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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program 2 Assessments of the Projects of the Exploration Technology Development Program This chapter contains the committee’s findings and recommendations on the 22 projects constituting NASA’s Exploration Technology Development Program (ETDP). Following a summary of each project’s objectives and status is the committee’s review of the quality of each project, the effectiveness with which the project is being developed and transitioned to the Constellation Program, and the degree to which the project is aligned with the Vision for Space Exploration (VSE). Each of the 22 ETDP projects was evaluated on the basis of the following criteria: The quality of the research effort, taking into account the research team, contacts with appropriate non-NASA entities, and the plan for achieving the objectives; The effectiveness with which the research is carried out and transitioned to the exploration program, including progress to date, facilities, apparent gaps in the program, and the likelihood that the required technology readiness level (TRL) will be reached1 (the committee decided that simply noting gaps, as stated in the study task, was too narrow an objective and that gauging “effectiveness” as defined here was more appropriate); and The degree to which the research is aligned with the Vision for Space Exploration (since the VSE includes the wording “in preparation for human exploration of Mars,” the committee chose to highlight any project that did not appear to have considered plans that included this aspect).2 In each of these three areas, the committee rated the projects using a flag whose color represents the committee’s findings on the project. A summary of the ratings scheme is provided in Table 2.1. A few projects were given two flag colors stemming from major distinctions between elements in the project. In the sections below, detailed observations on each project are presented, and gaps within a given project are identified. As is noted at 1 See Appendix D for definitions of technology readiness levels. 2 The committee notes that after the completion of its assessments of the 22 individual projects in late 2007, the Congress passed the fiscal year 2008 Omnibus Appropriations Bill, which contained a provision prohibiting NASA from funding any activities devoted solely to preparing for the human exploration of Mars. The committee chose not to modify its findings on alignment with the VSE based on this language for several reasons. First, the committee interpreted as dominant its statement of task, which includes reference to the entire Vision for Space Exploration, explicitly including the human exploration of Mars. Second, by and large, on this alignment criterion the committee was critical of technology projects that did not consider extensibility of their technology to Mars. An example of potentially extensible technology is the Orion thermal protection system for Earth reentry. The committee did not criticize in the assessment of the 22 projects the absence of a Mars-unique technology, an example of which is a martian aerodynamic entry descent and landing system.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program TABLE 2.1 Summary of the Committee’s Assessment Ratings Scheme Criterion Description of Criterion Gold Star Green Flag Yellow Flag Red Flag 1. Quality of research Research plan Capability of team Non-NASA contacts All criteria under Green Flag were highly rated. Technical approach and tasks described. Success criteria defined. Resources adequate for tasks; personnel competent. Good contacts made with appropriate non-NASA entities. Project plan not clear. Technical approach is marginal, activity duplicates existing capability, plan does not address TRL 6. Team not balanced. Not making use of knowledgeable non-NASA entities. Little evidence of a plan. Team not up to the task. Resources not adequate to accomplish tasks. 2. Effectiveness with which project is being developed and transitioned Transition to exploration program Appropriate facilities Progress Gaps Likelihood of achieving desired TRL All criteria under Green Flag were highly rated. Transition plan defined. No gaps. Progress being made and milestones being met. TRL 6 achievable by transition date. Gaps identified. Important scheduling or funding or performance risks. Milestones are slipping significantly. Likelihood of TRL 6 is at risk. No viable plan to achieve TRL 6 by the needed date. No transition plan. Status threatens success of overall program. 3. Alignment with VSE Project supports VSE objectives. Project supports Constellation objectives. Project is investigating enabling technologies for lunar and Mars exploration Clear linkage to all VSE goals. No linkage to post-lunar exploration. Not employed for this criterion. NOTE: TRL, technology readiness level; VSE, Vision for Space Exploration. The flag colors can be summarized as follows: • Gold star. Quality unmatched in the world; on track to deliver or exceed expectations. • Green flag. Appropriate capabilities and quality, accomplishments, and plan. No significant issues identified. • Yellow flag. Contains risks to project/program. Close attention or remedial action is warranted. • Red flag. Threatens the success of the project/program. Remedial action is required. (This level was not used in assessing a project’s degree of alignment with the Vision for Space Exploration.) the end of the chapter, the ratings constitute the committee’s findings on the 22 projects. The committee’s general recommendation is that those projects should be improved whose ratings indicate the need for positive change. The 22 projects assessed, with a short description of each, are as follows: 01 Structures, Materials, and Mechanisms: Technologies for lightweight vehicle and habitat structures and low-temperature mechanisms. 02 Ablative Thermal Protection System for the Crew Exploration Vehicle: Prototype, human-rated, ablative heat shield for Orion (the crew vehicle) and advanced thermal protection system materials. 03 Lunar Dust Mitigation: Technologies for protecting lunar surface systems from the adverse effects of lunar dust. 04 Propulsion and Cryogenics Advanced Development: Non-toxic propulsion systems for Orion and the Lunar Lander. 05 Cryogenic Fluid Management: Technologies for long-term storage of cryogenic propellants.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program 06 Energy Storage: Advanced lithium-ion batteries and regenerative fuel cells for energy storage. 07 Thermal Control Systems: Heat pumps, evaporators, and radiators for thermal control of Orion, and lunar surface systems such as habitats, power systems, and extravehicular activity (EVA) suits. 08 High-Performance and Radiation-Hardened Electronics: Radiation-hardened and reconfigurable, high-performance processors and electronics. 09 Integrated Systems Health Management: Design, development, operation, and life-cycle management of components, subsystems, vehicles, and other operational systems. 10 Autonomy for Operations: Software tools to maximize productivity and minimize workload for mission operations by automating procedures, schedules, and plans. 11 Intelligent Software Design: Software tools to produce reliable software. 12 Autonomous Landing and Hazard Avoidance Technology: Autonomous, precision-landing and hazard avoidance systems. 13 Automated Rendezvous and Docking Sensor Technology: Development of sensors and software to rendezvous and dock spacecraft. 14 Exploration Life Support: Technologies for atmospheric management, advanced air and water recovery systems, and waste disposal. 15 Advanced Environmental Monitoring and Control: Technologies for monitoring and controlling spacecraft and habitat environment. 16 Fire Prevention, Detection, and Suppression: Technologies to ensure crew health and safety on exploration missions. 17 Extravehicular Activity Technologies: Component technologies for an advanced EVA suit. 18 International Space Station Research: Fundamental microgravity research in biology, materials, fluid physics, and combustion using facilities on the International Space Station. 19 In Situ Resource Utilization: Technologies for regolith (loose rock layer on the Moon’s surface) excavation and handling, for producing oxygen from regolith, and for collecting and processing lunar ice and other volatiles. 20 Fission Surface Power: Concepts and technologies for affordable nuclear fission surface power systems for long-duration stays on the Moon and the future exploration of Mars. 21 Supportability: Technologies for spacecraft and lunar surface system repair. 22 Human-Robotic Systems/Analogs: Technologies for surface mobility and equipment handling, human-system interaction, and lunar surface system repair. Descriptions of the ETDP and its technology infusion plans can also be found in two public documents.3,4 01 STRUCTURES, MATERIALS, AND MECHANISMS Objective The Structures, Materials, and Mechanisms project has two goals: (1) to develop lightweight structures for lunar landers and surface habitats, which may be used in future modes of the Crew Exploration Vehicle (CEV) and crew launch vehicle to save weight and/or cost, and (2) to develop low-temperature mechanisms for rovers, robotics, and mechanized operations that may need to operate in shadowed regions of the Moon. Status The structures element of the Structures, Materials, and Mechanisms project consists of inflatable (expandable) structures for buildings on the surface of the Moon and very large single-segment propellant tank bulkheads made 3 C. Moore and F. Peri, “The Exploration Technology Development Program,” AIAA Paper 2007-136 in 45th Aerospace Sciences Meeting Conference Proceedings, American Institute of Aeronautics and Astronautics, Reston, Va., 2007. 4 D.C. Beals, “Technology Infusion Planning Within the Exploration Technology Program,” IEEEAC Paper #1108, available at http://ieeexplore.ieee.org/iel5/4161231/4144550/04161576.pdf.