This chapter makes several observations that NASA may wish to consider as it prepares to update its draft roadmaps. These observations concern general management practices, recommendations from recent decadal surveys, an integrated approach to technology development, validation testing of models and simulations, and human factors and knowledge integration.
Roadmaps that focus on the highest-priority technologies will increase the utility of NASA’s technology development program. The Office of the Chief Technologist (OCT) has recognized the value of input from the aerospace community in developing a consensus on those priorities by asking the NRC to undertake this study. The effectiveness of the program can also be enhanced by employing proven management practices for technology development, a few of which are noted here in this interim report:
• Program stability,
• Evolutionary improvements and intermediate goals,
• Focus and flexibility,
• Flight testing and demonstration,
• Facilities, and
• Cooperative development of new technologies.
Clearly, NASA recognizes the importance of these practices and the steering committee understands that some involve issues, such as facility capability and workforce needs, that are not directly OCT’s responsibility and that are addressed in detail in other recent reports by the National Research Council (NRC), such as Capabilities for the Future: An Assessment of NASA Laboratories for Basic Research (NRC, 2010a) and Building a Better NASA Workforce: Meeting the Workforce Needs for the National Vision for Space Exploration (NRC, 2007a).
The productivity and the effectiveness of any technology development program, regardless of its size, are diminished when direction, content, and/or funding vary widely from year to year. Some redirection of effort based on program progress, results, and new understanding is expected and even encouraged, but when changes are caused by external factors or policy changes, they can be extremely disruptive and, in particular, adversely affect research funding at universities. Reconstituting lost capabilities or recovering from major changes in program direction can take years. Stability is important in the short term to avoid disrupting individual programs and in the long term to ensure that other federal agencies, industry, academia, and foreign organizations recognize NASA as a reliable partner.
Disruptions caused by reduced budgets and changing goals of space technology programs within NASA and other federal agencies can cascade from one agency to another. Reduced support by one
agency can threaten the viability and the continuation of multiagency efforts. In some cases, the resulting disruptions have led to a loss of experienced technology specialists. These losses impact NASA as well as the national aerospace community (NRC, 2009a, 2010a). Consequently, the need to restore technological capabilities across NASA, industry, and academia and to preserve stability and continuity in a core space technology program has become a national issue.
Evolutionary Improvements and Intermediate Goals
The successful development of game-changing technologies that lead to revolutionary capabilities applicable to a wide range of potential missions is a priority. In some cases, however, maintaining (or reestablishing) a technology base that produces a pipeline of evolutionary improvements over time can be important as well. For example, a steady stream of year-by-year, decade-by-decade improvements in solar-power systems has produced substantial improvements in the capabilities of solar-powered spacecraft and enables new classes of missions that could not have been conducted in past decades. In particular, the solar-powered Juno mission to Jupiter (launched on August 15, 2011) would not have been possible 10 to 20 years ago. In fact, Juno will be the first solar-powered spacecraft operating so far from the Sun. The state of the art in operational spacecraft solar arrays has evolved from the International Space Station (with panels that convert sunlight to electricity with 13 percent efficiency) to recent planetary spacecraft (with efficiencies of up to 20 percent) to the Juno spacecraft (with an efficiency of 26 percent).1 Looking ahead, new solar-electric propulsion missions are likely to become feasible as the photovoltaic power output per unit mass increases.
Conversely, some of the game-changing goals established in the draft roadmaps, such as the development of long-life rechargeable batteries with a power-to-mass ratio of 500 watt-hours per kilogram, are so advanced relative to the state of the art that no technological approach to this goal has been identified. In these situations, intermediate goals are required so that technology development can proceed with a reasonable likelihood of success.
Pursuing evolutionary improvements and setting intermediate goals have many benefits. These practices lead to time-phased applications, promote sustainable facilities and workforce within industry, and improve NASA’s ability to manage its resources and provide effective oversight.
