service life of the structure. Therefore, the corresponding vibration reduction measures should be taken. In this paper, reasons of abnormal vibrations for Xiaoshunjiang Pumping Station can be diagnosed combining with the frequency spectrum analysis and structural modal analysis. Through the Discrete-Time Fourier transform of vibration signal, the frequency distribution characteristics of the vibration source and structural response are obtained. The finite element model of the pumping station is established and the natural vibration characteristics are obtained by the modal analysis. The results show that abnormal vibration is caused by the structural local resonance and thus the local area should be strengthened to avoid the occurrence of resonance.

Using extended finite element method on ABAQUS platform, the analysis method of rock slope stability is discussed; the rock slope model with cracks is established. Simultaneously, both the method and the model are applied to investigate the deformation rock mass No. 2 of Xigu Hydropower Station on the Jiulong River in Sichuan Province, China. The deformation rock mass No. 2 is a high slope, with large scale deformation, high elevation distribution, steep slope toe, and multi-level tension cracks. In this manuscript, the mentioned deformation rock mass is divided into a deep zone (No. I) and a shallow zone (No. II). The development process of cracks and its effects on deformation rock mass No. 2 are studied by using extended finite element model. In addition, slope stress field, displacement field, safety factor, and slope control measures are all obtained. Results indicate that the global stability of deformation rock mass No. 2 is weak and its safety factor regarding slope stability is 1.10, which cannot meet the minimum requirement of required specification. Considering the mutation of stresses and displacements, the low tensile fracture strength of tension cracks, the instantaneous instability of slope will be induced once multilevel tension cracks cut through the interface of zone I and II. Consequently, the practical reinforcement scheme, which combines the drainage, the anchorage, and revetment are offered for reinforcing the deformation rock mass.

This paper describes a deployable launch system capability being developed at NASA KSC that was publicly announced in May 2015. It is a set of multi-user ground support equipment that will be used to test and launch small class launch vehicles. The paper also describes a transportable modular launch/landing pad concept that was developed to support vertical takeoff vertical landing vehicles, such as the NASA JSC Morpheus Lander, and discusses rocket plume effects on launch/landing pad surfaces.

During airplane landing operations the airplane may rebound causing it to become airborne after touchdown. Rapid de-rotation of the nose of the airplane during rebound without the main landing gear (MLG) firmly planted on the runway has been cited as one of the key potential contributing factors for causing significant aircraft structural damage including hull loss in several large transport airplane accidents. Due to the fuselage length and flight deck location of large airplanes, the flight crew may not clearly recognize the MLG position and movement relative to the ground because the flight deck may be moving at a different rate and even in the opposite direction than the MLG. This paper provides a discussion of the root causes related to rebound during landing and its potential adverse effects on large transport airplane operations, and design details of the airplane off-ground advisory system (OGAS). When installed, OGAS provides a real time flight deck visual indication if the aircraft rebounds off the runway after touchdown enabling the flight crew to take appropriate action.

In this paper we investigate the use of the cold gas thrusters for a small spacecraft that can utilize planetary and asteroid local resources of cold gas for propulsion. A model is developed of the fluid system for the cold gas propulsion dynamics. In this paper the craft is considered to have one main gravity offloading thruster and four smaller maneuvering thrusters. The fluid model is used to design and simulate a control algorithm for the main gravity offloading thruster. The nonlinear feedback method will track and control a desired thrust as demanded from an upper level attitude control system. The main thruster is actuated by a pressure regulator to provide small continuous tracking of main thrust demands. The control algorithm is shown to successfully track a desired thrust in simulation.

Bond slip damage can reduce the structural load capacity. In this paper, authors propose a shear wave based active sensing approach to detect the bond slip damage, including the early age warning and further development. A small-scale concrete-encased composite structure was fabricated and investigated. In the active sensing approach, one shear mode smart aggregates (SAs) is embedded in the concrete to generated shear stress wave along the interface between the concrete and steel plates. Distributed piezoceramic (PZT) patches are installed on the internal surface of the steel to detect the wave response. When bond slip occurs, the propagating stress wave attenuates which decrease the energy of signal received by PZT sensors. To quantitatively evaluate the degree of bond slip damage, a wavelet packet-based bond slip index was developed. Distributed PZT sensors deployed in the structure is capable of providing the severity of the bond slip damage in different locations.

