Recapturing a Future for Space Exploration Life and Physical Sciences Research for a New Era (2011) / Chapter Skim
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10 Translation to Space Exploration Systems
10 Translation to Space Exploration Systems
Pages 299-354
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From page 299... ...
; life support; fire safety; space resource extraction, processing, and utilization; and planetary surface construction. This chapter describes necessary scientific research and technology development in each of these seven areas and categorizes the research recommendations in one of two time frames: either "Prior to 2020" or "2020 and Beyond." The two time periods are used to indicate when, given a best-case scenario, an operational system or exploration activity is likely to be implemented.
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From page 300... ...
RESEARCH ISSUES AND TECHNOLOGY NEEDS Space Power and Thermal Management NASA's power generation, energy storage, and heat rejection technology needs in the coming decades are driven by three major and diverse categories of missions: (1) platforms for near-Earth science, resources (such
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From page 301... ...
. These power demands will be met by a variety of evolutionary and revolutionary technologies for providing prime energy sources, energy conversion, energy storage, thermal management and control, and heat rejection.
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Solar cells for terrestrial applications using concentrators have now demonstrated energy conversion efficien cies of 38.5 percent; efficiencies of 45 percent are on the near horizon and will enable further reductions in array area. Terrestrial systems capable of producing tens of megawatts are planned; such surface-based systems would have application to the exploration of planetary bodies with or without atmospheres.
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The total mass of a photovoltaic-based power generation system capable of producing tens of kilowatts on the lunar or martian surface will be driven by the energy storage components (e.g., batteries, regenerative fuel cells [RFCs] ,§ or thermal energy reservoirs)
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* Fission surface power systems are "an attractive power option for some lunar and Mars mission scenarios,"11 and NASA has identified nuclear power reactors as one of 19 game-changing technologies for the lunar exploration architecture.12 NASA has identified nuclear power as a high-priority technology because it releases many other exploration technologies from severe constraints on power use.13 The recent confirmation of water at the lunar poles and on Mars underscores the need for ample power to enable ISRU for propellant production and life support.14,15 The availability of nuclear reactor power systems would make it possible to relax stringent power constraints, thus reducing development costs across the entire lunar exploration architecture -- except for the cost of the power system itself.
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From page 305... ...
operates at a higher temperature and in an isothermal mode, and so the size/mass of the heat rejection system is much smaller. Figure 10.2 compares various thermal energy conversion systems for producing electrical power as a func tion of specific mass (kilograms per kilowatt-electric)
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From page 306... ...
However, the issues of dead-ended gas flow paths versus through-flow, cryogenic versus pressurized gas storage, thermal management, and reliable long-life operation (i.e., years) under reduced gravity and extreme temperatures all remain to be demonstrated for both planetary and orbital applications.
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From page 307... ...
19 The benefits of two-phase flows are illustrated in Figure 10.5, in which boiling heat transfer coefficients exceed single phase heat transfer coefficients by multiples in all cases. While the thermal management technology requirements for NASA's different missions overlap, there are unique challenges posed by each environment.
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From page 308... ...
thermal management technologies yet to be dem onstrated in microgravity and in lunar and martian partial gravity. Gas and liquid phases in components such as boilers, condensers, and heat pipe radiators behave differently in other than Earth gravity due to the change in body force.
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Summary of Enabling Science and Technologies for Space Power and Thermal Management Power and thermal management improvements will become increasingly important for future NASA mission needs, especially for missions that include ISRU. Important exploration technologies in space power and thermal management that would benefit from near-term R&D include the following: ‡‡ A high thermal diffusivity is crucial for thermal energy storage because it allows a material's heat capacity to be utilized.
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From page 310... ...
NASA would benefit from the enhanced flexibility in power and energy storage offered by regenerative fuel cells. The necessary research should be conducted to allow regenerative fuel cell technolo gies to be demonstrated in reduced-gravity environments, including research related to dead-ended gas flow paths versus through-flow, cryogenic versus pressurized gas storage, thermal management, and reliable long-life opera tion.