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program of aluminum-lithium (Al-Li). The materials element consists of parachute material, radiation shielding kit materials, and Al-Li for very large propellant tank domes. Little in the way of advanced materials for lightweight vehicles, landers, rovers, and habitats was presented to the committee. The mechanisms element consists of gear boxes, electric motor sensors, and motor controls for robotic systems that would operate in continuous darkness at the poles. Most elements of this project use system engineering principles to provide minimum risk and to ensure on-time delivery. Designing, fabricating, and testing a piece of demonstration hardware are aspects of all three elements. This project is staffed and conducted primarily at NASA, with a few industry and academic partnerships. The potential application of lean manufacturing and rapid prototyping technologies needs to be fully explored in the current ETDP. Experience has shown that these technologies can have a significant impact on cost and schedule. Ratings Quality: Yellow Flag Some team members appear to have little or no expertise in their project area. A lack of experience combined with limited interaction with industry can have a serious adverse impact on the quality of work. The lack of interaction with industry has resulted in situations in which NASA work has not yet reached the TRL level of similar projects in industry that are currently at TRLs of 6 or 7. An example of industry capability is Al-Li structures and welding. In addition, industry has demonstrated large friction stir weld-spun domes that are very close to the Ares I requirements. The alloy Ti Al Beta 21 S is currently being used by industry and is not being considered by NASA in the VSE program. The project group itself identified some existing manufacturing techniques not being used by NASA owing to licensing issues rather than technology development issues. It also appears that a lack of specific requirements in some cases has allowed in-house projects to float goals and produce simplistic measures of success. Effectiveness in Developing and Transitioning: Yellow Flag This set of activities seem to lack direct tie-in to an integrated, overarching plan. The objectives for most of the tasks are not rooted directly in supporting the VSE or Constellation Program requirements, which limits their ability to be transitioned to the customer. While this limits the risk to the customer, it also limits the overall effectiveness of the work. It is not clear why some specific elements of this project were selected; nevertheless, overall, the project is proceeding in a timely manner and the results are expected to be available to meet VSE and Constellation Program schedules. Following are comments of the committee on specific project issues: Aluminum-lithium manufacturing: friction stir weld-spun domes. The metals industry has been crafting friction stir weld and spun domes for a long time. The main reason for pushing this technology is the required size—that is, the 5.5-meter diameter. However, other non-NASA organizations have achieved this technology in sizes very close (5.2 m) to what NASA is trying to achieve. The benefit to the Constellation configuration from incorporating this technology with a small delta in dimension from the state of the art is not clear. Low-temperature mechanisms. This project element has selected a few components and tested them under the cold temperature extremes present on the Moon. However, when asked about its specific application, the project team was unsure. Some components may work individually under the specified environment but may not function as part of higher-level subsystems or systems. Advanced material for parachutes. This project element lacks a useful figure of merit. Material is being evaluated for potential application as the CEV parachute material. Team members stated that this material has a strength-to-weight ratio approximately twice that of other currently available fibers, and consequently, that it will yield more than 40 kg in mass savings for the three CEV parachutes. Unanswered is the question of the cost per kilogram to achieve this reduction in mass and the resulting overall gain in system performance.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Expandable structures. This project element uses lunar regolith as part of a pressurized architecture, which is somewhat cumbersome. It is not clear that this is the best design solution because, for example, the abrasive dust in a low-gravity situation could be a menace to equipment and personnel. Advanced composite structures. Exotic materials, such as lightweight composites, often promise great advantages on paper and sometimes in practice. It was not clear from the presentation of the team responsible for this element how and where these composite materials were going to be applied throughout the Constellation Program. The performance benefit or the figure of merit was not clearly identified. Composite materials may potentially provide significant advantages in weight reduction, but system trade-offs are needed in order to identify and quantify those gains. Facilities. No new facilities were identified by the committee as needed to validate performance capabilities. Radiation shielding kit. This technology, which proposes a type of blanket or sleeping bag approach as a portable shield, is a good fundamental research area. However, unless its specific application to various program elements is identified, it is very difficult to see its impact. The use of this kit was not traded against other competing options, and it requires figures of merit. Alignment with the Objectives of the Vision for Space Exploration: Yellow Flag The performance benefit to the VSE and Constellation programs from the Structures, Materials, and Mechanisms project may not be fully achieved because of an apparent lack of specific requirements coming from the Constellation Program office. There appears to be little in the way of enabling technology in this project. Therefore, a strong push for these technologies by the customer is not apparent. 02 ABLATIVE THERMAL PROTECTION SYSTEM FOR THE CREW EXPLORATION VEHICLE Objective Extremely large heat fluxes are experienced by the Crew Exploration Vehicle (CEV) during reentry from the Moon or Mars. An ablative heat shield is required for thermal protection. The heat shield design and thermal protection system (TPS) material qualification represent major technological challenges. The NASA team for this project stated that the present TRL is 4. The TRL needs to be advanced to 6 to support the CEV project. Status The project team is composed of NASA, the companies producing the materials, and the CEV contractor. The work is being carried out in a coordinated manner and, overall, is of good quality. The currently used metrics are appropriate. It appears that an upgrade to the arc-jet facility at NASA’s Ames Research Center (ARC) will take place that will improve its flow simulation capabilities. Material test specimens and TPS materials for the primary and backup CEV heat shields are being produced by aerospace companies. The CEV contractor has built a full-scale heat shield test article and will build the flight heat shield. These developments are being directed and reviewed by NASA to ensure the coordinated consideration of reentry mechanical and thermal loads. There is no possibility of alternate technologies being developed within the ETDP. The plan is to have an acceptable TPS design by CEV Preliminary Design Review (PDR) and to have the technology matured by CEV Final Design Review (FDR). Ratings Quality: Yellow Flag The heat shield is being designed using heating rate predictions from an uncoupled analysis; that is, the char surface temperatures are assumed to be radiation equilibrium temperatures rather than being calculated from a heat
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program balance for the ablating heat shield. The injection of the pyrolysis gases and char oxidation products (which may significantly change the prediction of the heating rate) is ignored. This approach does not represent the current state of the art and could lead to either an over- or underprediction of the bond-line temperatures late in the entry. While industry has been involved in producing candidate TPS material, there is no significant involvement of the national laboratories. However, organizations such as Sandia National Laboratories as well as other Department of Energy (DOE) and Department of Defense (DOD) laboratories could contribute to this effort. Effectiveness in Developing and Transitioning: Yellow Flag Even though 40 years have elapsed since the Apollo 4 flight test and the state of the art in heat shield design has advanced significantly during that time, the ability to simulate a lunar-return Earth entry in ground-based facilities still does not exist. The planned ground-test arc-jet facility improvements are desirable, but they will not provide an adequate approximation of all flight conditions and cannot be scaled to the full heat shield dimensions. Within the present state of the art, it is not possible to build ground test facilities that will duplicate (or even adequately approximate) flight conditions. Only a reentry flight test at lunar-return velocity and at a scale sufficient to assess the effects of joints and gaps between the heat shield panels will qualify the heat shield for use on a crewed lunar-return mission. Because NASA had not made a decision at the time that the committee was carrying out its data gathering, the committee was not clear as to whether an uncrewed flight test is planned; if not, the effectiveness with which this project is being developed and transitioned would be labeled with a red flag. Alignment with the Vision for Space Exploration: Yellow Flag Planetary-return heating rates are much higher than lunar-return heating rates. A CEV-like vehicle entering at 13 km/s from Mars will experience peak stagnation-point heating rates (convective and radiative) three times greater than the lunar-return values. Furthermore, at 13 km/s the stagnation-point heat load is approximately 70 percent radiative, whereas for lunar-return entries it is less than 25 percent. Therefore, an entirely different heat shield design may be required for reentry from Mars; hence the present technology does not fully support the entire VSE. 03 LUNAR DUST MITIGATION Objective Dust was an issue for the Apollo astronauts, and it continues to be an issue for the Mars Exploration Rovers (MERs). Dust presents both a health risk (e.g., from inhalation and damage to spacesuits) and a mission risk (e.g., for its obscuring of landing sites, causing equipment to overheat, and covering solar arrays). In response to these dust issues, NASA established the Lunar Dust Mitigation project, with the goal of providing the “knowledge and technologies (to TRL 6) required to address adverse dust effects to humans and to exploration systems and equipment, which will reduce life cycle cost and risk, and will increase the probability of sustainable and successful lunar missions.”5 Status The Lunar Dust Mitigation project has clearly defined requirements that have been delineated into well-stated project plans to bring the TRL to 5. The development objectives of each of these plans were understood by the team members as clearly stated deliverables. Interaction within the NASA organizations involved in the project seems appropriate. The expertise of dealing with regolith resides within NASA, but outside sources are being sought in appropriate areas where industrial cooperation can benefit the program. The extensibility to Mars appears to be assumed, as the Moon is the current focus. The team seems to be motivated and enthusiastic about achieving its 5 National Aeronautics and Space Administration, Exploration Technology Development Program. Technology Development Project Plan. Dust Management Project Plan, Document No. DUST-PLN-0001, NASA Glenn Research Center, Cleveland, Ohio, November 2007.