The frequency-change square ratio vector (FSRV) is a function of structural damage location and can be easily used for health monitoring; however, how to construct a precise FEM of real structure and then build the benchmark database for damage localization is still a great challenge for FERV-based damage detection methods. In order to overcome this disadvantage, a virtual theoretical model, which had the same eigenvalues with actual structure, was first proposed in this paper by assuming and constructing using the improved restoring force technique according to the acceleration time-histories data for each level of the shear building in health condition. Subsequently, the FERVs came from different damage location of shear building were calculated and used to build a benchmark database for damage location, then damage extent benchmark database was also built following the same procedure. Finally, model assurance criterion (MAC) and normalized modal difference (NMD) were employed as an evaluation index to calculate the similarity between the FSRVs, which came from the actual structure and damage location benchmark database, separately. Then the damage location corresponding to the sample with largest MAC value will be regard as the actual damage location, the damage extent can also be diagnosed using the same process after damage location was confirmed. A numerical simulation was employed to validate the proposed approach. The simulation results show that the proposed method could detect the presence of structural damage, locate damage, and determine damage severity just based on the actual measured frequencies.

Concrete is the most widely used building material for civil structures. During the pouring process, the formation of secondary pouring interface in concrete is one of the most common problems, which may cause future structural damage and reduce the structural service life. It is desirable to develop a monitoring system that can detect the formation of secondary pouring interface in concrete structures. In this paper, an active sensing approach using piezoceramic based smart aggregates was developed detect the secondary pouring interface. Two smart aggregates function as the stress wave transmitter and receiver, respectively. Secondary pouring interface in concrete structure induces wave impedance mismatch, which attenuates the stress wave propagating through the interface. In this research, two concrete specimens, including one intact and other one with an artificial secondary pouring interface, were investigated. Compared to the intact concrete specimen, the energy of the signal received by the smart aggregate in the one associated with the secondary interface is much lower. A wavelet packet based energy analysis was used to compute the signal energy values to assist the detection. Experimental results demonstrated that the proposed approach can detect the formation of secondary pouring interface in concrete structures.

In this paper, a new implementation approach for developing a remote PID motor controller experiment is presented. The remote PID controller experiment aims to offer students hands-on experience in demonstrating the characteristics of proportional (P), proportional-integral (PI), proportional-derivative (PD), and proportional-integral-derivative (PID) controllers and visualize the process of remote tuning. The new remote PID motor controller experiment based on a novel unified framework has been implemented at the Smart Materials and Structures Laboratory at University of Houston for mechanical engineering teaching. With this new remote experiment, the user can remotely conduct the PID motor controller experiment by using most of web browsers on desktops or portable devices without installing any plug-in.

Remote laboratory has played an important role in online learning. It is also an effective tool for the science, technology, engineering, and math (STEM) education. Meanwhile, the collaborative and cooperative learning has been proved to be a very effective approach for STEM learning. In order to enhance the remote experiment for STEM learning, a wiki-based novel collaborative, and cooperative remote laboratory architecture is proposed in this paper. The design and implementation process of the novel collaborative and cooperative remote laboratory architecture is presented. A remote smart vibration platform (SVP) experiment is successfully revamped to demonstrate the feasibility and effectiveness of the proposed novel architecture. The students can effectively learn engineering knowledge with collaborative and cooperative way via using most of popular web browsers on desktops or portable devices without installing any plug-in.

Over the past few decades, structural health monitoring (SHM) has been extensively used to identify, locate, and quantify structural damages. Great advancements in sensor technology and application of piezoceramic materials have resulted in novel methods for SHM. The coupled electro-mechanical properties of piezoelectric materials enable scientists to generate and capture waves that can be effectively employed for damage detection. Among piezo-based SHM techniques, Lamb waves are widely used since they can propagate long distances without much attenuation. Lamb waves are guided waves which propagate in plate-like mediums bounded by two surfaces and arise as a result of superposition of multiple reflections of longitudinal waves and shear vertical waves from bounding surfaces. Apart from the lamb waves, an independent set of waves called shear horizontal waves (SH-waves) also exists in plates with in-plane particle motions parallel to the plate’s surface. Since the first symmetric shear horizontal mode (SH0) is non-dispersive and travels with constant velocity, scientists have been encouraged to use transducers which purely excite SH waves for SHM of plates. In present study, existing modes of the compressive and shear piezoelectric actuator/sensor used for excitation of lamb and SH waves are described and compared. Then, the effect of piezoelectric coefficients on the characteristics of generated waves are investigated numerically by actuating and sensing compressive (S0), flexural (A0), and shear wave modes in metallic plates using both compressive and shear PZT transducers.

The structural health monitoring system was designed for the roof structure of Dalian Gymnasium which was suspend-dome structure in order to ensure safe operation of the roof structure in construction and the future service. This paper first presented a monitoring method for those physical parameters which may cause failure of the structure. After that the hardware and function of the Dalian Gymnasium structural health monitoring system were discussed. In the end, lots of information about the gymnasium health condition was obtained by analyzing monitoring results. Analyzing the data obtained during the construction and normal operation of the gymnasium, the structural health condition was evaluated and the structural damage could be located.