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For lunar missions, the Ares V could be eliminated, and for Mars missions, the majority of Ares V launches could be eliminated. 31 On-orbit refueling increases operational complexity and requires advanced cryogenic fluid transport and handling technology for reduced gravity, but 80 to 90 percent of the initial mass in low Earth orbit (IMLEO)
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Cryogenic Fluid Management Advances in in-space cryogenic fluid management technology can improve the affordability and performance of orbiting cryogenic propellant depots and hence the feasibility of long-duration exploration missions. 37 Research areas of particular interest include passive insulation and active cooling for zero boiloff; zero-gravity propellant transfer, including the automated coupling of cryogenic fluid lines; gauging the quantity of propellant in the tanks;38 and the role of capillary forces in propellant management.39 In addition, low-mass, cryogenic compatible, thermally insulated multifunctional materials for tank storage and fluid line transfer could potentially enhance safety and affordability over using multiple layers of material for each function.
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Although the technology for these engines is well known for Earth applica tions, critical technologies are needed for lunar and planetary descent and ascent in zero or reduced gravity, includ ing engine start, combustion stability, and deep throttle. These technologies require research in cryogenic fluid management, propellant ignition, flame stability, and active thermal control of the injectors and combustors.
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Technology gaps include recapturing and updating the technology proven in the 1960s, ground tests, improving safety, reducing mass for affordability, and investigating long-life performance and reliability. Specific research and technologies include thermal control systems, efficient energy conversion and thermal transfer technologies, and lightweight/very high temperature thermal structures, along with safe and acceptable testing facilities.
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Ground-based experiments, advanced modeling, and in-flight demonstrations would advance the understanding of fundamental processes involved in electric propulsion, leading to thrusters with greater performance and longer life, thereby enabling or enhancing some future exploration missions. Solar Electric Propulsion SEP is another low-thrust option appropriate for transferring cargo to the Moon or Mars.
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Advances in propulsion performance (specific impulse, efficiency, thrust-to-weight ratio, propellant bulk density) , reliability, thermal management, power generation and handling, and propellant storage and handling are key drivers to dramatically reduce mass, cost, and mission risk.
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Required technologies include thermal control systems, efficient energy conversion and thermal transfer technologies, and lightweight/very high temperature thermal structures, along with safe and acceptable testing facilities. Enabling physical science research has been identified in the section "Space Power and Thermal Management." Additional physical science research is required on liquid-metal cooling under reduced gravity, thawing under reduced gravity, and system dynamics.
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However, despite the advantages of EVA capability, early space shuttle designs did not include the means to perform EVA." 65 Historically, an EVA system has consisted of the following components: a spacesuit; a portable life support system that provides the suit with a breathable atmosphere while removing carbon dioxide, water vapor, and trace contaminants; suit subsystems providing pressurization, mobility, temperature control, power, communications, and data systems, as well as protection from radiation and particle impacts; rovers and mobility aids; and tools (includ ing robotic tools) that enable the EVA crew member to accomplish necessary mission tasks.
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The focus here is on issues relevant to NASA in the next decade for achieving a translational portfolio to enable exploration missions to meet research and operational objectives in the life and physical sciences. Future Extravehicular Activity Needs The requirements for future EVA systems include (1)
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500 0 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024 2026 2028 2030 Year FIGURE 10.7 Annual cumulative hours of projected extravehicular activity (EVA) , showing "mountain of EVA" for Exploration missions.
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From page 321... ...
The current EMU glove has caused problems with astronaut finger tip trauma. Improving space suit glove design is a suit-independent design challenge and represents a crosscutting, multidisciplinary research question.88-91 Developing a new EVA system to support anticipated surface operations on the Moon, Mars, or asteroids presents significant technical challenges, especially with regard to providing "mobility equal to that of an Earthbased geologist."92 The engineering and biomedical requirements for pressure production, a breathable atmosphere, thermal control and ventilation, carbon dioxide removal, and waste management for surface EVA systems are understood and well specified in the current EVA system plans.
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Biomedical and EVA systems relationships and synergies should be identified for exploration missions. EVA technologies, human performance, and life and physical science phenomena in partial gravity need to be better understood.