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program goals. The team has test plans within the scope of available resources—that is, test facilities—but the need for full-scale testing is not reflected in the current project plan or the Constellation plan. Individual experiences within the Apollo program are being folded in to the development of the projects, except for the overall experience of equipment being crippled by dust contamination on the surface. Ratings Quality: Green Flag The Lunar Dust Mitigation project plan has well-developed requirements and an appropriate layout of program elements to achieve a TRL of 5. Requirements from many sources are driving the correct program development to satisfy the goals. Outside sources have been sought for expertise in dust mitigation within the mining industry—more interaction with hard-rock mining would enhance this effort. Small Business Innovation Research (SBIR) projects are also being used to solicit outside expertise and advance the TRL in some areas. Apollo experiences with dust effects are being folded in to the technology plans. Component-level testing of various mechanisms in a vacuum environment is a good element of this program. Effectiveness in Developing and Transitioning: Red Flag Low-TRL ideas that would be matured later than 2013 are not being considered currently in SBIR or other programs; this will limit the continuity of new ideas being inserted into this project’s long-term goals. The production of regolith simulant in the time necessary to allow for testing also poses a risk to this effort. Currently, the risks are very high owing to the lack of full-scale, long-term testing to prove the effectiveness of the developed products. A full-scale test facility and the testing of equipment (e.g., bearings and seals, robots, EVA suits, crawlers) under long-term exposure are necessary for the ETDP to develop and prove the criticality of these vital resources on the Moon and Mars. The lack of plans to include a full-scale test facility negatively impacts the effectiveness of the effort in a major way and if left unresolved virtually guarantees failure to reach project goals expressed as TRL 6. Alignment with the Vision for Space Exploration: Yellow Flag The impact of the Lunar Dust Mitigation project on the VSE is clearly enabling, and this is understood by the Constellation Program. Without control of the effects of dust, exploration on the surface would be seriously compromised. Even robotic precursors could be less effective without this control. This is recognized by the NASA team and included in its project plans. The yellow flag rating reflects the lack of any development for the Mars environment—which may have its own problems with dust as shown by the MERs—as the lunar environment appears to be the sole focus of this project. 04 PROPULSION AND CRYOGENICS ADVANCED DEVELOPMENT Objective The Propulsion and Cryogenics Advanced Development (PCAD) project is focused on the development of the ascent and descent propulsion systems for the Lunar Lander. The team is working on three main areas: the descent main engine, the ascent main engine, and reaction control system (RCS) thrusters for the ascent propulsion system. According to NASA, the ascent liquid oxygen/methane (LOX/CH4) main engine is currently at TRL 3, the RCS thrusters are at TRL 4, and the descent main engine is at TRL 5. Status The PCAD team is composed of NASA employees and several contractors for the main engines and the RCS. The contractors include major aerospace companies and smaller companies. The PCAD project is well focused
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program around the established risk areas for each of the three main project elements that are being worked on. The main customers of PCAD are the Lunar Lander Projects Office (LLPO) and the Orion Crew Module Project Office. For the descent main engine, the current choice of propellants is liquid oxygen/liquid hydrogen (LOX/LH2). This choice was made to meet the lander weight budget because the performance of LOX/LH2 is better than that of storable propellants. Meeting the throttle requirement for this engine (currently about 30 percent, but for some versions it could be lower) is mission enabling for the Lunar Lander. The main risks with this engine are stable throttling, performance, and reliable ignition. For the ascent propulsion system, nitrogen tetroxide/monomethyl hydrazine (NTO/MMH) and LOX/CH4 are under consideration. However, the current technology project is focused only on LOX/CH4, since this is a new propellant combination to be used for this application. The projected benefits of using LOX/CH4 versus hypergolic fuels are higher performance, which translates into mass savings of approximately 180 kg to 360 kg; lower costs; and a comparable development schedule and achievable reliability. The main challenges that need to be resolved for the LOX/CH4 engine to be chosen over the storable propellants are reliable ignition (especially after long-term missions on the order of 6 months), performance, and fast start. RCS thrusters using LOX/CH4 are also being developed that are intended to have higher performance and maneuverability than those using storable propellants. In this case, the major risks are reliable ignition, performance, storability, and repeatable pulse width. Although Russia, Korea, Pratt & Whitney Rocketdyne, and others are designing or have designed liquid oxygen/methane (LOX/CH4) engines, they are not designed for a similar application and therefore are not being used as a baseline for comparison with the current ascent engine being developed. Both main engines and the proposed RCS described above minimize the contamination of the vehicle and landing area and improve ground procedures on the launch pad. Ratings Quality: Green Flag The work of the PCAD project seems to be well coordinated among the primary customers, namely, the Lunar Lander Projects Office and the Orion Crew Module Project Office, the NASA technology development teams from the NASA Glenn Research Center (GRC), the NASA Johnson Space Center (JSC), and the NASA Marshall Space Flight Center (MSFC), and the contractors. The existing test facilities seem to be sufficient for this project. For the descent engine, the team is pursuing a LOX/LH2 engine based on the RL-10 and is working with Pratt & Whitney Rocketdyne to develop the new engine. The team is tackling critical design issues, such as the injector design. Its metrics are well defined and relevant to the development program. The team is aware of the risks that it faces. However, there are gaps in the project that the team is aware of but could not address owing to insufficient resources: controls, turbomachinery, and high-heat-transfer chambers. For the ascent module, the team is focusing on LOX/CH4 for the reasons mentioned above. The team plans to mature this technology before the LLPO has to choose between this new technology and hypergolic fuels. The team is very aware of the key parameters that it must demonstrate: reliable ignition, performance, and fast start. Its program is well tailored to these objectives. The team is simultaneously carrying out a development project for LOX/CH4 RCS thrusters that would go hand in hand with the main engine. Effectiveness in Developing and Transitioning: Green Flag The LLPO is considering two choices for the main ascent engine: LOX/CH4 and storables. Because the risks associated with developing an LOX/CH4 engine are greater than those associated with developing a storable propellant engine for this application, the decision has been made to focus only on the LOX/CH4 engine in the technology project. As a result of a first set of vehicle studies carrying out both options, the LLPO found that an LOX/CH4 engine could result in a mass savings of 180 kg to 360 kg. As of this writing, the decision about which type of engine to procure was slated for 2011 or so, after the PCAD team has had a chance to investigate in detail the prospect of using LOX/CH4 and has given its results to the LLPO and others to support an informed decision.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Within PCAD, preliminary tests carried out by the two contractors working on the LOX/CH4 engine are underway. Alternative designs are also being considered. The PCAD team and the LLPO are working closely to feed each other the results from their studies. For the descent engine, the team is carrying only one contractor, Pratt & Whitney Rocketdyne, owing to cost constraints, which means that only one design is being considered. However, in terms of transition, the team is well positioned because the contractor has been involved from the beginning and has the experience to complete the full cycle of design, development, testing, and production. Alignment with the Vision for Space Exploration: Green Flag An LOX/CH4 main ascent engine would be a great benefit for Mars exploration because it is amenable to in situ resource utilization. The team has also tried to foresee what requirement changes the LLPO might present to it and has tried to develop flexible designs. For example, its LOX/CH4 engine project is expected to be flexible with respect to thrust changes and the number of the starts required. The PCAD technology development team is pursuing “green” propellants such as LOX, LH2, and CH4, as opposed to hypergolic fuels, for both the descent and the ascent engines. One can only assume that such “green” propellants will continue to be the preferred choice for other exploration-class missions. 