Earth and Space 2018: Engineering for Extreme Environments

Since 1960, multiple samples of lunar soil have been available for scientists. These samples are so limited in volume that they can be used only for the most important tests. Therefore, over the years there have been developed numerous artificial lunar soil materials, called lunar soil simulants, to enable lunar research programmes. Feasibility and scientific success of these projects, focused on a wide range of topics, are dependent on physicochemical and mechanical properties of a given lunar soil simulant. Generally, simulants are supposed to be effective copycats of lunar soil in every possible aspect: from chemical composition and mineralogy to grading and mechanical properties. Nevertheless, numerous out of produced simulants have not met expectations and proved not to be suitable for specific purposes. There is an urgent need for a complex but at the same time fast and reliable method for the assessment of lunar soil simulants. In authors’ opinion a method based on multivariate statistics involving multiple parameters of a given simulant would be the best solution to the problem.

This paper describes the processes and challenges of producing high-fidelity asteroid simulants. DSI (in partnership with UCF) is producing four families of carbonaceous chondrite simulants: CI, CR, CM, and C2. Britt provided target mineralogies, recommendations for researcher safety considerations, and target physical characteristics of selected meteorites, described separately. Here, we describe the source materials, elemental fidelity, the processes used to prepare the minerals and produce those simulants, and the resulting physical characteristics of various simulant morphologies. We selected reproducible mineral sources available at modest cost, requiring some compromises in elemental fidelity. In some cases, closely-related minerals were substituted to improve the physical characteristics of the resulting simulants. The source materials were cleaned, crushed, powdered, and stored, in oxygen-free conditions where appropriate, creating a library of source materials for a variety of asteroid simulants. Each mineral is documented, both for elemental composition and particle size distribution. Issues with comminution led to changes in several processes. To create each simulant, several stages of processing are typically required, and the conditions are varied to control the resulting density/porosity, hardness/breaking strength, and morphologies. To create regolith, prepared simulant is subjected to impacts which create a power-law particle size distribution, mimicking what we expect to see on an actual asteroid. This effort resulted in a variety of carbonaceous chondrite simulants, available to researchers in several forms, with consistent and well-documented characteristics.

The helium extraction and acquisition testbed (HEAT) is a prototype volatiles extraction system built to demonstrate a process for acquiring solar wind volatiles such as helium-3 (³He) from lunar regolith. There are many useful volatiles released from the extraction process being investigated. The ³He could be used to fuel future fusion power plants that would produce little to no radioactive waste and efficient rockets for Solar System travel. Hydrogen, helium-4, carbon dioxide, carbon monoxide, methane, nitrogen, and water (from hydrogen reduction of ilmenite) are also products of the process. These volatiles could be vital in supporting propellant and/or life support needs of people in space (space stations, Lunar, or Martian outposts) for extended periods of time. In the present research, helium or other volatile gases are implanted into <100 μm JSC-1A regolith simulant using a device called the solar wind implanter (SWIM). The HEAT system is used to extract them by heating the material to 700 °C within a moving bed heat pipe heat exchanger. In this paper, key aspects of the granular flow and heat transfer modeling for the HEAT device are presented.

Granular regolith simulants such as the Martian regolith simulant (MRS) have been extensively used in the preparation of space missions to test rovers and scientific instruments. In this work, a grading and shape-dependent discrete element model is developed based on the realistic particle shapes and particle size distributions of an MRS characterized through advanced imaging technique (X-ray computed tomography) and conventional soil mechanics tests. Numerical biaxial compression tests are conducted to study the shear behavior of MRS. The microscopic features (e.g., coordinate number, contact force distribution, mobilized contact friction, and fabric anisotropy) and their evolutions during the shearing process are investigated in details. Of particular interest is the effect of particle shapes on the microscopic features and macroscopic strength of the MRS.

The gas-granular flow solver (GGFS) multi-phase flow computational framework has been developed to enable simulations of particle flows of complex extra-terrestrial regolith materials. Particle flows of interest include the damage of unprepared spacecraft landing sites from rocket plume impingement on Moon, Mars, and asteroids. The flow solver implements an Eulerian-Eulerian two-fluid model with fluid representation of the gas phase and granular phase to avoid the need to model billions of particle interactions. The granular phase is modeled as an Eulerian fluid with constituent physics closure models derived from first-principle discrete element model (DEM) particle interaction simulations that capture the complex, non-linear granular particle interaction effects. Granular phase constituent models have been developed and integrated that address the granular material mechanics complexities resulting from both, the irregular, jagged particle shapes and poly-disperse mixture effects encountered in extra-terrestrial regolith, with lunar regolith as the extreme. The GGFS capabilities are being integrated into a proven NASA plume-surface interaction and debris transport simulation framework featuring the Loci/CHEM CFD program and debris transport analysis (DTA) post-processing tools for applications in robotic and human Moon and Mars lander development. Integration of the three simulation tool components, Loci/CHEM, GGFS, and DTA, into a coordinated simulation framework will enable time-accurate spacecraft landing simulations that account for the alteration of the landing surface through plume induced cratering and the resulting redirection of plume impingement flow and debris transport. Initial implementation of this simulation framework and application examples will be presented.

Under a NASA SBIR Phase 1 project, TransAstra Corporation in collaboration with the Colorado School of Mines and Grainflow Dynamics, Inc. is developing and testing a prototype micro-g granular material research (MGMR) facility for the International Space Station (ISS). The proposed facility will provide a unique opportunity to gain understanding of the fundamental physical behavior of granular solids in microgravity over a range of solids fractions that are unobtainable terrestrially due to gravitationally induced settling. Although it is known that behavior of granular materials under microgravity is strongly influenced by cohesion among particles (e.g., aggregation of particles can result in the formation of gel-like structures which grow to fill available volumes) details of these processes are not well understood. Applications of this work include fundamental science associated with planetary accretion, space habitat air filtration system design, control of particles for microgravity additive manufacturing, and process design for the fabrication of radiation shields from regolith in microgravity. The ISS facility will be suitable for studying steady or variable gas-solid flows over a nearly 2-order of magnitude range in particle size and 4-orders of magnitude in solids-fraction at gas pressures ranging from atmospheric to near-vacuum and flow velocities from on the order of 10 m/s to stationary. The Phase 1 ground demonstration unit uses low-density particles and gas fluidization to mimic the micro-gravity transport of granular solids through the ‘micro-gravity’ granular-solids test section, and employs gravity-independent centrifugal settling to provide gas-solid separation in a manner analogous to the proposed ISS facility. This paper describes the mid-term status of the SBIR project.

One of the top priorities in exploring planets and moons in the solar system is to find the existence of water as it is a basic resource for human habitation and a feed material to make fuel. In many likely locations, water will exist in form of ice crystals scattered among the voids between granular particles. Developing a reliable and simple technique to detect the existence of ice crystals can bring significant benefits to such exploration missions. In this study, wave velocity measurement is conducted on soil samples with different water contents so as to investigate the influence of ice crystals on the measured wave velocities. A wide range of water contents are used in the experiment to establish trend lines for the influence. The goal is to establish basic science principles for future surface exploration on the moon or Mars in hope of detecting the existence of ice in the regolith using the data of wave velocity measurement.

Within the frame of the major national research project ROBEX dealing with the robotic exploration of extreme environments, dynamic penetration tests combined with seismic tests have been conducted at an altitude of over 2,600 meters on Mt. Etna. Focus was placed on the assessment of the near-surface soil properties. A light dynamic sounding penetrometer with variable impact energy has been employed. Parallel to this, seismic data generated by a surface impact source were collected with geophones mounted on embedded spikes of different lengths. In addition to the performed in situ tests, samples of the volcanic soil were collected for classification and shear strength testing in the laboratory. The paper describes the experimental set-up and the deduced soil properties from the two types of in situ test. The results show the limits of available empirical relationships derived for routine geotechnical applications. After refinement, the methodology employed may be transferred to planetary missions.

Since the Apollo program or earlier it has been widely believed that the lunar regolith was compacted through vibrations including nearby impact events, thermal stress release in the regolith, deep moon quakes, and shallow moon quakes. Experiments have shown that vibrations both compact and re-loosen regolith as a function of depth in the lunar soil column and amplitude of the vibrational acceleration. Experiments have also identified another process that is extremely effective at compacting regolith: the expansion and contraction of individual regolith grains due to thermal cycling in the upper part of the regolith where the diurnal thermal wave exists. Remote sensing data sets from the Moon suggest that the soil is less compacted in regions where there is less thermal cycling, including infrared emissions measured by the Diviner radiometer on the Lunar Reconnaissance Orbiter (LRO). Here, we performed additional experiments in thermal cycling simulated lunar regolith and confirm that it is an effective compaction mechanism and may explain the remote sensing data. This creates a consistent picture that the soil really is looser in the upper layers in polar regions, which may be a challenge for rovers that must drive in the looser soil.

Flawless operation of mobility systems, excavation, mining and in situ resource utilization (ISRU) operations, regolith transport, and many others critically depend on knowledge of the geotechnical properties of the soil. This paper presents Stinger, a geotechnical instrument design for robotic and astronaut deployment. Stinger combines an Apollo-based penetrometer approach for measuring bearing strength with a Lunokhod approach for measuring shear strength. The shear vane is initially housed inside the cone and is pushed out whenever shear tests are required. When the shear vane is out, the cone-vane is rotated to measure the shear strength of the soil. The test data from the Stinger breadboard shows a very good correlation with a stand-alone cone penetrometer and shear vane data.

An investigation was undertaken to explore the feasibility of interrogating granular soil mechanical properties through high energy impacts and mechanical wave propagation. Measurements of acoustic and inertial waves were obtained with piezoelectric strain elements embedded into the surface of the soil. Wave speed, signal strength, and local and long range wave propagation were explored. The data obtained was used to show the dependency of the wave speed on material density and its distance from the impaction source. The amplitude and energy of the wave near the impact source and at far field distances was also investigated. Lastly, the role of impact energy on the wave character is also presented.

Material strength determines the optimum mining approach and brackets the upper limit of excavation forces, energies, and size of mining equipment. In particular, knowledge of the strength of volatile-rich deposits on Mars and the Moon for the purpose of in situ resource utilization (ISRU) would be critical to the success of ISRU missions. Numerous tests were performed to determine unconfined compressive strength (UCS) of JSC-1a lunar soil simulant at various densities, water contents (wt%) of 3%, 5%, and 12%, and temperatures of 253 K and 77 K.

One of outstanding questions about primitive asteroid surfaces with respect to in situ resources utilization (ISRU) and the potential to retrieve boulders off asteroidal surface is the effect of thermal cycling in near-Earth space on the strength of the boulder material. To address this issue we used the UCF/DSI Orgueil-type CI simulant formed into “pucks” 3 inches by 1.5 inches and thermal cycled them 220° C over four hours to mimic the rotational heating and cooling of an asteroid day/night cycle. We performed a total of 677 cycles and measured the Vickers hardness of the puck surface at regular intervals. The hardness of the surface material dropped by approximately 50% over the first 380 cycles and then leveled out to a constant hardness for the rest of the testing period. This suggests that differences in the coefficient of thermal expansion do weaken the surfaces of asteroidal materials, but that the weakening is limited and rapidly achieves a steady state.

The needs for accurate measurements of physical properties of asteroidal material continue to grow in light of current and future missions involving C-type asteroids, scientific studies, threat mitigation, and ISRU. Adhesion values (here including cohesion) are critically important in explaining several intriguing observations related to the strength and rigidity of small asteroids. Current knowledge suggests that asteroids smaller than ~1 km behave as loose granular aggregates and are subject to disruption from YORP spin-up. Models of asteroidal processes are highly dependent on values for adhesion, but without in situ or laboratory measurements on appropriate materials these models assume or derive values. We conducted a series of experiments to produce the first measurements of adhesion in asteroid derived materials (meteorites). Our focus has been CM2 meteorites as proxies for regolith of C-type asteroids. These experiments were performed with NASA Glenn Research Center's “Adhesion Rig”—custom equipment consisting of a torsion balance in an ultrahigh vacuum (10^-10 torr) chamber. Adhesion caused by Van der Waals forces and electrostatics was observed. Measurements we made both with natural heterogeneous meteorite specimens and individual minerals to search for plausible terrestrial analogs to regolith and increase the relevance of our measurements for observed mineralogical variation among C-type asteroids. Our results suggest adhesion within bulk CM2 material is low relative to some individual minerals, but not negligible. Additionally, the use of some suggested terrestrial proxies for asteroidal regolith (like serpentine-group minerals) will overestimate adhesion and thus overall strength of small C-class bodies.

This paper presents a framework that allows to holistically predict the mechanical behaviors of cohesive granular materials. The framework integrates both the experimental characterization and the computational model to capture the crucial components affecting the overall behaviors of cohesive geomaterials, which are particle size, shape and topologic interactions, and interaction forces that includes both contact and non-contact forces. The particle shape and topologic effect are captured with discrete element method (DEM) that considers the characteristics of particles. The interaction forces between particles are captured by atomic force microscope (AFM), from which the interaction force models are calibrated. The parameterized interaction force models are programmed into DEM to simulate the bulk behaviors of cohesive soils. Besides the prediction of bulk mechanical behaviors, properties such as the memory of cohesive granular materials under compression are elucidated with the integrated model.