Focus and Flexibility
Balance is needed between support of focused technological approaches and support of technologies that accommodate a wide range of destination and schedule options. When multiple technological approaches are available to address a specific, significant challenge, down-select points would allow the roadmaps to focus on whatever approaches show the most promise. However, when the ultimate application of a technology is uncertain, it is also important to use a flexible approach that can meet a range of likely future needs. For example, the draft Entry, Descent, and Landing (EDL) roadmap is focused largely on meeting the needs of a human mission to Mars. While this mission beneficially stresses and challenges the technology envelope in EDL, it would be prudent to ensure that the EDL technology under development is not tied too closely to a specific mission or destination. Technologies that enable a broad spectrum of future missions tend to be highly valued.
1 Stated efficiencies are approximate values at beginning of life at one solar radius from the Sun.
Flight Testing and Demonstration
Many of the technologies in the roadmaps need flight opportunities to test and demonstrate their performance under realistic flight conditions. Mission managers often decline the opportunity to adopt new technologies until successful flight demonstrations show that associated risks are reduced. For a technology to be adopted, it is often essential to continue technology development to the point of system demonstration under realistic mission conditions. There is a TRL gap (typically spanning TRL 4 to 6) or “valley of death” that often prevents or delays the utilization of important new technologies. Early maturation and demonstration of key technologies is a reasonable and prudent step toward mitigating cost and schedule risks (NRC, 2010b).
Examples of areas where such a capability is sorely needed include the testing of potentially game-changing new science instrument technologies, evaluation of prototype EDL technologies, and demonstration of innovative new spacecraft system technologies that could enhance performance and reduce mission costs. A variety of platforms are available to provide the needed flight testing, depending on the technology and application in question. These include high-altitude airborne flights, suborbital spaceflights, and orbital flights on low-cost launch vehicles, government or commercial spacecraft (if new technology can be tested on a secondary payload), and on the International Space Station (ISS). However, these platforms are often not available to developers because of cost and, when technology flight tests are proposed as secondary payloads or ride sharing, because the flight test package is perceived to increase the budget and schedule risk of the primary mission without contributing directly to the goals of the primary mission.
Flight test programs also provide powerful opportunities to train new members of the workforce. Flight technology demonstrations give new systems engineers and instrument scientists hands-on experience across the full span of spaceflight mission phases, encompassing design, development, fabrication, testing, integration, launch, flight operations, and data analysis over a relatively short time span and in risk-tolerant environments.
Adequate facilities are needed to validate the performance of new technologies and the models used in their development. In some cases, new testing technologies may be needed to conduct validation testing. This is generally consistent with, and reinforced in, a recent NRC report on NASA laboratory capabilities (NRC, 2010a).
Facility issues are of immediate concern for some key technologies covered by the draft NASA roadmaps. For example, the ability to conduct EDL-related technology development is closely coupled to the availability of specialized testing facilities, especially facilities for testing arcjets, which are a primary area of concern for NASA. The episodic sponsorship of new EDL mission capabilities tends to overstress facilities and their related staffs at times and then leave them underutilized for other stretches of time. Technology development could help fill the gap in facilities’ usage between missions. Dedicated experiments to validate analytical and computational models are vital. Although facility capability is outside OCT’s direct line of responsibility, a sustained in-house technology research program could help create a sustained user community for some facilities. This would help justify (1) retaining and modernizing those facilities and (2) maintaining a core capability in facility support staff. For example, NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA), supported continuous in-house research programs that provided a strong base of data and intellectual thought that was of broad interest to other branches of the government, industry, and academia because it was not tied to operational parameters of specific missions or applications. A culture change within NASA would be needed for NASA to recreate this model.