05 CRYOGENIC FLUID MANAGEMENT Objective The objective of the Cryogenic Fluid Management (CFM) project is to develop the technologies for the long-duration storage and distribution of cryogenic propellants in support of all Exploration missions. The development of these enabling technologies is crucial for various NASA customers in the Constellation Program including the Lunar Lander, Earth Departure Stage, and Lunar Surface Operations projects as well as for the Mars program. Status The scope of the Cryogenic Fluid Management project includes a number of interrelated elements: Long-Duration Propellant Storage, Cryogenic Propellant Distribution System, and Propellant Management Under Low-Gravity Environment. A number of design and test qualification tasks under each of these elements have been defined and are being executed according to the plan in place. The tasks are being performed primarily at various NASA centers—specifically, GRC, MSFC, JSC, ARC, Goddard Space Flight Center (GSFC), and Kennedy Space Center (KSC). The project includes a relatively smaller involvement from external agencies, including universities and small companies. The current TRLs were stated by the NASA team as follows: Propellant Storage—TRL 4, Propellant Distribution—TRL 5, Liquid Acquisition—TRL 4, Mass Gauging—TRL 3. However, based on the current technical maturity, a TRL of 4 for the Propellant Distribution System would be more appropriate. The plans to achieve the desired TRL of 6 by the PDR of various Constellation elements include a combination of analytical modeling with component and integrated system tests under specified nonspace and simulated space environments. In some cases, such as Mass Gauging systems, a number of competing systems such as the Pressure-Volume-Temperature system, Radiofrequency Gauge, and Optical Mass Gauge are in the process of being evaluated. Ratings Quality: Yellow Flag The CFM project is spearheaded by a very competent group. The involvement of industries and universities appears to be minimal compared with the direct NASA involvement. The analytical modeling work or the subscale-
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program level testing under a nonspace environment cannot be extrapolated to determine the performance and functions of the full-scale systems under zero- or low-gravity applications. Effectiveness in Developing and Transitioning: Yellow Flag A number of technology gaps may have serious consequences for the overall exploration program. Testing subscale or full-scale systems under low gravity is essential in order to demonstrate the applicability of the selected technologies or systems. The achievement of a TRL of 6 or higher before the PDR of various exploration elements may not be realized owing to the lack of these essential tests, mostly caused by funding or scheduling limitations. In some cases, the lack of a fully integrated system test before the flight may lead to undesirable risks. It was mentioned that the Constellation Program Office is evaluating the risks associated with bypassing some of these tests or the eventuality of not achieving the desired TRL 6 by the PDR. This position is in direct conflict with the “Enabling Technologies” designation assigned to the CFM project by the Exploration Program Office. (An “enabling technology” is understood to mean one that must be achieved to enable the success of the mission or an important component of the mission.) However, the committee did not see the absence of achieving a TRL of 6 as a major deficiency if an analysis of the program-level risks, underway at the time of writing, concludes that a TRL of 6 is not required. Alignment with the Vision for Space Exploration: Yellow Flag The architectural benefit of using cryogenic propellants in the exploration program is well understood and identified. The selection of LOX/LH2 for the Earth Departure Stage and the Lander Descent Module provides a significant performance benefit compared with other competing propellant systems. However, a number of technical risks associated with the long-duration-in-space storage, propellant distribution, and acquisition remain unresolved. Similarly, the same issues exist for the LOX/CH4 propulsion system that is currently being evaluated for application in the Lander Ascent Module. The lunar surface operations for later and longer missions covering up to 210 days require well-proven technologies for long-term cryogenic storage and fluid transfer between surface assets. However, the relationship and dependencies of the CFM systems and the lunar surface concepts of operations (CONOPS) were not described or presented to the committee. The applicability of the technologies and the design solutions identified for lunar missions to long-duration missions to Mars and beyond were not addressed. 06 ENERGY STORAGE Objective The objective of the Energy Storage project is to reduce risks associated with the use of lithium batteries, fuel cells, and regenerative fuel cells for the Lunar Lander, lunar surface systems, EVA, and both Ares I and Ares V. Major deliverables are rechargeable batteries for lander ascent, EVA, and lunar surface mobility; primary fuel cells for lander descent; and regenerative fuel cells for lunar surface power and lunar mobility. Rechargeable batteries and regenerative fuel cells are energy storage devices and cannot by themselves provide all the power needed for long-duration missions; a power source (solar or nuclear) is also needed. The objective is to deliver TRL 5 technologies to Constellation System Requirements Reviews and TRL 6 hardware for their PDRs. Status The battery and fuel cell research for the Energy Storage project is being carried out at GRC, the Jet Propulsion Laboratory (JPL), JSC, KSC, and a few university and industrial collaborators and contractors. NASA has very good facilities for both battery and fuel cell research and testing. The project is well coordinated among the NASA centers.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program It is not clear if the current performance targets for the Energy Storage project will meet the future mission requirements. Customer requirements are not yet well established but presumably will be much better defined in the future. The present metrics are based on a bottom-up approach and, in lieu of established customer requirements, are appropriate as a temporary measure. The NASA research effort is quite small compared with that of other agencies and of the battery and fuel cell companies. Consequently, by focusing on issues that are specific to its needs rather than trying to make fundamental advances in the technology, the project will reach its goals more effectively and at lower cost. Some NASA-focused issues include low-temperature operation and lightweight packaging for batteries, and fuel cell technologies that achieve high performance and long-term reliability without the cost constraints of the commercial market. Ratings Quality: Fuel Cells: Green Flag; Batteries: Yellow Flag NASA’s needs for fuel cell development will not be met solely by the commercial market in that NASA’s focus is on mass reduction and the commercial market is focused on cost reduction. Furthermore, NASA fuel cells will operate on H2/O2, whereas commercial products operate on H2/air or gas mixtures (H2, CO2, and so on) derived from the reforming of conventional fossil fuels (e.g., natural gas, propane). The NASA fuel cell team is conducting high-quality research with modest resources. The project is fully cognizant of ongoing work in industry and other agencies and makes good use of related research underway in the broader fuel cell community. The team has benefited from a good investment in research and testing facilities. Although GRC has a long history in electrochemical technology, the current battery team is in a state of transition, with a new project manager and a new principal investigator. Little evidence was presented to the committee to indicate that the battery work is well coordinated with non-NASA efforts. There appears to be only limited collaboration with DOE and DOD efforts. The battery team’s characterization of the current performance of space-rated batteries as a specific energy of 130 Wh/kg at 30°C at the cell level significantly underestimates the current state of the technology: space-rated cells with specific energies of greater than 165 Wh/kg are currently available from ABSL Space Products, SAFT S.A., and Quallion, although these cells are not yet qualified for human-rated applications. The team has good facilities for research and testing but does not have a capability for fabricating 18650-size cells (18 mm diameter by 65 mm length, a size commonly used in laptops) or larger cells. This indicates a lack of a well-developed plan and/or capability for transitioning NASA’s electrode and electrolyte materials development into full-scale hardware and its subsequent technology insertion into the Constellation Program. However, GRC is conducting a testing program on large cells procured from industrial battery developers, and other NASA centers are conducting a materials development effort in which new materials are tested in very small cells. Effectiveness in Developing and Transitioning: Fuel Cells: Green Flag; Batteries: Yellow Flag The current battery and fuel cell technologies used on EVA and the space shuttle are old technologies, and even technologies available today would provide significant performance benefits. The NASA development plan offers the potential for significant improvements over the state of the art, and it is on track to deliver the hardware at the needed TRL at the appropriate time for advanced lithium-ion batteries. However, lithium-sulfur and lithium-metal batteries will probably not reach the required TRLs to meet the Constellation Program’s schedule for the Lander Ascent Vehicle, EVA, and lunar surface mobility. The time line requires TRL 5 hardware for the Lander system requirement review by March 2012 and TRL 6 hardware for the EVA PDR by September 2012. This is due to the combination of the present state of development of lithium-sulfur and lithium-metal batteries and the very low level of planned future resources allocated to their development, particularly in the areas of safety and cycle life. Similarly, while the work on primary fuel cells is nearly on track to meet schedule requirements, that on regenerative fuel cells needs to be accelerated to meet the Constellation Program’s schedule requirements for the lunar surface systems.