The paper presents the response obtained from finite element model and field test of a railroad bridge under moving trains. The structure selected is the two-track through truss Devon Bridge in the busy Northeast Corridor at Milford, CT, U.S.A. Vertical displacement response, under various trains, along with the modal parameters (mode shapes and frequencies) of the bridge were obtained from FEM and field tests. The responses obtained from the FEM and field tests were compared and the FEM was refined. The result from this study is helpful in addressing the rising concerns over the safety of old steel truss railroad bridges, similar to the Devon Bridge, under moving passenger trains.

The water existing in wide cracks of concrete structures is a serious factor that affects the reliability of concrete structures, and sometimes may lead to failure of the whole concrete structure. However, the investigation on the presence detection of water in concrete cracks was less reported. Using PZT wave-based method, the presence and level of the existing water in artificial cracks of concrete structures were researched in this paper. PZT-based sensors were embedded in the concrete structures and utilized as transducers to generate and receive detection signals. Meanwhile, wavelet packet analysis method was used to analyze the energy value of received signals to determine the level of the existing water. The experimental results showed that the concrete cracks can reduce the stress wave propagation and enable to attenuate energy of the received signal to about 10%-20% of the one in the healthy condition. Under the same width crack condition, the signal energy decreased slightly with the increase in the depth of the cracks. However, when the crack of the concrete structure was filled with water, the signal energy increased to approximately 3-4 times than no water conditions. From the experiment, it can conclude that it is feasible to detect the concrete structure crack whether it contains water or not by using PZT wave-based method to determine the existing water level in cracks of concrete structures according to the detection signal energy index.

Carbon nanotubes (CNTs) have become prominent smart materials due to their unique electrical, mechanical, and sensing properties. The great properties of carbon nanotubes represent a potential for developing a piezo-resistive strain sensor with smart structure for structural health monitoring (SHM) applications. The objective of this study is to fabricate multi-walled carbon nanotubes (MWCNT) sensors by a novel digital controlled spray deposition process. In this study, a new spraying-evaporation deposition process that uses a 12-array bubble jet nozzle attached to a digital x-y plotter combined with a heated substrate which induces evaporation of the solvent was employed to produce carbon nanotube strain sensors. This system is able to produce MWCNT sensors with variable thickness in defined locations and geometries. The effectiveness of the fabricated MWCNTs as strain sensors was investigated. Four point probe apparatus was used to measure the electrical resistivity of MWCNTs sensors. For sensors with 30 printed CNT layers, the sheet resistivity of carbon nanotubes could be as low as 95 Ω/sq. Real-time strain response of the MWCNTs sensors under tensile load was also studied. The printed carbon nanotube strain sensor has a gauge factor of 5.02. These research results indicated that this new spray deposition process is effective for the fabrication of a CNT strain sensor for structural health monitoring applications.

Recent experimental study results show the piezoceramic lead zirconate titanate (PZT) based active damage detection technology has been successfully employed in interfacial debonding detection for concrete-filled steel tubulars (CFSTs). In order to investigate the elastic stress wave propagation in CFSTs with and without interface debonding defects, a two dimensional spectral element model for a cross section of a CFST member is established and the stress wave propagation within the section is simulated under dynamic excitation with spectral element method (SEM). The interface debonding between steel and concrete is mimicked by splitting the nodes between the steel tubular and concrete. Comparison on the stress wave field between the models with and without interface debonding defect is made and the result shows that the existence of interface debonding detection affects the wave propagation and displacement responses of specified points. SEM provides an efficient way for simulation of elastic stress wave propagation in CFST and some references to damage detection of interface debonding.

In the paper, a new method of monitoring early-age strength of concrete based on the influence of the stress wave to the Young’s modulus of concrete is developed using PZT wave propagation technology and considering the thermal effect. The PZT patches are encapsulated into newly developed multi-functional smart aggregates which use epoxy resin as the encapsulated material instead of normal fine aggregates to increase the capabilities of the temperature acquisition and achieve real-time monitoring of the smart aggregate internal temperature. The monitoring system based on Compact RIO embedded platform is used in the test to keep monitoring the concrete early-age strength and extracting the signal parameters value within 28d. Meanwhile, the concrete standard destructive test for standard concrete test blocks under the same curing conditions is carried on by using a universal compression testing machine to obtain the compressive strength value for validation. The experimental results show that the detection signal energy value in the monitoring test and strength development of concrete are basically synchronous and highly correlated, indicating that the proposed monitoring method can reveal the strength development trends. For simplification, the signal energy and concrete strength are normalized to two comprehensive indexes including energy ratio and strength percentage, and the relationships among the two indexes and concrete age accord with a cubic polynomial fitting function.