In 2016, Ontario Drive & Gear Limited (ODG) and Canadensys Aerospace Corporation completed the design and fabrication of a pair of small to mid-size lunar rover prototypes funded by the Canadian Space Agency (CSA). These lunar rover prototypes were intended to demonstrate the compatibility of the CSA’s rover architecture with higher technology readiness levels, with a target of achieving technology readiness level 6 (TRL-6) qualification for the driveline subsystem, including motors, gearboxes, structure, and a compliant, metallic wheel. To that end, a series of thermal vacuum (TVAC) tests was conducted at NASA Glenn Research Center (GRC) and NASA Langley Research Center (LaRC). The first test was conducted at NASA GRC in Cleveland, Ohio, in late 2015. The mid-size VF-13 vacuum chamber used at GRC allowed the equipment to be tested with a lunar simulant present under a variety of thermal scenarios. The drivetrain survived exposure to vacuum and temperature extremes from -175 °C to +130 °C and was driven approximately 30 km in a dusty environment at temperatures ranging from -70 °C to +130 °C. The design of the multi-stage non-contact dust seals was proven to be effective. During the first test campaign, one of the position sensor magnets in the motor was displaced after being subjected to -130 °C and then operated at +130 °C. A review of the motor design was conducted by the manufacturer and the design was subsequently improved to eliminate the failure mode. A subsequent vacuum test was conducted at NASA LaRC to ensure that the failure would not reoccur and that the motor would be able to withstand exposure to lunar night conditions. A motor module assembly, consisting of an updated motor, brake, and gearbox, was installed in the cryo-mechanisms chamber and connected to a dynamometer to apply load. A compliant metallic wheel was also installed in the chamber in a statically-loaded state. The motor was operated under load at temperatures ranging from -70 °C to +130 °C. Additionally, the motor was exposed to a minimum temperature of -242 °C overnight, after which it was again operated successfully at temperatures between -70 °C and +130 °C, with no degradation in performance observed. The wheel was subjected to temperatures ranging from -149 °C to +108 °C while under a load of approximately 647 N.

Snakes move through cluttered habitats and tight spaces with extraordinary ease, and consequently snake robots are a popular design for such situations. The remarkable locomotor performance of snakes is due in part to their diversity of locomotor modes for addressing a range of environmental challenges. Concertina locomotion consists of alternating periods of static anchoring and movement along the snake’s body, and is used to negotiate narrow spaces such as tunnels or bare branches. However, concertina locomotion has rarely been implemented in snake robots. In this paper, the anchor formation process in live snakes during concertina locomotion is quantified and used to implement concertina locomotion in a snake robot, with automatic detection of the width of the tunnel walls to modulate the waveform. This allows effective concertina locomotion in tunnels of unknown width, without prior knowledge of tunnel geometry, expanding the range of gaits in snake robots.

Much like their Earth-based counterparts, the requirements of future space habitat structures can be defined by their ability to protect their occupants and provide usable space to live and work in an extreme, isolated environment. Due to the high cost of transporting resources off of Earth’s surface, recent efforts focus on developing increasingly Earth-independent structural designs. These new designs use local regolith-based materials as a possible solution for long-term extraterrestrial sustainability. With a focus on an Earth-independent habitat, this research looks at architectures that use spherical regolith-based concrete shells with carbon fiber polymer reinforcement. The research approach is to formulate the structural design problem as a multi-objective optimization of the habitat shell. The objectives that apply to the shell geometry and cross section include the minimization of transportation and construction costs, and the minimization of the probability of loss due to radiation and micrometeorite events. Direct trade-offs arise. The multi-objective optimization applies Pareto optimization to determine which design elements or options afford the greatest effectiveness or efficiency. The authors examine candidate design solutions based on priorities and performance thresholds which indicate that ISRU-based reinforced concrete may be a valuable future investment. While the cases presented here are limited to lunar surface systems, both the general architectures and the methodology for analysis and design are applicable to future Mars settlements.

This paper discusses fundamental design considerations for developing a habitat to support NASA’s goals of establishing Mars surface capabilities with commonality for in-space transit habitat architectures. The mission requirements for this study are based on NASA’s Human Exploration of Mars Design Reference Architecture 5.0. Our methodology includes the analysis of reference mission requirements, the examination of functionality and constraints for on-surface and in-flight conditions, the definition of primary characteristics of a habitat for each environment, and summarizing those characteristics in the form of figures of merit to develop design selection criteria. The long term vision of our study is the development of a module and its systems design that can effectively provide a livable and comfortable volume that can be adjusted and scaled for multiple mission support functions. This paper discusses the potential of a common module layout for zero- and partial-gravity conditions as well as human factors considerations and problems of implementation.

The automated construction of expeditionary structures, phase 3 (ACES 3) project incorporates a liquid goods delivery system (LGDS) into a dry goods delivery system (DGDS) structure to create an integrated and automated ACES 3 materials delivery system (MDS) for 3D printing structures with ordinary Portland cement (OPC) concrete. ACES 3 is a prototype system which 3D prints barracks for soldiers in forward bases, here on Earth. The LGDS supports ACES 3 by storing liquid materials, mixing recipe batches of liquid materials, and working with the DGDS previously developed for ACES 2, combining a specialized concrete recipe of materials that are eventually extruded out of the print nozzle. ACES 3 is a project led by the U.S. Army Corps of Engineers (USACE), Engineering Research and Development Center (ERDC)—Construction Engineering Research Lab (CERL), and supported by NASA Kennedy Space Center (KSC) and Marshall Space Flight Center (MSFC). The equivalent 3D printing system for construction in space is designated additive construction with mobile emplacement (ACME) by NASA.

There are lots of questions about how to build a permanent facility on the Moon, which scientist and engineers are diligently solving. However, an equally important question is “What will the contract to deliver this project look like?” There has been a steady transition from government funded missions to private enterprises launching their own endeavors. Developing a permanent lunar facility would be one of the greatest projects ever undertaken by the architecture, engineering, and construction industry. Who is going to prepare the request for proposal (RFP) for front-end engineering and design (FEED) of this facility? Will the project delivery method be lump sum, cost reimbursable, a public private partnership, build own operate and transfer, or a new and innovative process? Will the project team be a joint venture, a consortium, a prime contractor and sub-contractors, or a combination of all three? How will the project be funded: private-sector, public sector, or public-private? What intellectual property, land ownership, mineral rights, etc., will the private interest, the developer, and/or the contractor have? Can it be owned or is this project simply “work made for hire?” This paper discusses possible project delivery methods and provides guidance for answering all of these questions.

NASA’s strategic goal is to put humans on Mars in the 2030s. The NASA Human Spaceflight Architecture Team (HAT) and NASA Mars Design Reference Architecture (DRA) 5.0 has determined that in situ resource utilization (ISRU) is an essential technology to accomplish this mission. Additive construction technology using in situ materials from planetary surfaces will reduce launch mass, allow structures to be three dimensionally (3D) printed on demand, and will allow building designs to be transmitted digitally from Earth and printed in space. This will ultimately lead to elimination of reliance on structural materials launched from Earth (zero launch mass of construction consumables). The zero launch mass (ZLM) 3D print head project addressed this need by developing a system that 3D prints using a mixture of in situ regolith and polymer as feedstock, determining the optimum mixture ratio and regolith particle size distribution, developing software to convert g-code into motion instructions for a FANUC robotic arm, printing test samples, performing materials testing, and printing a reduced scale habitable structure concept. This paper will focus on the ZLM 3D print head design, materials selection, software development, and lessons learned from operating the system in the NASA KSC Swamp Works Granular Mechanics and Regolith Operations (GMRO) Laboratory.

Space pioneer Kraft Ehricke characterized the “Extraterrestrial Imperative” as mankind’s evolutionary need to create an “open economy” without resource limitations by developing the near Solar System and beyond, to ensure success of our species. Lunar development of Helium 3 sources coupled with a crash driver of fusion development and engineering in the United States and cooperatively, would be the first step towards creating a space faring civilization. It is noted that U.S. infrastructure systems suffer from consistently inadequate rates of investment and technological obsolescence, reducing competitiveness. $5 trillion to $10 trillion on new systems would replace depleted stock, but not remedy technological attrition. Necessary physical infrastructure and production policy must include commitment to near solar system development and fusion energy. Fusion yields the technical means to replace outmoded infrastructure systems at increasing rates. Successful infrastructure systems improve thermodynamic efficiency of an economy, fostering “creative powers” of a growing labor force employed in increasing rates of technological production and international cooperation, extinguishing financial debt through increases in productivity, per capita. An “American System” model is proposed, deliberately increasing technological obsolescence of infrastructure systems generated by increasing rates of human creative discovery. Such “revolutionary” measures also reduce environmental and resource depletion, and provide flexibility to address variable climate, natural disaster, war avoidance, and rapid “Third World” development.

Current and future goals for human activities on the Moon could be facilitated by the creation of underground tunnels. Human habitation will require shielding from radiation, protection from micrometeorites, structures to maintain atmospheric pressure in living quarters, and a means to survive the cold lunar night. Locating a human habitat several meters below the lunar surface would provide greater protection from these hazards than a surface habitat covered in regolith, while also providing a more stable thermal environment than the surface. Design of a custom lunar tunnel boring machine (LTBM) specifically for use in the lunar environment and boring in lunar material can leverage decades of technology developed by the mining and civil tunneling industries. One advantage of a LTBM over lunar surface excavation for cut and cover structures (C&C) is that the cutting forces needed to penetrate the ground is provided by wall grippers as opposed to surface excavation that relies on the weight of the machine, which is only 1/6^th the weight on earth. An LTBM could also be used to excavate an access ramp to Lunar Rilles (lava tubes) or skylights, providing a safer alternative than entry through collapsed sections. This would reduce the hazard of rock fall when exploring these types of lunar features. LTBMs could also be adapted for the icy-regolith in the permanently shadowed craters at the lunar poles, which may be an attractive option for access to lunar ice resources with minimal surface disturbance and the potential for volatile loss. This paper and presentation will discuss lunar base design concepts and other applications using a LTBM. Design constraints of a LTBM, such as cutter design, mass, and power, as well as potential solutions to address such constraints will be presented, including the potential use of lunar resources to fabricate heavier elements of the LTBM.

Agricultural science has accumulated deep knowledge about plants, animals, and agriculture on this planet over 7 millennia and within our local gravity level (1 g). Researchers have, over the past few decades accumulated on Mir and the ISS a body of factual data about some species of plants and animals, living in micro-gravity (about 1/1000th g). But this knowledge base is insufficient to prepare for the creation of new permanent homes for humanity beyond Earth. Future settlements need accurate data on the growth, development, and interactions in full biomes of plants and animals and their associated microorganisms, in gravity levels between zero and one. The most critical gravity levels for research are sixteen percent (Earth’s Moon), thirty-eight percent (Mars), and ninety-one percent (Venus) since space settlements have been proposed for each of these celestial bodies. This paper proposes a conceptual design for a facility designed to house all three gravity options within one structure in order to conduct such research in the appropriate gravity levels. The goal of this proposal is to minimize the infrastructure cost, and to allow for redundant and parallel experiments in a series of habitats. Risk is always present in such research, and redundancy will be a critical need. Although generally more is learned from the failures than success, it is still important to design the redundancy into to keep the damage from a failure to a minimum. The central facility proposed to house these habitats will also provide a construction jig to facilitate the construction of more such facilities for other purposes.

Clearly the need for autonomous robots and automated systems is more critical for space construction than terrestrial construction work. It is the collective performance of these devices rather than their individual performances that should be optimized, which calls for the highest level of precision and coordination among all active agents in the field. The control and coordination of swarms of robots can be done through agent-based modeling which is a potentially effective method of coordinating multiple agents with complex behaviors without central control. This leads to a more efficient but complex workflow that minimizes collisions between robots, decreases their idle time, and reduces their travel distances for example. In this paper, the needs for new construction management techniques for space construction projects is discussed. Also, a discussion of the need for implementation of agent-based modeling, as an efficient decentralized coordination technique is presented.

When landing on the Moon or Mars the rocket exhaust plume interaction with the regolith results in sandblasting surrounding facilities at best or excavating a large hole underneath the lander at worst. When a lunar or Mars base is established, multiple landings and launches are needed and thus a landing pad would be required. Several methods have been proposed for constructing a landing pad but so far none are adequate. Local rocks were chosen as the in situ construction material due to the rocks being abundantly available in many locations. This paper presents and discusses the results of a Phase I NASA STTR project in the form of a landing pad CFD analysis to estimate expected forces on the rocks due to the rocket plume and landing pad construction material experiments in the form of rock bonding.