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Metabolic Temperature Swing Absorption was identified through a competitive procurement process. Company independent research and development funds have taken this technology to a TRL of 3. It is questionable whether this project element can be developed mainly through SBIR funding. The utility of the variable-pressure regulator is very novel and useful for the VSE, a great innovation. The current plan seems achievable, but this was one of the lowest TRL elements shown. The communications radiation-hardening effort would benefit from increased contacts with industry and the DOD laboratories to achieve its goals. The PCAI team has developed useful contacts with the DOD in the areas of audio communications, batteries, displays, and speech recognition that should prove beneficial. Effectiveness in Developing and Transitioning: Yellow Flag Resource limitations and disparate development organizations (not identified on a single project element chart) negatively impact the EVA Technologies project. An integrated EVA team (PLSS and suit) would focus goals and result in better alignment than that achieved by the current, arbitrarily separated pressure suit effort. The lack of long-term funding and an unclear alignment between the ETDP, the Constellation Program, and the Space and Life Sciences Directorate at JSC that defines the human risks and suit design requirements present a substantial risk to this critical element of future planetary surface exploration effort. No new technologies or design concepts to mitigate the locomotion and mobility issues that will arise during lunar and Mars surface exploration missions were apparent during the committee’s visit to the EVA Suit Laboratory. There was no new materials or systems research presented to address the significant abrasion and dust mitigation problems that will be encountered in the lunar regolith or on the surface of Mars. An environmental facility simulating as closely as possible lunar and/or Mars conditions, including the abrasive lunar regolith or martian soils, could lead to a significant reduction in the risks associated with long-term exploration on the surface of the Moon. Gaps in the efforts include (1) a fully nested analysis effort to optimize the protection, weight, and sizing of the PLSS; (2) incorporation of radiation protection within the suit elements; (3) identification of new heat-rejection technologies, including both passive and active systems such as new materials for the suit, new phase-change materials, and alternative designs for the present cooling garment; (4) lack of obvious integration of the anthropometric requirements for crew selection with the anthropometric optimization of suit design (relevant HRP risks and lessons learned from past programs using either custom suits, one size fits all, or a small selection of standard sizes should be shared with designers starting at TRL 1); and (5) consideration for integrating advanced technologies into the overall system, rather than relying solely on incremental improvements. In addition, a study of the recent request for proposals (RFP) for the new Constellation suit indicates that the effort will be directed to a single suit for Earth launch to orbit, EVA on orbit, and lunar planetary operations. The RFP further stated that the contractor selected would not be required to initiate new technology research but would be expected to increase the TRL level of NASA-initiated research. This new suit may require research and technologies that are not currently identified within the existing program. Alignment with the Vision for Space Exploration: Yellow Flag The benefit of EVA systems is obvious within the VSE; not providing the enabling EVA systems on time and within requirements will jeopardize mission success. The current effort is directed toward general EVA and Lunar Surface Operations. However, the current program and the EVA suit RFP mentioned above explicitly excluded development of a suit for use on the surface of Mars. 18 INTERNATIONAL SPACE STATION RESEARCH Objective The International Space Station research project is broadly divided into two elements: direct exploration support and more general microgravity/radiation research. Both elements span the physical and life sciences.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program The goal of the exploration element is to employ the ISS as a low-TRL testbed to bring technologies to higher TRLs in the areas of life support, fire safety, power, propulsion, thermal management, material technology, habitat design, and so on. The goal of the non-exploration element is to sustain U.S. scientific expertise and research capabilities in fundamental microgravity research, primarily in the life and physical sciences. The U.S. Congress mandated the allocation of at least 15 percent of ISS research to ground-based, free-flier, and ISS life and microgravity science research that is not directly related to supporting the human exploration program. Status Nearly all exploration-related tasks are research projects onboard the ISS, with a few being ground-based research. All currently funded tasks are carryovers from the original ISS program with a budget that was many times larger in 2005. Some are onboard ISS and some are scheduled to be delivered by the space shuttle or Soyuz up to early 2009. NASA’s briefing charts indicate a funding profile of one U.S. research experiment per rack every 2 years. Ratings Quality: Green Flag The ISS research projects will support the following test facilities: Microgravity Science Glovebox (On-Orbit), a Fluids and Combustion Facility, and a Materials Science Research Rack in the ISS National Laboratory. The latter two will be launched in the next 2 years. Because they are in use or qualified to be used in the ISS, the test facilities have met the stringent operational and safety requirements imposed by the ISS. The ISS Research projects have met some of the National Research Council (NRC) recommendations related to the following: Effects of radiation on biological systems, Loss of bone and muscle mass during spaceflight, Psychosocial and behavioral risks of long-term space missions, Individual variability in mitigating a medical/biological risk, Fire safety aboard spacecraft, and Multiphase flow and heat transfer issues in space technology operations. Four foundational research efforts have relevance to Exploration: Smoke and Aerosol Measurement Experiment to help design a useful spacecraft smoke detector, Microbe by way of virulence in a rodent infection model might be applicable to human spaceflight, Zero Boil Off Tank (ZBOT) Experiment for spacecraft tanks, and Vegetable Production Unit (VPU) to study space growth of plant species and their supporting equipments, along with assessment of crew member reactions. These projects would satisfy NRC recommendations related to items 3, 5, and 6 listed above. There are 8 other exploration research efforts related to physical sciences including fluid physics and combustion science that are led by university professors and researchers from Glenn Research Center. There are 17 other non-exploratory efforts related to physical sciences including fluid physics, combustion sciences, material sciences, and acceleration environment characterization. The principal investigators are mostly university professors. The quality of the research is considered to be very good and is presumed to have been subjected to the NASA peer review process.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Effectiveness in Developing and Transitioning: Yellow Flag Since most experiments are performed on the ISS in a microgravity environment, they cannot address the fractional gravity application on lunar or Mars surfaces. They can, however, address technology needs for the vehicle transit, assuming a constant microgravity environment. It should be noted that since the Cryogenic Fluid Management project in ETDP cannot validate its technology in microgravity or fractional gravity owing to project costs and schedule requirements, it may not be able to use results from the ISS experiments to support the Constellation Program’s development. This is an example of a disconnect or gap that exists between the ISS research and ETDP’s customers. Before each project is launched to the ISS, it has to be assigned a manifest position in the shuttle or the Soyuz cargo manifest. Months of integration are also required before each flight. Therefore, the committee assigned a yellow flag to most of these ISS research projects because it appears that they cannot meet the schedule requirements of the ETDP. The ISS collection of experiments is generally at the lower TRL levels, performed primarily by the university community. The transition of results is an indirect one, through conference papers and reports. There appears to be no regular communication between the ISS research project and other ETDP projects. Alignment with the Vision for Space Exploration: Yellow Flag The Exploratory Research Program on the ISS consists of projects that are at or below TRL 3. Therefore, they do not yet meet Constellation’s needs. The relevancy of such projects is based on endorsement letters from other ETDP projects. The logic is that these research projects may be successfully picked up for further TRL development in future ETDP projects. However, most projects are carryovers from previous ISS projects and use facilities onboard the ISS. The pool of investigators is from the original ISS research community, and the selection is based on the ISS project’s own interpretation of exploration needs rather than the other way around. Thus, there appears to be a gap between research projects and other ETDP customers such as Constellation. Nonetheless, the projects listed above represent valid scientific research and can be considered to align with future Mars Exploration missions, but the possible application of results toward Constellation is not clear. NASA, in general, should continue a robust utilization of the ISS for both scientific and engineering research to support exploration and mitigate risk, and then it should ensure that those experiments ready for transition into either lunar or martian exploration are put on a clear project path for systems integration. 19 IN SITU RESOURCE UTILIZATION Objective The basic concept of In Situ Resource Utilization (ISRU) is to extract elements and minerals from the land and/or atmospheric resources that are present on the Moon and Mars. The idea of “living off the land” has been investigated for the past two decades. The proposed benefits argue that each kilogram of material that is produced on the Moon or Mars saves funds, launch mass, acquisition time, and payload volume. At roughly $100,000 per kilogram to put material on the Moon, these savings have been shown to be considerable. In addition, by producing needed materials at the base, the crew has an increased chance of dealing with unforeseen emergencies. The near-term goal is to produce oxygen from lunar regolith for life support at about 1 metric ton per year. The midrange goal is to produce about 10 metric tons per year to refuel the propellant tanks on the ascent vehicle. The long-range goal is to use the extracted metals for fabrication of parts. Status The ISRU project will demonstrate regolith excavation and transport by both large and small rovers in analog environments. Oxygen production from regolith is to be demonstrated on the scale of an outpost-scaled plant. A precursor demonstration is being developed. It is hoped that this demonstration can be flown through a partner-