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Future Life Support System Needs The LSS must provide adequate thermal control to maintain a suitable internal temperature regardless of internal activities (by astronauts and equipment) and the external environment.
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Knowledge gaps in two-phase flow in partial gravity need to be filled. 108 The Constellation Program's lunar architecture specifically emphasizes the goal of improving reliability and functionality of EVA and LSS.109 Dust mitigation and thermal control on the lunar surface should be high priorities, but they had been omitted from NASA's prior lunar architecture.
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Fire Safety Although they are relatively rare events, fires have occurred in space vehicles and habitats and will occur again. Fire safety is critical to any human space exploration because fires can have devastating consequences, including loss of life, loss of vehicle or habitat integrity, and mission failure.
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Furthermore, the potential for damage to mission-critical systems necessitates that strategies be developed and put in place for post fire clean-up and recovery, especially for operations far from Earth, where terrestrial help for recovery is unavail able on any reasonable time frame. Unfortunately, much of fire safety to date has been predicated on assumptions about fire behavior in reduced gravity environments that have been called into question by recent research.
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. This belief was based largely on fundamental combustion experiments carried out in microgravity, rather than on projects specifically designed to assess fire detection in reduced gravity.
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Most of the efforts in fire safety have been directed toward prevention, detection, and suppression. Some recent work has begun to examine what the toxic environment will be after a fire.
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NASA should develop and implement a standard methodology for qualifying suppres sion systems in relevant atmospheres and gravity levels and with various delivery systems. Research is needed to characterize the effectiveness of various fire suppression agents and systems under reduced gravity so that the qualification is based on physical principles.
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Research is needed on explosion suppression agents and/or methods to remove reactant components from a closed environment under reduced gravity. Two other important recommendations for fire safety involve the organizational integration of fire safety R&D into operational fire safety for space vehicles and habitats.
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space transporta tion elements. Creation of cryogenic propellant depots in space, supplied from propellant sources on the Moon, can change dramatically the architecture and economic cost of exploration activities beyond low Earth orbit.
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(2) How do flow processes work for granular solids at cryogenic temperatures in reduced gravity?
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is needed to validate operations of gravity-dependent processes in the 1/6- g lunar surface environment and to provide design requirements for a lunar outpost system. Physical modeling is needed of all elements of an end-to-end system that incorporates the relevant environments (vacuum, reduced gravity, static charging effects)
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* and might make use of lunar assets, such as thermal wadis comprising regolith-derived thermal mass materials, as platforms that enable rovers and other exploration hardware to survive periods of cold and darkness on the lunar surface.
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From page 335... ...
robotic exploration missions to characterize near-Earth asteroids and return samples that would demonstrate their potential resource value. Finally, expansion of technical capabilities such as improved power production and storage and development of in-space propellant depots will improve the potential for utilizing off-Earth resources.
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Robotics is a major gap not represented in the NRC's previous report, Microgravity Research in Support of Technologies for the Human Exploration and Development of Space and Planetary Bodies.165 Autonomous, semi-autonomous, or teleoperated robots may prepare a site for construction, unload equipment from a lander, and provide transport to temporary or permanent sites. Robotic systems may also be used for assembling, deploying, and constructing many of the systems and infrastructure of a surface outpost.
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. Robotic systems that were designed for operations on Earth or on Mars will have to be adapted if they are to be applied to accomplishing tasks on the lunar surface.
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Any human habitat, whether on a planetary surface or for deep-space exploration, will be required to house the following systems and subsystems: • Food -- preparation, delivery, consumption, and long-term storage; • Hygiene and waste management -- water dispensing, sinks, toilet, and personal toiletries; • Health maintenance -- exercise equipment, medical care equipment; • Sleeping accommodations -- horizontal bunks, privacy, crew personal equipment; • Operations center -- wardroom activities, communication and control; • Lighting -- general, task, emergency, EVA operations; • Furnishings -- seats, bunks, restraint systems, working surface, and scientific equipment; • Storage -- refrigerated, frozen, ambient, dry, and wet; • Acoustics -- surface materials, geometry layouts, equipment design, fireproof fabrics; • Airlocks -- egress and ingress, EVA suit donning, dust control; • Berthing ports -- connection between modules and rovers in a dust environment; • Dust control -- laminar flow air systems, materials, flooring systems, vacuums; • adiation protection -- water, ice, polyethylene and other low-density and high-hydrogen-content materials, R equipment layout, in situ materials; and • Mobility -- drives, wheels, suspension, winches, skids, etc. Power and cooling for planetary habitats are considered in the "Space Power and Thermal Management" sec tion of this chapter.