To mitigate dust problems during launch/landing operations in lunar and Mars missions, it is desired to build solid pads on the surface. Recently, strong tiles have been fabricated from lunar regolith simulants using high-temperature sintering. The present work investigates combustion joining of these tiles through the use of exothermic intermetallic reactions. Specifically, nickel/aluminum (1:1 mole ratio) mixture was placed in a gap between the tiles sintered from JSC-1A lunar regolith simulant. Upon ignition by a laser, a self-sustained propagation of the combustion front over the mixture occurred. Joining was improved with increasing the tile thickness from 6.3 mm to 12.7 mm. The temperatures sufficient for melting the glass phase of JSC-1A were recorded for 12.7-mm tiles, which explains the observed better joining.

Prior to human arrival to the Moon or Mars, some infrastructure will be required to ensure success of the goals of the mission. Such infrastructure may include landing pads, dust mitigation surfaces, thermal wadis, and shelter/habitats. To reduce the mass of construction materials to be transported from Earth, it will be critical to utilize in situ resources as the main construction material. Regolith seems to be the most logical choice given its abundance and easy access. There are two critical components to this task: materials: the ideal material to exploit, given its abundance and accessibility is regolith. Regolith-derived feedstocks that can be used to manufacture parts, tools, and construction materials to ensure a constant supply of raw materials for the success, maintenance, and expansion of a mission. Automation: some of this work is expected to be done before human arrival through robotic operations. Even after human arrival, resource extraction, collection, sorting, processing, and construction should be done tele-robotically to reduce crews’ extra vehicular activity (EVA) time and radiation exposure. This will require equipment that can operate autonomously/semi-autonomously to perform all the tasks involved. Honeybee Robotics, the Pacific International Space Center for Exploration Systems (PISCES), and USC’s Viterbi School of Engineering and School of Architecture are working together under a NASA STTR Phase I contract to design and test a prototype building block using Hawaiian basalt that can be used for both horizontal and vertical construction projects. The final product should be able to meet construction standards, be manufactured without any additives, have a design that allows for robotic emplacement, and have either an interlocking design or a mechanical joint.

The ultrasonic planetary core drill (UPCD) project sought to develop and conduct a field trial, in an analogous Martian environment, of a space-compatible regolith-sampling tool. The project implemented a number of key technologies to achieve this aim: a drilling control loop based on ultrasonic power feedback, a bayonet interface system to allow a drillstring to be built up in situ then disassembled after use, a coring design which captured the cores drilled out, and a mechanism for caching the core samples in sealable containers. The system was demonstrated in the laboratory with results indicating low power, low weight on bit, achievement of the targeted depth, and the retrieval of still-frozen core samples. The routines to allow the system to become fully autonomous were also demonstrated. The drill was deployed to Coal Nunatak on Alexander Island, Antarctica, for analogue trials. The drill was demonstrated to work, as was the caching and drill assembly/disassembly system, but the target depth was not achieved. A review of drill depth is provided along with a laboratory solution to the problems encountered in the field. Further work using the UPCD is also discussed.

Drilling deep into the subsurface of planetary bodies in the Solar System for samples acquisition enables critical capabilities for future NASA exploration missions in its quest to understand the origins of the Solar System and potentially the search for life. Such planetary bodies as Mars and Europa are key targets for potential missions that would require reaching great depths. Performing drilling while using minimal mass/volume systems and with low energy consumption are the main requirements that are imposed on such technologies. A wireline deep drill, called Auto-Gopher-2, is currently being developed as a joint effort between JPL and Honeybee Robotics Ltd. The Auto-Gopher II is a wireline rotary piezo-percussive deep drilling mechanism that combines formation breaking by rotating and piezoelectric actuator hammering and cuttings removal by rotating a fluted bit. The hammering mechanism is based on the ultrasonic/sonic drill/corer (USDC) mechanism that has been developed as an adaptable tool for many drilling and coring applications. The USDC uses an intermediate ball-shape free-mass to transform high frequency vibrations of a piezoelectric transducer horn tip into sonic hammering of the drill bit. The lessons learned from the previous studies are being implemented into the development of the Auto-Gopher-II, an autonomous deep wireline drill with integrated cuttings and sample management and drive electronics. Subsystems of the wireline drill are being developed in parallel at JPL and Honeybee Robotics, Ltd. Issues related to the bit and its ability to retain the cuttings for caching and removal are currently being addressed. This paper presents the development efforts of the piezoelectric actuator, cuttings removal and retention flutes, and drive electronics.

The ultrasonic planetary core drill (UPCD), recently developed by a consortium of European partners with co-ordination from the University of Glasgow, is a planetary sample acquisition and caching systems testbed, recently field tested at Alexander Island, Antarctica. During the early development of the technology, laboratory-based drilling tests at ambient pressure, utilizing volatile-laden permafrost simulants, revealed the need for an enhancement of the existing control algorithm which autonomously governs the rate of progress of the drill through the terrain. Such modifications have been deemed essential if failure modes relating to re-solidification of unbound volatiles are to be avoided. In the preliminary development of this thermal control algorithm, multiple sensors have been utilized in order to enhance the reliability of the system. It is hoped that this sensor suite may also allow data concerning the thermal environment of the terrain to be exploited, improving the scientific return of the mission. This paper details the early progress made towards a robust thermal control system for the ultrasonic planetary core drill, featuring results of laboratory testing under ambient conditions in to targets consisting of simulated permafrost, pure ice, and frozen saturated rock. Results from this series of preliminary tests show that, when required, the control algorithm developed has proven to be a useful addition to the UPCD control system through its ability to prevent freeze-in faults.

Seeking the evidence of potential life is one essential and perpetual driving force for human planetary explorations. Compared with other technical solutions, sampling the planetary soil and returning it back to Earth for further analyzing may be the most direct method to realize this goal. Due to the fact that sample’s geological stratification along the longitudinal direction completely records early stars’ geological evolution, it should be better to adopt suitable sampling methods to preserve the whole sample well. Flexible tube coring (FTC) method, applying a series of hollow coring tubes into the auger to sample the subsurface regolith, can preserve sample’s geological stratification without any losses, hence it has been adopted in the China Chang’e III project. However, it should be noted that the final coring results and online drilling loads that drill tool sustained are both greatly influenced by the uncertain physical properties of lunar regolith, hence proper drilling parameters should be tuned immediately in drilling process. Otherwise, only a small amount of cored soil sample would be acquired and serious overloads drilling faults could occur correspondingly. In order to comprehend the soil flow characteristics and avoid potential drilling faults, a novel soil flow characteristics monitoring method was proposed by employing an ultrasonic sensor and an industrial camera to monitor the coring results and removal states. Experiments in one typical lunar regolith simulant revealed that penetration per revolution has great influences on drilling states and should be optimized further.

The Atacama rover astrobiology drilling studies (ARADS) project is iteratively developing a simulated Mars rover biomarker-detection mission over four successive field deployments at the Atacama Desert Mars-analog site in 2015-2019. The second ARADS deployment in February 2017 gathered ground-truth samples, studied biomarker distributions, tested an integrated 2 m sampling drill and sample transfer arm on the KREX2 rover, and tested four astrobiology instruments at sites near Yungay Station in the Atacama Desert.

As remotely operated interplanetary drills probe deeper strata, autonomous health monitoring and fault recovery is required to accommodate communication delays that well exceed the time required for such systems to become stuck. This paper will discuss work on autonomous diagnostics and fault recovery software coded in the plan execution interchange language (PLEXIL). By caching sensor and motor data as it is collected in real-time, the software evaluates the drill’s current operational state and classifies the state as either nominal or one of a number of uniquely defined off-nominal fault states. Each drill fault requires its own unique recovery procedure, which is executed by the software upon detection. The software verifies the success of the recovery based on a series of goal conditions that are dependent on the fault being recovered from. If the recovery attempt succeeds, the drilling operation is resumed; otherwise, the recovery procedure is reattempted as many times as needed until the goal conditions are achieved. The software has been tested on 3 different rotary-percussive, Mars-capable robotic drills; the latest of which is the Atacama rover astrobiology drilling studies (ARADS) drill. Tests on the ARADS and other drills occurred in a variety of Mars analogue environments, including: the arid Atacama Desert, the permafrost encrusted Devon Island, and the anaerobic bacteria habitats around the Rio Tinto. An overview of the autonomous diagnostic and recovery system, with analyses of how they performed in these Mars-like conditions, are given.

This paper describes the effects of combining ultrasonic vibration with hammer-action style penetrators, such as the HP³ probe on the InSight mission. By synchronizing short pulses of vibration with the impact of the hammer, the number of hammer strikes required to reach a specified depth was reduced by over a third in some cases, depending on the sand and amplitude of vibration used. Additional investigations looked at comparing the performance of pure hammering with pure pulsing, allowing recommendations for operational procedures if this technology were to be taken forward in the future.

We used a Mars analog, the Chilean Atacama Desert, to simulate a drilling mission to Mars, as part of the Atacama rover astrobiology drilling study (ARADS) grant through NASA’s PSTAR Program. Automated drilling from a rover platform within one meter of a conventional science dig allowed us to make a direct comparison of manned vs. unmanned data return at a potential two-million-year-old lake bed/evaporite site near Yungay Station. Science observations of soil type and biomolecule content compared well to planetary mission-type data of size distribution, cuttings angle of repose, drill telemetry, and instrument readings. Drill telemetry data taken during four companion studies allowed us to characterize soil horizons that might affect instrument results. Water signatures were encountered during a tracer study which demonstrated how much contamination is brought into a cohesive borehole by three different vectors: the drill itself, surface in-fall due to downstroke, and surface in-fall due to retraction. Water signatures were also encountered during a study of polygonal structures to interpret data variation in these large-scale soil formations also observed on Mars. Salt horizons were encountered during a biomarkers/halite transect study. Salt horizon data was also gained from a second polygon edge study in hyperarid soil, which linked lower drill torque at polygon edges with increased in-fall and mixing compared to that of polygon interiors. Characterizations of how a drill transforms and makes available subsurface information from this analog environment can help us interpret results of a drill-based mission to Mars. Results obtained in the Atacama indicate drill telemetry and cuttings offer a wealth of accurate subsurface data.

Solar power satellites and/or solar shield satellites are two complementary solutions to solving the climate change problem. The combination of lunar in situ resource utilization and self-replication technology offers a means to circumvent the launch cost barrier. We describe how self-replication technology based on lunar resources, premised on the notion that 3D printing constitutes an universal construction mechanism, might be realized.

Sustaining activities in space requires the ability to produce commodities from the natural resources there. This begins with exploration and proceeds through mining and processing to manufacturing. Successful in situ resource utilization (ISRU) will depend on the body of knowledge gained from millennia of terrestrial mining experience as well as aerospace engineering. Mineral production entails a sequence of operations to separate the desired material from all other material, passing it on in a form appropriate for manufacturing. Designing this process requires specific knowledge of the available technologies and their constraints in the working environment, so appropriate design choices can be made. This paper examines some potential approaches to translating terrestrial mining and processing experience to space locales.

One of the NASA’s long-term goals is to extend and sustain human activities in space; an important part of this goal is to develop technologies to sustain human presence in space and provide enough time for performing mission activities, while reducing dependence on the earth. This is expected to be achieved primarily through in situ resource utilization (ISRU), using the locally available resources, to reduce the need for bringing materials from the Earth, thereby reducing the launch weight of the mission. A variety of challenges are seen for ISRU to be successfully implemented. These mainly center on the differences between Earth and Lunar environments. For instance, key challenges in mining lunar rocks include low gravity, solar radiation, solar flares, micro-meteorites, and extreme temperature changes and their effects on mining processes; and for processing of lunar minerals include the shape of particles and its effect on the transport, wear, and separation of particle types. This creates design opportunities that are difficult to understand and test on Earth. This paper discusses the possible concepts of mining (using shape memory alloys), mineral processing (electrostatic and magnetic separation), and materials manufacturing (laser, electron beam, and friction based advanced manufacturing) by utilizing the in situ materials available on site on the lunar surface.

This paper presents the results of a program of computational modeling focused on elucidating the physics and chemical processes associated with the extraction of volatile materials from asteroid feedstocks with an eye toward use of the extracted materials for propulsion, radiation shielding, and replenishment of mission consumables. We present a math model of conductive heat transport, chemical processes, and gas escape by Darcian diffusion. Chemical processes in the model include pyrolysis of organic chemical constituents and thermal dehydration and decarbonization of hydrates and carbonates. The model is implemented in a spherical finite difference computational engine that predicts time histories of gas release and flow rates, interstitial gas pressure, and material temperature profiles as a function of the time history of the outer surface of the sample being modeled. Samples of materials modeled include solid and granular forms of terrestrial clays, engineered stimulants, asteroid material based on canonical CI and CM type meteorites, and one particular CM type meteorite which was tested in a related experimental effort. Modeling results show good agreement with experimental results suggesting that the model is largely complete and descriptive demonstrating a practical understanding of the process as needed for engineering applications. Particular unknowns associated with certain chemical processes, for example vacuum pyrolysis of bitumen and kerogen, as well as vacuum TGA analysis of certain phyllosilicate materials are identified as needs for future basic supporting research. After presenting direct comparisons of model outputs with recently completed experimental results, in effect validating the model, the model is applied to hypothetical meter, decameter, and hectometer scale asteroids in a hypothetical solar oven. This analysis motivates an extension of the model to address Optical Mining technology which has certain advantages over bulk heating as specified in the paper. An outline of our plan for a finite difference model of the Optical Mining process is presented. The importance and the value of terrestrial macroscopic thermal oven experiments for fundamental research supporting Optical Mining is clarified.