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program ship with Europe, Japan, or India. There is also some support work, in the form of modeling, regolith simulant development, and facility identification. There are some collaborative programs with the Canadian and Japanese space agencies, and limited procurements from industry and academia. Ratings Quality: Green Flag The various elements of the ISRU project appear to have high quality in both development path layout and the knowledge and abilities of the participants. The project has made good use of the expertise at all relevant NASA research centers and works in a well-coordinated manner. This project has also involved several universities and a few industries. The ISRU technology roadmap is closely linked to the NASA Science Mission Directorate and has a good link to NASA’s life support development activities. However, the planning between the NASA Exploration Systems Mission Directorate’s Lunar Lander Project Office and the ISRU activities is not currently well coordinated enough. According to the NASA presenters, the TRLs of most of the elements of the ISRU project are about 3, with some concepts around 2. The effort could benefit from the involvement of more universities and others in investigating new concepts at TRLs of 1 or 2. An important issue to be resolved is whether the implementation of the equipment needed to produce materials from the lunar regolith would cost more than the savings offered by producing the material on-site. To the extent possible, the project has taken full advantage of related non-NASA work in an ancillary manner—that is, not as part of the critical path to achieving the project’s goals. An example is the project’s drawing on advances in mining technology developed by the Canadians. Effectiveness in Developing and Transitioning: Red Flag The risks in achieving the ISRU project’s goals are very high due to insufficient resources: SBIR support will not solve this problem within the necessary time frame for implementation, and relying on foreign partners to maintain this project is problematic. In addition, this project is different from most of the ETDP projects as it has no Apollo experience to build on, and without another application in a commercial market there is no non-NASA entity to develop the technology. The committee has identified three technology gaps that inhibit the effectiveness of the ISRU project: High-fidelity lunar environment testbed. The lunar environment is a hard vacuum, has large temperature swings, is very dry, and possesses a layer of fine, abrasive dust. All of these conditions may strongly impact the performance or lifetime of robotic systems, mobile transports, heat radiators, and human respiration. Except for gravity, these conditions can be duplicated on Earth to validate the performance of candidate systems and operations. In addition to environmental testing, there are currently technology gaps due to funding limitations in lunar soil stabilization studies and operations/control software for startup/operation/shutdown in the low gravity, vacuum, dust, and lunar thermal cycles. NASA’s program lacks a facility that duplicates the dusty environment, vacuum, and thermal cycles of the Moon. Without such testing, no quantification of lifetime margins is possible. Repairs versus spares. Historically, missions have been of short duration so that systems and components were not expected to break down during the missions; consequently, technology was not pushed to extend reliability. For long-duration missions, however, breakages are inevitable. One solution is to take along an inventory of spare parts. However, this is mass-intensive, and no inventory can be exhaustive. The alternative is to “take the tools, not the parts.” Advances in rapid prototyping have produced commercially available machines that can produce parts of a complicated, three-dimensional nature, given power and an electronic file describing the object. The downside of this approach is a higher power requirement and the need to carry the necessary feed materials, furnaces, and so on. However, if a “power rich” approach is part of the architecture, this is readily accommodated. An assessment of the potential benefits of rapid prototyping of spare parts needs to be included.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Studies of trade offs, which must take into account the additional mass associated with the tools, may suggest an optimal solution. Robotic precursor missions to the Moon prior to human landing. Every kilogram of equipment taken to the lunar surface needs to perform for as long as practical while remaining cost-effective. Although the surface conditions can be closely approximated, no simulation can totally mimic the lunar environment. NASA has no current plans to fund an ISRU precursor demonstration; a precursor mission is dependent on an opportunity with one of NASA’s international partners. Alignment with the Vision for Space Exploration: Green Flag The benefits of the ISRU project to both lunar and Mars exploration are well aligned with the goals of the VSE because this technology can dramatically improve the probability of successfully achieving lunar and Mars mission goals. The performance benefit of consumables production on the surface allows an extended science mission for the VSE, not simply a quick visit. This research project is unique in the world; no other country at present is known to be seriously developing technologies for ISRU. 20 FISSION SURFACE POWER Objective The objective of ETDP’s Fission Surface Power (FSP) systems project is to develop an FSP system concept that meets surface power requirements, including the periodic recharging of long-duration portable power sources, at reasonable cost with added benefits over competitive alternatives. To achieve this objective, NASA has organized a joint NASA and DOE team with representatives from NASA’s GRC and MSFC and DOE’s Idaho National Laboratory, Los Alamos National Laboratory (LANL), Oak Ridge National Laboratory, and Sandia National Laboratories. In addition, NASA and DOE have involved industrial teams (e.g., Lockheed Martin and Pratt & Whitney Rocketdyne) and universities in their studies. The initial focus is on providing a 40-kWe nuclear reactor that could power the proposed Shackleton lunar base and provide the added assurance that such a concept could also be used to power a Mars base. The FSP concept is at a fairly high TRL, which should reduce both the risk and the cost of developing it. Status If NASA chooses FSP as its source of electrical power, the 40 kWe reactor would be designed to operate for at least 8 years at full power within the mass envelope of the Lunar Surface Access Module and could be used at any location on the Moon. Shielding would be provided by the lunar regolith, that is, inserting the reactor in a pre-excavated hole and adding upper plug shielding. The reactor would use uranium dioxide fuel and Type 316 stainless steel (SS-316) cladding. Both of these materials have been used in terrestrial reactors. The coolant would be a eutectic of sodium and potassium referred to as “NaK.” This coolant has also been used in terrestrial reactors. For the power conversion system, NASA is proposing to use Stirling power conversion, a technology that NASA has been studying in various technological forms for about 20 years. A backup power conversion option is Brayton technology, building on what was developed for the proposed Jupiter Icy Moons Orbiter (JIMO) nuclear power system. Ratings Quality: Green Historically NASA and the DOE have been the leaders in space nuclear power, and that continues to be the case now. There is no evidence that international entities will enter this field within the schedule envisioned for the VSE, although it is pointed out that the Russians have or did have space nuclear reactor experience. Given that