Cooperative Development of New Technologies
Programs such as the ISS demonstrate the benefit of interagency and international cooperation at the mission level. Cooperative efforts to develop new technologies are also beneficial. The development of many technologies relevant to NASA is supported and/or conducted by other federal agencies, foreign governments, industry, and academic institutions. In many cases NASA is already cooperating with other organizations to develop critical new technologies and/or adapt the results of work by others to meet NASA’s needs. NASA’s 2011 Strategic Plan confirms NASA’s intent to continue such cooperation, noting that NASA should “facilitate the transfer of NASA technology and engage in partnerships with other government agencies, industry, and international entities to generate U.S. commercial activity and other public benefits” while “expanding partnerships with international, intergovernmental, academic, industrial, and entrepreneurial communities and recognizing their role as important contributors of skill and creativity to our missions and for the propagation of results” (NASA, 2011, p. 3-5). Department of Defense research laboratories have space technology development efforts that the workshops identified as areas where collaboration with OCT would be mutually beneficial. Europe has made significant long-term investments in basic and industrial research to advance and sustain its space program. Similarly, the space programs of Japan and other Asian countries are also advancing rapidly.
NASA’s technology roadmaps would be more valuable and actionable if they provided more detail about how various goals may be accomplished through partnerships with outside organizations. With some technologies, international partnerships are hampered by limitations imposed by the current implementation of International Traffic in Arms Regulations (ITAR). Even so, technology development efforts by OCT provide a new opportunity for NASA to engage in cooperative development of new technologies. This cooperation could enable NASA to achieve more of its technological goals with available funding, in part by drawing on the available specialized expertise and prior investments made elsewhere.
Some of the draft roadmaps refer to decadal surveys that provide guidance to NASA space science programs. For example, the roadmap for TA08 (Science Instruments, Observatories, and Sensor Systems) mentions decadal surveys produced by the NRC on astronomy and astrophysics (NRC, 2010c), Earth science and applications from space (NRC, 2007b), planetary science (NRC, 2003a), and solar and space physics (NRC, 2003b). After NASA drafted the 14 roadmaps under review by this study, the NRC issued two additional decadal surveys:
• Recapturing a Future for Space Exploration: Life and Physical Sciences Research for a New Era (NRC, 2011a); and
• Vision and Voyages for Planetary Science in the Decade 2013-2022 (NRC, 2011b).
These decadal surveys address many technology needs relevant to the draft roadmaps, and the steering committee has concluded that NASA’s roadmaps would benefit from being updated with this new information. For example, the decadal survey on life and physical sciences recommends development of strategies for dust mitigation on lunar and martian surfaces that lead to practical methods for mitigating the adverse effects of dust on seals, sensors, and solar panels. As part of this effort, the report recommends performing experiments on dust accumulation, including electrostatic effects, on the ground and on the International Space Station (NRC, 2011a). Chapter 11 of the planetary science decadal survey discusses recommendations for specific technology investments related to science instruments, survival in extreme environments, in situ exploration, solar system access, and other core technologies (NRC, 2011b). Technology development guidance in the decadal surveys can help ensure that new capabilities are linked to plausible missions.
Ultimately, the development of new technologies is important only to the extent that they result in new capabilities. Many capabilities critical to the future of complex endeavors such as space science and exploration require the coordinated development of many diverse technologies. Accordingly, system analyses that identify critical technologies cutting across multiple roadmaps (as well as factors that affect multiple technologies within a single roadmap) can help NASA guide, plan, and prioritize the technology development program as a whole. This would ensure that technologies are brought to maturity at the same rate either within NASA or elsewhere. For example, the steering committee and panels identified the following four areas that would particularly benefit from an integrated approach to technology development:
• Precision landing systems;
• Guidance, navigation, and control;
• Radiation protection; and
• Launch from locations other than Earth.
Precision Landing Systems
The ability to set down at a precise, pre-selected location on a planetary surface and to avoid hazards that are detected in the landing area during descent is essential to enable advanced exploration and planetary science missions at reduced risk. Precision landing and assured hazard avoidance capabilities do not yet exist, and as a result, several missions have come very close to failure during the landing process. Viking 2 landed on a rocky plain littered with boulders, and the lander settled down with one leg on top of a boulder, which tilted the spacecraft at 8 degrees (NSSDC, 2011). Surveyor 5 landed on the edge of a small crater and one footpad slid about a meter downslope, nearly toppling the spacecraft. Each of the six Apollo Moon landings had to avoid potentially mission-ending hazards (rocks, craters, and slopes) in the landing site while simultaneously dealing with diminishing fuel reserves. To mitigate the risk posed by these hazards, mission designers restricted the choice of Apollo landing sites to those with near-ideal lighting conditions. Even so, three Apollo missions resulted in the lander settling on the lunar surface at angles of 7 to 11 degrees from the horizontal, close to the design limit of 12 degrees (Brady and Paschall, 2010).