Several experimental results in the literature demonstrate that excavation forces increase dramatically as soil accumulates ahead of a cutting blade, however these effects are not always modeled; when they are added to classical models, they are included as a surcharge force without consideration of the soil properties of the piled soil, other than mass. This work introduces a modified McKyes excavation cutting model, that takes into account the friction angle and cohesion of the piled soil when computing the failure plane of a cut. Simulation results show that this new model replicates the decreasing failure plane angles, as a cut proceeds, observed in experimental and discrete element model (DEM) results in the literature. Simulations at 1 g and 1/6 g gravity, with various levels of cohesion, show that excavation forces due to soil accumulation are especially sensitive to cohesion in planetary excavation. These results elaborate on prior work in the literature showing that cohesion plays an important role when soil accumulation is not considered. Modeling such aspects of excavation without resorting to computationally-intensive DEM is especially useful in planetary excavators where computing power is limited or in autonomous terrestrial excavators that must model and plan cutting in real-time.

The effect of dust and adverse lighting conditions on telerobotic perception systems sensors was investigated to better assess and refine regolith operations for asteroid, Mars, and lunar missions. Low illumination and low-angle-of-incidence lighting pose significant problems to computer and human vision. Levitated dust on asteroids interferes with imaging and degrades depth perception. Dust storms on Mars will pose significant hazards to autonomous robot operations if robotic perception problems are not solved. The industrial partner for this project was Caterpillar Inc., who provided the sensors for environmental testing and characterization. The telerobotic perception systems testing performed in this work is also relevant to terrestrial operations with autonomous vehicles in mines, on construction sites, and on roads. Testing was performed in the Swamp Works Granular Mechanics and Regolith Operations Lab at Kennedy Space Center using the regolith test bed (RTB). The RTB is an enclosed volume filled with approximately 120 tons of Black Point-1 basalt rock regolith simulant. The test equipment included Caterpillar, Inc. telerobotic sensors, dust density measurement system, and a pneumatic dust generation system (DGS). The Caterpillar telerobotic sensors included a light detection and ranging (LIDAR), radio detection and ranging (RADAR), and a stereovision camera. The DGS was used to loft regolith fines and dust into the air to simulate dusty environmental conditions while the dust density measurement system measured the dust density as the dust settled.

In situ resource utilization (ISRU) enables future planetary exploration by using local resources to acquire mission consumables. Water-bearing regolith has been identified on the Moon in the permanently shadowed craters. Missions designed to retrieve these resources will require testing in relevant environments. The Planetary Surface Simulation Facility (otherwise known as “VF-13”) at the NASA Glenn Research Center can create these relevant environments for ground based testing. This dirty thermal vacuum chamber is 3.6 m tall, 1.5 m in diameter, and can achieve pressures on the order of 10^-6 Torr. The internal wall of the chamber and the soil bin are separately temperature controlled using liquid nitrogen. For the past four years, the chamber has been used by NASA’s Resource Prospector to characterize volatiles loss during regolith sampling operations. Observations from 43 samples suggest agitating the sample during delivery has a significant impact on the volatiles loss. Calculated mass loss rates are consistent for similar size samples. However, the variations in moisture loss do not clearly correlate with measured conditions. Continued testing will examine the impacts of the mechanical sample delivery process.

In situ resource utilization (ISRU) is a critical part of sustainable and cost-effective space exploration. This paper presents a method of extracting volatiles from ice, ice-rich regolith, and hydrated soils from the Moon, Mars, and asteroids. Planetary volatiles extractor (PVEx) is a double-walled coring auger with a heated inner wall. It drills to a target depth, obtains a core sample, heats it up, and captures volatiles in a condenser above the surface. Once extraction is complete, the corer is retracted and a dry core is left behind. A breadboard version of PVEx has been designed, fabricated, and tested. Initial tests were performed in limestone and blocks of ice to evaluate mechanical aspects of the system. During these tests, minor mechanical issues were identified and resolved. PVEx reached a 50-cm depth in limestone in 10 minutes and a similar depth in -20 °C ice blocks in 7 minutes, creating 5-cm-diameter cores. Future tests will include drilling in a vacuum chamber and water extraction.

Modeling has been developed to support the development of volatile extraction technologies for the Moon, Mars, asteroids, or other bodies. This type of modeling capability is important to avoid the high cost of multiple test campaigns in simulated lunar conditions as the hardware design is iterated. The modeling uses the Crank-Nicholson algorithm applied in a two dimensional (2D) axisymmetric (extendable to 3D) finite difference formalism. It uses soil thermal parameters developed from Apollo soil measurements with adaptations for asteroid regolith. Simulations show that it successfully replicates thermal measurements on the surfaces of asteroids and the Moon and helps interpret those measurements to provide insight into the subsurface properties of those bodies. The 2D simulations have provided insight into the cooling of a lunar drill bit and provide a method to determine the original subsurface temperature despite the presence of the warm bit.

To demonstrate proof of concept water extraction from simulated Martian regolith, an open reactor design is presented along with experimental results. The open reactor concept avoids sealing surfaces and complex moving parts. In an abrasive environment like the Martian surface, those reactor elements would be difficult to maintain and present a high probability of failure. A general lunar geotechnical simulant was modified by adding borax decahydrate (Na₂B₄O₇·10H₂O) (BDH) to mimic the ~3 percent water content of hydrated salts in near surface soils on Mars. A rotating bucket wheel excavated the regolith from a source bin and deposited the material onto an inclined copper tray, which was fitted with heaters and a simple vibration system. The combination of vibration, tilt angle, and heat was used to separate and expose as much regolith surface area as possible to liberate the water contained in the hydrated minerals, thereby increasing the efficiency of the system. The experiment was conducted in a vacuum system capable of maintaining a Martian-like atmosphere. Evolved water vapor was directed to a condensing system using the ambient atmosphere as a sweep gas. The water vapor was condensed and measured. Processed simulant was captured in a collection bin and weighed in real time. The efficiency of the system was determined by comparing pre- and post-processing soil mass along with the volume of water captured.

The NASA Jet Propulsion Laboratory (JPL) is studying excavation and collection of a sample from an icy surface for a potential landed mission to Europa. Europa presents unique challenges in planetary sampling. Very little is known about the local topography and material composition of the surface. The environmental conditions of being cryogenically cold (80-130 K), low gravity (~1/7th Earth), no atmosphere, low lighting conditions, and limited ground in the loop opportunities have forced JPL to look at sampling differently than past missions. Interacting with the surface of the Jovian moon requires a sampling system that is robust to local topography on the scale of the lander and/or the tool. In addition, the sampling system must be capable both of detecting faults and automatically adjusting to them to achieve the mission objectives without ground in the loop feedback. Presented here is an overview of a sampling system concept that involves a two-stage approach for collecting a sample. The first stage uses an excavation tool to prepare the surface site for sample collection by removing the top layer of irradiated material and clearing tailings from the hole. The second stage then generates and collects a sample for delivery to instruments on-board a lander. Also presented is an introduction for how autonomy and sensing technologies might be employed to enable mission success.

The LiRS combined LIBS and Raman spectrometer elegantly integrates laser-induced breakdown spectroscopy using 1064 nm excitation for elemental composition, deep UV (DUV) Raman using 248.6 nm excitation to provide information on the bonding structure of the elements, fluorescence for the ppm sensitive detection of the presence of organics, and a bore-sighted colour micro-imager for complementary information on the sample morphology, LIBS plume, and resultant crater. This paper discusses the LiRS laboratory breadboard and the associated relevant laboratory and thermal-vacuum validations. LiRS is applicable to the analysis of both solid and liquid samples for their mineralogy, organics, and bioindicators. The potential space mission applications for this technology for beyond LEO astrobiology are discussed.

The Europan molecular indicators of life investigation (EMILI) is an instrument investigation designed to address the top science objectives of a future Europa lander mission, such as documented by the recent Europa Lander Science Definition Team (SDT). EMILI seeks to detect and characterize potential organic molecular biosignatures, which may be present only at ultralow (nM) concentrations. EMILI also characterizes key aspects of the mineralogical context of the samples collected from the Europan near-subsurface to discern the provenance and degree of radiative or oxidative processing they have undergone. Here we present selected EMILI instrument features, including recent prototype mass spectrometer (MS) developments, and preliminary results.

Saturn’s moon, Titan, is one of the largest moons in the solar system, as well as one of the most dynamic. Under a thick nitrogen atmosphere, the Cassini probe has detected stable surface seas composed of liquids methane and ethane. Methane is evaporated form the seas and rains down on the surrounding solids in the equivalent of the hydrological cycle on Earth. The vicinity of these seas promises a host of discoveries in fields including geology and chemistry. Several missions have been proposed to explore the landscape of Titan, including airships and floating landers, but a submarine is one of the best for observing the passage of liquid throughout the seas. Such a design has been proposed as a stand-alone vehicle. One of the most important subsystems of the design is the ballast system, which controls rising and sinking. In the current design, a ballast tank is flooded at the surface to sink while neon or helium gas expels the liquid to rise. This paper will consider an alternative ballast system that draws in situ nitrogen vapor from the atmosphere to expel the sea liquid. Because nitrogen is condensable at Titan temperatures, the required changes may make the system more complicated and impose severe operational limits compared to supercritical neon or helium.

Polyether ether ketone (PEEK) is a high-performance, semi-crystalline thermoplastic that is used in a wide range of engineering applications, including some structural components of aircraft. The design of new PEEK-based materials requires a precise understanding of the multiscale structure and behavior of semi-crystalline PEEK. Molecular dynamics (MD) modeling can efficiently predict bulk-level properties of single phase polymers, and micromechanics can be used to homogenize those phases based on the overall polymer microstructure. In this study, MD modeling was used to predict the mechanical properties of the amorphous and crystalline phases of PEEK. The hierarchical microstructure of PEEK, which combines the aforementioned phases, was modeled using a multiscale modeling approach facilitated by NASA’s MSGMC. The bulk mechanical properties of semi-crystalline PEEK predicted using MD modeling and MSGMC agree well with vendor data, thus validating the multiscale modeling approach.

Numerous research efforts have been focused on developing lightweight epoxy-based composite materials that can rival expensive metal alloys in specific aerospace structural components. Due to their high-specific stiffness and strength and corrosion resistance, epoxy-graphene nanoplatelets (GNP) composite materials can be used as the matrix of carbon fiber-reinforced hybrid composites. This work provides a multiscale computational analysis to simulate the hybrid composite and predict its effective mechanical properties. The work-flow of this study involves two main sequential stages that can be specified towards acquiring the effective mechanical properties of the hybrid composite. Molecular dynamics (MD) simulations using large-scale atomic/molecular massively parallel simulator (LAMMPS) to create a nanoscale unit cell from EPON 862-DETDA epoxy and GNP was the first stage. The reactive force field (ReaxFF) was chosen to represent the atomic/molecular level interactions in these simulations. The interaction between aromatic rings in epoxy molecules and GNP was investigated in this study. It was found that such interactions can affect the spatial density distribution of the epoxy molecules at the GNP/epoxy interphase. The second stage involved a micromechanical analysis of the carbon fiber-reinforced hybrid composite using NASA's micromechanics analysis code based on the generalized method of cells (MAC/GMC). The effective mechanical properties of the hybrid composite were predicted at different volume fractions of GNP in the composite matrix.

DSI, in partnership with UCF, explored the feasibility of using clay regoliths as construction materials in Mars, Phobos, and near-Earth asteroids. This paper presents the results of that work. Clays are a known component of Martian regoliths as well as of many NEAs, likely to include Phobos and Deimos. We explored the production of clay-based building materials, using asteroid and martian simulants, both as-prepared, and after various beneficiation processes. Construction approaches evaluated included additive manufacturing (3-D printing) and traditional bricklaying (using mortars) as well as interlocking bricks (3-D assembly). We modeled 3-D printing approaches using simple extrusion techniques, and bricks using molds. We encountered multiple problems, largely related to the necessity of recovering process water, and the significant expansion and shrinkage of many clay materials.

Extraterrestrial construction presents many interesting and new challenges. Unlike Earth, there are very limited naturally occurring resources readily available in extraterrestrial environments, such as the Moon or Mars. Transporting large amounts of materials from Earth is cost prohibitive. Thus, this work focuses on a novel class of composites for use in limited resource environments: protein-bound soils. For space applications, the term regolith is used to refer to the loose soil-like material on the Moon, asteroids, and other planetary bodies. The composite is produced by mixing soil, water, and a biopolymer binder (protein or other biopolymer) to create a versatile composite with compressive strength comparable to that of ordinary Portland cement concrete. This paper proposes a multi-scale framework to model the composite’s fracture properties in order to design a durable material that can resist extreme environments. At the nanoscale, nanoindentation is used to obtain the mechanical properties of the dry protein after dissolving in water and desiccating. At the microscale, the creation of statistically equivalent periodic unit cells captures the interactions between soil particles, protein, and voids. Virtual tests are then used to obtain basic mechanical parameters. At the mesoscale, a rigid body spring model (RBSM) is used to simulate fracture using the homogenized properties obtained at the microscale. At the macroscale, triaxial testing and digital image correlation tests are used to corroborate and modify the simulations. The final goal of this project is to have a robust computational simulation that can enable the prediction of the mechanical properties of the protein-bound regolith material to be used to design future structures on the Moon, Mars, or other celestial bodies.