In order to reduce the response of the base-isolated structure subjected to Chi-Chi earthquake, the fuzzy logic method is proposed to adjust the control force of variable friction damper that is served as a semi-active control device installed on the base isolation story of the base-isolated building. In the proposed fuzzy control method, the displacement and acceleration of the base story are employed as input variables, and output variable is control voltage that acted on the variable friction damper. The fuzzy controller can determine the control voltage of the variable friction damper according to the responses of the base-isolated structure under Chi-Chi earthquake. The efficiency of the proposed control method is demonstrated by a series of numerical simulations. The numerical results show that the fuzzy logic controller can effectively reduce the responses of based-isolated buildings subjected to Chi-Chi earthquake.

Structural engineering is evolving towards tuned performance structures through the integration of active control. Tensegrity structures are cable-truss structures that can combine actuators, sensors and structural elements. A tensegrity-ring system that has been found viable for an active deployable footbridge application is presented in this paper. Active cables are employed to simultaneously adjust several degrees of freedom and enhance performance through independent actuation. Numerical results were validated experimentally on a near-full-scale actively controlled physical model. However, predefined actuation steps do not always result in the same position. Therefore, the configuration of the model is improved through a sequence of correction-control commands that are tested and selected according to direct measurements. The two-stage strategy is able to generate effective cable actuation for the mid-span connection of the deployable tensegrity-ring footbridge system and it is likely to be applicable for a range of complex structures where exact modelling of true behavior is difficult.

Jumper pipelines are crucial for hydrocarbon exploration. In offshore environment these jumpers are exposed to vibration inducing environments, such as external flow (vortex) around pipe and internal flow through a pipe. These flows excite the various vibration modes in jumpers. These vibrations cause additional stress on the jumper joint and adversely affect the fatigue life of jumpers. This paper presents research on the pounding tuned mass damper (PTMD) applied to a subsea jumper for passive vibration suppression. A preliminary finite element based analysis is performed to understand the behavior of the PTMD on a mock up jumper, both in air and underwater. A key component of the modeling is to understand the modal behavior of the jumper for development of the PTMD. During the initial phase, effectiveness of the PTMD damper on vibration attenuation of the jumper in air is evaluated with free vibration testing and resonant vibration testing. For the second phase, the test setup was submerged underwater. Test results show that the PTMD is more effective at suppressing the first mode (vertical) than the later modes. Results also indicate that the PTMD successfully dampens jumper vibrations under submerged conditions to a satisfactory level. The observed reduction in vibration amplitude can help to reduce fatigue damage to jumpers, increasing their life span considerably. This makes the PTMD a desired solution for vortex induced and flow induced vibration suppression for deep sea applications.

Intake towers as the entrance of spillway or diversion system constitute the most common structural configuration in large water conservancy and hydropower engineering. The safety and functional capability of intake towers in the event of a major earthquake are crucial, since the controlled release of the reservoir could help to prevent catastrophic failure of a dam after an earthquake by reducing the hydrostatic loads. Therefore, the seismic capacity of intake towers is a key technical issue. In this paper, giving proper consideration to the dynamic interactions of the main tower with the hoist chamber, reservoir, and foundation effects of the fluid-structure interaction on dynamic responses of intake towers and seismic whiplash effects of hoist chambers were studied. Based on a practical project, potential-based fluid elements were employed to analysis and investigate the effects of the reservoir compressibility on natural vibration characteristics of the integral structure, hydrodynamic pressure, and seismic responses of the main tower and hoist chamber.

The lightweight steel column (LSC) plays an important role in resisting the combined action of fire and blast for lightweight steel structures. The material performance of LSC is more sensitive to these combined effects than other forms of steel structures. Thermal softening of the steel material under elevated temperatures makes the steel weaker under blasting loading. However, very limited researches have been conducted to analyze the anti-blast performance of LSC subjected to elevated temperatures, though these two issues have been systematically investigated separately. In this paper, anti-blast performance of LSCs with different cross-sections, namely H-type, rectangle and round sections, are numerically analyzed using ANSYS/LS-DYNA. Isothermal property is assumed under elevated temperatures and the blasting loading is applied on the side surface of the LSCs when establishing the finite element analysis (FEA) models. The failure mode and severity of the LSCs are investigated from the numerical results to study the performance of LSC due to different temperatures, blast loadings and cross-sections. Results show that the LSC with short side facing the blast, has the best anti-blast capacity in high temperatures while the LSC with circular section is the worst. The results from this study may provide useful reference for the design of the structures under the combined effect of elevated temperatures and blast loading.