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program this project is driven by the VSE and therefore concentrates on relatively small-scale reactors in which there is no obvious commercial interest, it is very doubtful that any non-NASA, non-DOE sources will develop a competing or alternative technology that NASA could use for this purpose. The project team in place is composed of NASA and DOE personnel who are working well together, and some of the members have worked on previous space nuclear reactor programs (e.g., SP-100 space nuclear reactor power system and JIMO) so they have experience in the field. The members do not have flight experience because the United States has not flown a fission reactor since 1965, nor do they have experience in burying fission reactors on the Moon; both skills will have to be learned. The FSP Systems project plan, as presented to the committee, lacked detailed specificity on the organizational interactions—for example, the structure of the DOE interrelationships. No lead DOE laboratory was identified. The details of NASA’s interaction with the DOE laboratories were not specified. Effectiveness in Developing and Transitioning: Yellow Flag The FSP Systems project’s technology roadmap envisions an interactive combination of concept definition and risk reduction work through FY 2012 to support an FY 2013 awarding of a prime contract to produce the development test models, engineering models, and flight models. Under this plan, NASA estimates that TRL 6 would be achieved by 2012. The proposed budget profile for this project incurs a large programmatic risk. Jumping from $14 million in 2013 to over $200 million per year in the subsequent years will strain U.S. industrial capabilities. Industry participation in the 2008-2013 period would serve to get industry vested in the project. However, the industrial base for nuclear engineering technologies has shrunk in the past 20 years owing to the standstill in commercial reactor construction, and there is a concern that that situation, coupled with an aging workforce, may mean that the industry may not be able to react to a sudden call in a few years to a NASA program just as the licensing of new commercial reactors appears to be significantly increasing. In addition, the committee is concerned about the potential consequences resulting from setting 2013 as the proposed date of decision. Other ETDP project teams, such as those for In Situ Resource Utilization, Lunar Dust Mitigation, and Cryogenic Fluid Management, stated that they would change their tasks if they knew that they would have access to 40 kWe rather than the use of the two or three modules of 6 to 10 kWe per module currently envisioned with a photovoltaic system. To wait until 2013 to make this decision may limit much of the work of these projects over the next few years. A potential gap in the FSP Systems technology development effort is the absence of a full-up ground test unit that incorporates both the nuclear reactor and the power conversion subsystem in a single, integrated unit that could be tested prior to use in an actual mission in the representative environment. The NASA and DOE team considered this option and concluded that it can demonstrate readiness through a combination of component, subsystem, non-nuclear, and zero-power nuclear testing; nonetheless, there is a concern borne out by other space projects that having a full-up ground test unit can allow the identification and correction of unforeseen problems (the “unknown unknowns”) and provide confidence that the flight unit will perform as designed. Before committing to the proposed program of no full-up ground test unit, an independent, detailed technical and programmatic review of the project’s proposal by NASA and the DOE would be beneficial. Alignment with the Vision for Space Exploration: Gold Star The availability of 40 kWe of continuous electrical power during the day and night would have major architectural benefits. Technologists working to develop In Situ Resource Utilization, Lunar Dust Mitigation, and Cryogenic Fluid Management would greatly benefit from the availability of increased electrical power. Obviously, the life support system and science instruments would benefit from more power. This is a critical enabling technology for human exploration of the Moon and Mars. The committee believes that the implementation of fission power of the magnitude considered by NASA would have a profound effect on major aspects of the entire VSE.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program 21 SUPPORTABILITY Objective The basic concept of supportability is to minimize the logistics footprint required to support exploration missions. Strategies to achieve this objective include broad implementation of commonality and standardization at all hardware levels and across all systems: interoperability, repair of failed hardware at the lowest possible hardware level, manufacture of structural and mechanical replacement components as needed, and logistics. The Supportability project consists of three elements: Component Level Electronic Assembly and Repair, which is further divided into manual repair, semiautomated diagnostics, and functional test and automated repair; Minimally Intrusive Repair, Detection, and Self-Healing Systems; and Smart Coatings. The goals of these elements are to decrease reliance on terrestrial support, reduce the mass volume of logistics spares, increase the operational availability of spacecraft systems, and provide robust, damage-tolerant systems. The benefits of supportability are such that all three tasks presented to the committee were ranked highly by the Constellation Program based on their impact on life-cycle costs. The selected tasks are already defined as either high ranking or as lunar-critical path items. Status The Supportability project team appears to have the expertise and innovation to complete the tasks as defined; however, this project seems to be a small subset of the tasks required for a general implementation of supportability. It needs to be expanded, as it appears to be implemented on the basis of specific technology requests as opposed to a systematic look at all the supportability requirements and options. This approach presents a risk that supportability will be available in some areas but not in others. The Apollo missions to the Moon were of short duration, and systems and components were not expected to break down during the missions—that is, technology was pushed to extend reliability. For long-duration missions, however, component failure is more probable. The issue of the logistics for the accommodation or replacement of damaged or failed parts must be addressed as part of the architecture. Historically, this problem of reliable operation was addressed by multiply redundant systems, which usually prevented a component failure from leading to system failure. This solution of multiple redundancies may not be practical for large-scale and prolonged operations such as a lunar or Mars base. Alternatives to long-term reliability include having spare parts available, commonality, and in situ fabrication. A simple approach to long-term reliability is to take along an inventory of spare parts. This may prove impractical for large-scale operations with thousands of parts. In addition, taking spares is mass-intensive and may not work, as the failure of a part may not have been anticipated. Carrying spares for everything is impractical and expensive. An operational alternative is to design commonality between similar parts used in different systems. If there is actual design commonality (e.g., in displays and controls or processor boards), less critical or no longer operating modules can be scavenged to provide components for more critical operating modules. This may reduce the number of spares needed, but it cannot accommodate all possibilities. A possible technological alternative applicable to some types of components is to “take the tools not the parts.” Advances in rapid prototyping have produced commercially available machines that can produce final net-shape parts of a complicated, three-dimensional nature. Fabrication of components made of plastic, ceramics, or metals has been demonstrated. While the committee is aware that NASA has a logistics study effort underway in the Constellation Program, the committee believes that NASA should examine the possibility of funding a technology project to examine if new technologies involving physical commonality and rapid prototyping could reduce the future need for having spare parts and the accompanying logistical burden. The ETDP Supportability project has recognized the issue of component repair and replacement as key to long-term reliability but is focusing primarily on electronic components. Replacement of Earth-fabricated mechanical or structural components is not being examined for long-term sustainability of lunar and Mars missions. The ETDP could evaluate the applicability of the current state of the art in rapid prototyping equipment to the exploration mission, and then evaluate the balance between system redundancy, design commonality, logistical
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program supply of spare parts fabricated on Earth, and fabricating components on-site using local resources to achieve the best cost and benefits for maintaining a sustainable exploration program. For those components that might feasibly be fabricated on-site and that would provide cost-benefit advantage over other approaches, a low-TRL ETDP technology development program could be initiated. There is a significant risk that advancing technology will eclipse many aspects of existing avionics systems. A task needs to be added to assess the impact of technology development on projected supportability options. Technologies developing on parallel tracks to electronics for sensing and control include bacteriorhodopsin-based state machines, artificial opal-based state machines, wavelength-routed fault-tolerant all-optical networks, optical sensors (all implemented in circuit or free space radio-frequency or infrared-based wireless networks), and living biological sensing systems based on “smart yeast.” These technologies reduce the need for a substantial amount of electronics and code, eliminate the need for copper wire carrying telemetry in many cases, and are so low in mass that they allow for massive redundancy, thus reducing the need for repair. Other examples are holographic-crystal-based memories and optical correlators for information processing (which would include Integrated Vehicle Health Management including diagnostics and prognostics) standardized microcontrollers, as well as polymer-based electronics and displays that can be manufactured with bubble jet printers. In addition to developing chemically responsive insulation polymers that heal themselves under a variety of conditions, approaches for detecting and repairing age-related damage to wiring should address techniques that can be carried out autonomously by microrobotics capable of locating faults by chemical detection of self-healed or degraded materials and by the presence and direction of electric fields or the direction of magnetic fields (stored in particles contained in the insulation) generated by a fault. These types of systems could spin polymers to repair insulation and install antichafing at the damage site and similar sites to prevent recurrence. Ratings Quality: Green Flag The various tasks under the Supportability project appear to have high quality in both the development path layout and the knowledge and ability of participants to complete the projects. The TRLs of the projects are in the TRL 2 range, with some concepts advancing to TRL 4 in 2008. This project has many affiliated universities and industries. The effort would likely benefit from the involvement of more universities examining competing concepts. Effectiveness in Developing and Transitioning: Yellow Flag The current level of effort limits the effectiveness of the Supportability project in achieving its goals. The risks are very high owing to this problem—the technology is at a low TRL, is specific to particular technologies, and lacks generality. The technology gaps identified are as follows: Component-Level Electronic Assembly and Repair Conformal coating on electronic circuit cards is conducive to neither repair nor diagnostics. Technology development is required to produce systems capable of removing and restoring coatings of arbitrary thickness or sensing parameters without disturbing the coatings. Diagnostics requires multiple types of complex instruments. Methods are required to sense and evaluate signals in such a way that the required information can be generated with a single analysis instrument. An alternative approach is to reduce the mass, power, and volume of the required diagnostic tools to an acceptable value. Minimally Intrusive Repair, Detection, and Self-Healing Systems Prototype conductive polymeric outer insulation layers are too dissipative to be used for detecting faults due to insulation failure. This is a materials issue that currently prevents fault detection via wire insulation from becoming a reality.