Biocementation is expected to be an energy efficient and environmentally benign alternative method for the production of cement products, and it has been extensively studied on Earth. This research is focused on developing bioprocesses to produce bioconcrete columns using Mars-compatible microalgae and simulated Martian regolith. A marine microalga, Thraustochytrium striatum was tested to make Martian regolith-based columns in the presence of CaCl₂/urea. Three different biogrouting methods were investigated including simultaneous, sequential, and batch circulation of microalga cell biomass and CaCl₂/urea in the columns. The need of post-biogrouting column soaking was also studied. The columns were characterized by the unconfined compressional strength (UCS), CaCO₃ formation by X-ray diffraction (XRD), and microstructure by scanning electron microscope. T. striatum is capable of biocementation and can produce urease to produce CaCO₃ precipitation for regolith columns. Overall, the sequential biogrouting is better than the simultaneous counterpart. The best UCS value found for the columns reached 523 kPa. Batch biogrouting has potential to achieve high UCS, but fast CaCO₃ clogging needs to be overcome in the future research. The column soaking is not needed because it worsened the UCS.

Lightweight cementitious composites (LWCC) are cement based material combined with lightweight fillers. Because of its advantages in reducing both structural weight and thermal conductivity, it has the potential to be used in the construction of terrestrial and extraterrestrial habits. Furthermore, since it has relatively small and spherical shaped aggregates, LWCC is also suitable for extrusion based 3-D printing. In this research, a comprehensive and thorough study was carried out to investigate the effects of different lightweight fillers on both the mechanical and thermal properties of LWCC. Various lightweight fillers including three types of hollow glass microspheres (HGM) and two fly ash cenospheres (FACs) are studied in conjunction with various particle size, shell wall thickness, and volume fractions. Both mechanical and thermophysical properties were tested. The results indicated that the thermal property of LWCC is mostly governed by the volume fraction of LWFs whereas the mechanical properties are heavily affected by the type and property of LWF particles included. In addition, to understand the materials’ mechanical performance under high strain rate, split Hopkinson pressure bar (SHPB) tests were conducted for strain rate ranging from 400 s^-1 to 1000 s^-1.

Long-term habitation outside of Earth’s atmosphere requires infrastructure that can protect astronauts and equipment from significant environmental hazards. In turn, the materials used to build these protective structures must be durable enough to withstand the environment over time. One notable hazard of the space environment is micrometeorite impacts. This research examines the effects of micrometeorite impacts on regolith biocomposite (RBC), a proposed material technology that transforms in situ materials, such as planetary or lunar regolith, into useful structural elements such as stable landing pads, pavements that prevent dust levitation, radiation shielding, and habitats. To characterize the relationship between the intensity of a hypervelocity impact and the incurred damage of RBC, a total of nine hypervelocity impact experiments were conducted. Resulting craters in the test materials were measured and transient crater dimensions were calculated. Analytical power-law relationships between impact velocity and transient crater diameter and volume were derived using Holsapple’s pi-group strength scaling laws.

Efficient in situ resource utilization is a critical component of NASA’s current and future Mars exploration missions. In this work, simulated in situ Martian materials were utilized to synchronize novel regolith-based composite materials for the creation of functional building blocks. More specifically, a Martian soil simulant and a thermoset polymeric material were used to manufacture composite building blocks as a potential structural component for Martian infrastructure. Curing technologies were explored to design simplified mass production techniques. The created composites were then tested for their mechanical (e.g. strength and modulus) properties to determine the feasibility of them being used as building blocks as well as the optimal compositions for desired engineering properties. The obtained results data were used to guide the development of mechanics-based numerical models for predicting mechanical properties and behavior of newly manufactured materials. As the complex temperature variation on Mars, the thermal properties of newly manufactured materials are also of interest and will be reported in a future paper.

The utilization of in situ resources will be critical to the success of any long-term manned missions to Mars. One of the many requirements will be the development of suitable materials for the construction of habitats and infrastructure. In this paper we present results on the development of a magnesium-based cementitious binder system, which could be produced from materials readily available on the surface of Mars. The magnesium binder system was combined with three different Martian regolith analogues and the mechanical performance characteristics of the mortar were evaluated. Results show that compressive strengths of the magnesium regolith system were comparable to conventional Portland cement mortar, and appropriate for potential civil engineering applications on Mars.

The multiphase and orthotropic nature of trees lead to their complex mechanical properties. In this paper, experiments and numerical simulation were conducted to investigate the deformation and failure processes of trees under impact loads. Gas gun system was applied for impact tests and high-speed camera was used to capture the impact failure process. An anisotropic constitutive model combined with strain hardening coefficients was applied to describe the dynamic response of wood materials. The presented numerical model was developed in commercial finite element software LS-DYNA to simulate failure process of a birch tree under impact of aluminum sabots at various velocities. The strain hardening coefficients were determined through correlation with the experimental measured energy absorption values under different impact speeds. The model was then further applied to study the impact resistance and energy absorption capability of the birch tree. The presented material model and modeling framework could be used for numerical investigation of various impact problems, e.g. vehicles’ impact with electrical pole and aircraft crashing into forest.

Triaxially braided composite is a state-of-art material used for engine fan case structure. The mechanical failure behavior of triaxially braided composite is very complicated due to its complex structure in the mesoscale. Extensive studies have been conducted experimentally and numerically to investigate its progressive failure behavior and size-dependent properties under quasi-static loading rates. In this paper, a mesomechanical model is presented to study the rate-dependent failure behavior of T700s/PR520 triaxially braided composite. Strain-rate dependent mechanical properties of the matrix are implemented into a micromechanical model to determine the mechanical properties of fiber tows at various strain rates (1×10^-5, 1, and 500 /s), which are then imported into the mesomechanical model to investigate the rate dependency of effective properties and failure behavior for the braided composite. Comparison studies on the strain and stress field, damage contours of triaxially braided composite under axial tension, and transverse tension of different strain rates are conducted using the presented model. The numerical results elaborate the effect of strain rate on the damage progression behavior and identify the main factors that affecting the failure strength. The results of this work can be useful for developing more accurate constitutive and damage model for impact modeling of engine fan case made from triaxially braided composite.

In this work, a multi-scale finite element analysis modeling approach in LSDYNA has been developed to simulate the impact of triaxially braided composite structures. This approach, referred to as the multiscale hybrid element analysis (MHEA), uses fine scale solid elements to discretize area of high interest and transitions to continuum shell elements in the surrounding far field region. In the primary impact zone a meso-mechanical finite element model is used to incorporate the detailed braided fiber architecture into the model to account for the local damage initiation and propagation of the individual constituents. A macro-mechanical finite element model based on an existing subcell approach is applied in the regions away from the impact zone to capture the global response of the entire structure in a computationally efficient manner. The proposed MHEA was calibrated and correlated with simulations of coupon tests where the material damage and failure in both the axial direction and transverse directions were studied. Impact simulation of a represented braided composite is conducted to demonstrate the predictability of the modeling approach on the damage pattern as well as damage initiation and propagation.

Estimating the trajectory of separated objects after disintegration caused by impact will be useful in crashes analysis of airplane, especially in the circumstance when the impact condition cannot be totally determined. Since the motion of an airplane’s fragments in air is highly effected by the aerodynamic loads, computational fluid dynamics with an automated unstructured tetrahedral mesh approach using spring-based smoothing and remeshing are employed. Three-dimensional compressible Navier-Stokes equations and six degree of freedom (6-DOF) rigid body motion equations are solved by Euler solver coupled with 6-DOF time integration module. Three different parts of the airplane whose aerodynamic characteristic can be described as regular or irregular and the flight stability is from stable to unstable such as: bomb-like object referred as the store and wingtip segment are investigated. Numerical simulations are performed under various initial conditions. Trajectory of the store structure results are validated with published data and found to be in good agreement.

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 use in the aerospace and automotive communities. The aerospace community has identified several key capabilities which are currently lacking in the available material models in commercial transient dynamic finite element codes. To attempt to improve the predictive capability of composite impact simulations, a next generation material model is being developed for incorporation within the commercial transient dynamic finite element code LS-DYNA. The material model, which incorporates plasticity, damage, and failure, utilizes experimentally based tabulated input to define the evolution of plasticity and damage and the initiation of failure as opposed to specifying discrete input parameters such as modulus and strength. The plasticity portion of the orthotropic, three-dimensional, macroscopic composite constitutive model is based on an extension of the Tsai-Wu composite failure model into a generalized yield function with a non-associative flow rule. For the damage model, a strain equivalent formulation is used in combination with a semi-coupled approach where the overall damage in a particular coordinate direction is assumed to be a function of the applied loads in all of the coordinate directions. For the failure model, a tabulated approach is utilized in which a stress or strain based invariant is defined as a function of the location of the current stress state in stress space to define the initiation of failure. The development and verification of the material model is discussed.

In March 2017, a vertical drop test of a 3.048-m (10-ft) section of a Fokker F-28 aircraft was conducted as part of a joint FAA/NASA effort to investigate the performance of transport aircraft under realistic crash conditions. The section was configured with two rows of aircraft seats, in a triple-double configuration. A total of ten anthropomorphic test devices (ATDs) were secured in the seats using standard seat belt restraints. The section was also configured with luggage in the cargo hold and two hat racks, each with added ballast mass. The drop test was performed at the Landing and Impact Research facility located at NASA Langley Research Center in Hampton, Virginia. The planned impact velocity was 9.144-m/s (360-in/s) onto soil. A second objective was to assess the capabilities of finite element simulations to predict the test response. A finite element model was developed for execution in LS-DYNA, a commercial explicit nonlinear transient dynamic code. The model contained accurate representations of the airframe structure, the hat racks and hat rack masses, the floor and seat tracks, and the luggage in the cargo hold. Concentrated masses were used to represent the inertial properties of the seats, restraints, and ATD occupants. The model was executed to generate analytical predictions of airframe responses, which were compared with test data to validate the model.

During the summer of 2017, a vertical drop test was conducted on a partial section of a Fokker F28 MK4000 aircraft as a part of a joint NASA/FAA effort to investigate the performance of transport category aircraft under realistic crash conditions. Ten anthropomorphic test devices (ATDs, a.k.a. crash test dummies) ranging from 5^th to 95^th percentile sizes were used for the collection and comparison of occupant loads. Additionally, overhead bin mass simulators were added to achieve a realistic fuselage configuration. The section was dropped with a downward facing pitch angle onto a sloping soil surface in order to simulate a local horizontal velocity in the airframe. Instrumentation consisting of accelerometers was installed to measure floor, seat track, ATD, and overhead bin acceleration responses. Self-contained data recorders logging accelerations and rotational rates were also used on the seat tracks and lower structure as evaluations for crash recording devices in potential future use cases. The right side of the section was painted with a stochastic black and white speckle pattern for use in full field photogrammetric imaging techniques. Results collected from the airframe accelerometers will be presented, and deformation and failures of the test article structure will be discussed. Finally, an examination of the test article motion will be presented using derived components of local velocities with their effect on the impact acceleration and airframe response.

A finite element (FE) model of a generic single-aisle narrow body transport aircraft was used for computational crash analysis to compare simulated deformations to those observed in the Turkish Airline Flight 1951 crash in Amsterdam in 2009. The simulation results predicted critical damage and demonstrated parameters such as survivable volume and egress paths as evidenced in the actual crash. Validated FE models expand the scope of research and provide clarity of concepts which can subsequently be translated into relevant safety requirements. The analytical tools minimize research expenses when compared to physical testing, by allowing several impact conditions to be studied that would otherwise be prohibitively costly and time consuming, in particular for large scale structures.

The Federal Aviation Administration (FAA) has a number of regulations that are designed to protect passengers in transport aircraft in the event of an emergency landing. These regulations focus primarily on the seat, occupant, and restraint interaction with the surrounding cabin interior environment. Industry typically meets these requirements through deterministic testing. In recent years, there has been interest in supplementing the process through the use of analytical methods. To support these efforts, the FAA has updated guidance on the use of modeling and simulation for the certification of seating systems. The guidance includes an overview of the required documentation, various metrics to be applied for acceptability, and lists of applicable areas and limitations on the use of the analytical methods. Several demonstration simulations have been conducted to show the efficacy of this method. In the future, the guidance will be expanded to cover other aerospace applications that will use dynamic analysis in the certification process.