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From page 339... ...
NASA would benefit from structures and materials technology development for habitats, rovers, and other surface infrastructure systems that enable development of structures that have low mass and improved radiation protection capability and that can be deployed in extreme temperatures. Basic structural systems and materials research in reduced gravity and all other extreme planetary conditions is needed in several areas, including extreme temperature composites, alloys, fabrics for space suits, and inflatable structures.
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TABLE 10.3 Current Research and Technologies Required to Support Objectives and Operational Systems up to 2020 340 Research Critical Environmental Crosscutting Recommendation Topic Current Gap Technology Enabling Research Constraints Applications T1 Space Inability to utilize multiphase Two-phase Harness ability to use active two-phase flow Partial and Space and surface power and flow systems to increase flow thermal thermal management in reduced gravity fields microgravity operations, propellant thermal performance management systems, EVA, life management technologies support, habitats, power, ISRU T2 Space Inability to limit boiloff of Zero-boiloff Research in such areas as advanced insulation Full gravity Space and surface propulsion cryogenic propellants to extend propellant materials, active cooling, multiphase flows, range operations, ISRU storage storage and capillary effectiveness systems T3 Space Lack of knowledge of cryogenic Cryogenic Research to enable microgravity propellant Partial and Enables propellant propulsion propellant flow, handling, and fluid flow, handling, and gauging microgravity depots, ISRU gauging in microgravity management technologies T4 EVA Inadequate mobility for suited EVA suit Research in suit comfort, trauma Partial and Space and surface crew mobility countermeasures, and joint mobility to microgravity operations enhancements provide crew the mobility to perform tasks over extended periods without injury T5 EVA Lack of suit durability in on-orbit, Dust and Research and test beds to deal with durability Partial and Space and surface lunar, and martian environments micrometeroid and maintainability issues of suits stemming microgravity, operations mitigation from micrometeoroid and orbital debris temperature systems damage, dust exposure, and plasma extremes T6 Life support Lack of understanding of partial- Fluid and air Design, test, and operation of highly reliable Partial gravity Propellant systems, systems gravity effects on life support subsystems life support fluid and air systems in reduced habitats and rovers, systems (fluid/air) gravity environments ISRU T7 Fire safety Lack of knowledge regarding Materials Research to describe the flammability Partial and Space and surface materials flammability and standards and toxicity of materials with respect to microgravity, operations, space toxicity in various atmospheres ignition, flame spread, and toxic/corrosive vehicles, habitats, various O2 and gravity fields; lack of gas generation in various environments and atmospheres rovers adequate standards to determine gravity fields acceptable materials based on flammability and toxicity T8 Fire safety Current fire detection techniques Particle Research to characterize particle sizes Partial and Space and surface lack reliability in reduced gravity detectors generated by smoldering and flaming fires; microgravity, operations, space fields identification of other fire signatures that can vehicles, habitats, various O2 facilitate fire detection atmospheres rovers
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T9 Fire safety Effectiveness of fire suppression Fire Research to describe the effectiveness of Partial and Surface and space systems in reduced gravity suppression fire suppression agents and systems against microgravity, operations, space environment is not well systems various types of fires in various spatial vehicles, habitats, various O2 understood configurations and gravity fields atmospheres rovers T10 Fire safety Lack of knowledge of postfire Post-fire Research to characterize post-fire Partial and Surface and space environment environment environment and clean-up strategies including microgravity, operations, space strategies removal of toxic gases vehicles, habitats, various O2 atmospheres rovers 341
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including research related to dead-ended gas microgravity, ISRU, surface thermal beyond current battery and fuel flow paths versus through-flow, cryogenic or extreme low operations, power, management cells pressurized gas storage, thermal management, temperature space vehicles and reliable, long-life operation T12 Space Current energy conversion Energy Research in high-temperature energy Partial and Surface operations, power and systems are not efficient for all conversion conversion cycles and devices coupled to microgravity ISRU, habitats thermal power regimes technologies for essential working fluids, heat rejection management low- and high- systems, materials, etc. power regimes T13 Space Photovoltaic and RPS systems Fission surface Research in high-temperature, low-mass Partial and Space and surface power and not always adequate for very power materials for power conversion and radiators microgravity operations thermal high power and high power management density; lack of technology demonstration exists for fission surface power T14 Space Lack of lunar and planetary Technologies to Research into cryogenic fluid management, Partial and Propulsion for propulsion descent and ascent propulsion enable engine propellant ignition, flame stability, and microgravity, crew rescue capabilities start after active thermal control of the injectors and extreme low and emergency long quiescent combustors over the full range of gravities, temperature maneuvers periods, orientations, fluid phases, etc.