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program The self-repair process mediated with chemically reactive microsphere fill-in wire insulation generates by-products that can accelerate the degradation of wire insulation. This is another materials problem that will require finding a reactive system which produces insulating polymers with the correct properties but no problematic by-products. Smart Coatings Remote detection of corrosion. A system is required to nondestructively detect corrosion in hidden places without the removal of paint and thermal control/protection systems that may cover the structure. This will require the use of chemical indicators, the release of detectable volatiles, or the exploitation of physical effects such as surface acoustic waves to detect the corrosion. Failure to achieve this capability might result in increased program costs; baselining will need to be carried out to verify this point. Stabilization of flame deflector refractory coatings. The current method of anchoring the refractory material to the flame deflectors has a poor performance record. Failure to develop more effective methods and materials will result in increased risks to personnel and equipment and costs to the program. Alignment with the Vision for Space Exploration: Green Flag The performance benefits from self-sufficiency with respect to maintainability and streamlined logistics will enable cost reductions in implementing both lunar and Mars exploration and thus the Supportability project work is well aligned with the VSE. 22 HUMAN-ROBOTIC SYSTEMS/ANALOGS Objective The main effort of the Human-Robotic Systems/Analogs project concentrates on reconfigurable, long-range robot vehicles and supporting technologies. This enables In Situ Resource Utilization (the unloading of the lander, the assembly/maintenance/transfer of the lunar base, longer range and longer duration of basic science investigations) and complements and/or augments astronaut safety and productivity. The plan is novel (it is unlike that used for Apollo) and aggressive (it is based around technologies not yet flown), but it appears feasible, and if it is successful it will not only enable the current Constellation Program architecture but will also significantly enhance it. Status The basic plan to coordinate the Human-Robotic Systems/Analogs project appears solid and seems to include all relevant expertise within NASA. The team has some outstanding individual members and groups, particularly at JSC in systems design and integration, at JPL in rover and vehicle development, and at ARC in software. It is not clear, however, that the members at the other NASA field centers in the plan add significantly to the effort. The NASA team stated that the technology is generally at TRL 4; it needs to be advanced to TRL 6. NASA appears to be planning to conduct almost all of the effort in-house. By ignoring external expertise, this approach may not produce the highest-quality or even the best-value product possible. The claim is that the team could not be strengthened without additional funding. However, it seems likely that the replacement of several existing components of the current team by external experts might well produce significantly superior results. Ratings Quality: Green Flag In contrast to its position in some other ETDP task areas, NASA is not the international benchmark in this technical area (robotics and human-machine systems). While the NASA team has some outstanding individuals
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program and the project leads are aware of the wider national and international research community, apart from a few small existing grants it appears that the strategy is to “go it alone.” While NASA is the clear world leader in planetary rovers and extraterrestrial vehicles and in some aspects of time-delayed teleoperation, the leading expertise in many of the other key technologies for this task lie outside NASA. It appears that the effort could benefit from a wider involvement of experts in academia and industry. However, the committee believes that the team could achieve the objectives and that it is a matter of how well or how cost-effectively the objectives would be achieved. Effectiveness in Developing and Transitioning: Yellow Flag Facilities to mature some ground-based aspects of the Human/Robotic Systems/Analogs technology are in place. However, NASA will need to provide significant additional resources if the developed technologies are to be tested in relevant environments, including in-orbit and realistic lunar environment testing. NASA seeks to transition the technology through analog testing, which integrates the testing of multiple subsystems among nine potential test sites. Analog field testing is designed to help identify technology gaps for future systems and to develop requirements for operational concepts. Detailed planning is needed to ensure that the 5-year notional plan on research and technology (RAT) studies can enable the Human/Robotic supporting technologies to achieve the desired TRLs and to ensure that these studies are relevant for all lunar considerations. (RAT studies are performed by a combined group formed of inter-NASA center personnel, collaborating with representatives of industry and academia, to conduct remote field exercises.) The main risks for meeting the current plan and schedule appear to be budgetary. This effort appears underfunded in the next 5 years or so. While the basic technology concept appears solid, significant costs are likely to arise in development and (particularly) in testing. If NASA does not make the commitment to meet these costs, the deadlines will almost certainly slip, and the effort could fail. Alignment with the Vision for Space Exploration: Green Flag The Human/Robotic technology has significant architectural benefits. It enables lower costs by employing a significantly higher percentage of lander mass in in situ operations (more of the landed mass is part of the lunar vehicles). It enables higher payload capability and lower operational risks (the lunar vehicles will robotically handle/transport/assemble high-mass and high-risk components). The technology has significant performance benefits. It enables longer and more distant (from the lunar base) missions (autonomously and with astronauts). It offers the possibility of transporting the entire lunar operation across the lunar surface, to access significantly more sites of scientific interest. The technology is generally robust to changes to the architecture (for example, exploration missions to Mars). The main issue preventing direct transfer to Mars missions is the longer time delay, which would prevent the proposed ground-based control mode for some of the robotic operations. FINDING AND RECOMMENDATION ON ETDP PROJECTS Consistent with its statement of task, the committee evaluated each of the 22 ETDP projects on the basis of the following: The quality of the research effort, taking into account the research team, contacts with appropriate non-NASA entities, and the plan for achieving the objectives; The effectiveness with which the research is carried out and transitioned to the exploration program, including progress to date, facilities, apparent gaps in the program, and the likelihood that the required TRL will be reached (the committee decided that simply noting gaps, as requested in the study task, was too narrow an objective and that gauging “effectiveness,” as defined here, was more appropriate and inclusive); and The degree to which the research is aligned with the VSE, specifically, the degree to which the program included exploration beyond the Moon.
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A Constrained Space Exploration Technology Program: A Review of NASA’s Exploration Technology Development Program Finding on Projects: The committee evaluated the 22 individual ETDP projects and rated the quality of the research, the effectiveness with which the research is carried out and transitioned to the exploration program, and the degree to which the research is aligned with the Vision for Space Exploration. The committee found that, with two exceptions, each project had areas that could be improved. In each of these three areas, the committee rated the projects using a flag whose color represents the committee’s consensus view. These ratings are indicated in the descriptions of the individual projects above and are summarized in Table 2.2. A few projects were given two flag colors owing to major distinctions between elements within a given topic. Recommendation on Projects: Managers in the Exploration Systems Mission Directorate and Exploration Technology Development Program should review and carefully consider the committee’s ratings of the individual ETDP projects and should develop and implement a plan to improve each project to a level that would be rated by a subsequent review as demonstrating “appropriate capabilities and quality, accomplishment, and plan” (green flag). TABLE 2.2 Summary of the Committee’s Ratings for Each ETDP Project with Regard to Quality, Effectiveness in Developing and Transitioning Technology, and Alignment with the Vision for Space Exploration NOTE: A few projects were given two ratings because of major distinctions between elements within a given project.