Development of general constitutive models that can be used to model composite structural systems subjected to impact loads is challenging. Often, approximations are introduced in these models in order to reduce their complexity. In other words, these models require a number of material parameters that characterize the composite behavior as input—the more sophisticated the model, the larger is the number of material parameters. A special version of LS-DYNA is being developed with a new composite material model called *MAT_COMPOSITE_TABULATED-_PLASTICITY_ DAMAGE or *MAT213. The minimum input to this model is a set of 12 stress-strain curves (at a known temperature-strain rate combination) along with material parameter values such as Young's modulus, elastic and plastic Poisson's ratio, yield stresses, etc. These data are needed to drive the elastic and inelastic deformation model. The damage and failure models require additional input. Generation of high-fidelity data is challenging for a number of reasons. In this paper, we discuss the experimental techniques to generate the material behavior data for a unidirectional composite—the T800/F3900 composite, for the deformation, damage, and failure models. The last part of the paper deals with the use of MAT213 to model an impact test.

Gas gun experiments can generate useful data for the design of jet engine containment shields at much lower costs. To replicate the damage modes similar to that on a containment shield in fan-blade-out (FBO) testing, the gas gun experiment has to be carefully designed. This work focuses on the design of projectiles. Gas gun experiments were performed for flat composite panel targets with three different projectiles. FBO conditions were simulated using spin pit tests. The damage modes on the flat panels used in the gas gun tests were compared with damage modes on cylindrical composite containment shields used in spin pit tests. The results show that to generate similar damage modes, it is critical to ensure the shape of the projectile used in a gas gun test accounts for the deformation of the released blade during initial contact in the spin pit test.

Advanced composite materials play vital structural roles in automotive, aerospace, marine, and many other industries. Recently, there has been a renewed interest in composite sandwich structures, whose flexural capability and performance far exceeds that of classical composite laminates. In this study, impact response of Divinycell H-100 foam core sandwich panels with woven carbon fiber reinforced polymer (CFRP) facesheets are experimentally investigated. Impact tests at two levels of energy 4 J and 8 J were examined under cold and room temperature environments. The composite sandwich specimens consist of two different facesheet thicknesses (0.25 mm and 0.75 mm), and a 6.35 mm foam core. Results show that exposure to lower temperature generally causes larger damage in the specimens. Post-mortem inspection evidently portrays clear relationship between damages in both core and facesheet and exposed temperature. Residual bending properties were evaluated using 3-point bending test. Bending characteristics after impact on both faces of the specimens were analyzed. Bending test data reveal that residual flexural properties after impact are more sensitive to the in-plane compressive property of the CFRP facesheet rather than the in-plane tensile property. Bending test results also indicate that degradation of flexural rigidity of the sandwich composite panel strongly depends on existing damage state of prior impact test. The findings in this work will lead to improved design for advanced composite structures with enhanced impact and flexural resistance in extreme cold environment on earth and in space.

At low rates of strain, plastic deformation is generally treated as isothermal; however, as the rate of deformation increases, conditions transition from isothermal to adiabatic. In the case of high strain rate impact events, adiabatic conditions prevail. Local temperature rises due to the conversion of plastic work to heat can cause thermal softening and subsequent localization, leading to a potentially substantial deviation from isothermal conditions. Thus, accurately modeling the effects of adiabatic heating is of utmost importance for the design and analysis of composite structures subjected to high strain rate impact loading, such as jet engine fan blade containment systems subject to blade-out. In this work, a strain rate, temperature, and pressure dependent state variable polymer constitutive model is used to model heat generation due to plastic deformation in the matrix constituent of braided polymer matrix composites. The constitutive model is embedded within the generalized method of cells micromechanics framework to investigate the effects of adiabatic heating on unidirectional composite response, which are demonstrated to be significant for transverse tensile and in-plane shear loading. A subcell-based approach is then used to discretize the mesoscale repeating unit cell of a representative T700/Epon 862 triaxially braided [0°/60°/-60°] composite material system into an assemblage of adjacent composite laminates, with ply layups determined from the braid architecture. A two-step homogenization procedure is applied to determine effective properties of the unit cell. Parametric studies are conducted to study how the effective in-plane elastic moduli of the triaxially braided composite vary with braid angle, strain rate, and temperature. Computed effective axial and transverse moduli agree well with available experimental data. The semi-analytical nature of this model allows for the rapid determination of effective properties for various braid architectures for which there is no available test data and lends itself well to implementation into finite element codes and optimization routines.

The National Aeronautics and Space Administration’s additive construction with mobile emplacement (ACME) project is developing construction materials with which infrastructure elements, including habitats, will be additively constructed for planetary surface missions. These materials must meet requirements such as the ability to be produced from available in situ resources to eliminate the cost of launching materials from Earth, the ability to be emplaced via three dimensional building techniques, the ability to resist aging in extreme environments including radiation and micrometeorite bombardment, and the ability to provide the necessary structural integrity for a given building. This paper reviews the constraints placed on such planetary construction materials and details the work of the ACME team in characterizing materials that could one day construct planetary surface structures on Mars or the Moon. Material compositions, compressive strength, and requirements for additive construction on planetary surfaces are discussed. Due to the multifunctional requirements of the material, an optimization is necessary to balance between the site-specific regolith composition, emplacement via additive construction techniques, and characteristics of the final structure.

Origami inspired structures are particularly useful for space exploration because they can be compactly stowed during launch and can be deployed to create functional and reconfigurable systems at their final destination. This work presents a finite element implementation for analyzing thin sheets that are folded into curve creased origami. The computational model uses shell elements to capture deformations of the sheet and rotational hinges to simulate the crease line. Different methods for folding, or actuating, the crease are presented and verified with empirical solutions for a curved crease structure. Findings show that the folding method can lead to different energy distributions in the thin sheet while resulting in essentially the same deployed shape. The computational framework is then applied to more complex curved crease structures which can be used to store potential energy for deployment and offer a unique final geometry.

The dust vacuum chamber is an essential infrastructure for the verification of space exploration equipment, especially extraterrestrial missions for in situ resource utilization (ISRU). This study presents a new approach in soil mechanics that is particularly applicable to the dust vacuum chamber. One of the main issues in operating the dust vacuum chamber is soil disturbance problems during the evacuation. Thus, the appropriate vacuum rate was suggested to minimize the soil disturbance in the dust vacuum chamber using theoretical and numerical approaches. Firstly, the simple analytical solutions were used to provide approximate maximum discharge velocity and evacuation time to finish air flow through a soil specimen at a given vacuum pressure. Then, a two dimensional finite element model was developed which simulates the hydro-mechanical behavior of the soil specimen in a vacuum chamber with respect to different vacuum rates. From the numerical analysis results, optimum guidelines have been proposed to ensure that soil disturbance is minimized.

Salty domes could not be mixed through cements types in the GOTVAND Reservoir Lake. Salty cements mixtures have no any hardening effects. At 2016 a series of salty concrete was mixed to study the breaking resistance by ionized salt. TSC—Turk salty concrete was made to prove the mixture design. Sample resistance increase to (80 kg/cm²) by ionized salt. Research is continued to complete the original salty materials behavior by the new—TSM—Turk salty mortar. Grouting will be produced by the green bentonite, well drilling bentonite clay, ceramic SHUSHTAR clay, powdered pure salty stone, water, and cement type II. Samples at 1 till 90 days are broken by the hydraulic pressing jacks (σ_z =70kg/cm²). Salty desert areas are the main potential of dust storm (SW of Iran). TSM method will stabilize the unknown soil types regions, salty lands, and outside terrestrial Earth areas that are surrounded by droughts and winds.

In this work, shakedown design strategies are demonstrated and tailored for concrete structural systems with reinforcement in extreme thermomechanical environments. It is found that allowing for shakedown to occur doubles the structure’s mechanical load bearing capacity under constant thermal load. The proposed model also allows for proposing design parameters for shakedown purposes. Two additional test cases are illustrated in which two different rebar diameters are used, namely 6 and 12 mm. In the first case an inadmissible behavior is depicted while in the second case, for the same loading and boundary conditions, the shakedown behavior is observed.

Passive damping devices are frequently used to control building vibrations under extreme environments. Among them are tuned liquid column dampers, consisting of a large U-tube with oscillating liquid, which have been shown to be effective at mitigating structural responses under wind hazards. However, conventional tuned liquid column dampers are often large and space consuming, and are only effective under a fixed limited frequency bandwidth. In this paper, we build on previous studies and further investigate the concept of tuned liquid multi-column dampers, which allow liquid to flow through various vertical tubes connected via a horizontal tube to provide a higher operating bandwidth. A new analytical model characterizing the dynamic behavior is derived, validated using computational fluid dynamics. The model is used to study the effect of orifice size on a 4-column tuned liquid multi-column damper.

As one of the most popular smart materials in recent years, Shape memory alloys (SMAs) attract more and more researchers' attention. It is an innovative research direction to use the coil springs made of SMAs to make tuned mass dampers (TMDs) for reducing vibration. Although some researchers have proposed interesting conceptions and numerical models of TMD, so far practical TMDs are seldom found in the literature. Therefore, more comprehensive research and tests need to be conducted. In this paper, the influence of multiple factors, which include spring processing technology, geometric dimension, and loading mode, on the pseudoelasticity of the SMA spring under indoor temperature is studied by a series of tests. Especially, the force-displacement relationship curves of the SMA spring under complex dynamic loads are obtained in detail. The results of this research are significant for us to further understand the mechanical performance of the pseudoelastic shape memory alloy helical springs, and it is useful to promote the application of shape memory alloy helical springs to the practical engineering, especially in the field of structural vibration control.

Finite element model updating has been effectively applied in numerous fields including aerospace engineering, mechanical engineering, civil engineering, and etc., meanwhile, various methods are available for practical applications. Among them, the iterative methods based on sensitivity analysis, the minimum variance methods based on statistical theory, the methods based on frequency response data, and several new methods such as cross-model cross-mode method and response surface method are currently the most influential methods. In this work, the above mentioned five methods are compared with a 10 degrees of freedom model. The limitations and advantages of the five methods are comprehensively discussed with suggestions on their engineering applications. Based on above discussions, the limitations of current finite element model updating methods are further analyzed, especially their inadequacy for nonlinear structures. Previous research has shown that taking no account of the existent nonlinear factors in actual structures in the course of finite element model updating could lead to inaccurate results in many cases. Accordingly, future trend of finite element model updating and the framework of nonlinear finite element model updating was sketched out.

Previous dynamic models of tensegrity systems either used finite element methods, which do not preserve correct rotational dynamics, or exact rotational dynamics with massless cables. This paper allows any specified discretization of the cable masses, while preserving the exact rigid bar dynamics. The model has a matrix second order form. This model is non-minimal (6 DOF for each bar instead of 5) in order to preserve the minimal complexity of the model. This is important since dynamic models can be solved more accurately in computer simulations if the mathematical structure of the model is simplified and exploited during the computations. This matrix representation of tensegrity dynamics has the simplest structure, yielding the most accurate simulations, we believe. The second simplification of these nonlinear dynamic equations is a characterization of the control variable as the force density in each cable. The actual control might be the rest length of the cable, but it is a simple yet nonlinear change of variable to convert to force density control variables, and this leads to the advantage of linear equations in the control variable, even though the model is very nonlinear in the state. This model allows skins and surfaces to be modeled on the tensegrity dynamics, a large improvement over previous nonlinear dynamic models of tensegrity.

Tensegrity robots consist of disconnected rods suspended within a network of length-actuated cables, which gives them a high degree of compliance and adaptability suitable for traversing rugged terrain. These vehicles, however, undergo complex contact dynamics that prevent the use of traditional control techniques based on mathematical analyses of equations of motion. Data-driven approaches are thus an appropriate choice for controller design but are themselves hindered by the high number of degrees of freedom and correspondingly large state spaces. This paper presents a scheme for exploiting the 24th-order symmetry of an icosahedral tensegrity robot to vastly reduce the breadth of the controller input space without loss of information. Symmetry properties and state-space reduction operations are detailed and placed in the context of a data-driven control pipeline. Results are illustrated by comparing the input and output of a locomotive controller in both raw and symmetry-reduced dynamical spaces. The findings suggest a strong relief of the data requirements for training locomotive controllers.

Large-size antennas are effective to harness significant amounts of electrical energy in order to enhance the functioning of a spacecraft. Since a rocket can only propel a spacecraft with low volume and mass into space, it becomes desirable that antennas be lightweight and have a high deployed-to-stowed ratio. A tensegrity structure comprising of cables and struts can greatly reduce the antenna mass and stowage volume. The tensegrity principle has been successfully applied to the design of cable domes in terrestrial applications such as stadia and sports arena roofs. This paper presents a new design for an antenna that is referred to herein as deployable tensegrity antenna (DTA). The modified features of the new cable-strut system and the key challenges that need to be overcome before establishing the design as a space antenna are discussed. The design enables the antenna to change focus so as to increase its adaptability and range. Static and dynamic structural behavior are examined. Furthermore, DTA has the potential to significantly enhance the performance of space antennas with appropriate control of cable stiffness to ensure accurate measurements and data collection. This research is intended to open new design possibilities for use of the tensegrity principle, modeling, analysis, and design of deployable outer-space applications.