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From page 343... ...
; and granular power and conditions at lunar poles demonstrate long-term operations in lunar materials, utilization environment vacuum, extreme temperatures 343 continued
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TABLE 10.4 Continued 344 Research Critical Environmental Crosscutting Recommendation Topic Current Gap Technology Enabling Research Constraints Applications T25 Space Lack of knowledge regarding ISRU capability Research (including remote assay and Partial Surface operations, resource physical and handling planning sampling) to characterize specific resources gravity, habitat construction, extraction, properties of in situ resources available at planned lunar and martian cryogenic propulsion, life processing, surface destinations available for ISRU granular support and planning and extraction materials, utilization extreme temperatures T26 Planetary Lack of understanding how to Teleoperated Research to determine how to best utilize Partial Surface operations surface effectively integrate human and and autonomous human and robotic resources for construction gravity, construction robotic operations construction and other surface operations extreme temperatures T27 Planetary Lack of information regarding Regolith- and Research to describe the physical and Partial Surface operations surface regolith mechanics and dust-tolerant mechanical properties of regolith to facilitate gravity, construction properties systems surface operations, construction, and ISRU extreme temperatures T28 Planetary Habitability requirements Habitability Research to define partial-gravity habitability Partial Surface operations surface for partial-gravity operations requirements requirements for surface operations on the gravity, construction unknown Moon and Mars extreme temperatures
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Due to the uncertainty surrounding the funding that will be allocated to these various research topics, the panel did not factor in the lead time that would be needed for these research activities to provide answers to the questions they address. For example, planetary surface construction appears in the "2020 and Beyond" table, but it is essential that these activities be undertaken well in advance of 2020 to lead to operational systems and implementation in the 2020 time period.
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From page 346... ...
Project, October 1, 2009; Dust Management Project Plan, DUST-PLN-0001, Rev. B, October 27, 2009; Energy Storage Project Lithium-Ion Batteries and Fuel Cell Systems, Document ES08-105, Revision C, October 2, 2009; EVA Technol ogy Development Project: Project Plan, CxP 72185, Annex 01, Rev.
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From page 347... ...
2004. Research in Support of the Use of Rankine Cycle Energy Conversion Systems for Space Power and Propulsion.
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2001. Prospects for Nuclear Electric Propulsion Using Closed-Cycle Mag netohydrodynamic Energy Conversion.
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2009. Research progress of portable life support system for extravehicular activity space suit.
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2009. "Environmental Control and Life Support in the Constellation Program," presentation to Panel on the Plant and Microbial Biology of the Decadal Survey on Biological and Physical Sciences in Space, October 8.
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2009. "Environmental Control and Life Support in the Constellation Program," presentation to Panel on the Plant and Microbial Biology of the Decadal Survey on Biological and Physical Sciences in Space, October 8.
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2009. Thermal energy storage and power genera tion for the manned outpost using processed lunar regolith as thermal mass materials.
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Presented at the AIAA 5th International Energy Conversion Engineering Conference, St. Louis, Mo., June 25-27.
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