Tensegrity structures have been applied in various fields in science and engineering. In civil engineering, tensegrity structures have been used to construct lightweight yet strong structures, while in aerospace applications, it has been shown that tensegrity systems have great potential for active applications such as planetary exploration. Therefore, active tensegrity systems have been under investigation for small, light-weight, and low-cost missions. However, the robustness or damage tolerance of a tensegrity structure is a function of its inherent self-equilibrated pre-stress states. Although research into tensegrity systems has resulted in reliable techniques for their form-finding and analysis, no technique has been found previously that integrates damage tolerance as an input or output parameter. This paper reflects an effort to integrate damage tolerance in the form-finding process of tensegrity structures through a bio-inspired approach that combines topology definition and form finding.

Tensegrities are unique geometry-based forms with complex distributed behaviour difficult to describe mathematically. Actuating them requires comprehensive knowledge of their action under stress. This paper discusses various ways to actuate tensegrity structures and to manipulate them simply and efficiently. The design strategies center on modular tensegrity construction with controllable tensegral articulations. We describe helical tensegrity masts, segmented tensegrity masts, integrated hubs, bistable tensegrity-prism 3D hubs, telescoping appendages, and interpenetrating modules. Systems built from independent tensegrity modules can form rugged complex three-dimensional linkages that are functional, controllable, and energy efficient.

Celestial body surface exploration benefits from efficient long-distance travel, precision inspection of objects-of-interest, and overall launch-to-landing weight reduction. Tensegrity structures can be inherently lightweight by using cable networks, while the impact resistance of these same structures may enable them to survive rough landings. This design aims to increase efficiency by taking on the form of a wheel.

The general perception around structures and architecture has changed with recent advances in active structural control, advanced computing, and parametric design. Through the integration of active elements, structures can now become dynamic objects capable of interacting with complex environments; a vital feature for structures in extreme environments as well as for planet exploration and base/settlement. Tensegrity structures are lightweight, materially and mechanically efficient systems that can combine actuators with structural elements. Although the form-finding and analysis of tensegrity structures has received significant interest and various control solutions have been successfully identified, the link between the topology and actuation mode employed with the desired performance/behavior of tensegrity structures has not yet been properly addressed. Therefore, a summer research studio with undergraduate engineering and architecture students was organized to investigate the performance of various tensegrity systems for shape control and locomotion.

In the following paper a complex aerodynamic modeling process using reverse engineering and computational fluid dynamics was shown. The research team from Military University of Technology digitized the external geometry of Tu-154M aircraft to create a virtual model that has been used for aerodynamic tests and numerical calculations. Capture 3D process utilized two complementary non-contact data acquisition devices ATOS II and TRITOP digital photogrammetry. The process of reproducing the external geometry of an airplane along with the develop of their numerical models is an extremely complex task in the field of reverse engineering. To perform aerodynamic tests in wind tunnel, scaled models of aircraft using acquired geometric data, fast prototyping methods, and 3D printing have been prepared. Furthermore in order to perform numerical calculations using finite volume method aircraft numerical models have been developed. Research was done for various airplane configurations, e.g. cruise, landing with slats and flaps extended, landing with a left wing damage. Results have been shown in the graphs form of aerodynamic force and moment components as functions of angle of attack. The qualitative results of a flow around the aircraft body have been presented. Moreover during research an influence of particular aircraft structural parts on aerodynamic characteristics has been analyzed. Obtained results are using in the process of analysis the plane crash of Polish government Tu-154M aircraft in Smolensk. Conducted research is an example of professional and innovative approach to the subject matter.

A new type of passive seismic control system was developed and experimentally validated. The new control system, known as periodic foundations, is inspired by the concept of phononic crystals that can block incoming waves having frequencies located within the frequency band gaps. This paper presents the development of one-dimensional (1D) periodic foundations from basic theory to actual tests. The ability of 1D periodic foundations to isolate engineering structures from the incoming waves was investigated through large-scale shake table tests. The test results demonstrated that a 1D periodic foundation can reduce the acceleration response on the superstructure by 90% compared to the input acceleration without generating large relative displacement at the isolator layer as conventional base isolation systems do. Moreover, finite element analysis was conducted and reproduced the test results. The research has proven that periodic foundations are very promising to be used as the next generation of seismic control systems.

Dynamic displacement is one of the most important measurements that describe the dynamic characteristics and safety of a structure. Measurement of dynamic displacement is also useful in structural control and structural identification. However, the effective estimation of dynamic displacement of structures is still a challenging task. To solve the difficulties and drawbacks of direct dynamic displacement monitoring. Multi-rate Kalman filtering for the data fusion of displacement and acceleration response measurements has been proposed. Furthermore, some improved techniques for dynamic displacement estimation by fusing biased high-sampling rate acceleration and low-sampling rate displacement measurements have also been developed in recent years. However, the recent technique can only take the constant acceleration bias into account. In this paper, based on the recent Kalman filter with unknown input proposed by the authors, structural dynamic displacement is on line estimated based on multi-rate data fusion of biased high-sampling rate acceleration and low-sampling rate displacement measurements. The time history of acceleration bias is treated as ‘unknown input’ information to overcome the limitations of the previous technique. A numerical example is used to illustrate the proposed approach for on line estimation of structural dynamic displacement.

Along with population, economy, and vehicle use growth, traffic congestion is rapidly spreading in big cities in Indonesia especially capital cities like Bandung. For the purpose of solving congestion problem by decreasing vehicles queue on the streets, a method with ANFIS system is proposed in this study. Using two adjacent intersections at Djuanda-Bandung as case study and ANFIS as controller, the system is divided into two subsystems which are capable of controlling traffic light phase duration for both intersections based on real-time traffic condition. Value of vehicles queue and change of the vehicles queue are used as ANFIS input. ANFIS will give an output as street urgency. Using MATLAB, simulation is run and the result is compared to fixed time cycle system which is conventional system applied to the intersections.

Breakwaters, serving as part of coastal management plan, are usually constructed to reduce the intensity of wave action in inshore waters and thereby reduce the wave impacts on coastal infrastructures and coastal erosion to provide safe harborage. However, recent post disaster surveys on hurricanes and tsunamis indicated that breakwaters did not perform as they were designed. During extreme events with strong winds and high waves, the breakwaters could turn into submerged condition. However, the performance of the submerged breakwaters subjected to strong waves is still not clear. This study is to evaluate the wave forces on the submerged breakwaters and the effects of the breakwater on the wave energy dissipation. Computational fluid dynamics (CFD) analysis are performed in OpenFOAM to simulate the interactions between the irregular waves and the breakwater. Sensitivity analyses are performed to investigate the effect of different parameters associated with breakwater geometries and incident wave properties on the breakwater performance. In addition, shear stresses acting on the crest of the breakwater were discussed, as well.

The vehicle safety evaluation on coastal slender bridges could be complicated due to the complex interactions among the bridge, vehicles, and ambient environments. Many traffic accidents, such as the rollover of trucks when travelling on long-span bridges under gusty winds, were reported. The present study presents a comprehensive framework on evaluation of the vehicle ride comfort and driving safety on slender coastal bridges subject to vehicle, wind, and wave loads. The vehicle dynamic responses are extracted from the coupled vehicle-bridge-wind-wave system to facilitate the ride comfort and driving safety analysis. The vehicle ride comfort is evaluated following the procedures as recommended by ISO 2631-1 standard based on the overall vibration total value (OVTV). Additionally, the roll safety criteria and the sideslip safety criteria are defined to facilitate the vehicle driving safety analysis. Finally, the proposed framework for vehicle ride comfort and driving safety evaluation is applied on a long-span cable-stayed bridge for demonstration. A parametric study is conducted to study the effects of various factors, e.g., the correlated wind and wave loads, vehicle moving speed, traffic lane locations, on the vehicle ride comfort, and driving safety.

This paper discusses the implications of spatial variation of earthquake ground motion on the dynamic response of a short span continuous girder bridge. The wave passage, incoherence, and site-response effects of earthquake ground motions between the piers on the internal forces are investigated. Four site conditions are considered representing soft soil, sandy soil, firm soil, and rock bed. A finite element model of the short span bridge is built up, and its seismic responses are numerically simulated under five cases: the uniform excitation and the non-uniform excitation considering traveling wave effect, incoherence, and local site effect. The soil-structure interaction is simulated using spring elements. The results show that, for short span continuous girder bridge (25 m in this case), the maximum internal forces of piers are reduced when wave passage effect is taken into account. The spatial effect of the ground motion depends on the properties of the layers of soil. With the decreasing of the stiffness of soil, the shearing force and bending moment at the bottom of piers increase when the short span continuous girder bridge is excited using spatially variable earthquake ground motions.

Viscoelastic dampers are usually used to mitigate vibration of high-rise buildings when subjected to seismic and wind excitations. In this paper, viscoelastic-wall damper, which could be installed at the shear-wall location of high-rise buildings, is proposed to improve the building’s energy disspation ability. Based on the proposed Kelvin mathematical model of the viscoelastic-wall damper and a 36-floor frame-shear wall high-rise building prototype model, two finite element models of the structure with and without the viscoelastic-wall dampers are created using the finite element software ABAQUS. Auto-regressive model is used to simulate the random wind dynamic loads. The wind-induced vibration performance was numerically analyzed on the high-rise building with and without viscoelastic-wall dampers. The numerical analysis results indicate that the wind-induced response of the high-rise building could be mitigated effectively when equipped with viscoelastic-wall dampers. The control efficacy of acceleration is more effective than that of structural deformation.

This paper presents an analytical methodology and experimental validation of determining the natural frequencies of a railroad truss bridge from the sensors mounted on a train passing over the bridge. This approach is first verified analytically using a spring mass system moving over an Euler Bernoulli beam, where the natural frequency of the beam was obtained from the vibration acceleration of the moving sprung-mass system. Field experiment was performed on a 109-year-old Devon steel open deck through truss railroad bridge over Housatonic River between Stratford and Milford, in Connecticut, USA. Accelerometers were placed on several selected locations on the bridge as well as a couple of locations in a coach of the train. Acceleration of the train-bridge coupled system were collected using accelerometers placed on-board train when it was moving at different speeds over the bridge. The accelerometer record was then processed using fast Fourier transform (FFT) to identify a first few fundamental frequencies of the bridge. These frequency results have been verified with those obtained from the field test acceleration data collected using the accelerometers directly attached to the bridge as well as those from the finite element (FE) modelling of the bridge. This information will facilitate the bridge damage and deterioration detection using shift in natural frequencies over time.

The Huanghe Center Stadium is located in Wuzhong, Ningxia, China, as part of the construction project of the Huanghe Convention and Exhibition Center. The stadium is a large-scale steel structure, which is composed of 42 cantilever space pipe trusses in the radial direction and 4 suspended lattice pipe trusses in the circumferential direction. The steel awning structure of the stadium has the characteristics of many rods, many seams, and complicated forces. In order to ensure the engineering quality and safety of construction, an integral unloading process order was developed, including the amount of the unloading for each step. In the construction of this project, a separate lifting scheme is adopted and a temporary tread frame is installed at the end of the horizontal section of the 42 cantilever trusses as an installation support which should be unloaded. According to the principle of “the whole structure classification and synchronization”, the temporary support is unloaded progressively. The key levers of 12 triangular trusses, 6 quadrilateral trusses, and 8 circle secondary trusses are selected to monitor in the monitoring project. The monitoring results show that the current sensor signal is stable with good durability and stability. The monitoring method can be widely applied to more structural forms and wider application fields.

In this study, a piezoceramic-based active sensing system was used for the health monitoring of a two story on bay space reinforced concrete (RC) frame structure under earthquake excitations. The RC moment frame instrumented with piezoceramic-based sensors was tested by using shake table with different ground excitation intensities. The distributed sensors embedded in the RC structures were used to monitor the health status of the structures during the tests. The sensitiveness and effectiveness of the proposed piezoceramic-based approach were investigated and evaluated by analyzing the measured piezoelectric signals. A simple and accurate method is proposed for the simulation of the dynamic responses of the RC frame. The displacement ductility demands of the structural members were calculated using the proposed method and compared with the damage indices determined from the sensing system. The comparison shows that the damage indices have an excellent agreement with the calculated ductility demands.

High-strength bolts as connection members are widely used in steel bridge due to its advantages of simple construction, easy maintenance, and replacement. But during their service, the high-strength bolts are prone to looseness damages since bumpiness of vehicles and corrosion environment. If high-strength bolts looseness damages fail to be discovered in time, it will not only affect the overall stability of the bridge, and even affect the safety of the bridge structure. Therefore, it is very critical to develop an efficient and reliable high-strength bolts loosening damage monitoring methodology. An active high-strength bolts looseness damage monitoring approach based on stress wave propagation method using lead zirconate tinanate (PZT) is proposed. In this research, two steel specimens were investigated. There were two PZT transducers at each steel specimen as actuator and sensor. In each specimen, three high performance steel sheets were connected by six high-strength bolts. The test results showed that an active sensing approach based on PZT using wavelet packet energy analysis can detect successfully the bolt looseness damage. During the process of the bolts looseness, the amplitude of signal received by PZT sensors continuously decreases in the time-domain signal. The research results present the high-strength bolts looseness damage can affect the propagation path of stress wave and reduce the signal received by sensor.

Mode shape curvature-based method was originally developed to identify the damage in one-dimensional beam structures. In this paper, the method is generalized to fit for identification of damages in plate structures, using two-dimensional mode shape curvatures. The modified method only requires the first few curvature mode shapes of the plate before and after damage. To evaluate the effectiveness of the proposed method, numerical simulations considering different types of and multiple damages as well as experimental modal analysis on a steel plate with clamped and free edges have been conducted. The final results show that the proposed method works well to detect the damages.

In this paper, the damage characteristics of polyvinyl alcohol fiber-reinforced engineered cementitious composite (PVA-ECC) beams with high temperature damage under low velocity impact load were studied. A series of low speed impact tests were carried out to simulate the impact energy on the beam, and the impact response of the PVA-ECC beam with high temperature damage were compared with that without high temperature damage. The crack evolution and the wave attenuation were detected by the smart aggregate based active sensing method. The crack development was indicated by the energy of the wavelet packet of the received waves. The results showed that the impact resistance of PVA-ECC beam was significantly weakened after exposure to high temperature. The PVA reached its melting point at 230 °C and lost its function as reinforcement. Therefore, PVA-ECC lost its strength, toughness, and fatigue resistance after exposure to high temperature damage.

Accidental impact of civil structures is a common type of damage in civil engineering. It may severely damage the structure, and further result in catastrophic losses. It is desirable to develop a non-destructive evaluation (NDE) system that is capable of detecting the impact damage and provide early warning to mitigate the damage. The main focus of this paper is the feasibility study of the detection of the impact damage in a beam structure using infrared thermography. The final intention is to detect the subsurface defects or cracks at the early stage after an impact event. In this study, a beam structure, made of polyvinyl alcohol fiber reinforced engineering cementitious composite (PVA-ECC), was investigated. A series of impact tests at constant impact energy were conducted. After each impact, infrared thermography was used for NDE of the structure. Sequences of images were acquired with starting and ending time sets so as to include all of the thermal evolution. An infrared thermography approach was developed to perform continuous monitoring during the entire process. The initiation and evolution of the impact damage altered the heat conduction along the beam’s surface, and then affected the heat distribution. Experimental results demonstrated that the proposed method is an innovative and effective approach to detect the impact damage.

Bolt pre-load monitoring in real time can help to ensure the safety of component connections and durability of the entire steel structure. A simple specimen called “smart washer”, fabricated by embedding a piezoceramic patch into two pre-machined flat metal rings, was invented and then introduced as an impedance transducer to detect the looseness of a bolted connection. In this research, the pre-load condition of a bolted specimen was investigated by using electro-mechanical impedance (EMI) method enabled by one “smart washer”. Since the installed smart washer is directly subjected to the same axial pre-load as that on the bolt, the piezoceramic smart washer with the EMI technique is uniquely suited for pre-load monitoring of a bolted connection. Experimental results clearly show that with the decrease of the bolt pre-load, the resonant frequency of the bolt joint also decreased. In particular, a decrease of the pre-load on a bolt connect results in the reduced of its resonant frequency, which can be revealed by the real part of the impedance.

Interfacial debonding in concrete filled steel tubular (CFST) members has an important impact on mechanical properties of CFST structures. The purpose of this paper is to propose a feasible method to detect the interface debonding of CFST members using piezoceramic ultrasonic guided wave technology. Taking a CFST column with a length of 1.5 m and a diameter of 220 mm as an experimental model, a debonding damage detection experiment system based on guided wave propagation technology is set up. The interfacial debonding detection is simulated by artificial damages. By compare of the healthy received signals to the received ones with a debonding damage, the change rule of the received signal is analyzed and a signal energy-based identification algorithm is proposed according to the signal amplitude. The experimental results show that the amplitudes of the received signals vary with the occurrence of the debonding damage and the proposed algorithm can be feasibly used to monitor debonding damages of CFST columns.

Interfacial debonding has significant influence on composite effects of concrete filled steel tubular (CFST) columns. Based on the ultrasonic guided wave theory, this paper presents a method which can describe the guided wave propagation characteristics in CFST columns, and lay a foundation for the interfacial debonding damage detection by using guided waves. The wave equations in concrete and steel are firstly established by using the elastic wave theory. Then, the dispersion equations in an infinite CFST member are theoretically set up according to boundary conditions and interfacial coordinate conditions. Under the given conditions of both material and geometric parameters, the transcendental dispersion equations are solved by using a numerical method. The characteristics of ultrasonic guided waves are classified and the dispersion curves of both group and phase velocities are drawn. An experiment is performed for validating the correctness of the theoretical group velocities. The results show that the ultrasonic guided wave propagation in CFST columns has the dispersion and multi-modes characters, which is not only related to the actuation frequency, but also the material parameters of steel and concrete.

Concrete recycling is an important element of sustainable development. Demolished concrete lumps (DCLs) can be blended with fresh concrete as a filler, but achieving good compactness of the compound concrete can be a problem. In this study a simple and rugged piezo-electric sensor for monitoring compactness using transient excitation was tested in the laboratory. The same sensor design was as both the excitation and receiving transducer, and compactness was monitored using directly-propagating longitudinal ultrasonic waves. The specimen tested is 600×600×1000 mm. It was instrumented with twenty-four transducers deployed at four heights with three parallel monitoring paths at each height. The excitation signal was a smoothed tone burst with amplitude of 45 V and a frequency of 70 kHz. Six cycles were used as the excitation signal. The amplitude and velocity of the directly-propagating signals showed a positive relationship with the compactness of the specimen. The amplitude was more sensitive to the compactness than the velocity. This technique demonstrated great potential in monitoring the compactness of demolished concrete lumps filled compound concrete.

The structural performance of steel plate-concrete (SC) composite structure could be improved by incorporating ultra high performance concrete (UHPC). With its dense microstructure and 22 ksi compressive strength, UHPC is expected to facilitate rapid construction of structural elements with thinner and lighter modules that could withstand overload conditions and harsh environments. The bond condition between the steel plate and UHPC is critical for the structural integrity of the steel plate-ultra high performance concrete (S-UHPC) element since bond-slip could decrease the load-carrying capacity and ductility. Most of the structural damage of S-UHPC initiates with local cracks in concrete and local bond-slip between the steel-plate and concrete. The detection of the local bond-slip is vital for providing early warnings of a structurally compromised element. In this study, a reliable health monitoring technique utilizing embeddable lead zirconate titanate (PZT)-based smart aggregates (SAs) has been employed to detect the local bond-slip damage between steel plates and UHPC. By using the active sensing approach, the propagating stress wave attenuates when the local bond-slip occurs. To quantify the local-damage degree, the wavelet packet-based damage index was adopted. The results show that the SA-based active sensing approach and wavelet packet-based damage index can give a quantitative estimation of the local bond-slip initiation and development.

In order to accurately measure the contact stress between work roll and strip, a contact stress sensor based on the improved inverse method has been designed. To improve the effectiveness and accuracy of the sensor, the two key parameters, radius of the measurement $r_m$, and number of measurement point $N_m$, are optimized by finite element method in this paper. It is found that increasing the radius of the measurement and the number of measurement point can improve the prediction accuracy, but the results will not be significantly improved when the number of measurement point is increased to a certain threshold. It is believed that the research of this work has a strategic importance for steel rolling industry.

NASA’s Jet Propulsion Laboratory (JPL) and its partner are planning a mission to explore an icy moon of Jupiter, Europa. The objective of the planned Europa Clipper mission is to gain insight into the key ingredients for this potentially habitable world. This mission will conduct investigations using a suite of instruments that includes a set of five remote sensing instruments, four in situ fields and particles instruments, and a two-channel ice-penetrating radar. Among its science objectives are to produce high-resolution images of Europa's surface, determine its composition, look for signs of recent or ongoing activity, measure the thickness of the ice shell, search for subsurface lakes, and determine the depth and salinity of Europa's ocean. Europa Clipper is expected to encounter a very challenging environment, particularly in radiation. This paper provides a comprehensive description of the challenging environments and the environmental requirements that are levied onto the Europa Clipper system design. The mitigations activities being conducted or planned to ensure compliance with the severe environments will be described. Also discussed will be how the environmental requirements are verified and at which level of integration to ensure mission success.

This paper has two main objectives: to review the current status of the Martian environmental conditions that impact Martian systems, and to derive from them the top-level requirements for the assembly, integration, and test (AIT) of Martian systems. Each planetary system must be space qualified in order to survive harsh planetary conditions on top of other mission phases like launch, cruise from Earth to the specific celestial body, entry, descent and landing (EDL), and end of operation. In general, Martian systems include three types of landers: long term permanent stations, rovers, and any other landers for long term operation required for unmanned or manned missions. The Martian environmental conditions from the engineering points of view include: temperature variation, radiation environment, Martian gravity, regolith/soil conditions (dust), and Martian geological features, depending on the Martian surface mission profile and their impact on any system operating on Mars for the required time range. Then, top-level AIT requirements for surface Martian systems are developed and presented based on knowledge of Martian environmental conditions. The impact of the most recent Martian landers and orbiters is explained. Future Martian missions are also briefly described. Special attention is given to AIT requirements associated with the thermal variation, radiation environment, Martian atmosphere, and dust. Finally, conclusions and recommendations from a Canadian perspective are also included.

The perspective of beyond-LEO landed missions increases the need for payloads, landers, rovers, and future manned vehicles with the ability to survive and operate in different extra-terrestrial environments for extended periods of time. In the near-term, this includes the lunar, Mars, and asteroid environments. The DTVAC facility offers a test environment suitable for testing under simulated asteroid, lunar, and Martian conditions. It facilitates the combined effects of simulated solar illumination, thermal control, fine dust simulant dispersion, and charging, as well as vacuum to different levels. A temperature-controlled platen can accommodate various test devices up to 1.0 m×1.0 m×0.9 m in volume, including devices such as solar panels, optical payloads, and various mechanical assemblies such as motors, wheels, and small robots. In the initial performance validation, the DTVAC facility was able to provide 21 days of continuous environmental simulation under computer control.

Thermoelectric energy harvesting is promising to provide sustainable energy source in the extraterrestrial environment. This paper describes procedures incurred in the fabrication of thermoelectric energy harvester on flexible substrates. An electrically parallel structure is proposed, which features higher energy efficiency than the counterpart electrically series structure based on theoretical analyses. As proof of concept, flexible thermoelectric harvesters in electrically parallel and series structures are prepared with thick film printing procedures. The performance of elements and device with different architectures are characterized. Both analytical and experimental comparison imply a promising improvement of energy conversion efficiency by using the electrically parallel structure.

To meet increasing demand of energy consumption, various renewable energy technologies have been investigated. Some of them have been quite successful in scaling up and almost becoming competitive with fossil fuel technology. Still, more needs to be done and each possible resource needs to be utilized. Around the world, many low-head water resources such as streams, channels, canals, small-to-medium sized rivers, collectively categorized as streams are untapped sources of hydrokinetic energy. A recent study puts new-stream-reach development potential, in the USA, at 65 GW. This paper introduces a novel and patent pending technique designed to extract hydrokinetic energy from such low-head resources turning them into beneficial sources of clean electricity for governments, industry, cities, towns, and people around the world. Ion Power Group LLC (IPG) is developing a technology known as the ‘shock wave engine’ (SWE) that utilizes the water hammer effect or fluid hammer to generate oscillating pressure waves or hydraulic transients. Research has demonstrated that the water hammer effect can develop a pressure differential of several orders of magnitude that can be harnessed to drive a piston-flywheel-generator assembly to generate electricity. Research into this low-head in-stream hydroelectric system has been qualitative so far. A proof-of-concept bench-scale model has been fabricated and tested that successfully validates the theory-of-operation placing the SWE project at technology readiness level 3 (TRL3). Similarly, few simulations of simplified models have been studied to understand the nature of hydraulic transients and associated pressure differentials.

Renewable solar energy has been increasingly used due to its efficiency and cleanliness. Currently, mounting systems are needed to install solar cells on the surface of supporting structures, such as building roofs. Attaching solar cells directly to the supporting structures can eliminate the mounting systems and reduce the cost. Once the supporting system is eliminated, solar cells become an integral part of the supporting structures and they are subjected to the same strains as those of the supporting structures, Therefore, it is necessary to study the performance of solar cells under different strain states, which is the objective of this paper. In particular, this paper will evaluate the performance of solar cells under compression. To this end, two extreme cases of supporting structures are considered, i.e., rigid (concrete) and flexible (thin fiber-reinforced polymer plate) substrates, which intends to introduce pure compression and buckling failure, respectively. Based on compression tests, the relationship between the performance of solar cells and strain were obtained. It was found that the performance of solar cells attached to rigid concrete remained unchanged until the specimens failed, while a degradation of the performance was observed for solar cells attached to flexible thin FRP plates due to buckling effect.