An integrated approach that advances many diverse technologies is necessary to mitigate risks during landing. Advances in guidance, navigation, and control (GN&C), propulsion, autonomous system, sensor, and EDL technologies—as well as related engineering development—are necessary to reduce navigational uncertainty. Such advances are needed during every phase of the EDL process, to detect surface hazards, and to reposition the spacecraft during descent to overcome positional errors and/or divert to a safe location to avoid hazards, and to do all of this with a high degree of confidence. For example, on Mars one of the major problems is realizing a small enough error at the end of hypersonic entry so that subsequent control authority can compensate for it. Also, martian winds generate additional errors when aerodynamic decelerators are deployed, which requires additional control authority. Long delays or gaps in communication travel time for distant planets such as Mars or the far side of the Moon require that uncrewed spacecraft be able to accomplish these goals autonomously. On both Mars and the Moon, the final stages of landing must deal with hazards such as small craters and boulders lying on the surface. In addition, the value of a mission may be greatly enhanced if the spacecraft can land in the proximity of key features such as ice in shadowed craters, scientifically interesting targets, or in the close vicinity of cached samples for return to Earth. Also, the goals for development of precision landing technologies and mobility technologies need to be integrated because, for some missions, the need for precision landing capabilities would be mitigated by advances in surface mobility. While precision landing is clearly relevant to the EDL roadmap (TA09), technologies in the roadmaps for communication
and navigation systems (TA05); robotics, telerobotics, and autonomous systems (TA04); scientific instruments, observatories, and sensor systems (TA08); and in-space propulsion systems (TA02) all play a contributing role in the development of an integrated precision landing system.
Guidance, Navigation, and Control
Guidance, navigation, and control is a highly coupled and interdependent set of capabilities consisting of software and hardware components including advanced fault-tolerant avionics. GN&C systems provide state measurements as well as trajectory and orientation management functionality that are essential to almost all space vehicle missions. Successful control is dependent on sufficiently accurate navigation knowledge that may include inertial and/or relative state measurements as a function of specific flight activities. Successful navigation may depend on effective spacecraft orientation control. An integrated approach to GN&C is required because one roadmap (TA05) is focused on communications and navigation systems, while guidance and control show up separately in at least two other roadmaps on robotics, telerobotics, and autonomous systems (TA04) and EDL (TA09).
Astronauts must be protected from the space radiation environment to avoid adverse health risks. This requires (1) a good understanding of the radiation environment in space and on the Moon or Mars for surface missions to those destinations and (2) a good understanding of the biological effects of space radiation. Space radiation risks are primarily associated with galactic cosmic radiation (GCR) and solar particle events (SPEs). GCR, which is well characterized, consists of energetic particles from beyond and within our galaxy. SPEs consist of high-intensity bursts of energetic particles from the Sun. These events may last just a few hours or endure for several days. The intensity of GCR and the frequency of SPEs vary gradually during the 11-year solar cycle. The radiation associated with SPEs is easier to shield than the higher-energy particles from GCR. However, the timing of SPEs is difficult to predict. Very few simultaneous measurements of SPEs near Earth and at Mars have been made, and available models cannot use detailed knowledge of SPEs in the near-Earth environment to predict the SPE environment at Mars (NRC, 2009c).
The primary challenge that must be overcome to predict accurately the human health risk posed by space radiation for long-duration missions to the Moon and Mars is the large uncertainty about the biological effects of space radiation (NRC, 2009c). An integrated approach is needed in the following technology areas to meet this and related challenges associated with space radiation:
• TA02 and TA03: coordination with radiation protection measures for nuclear propulsion and power systems;
• TA03: survivability of solar power cells and other power system components in extreme radiation environments;
• TA06: astronaut health;
• TA08: instrumentation for particles, fields, and waves;
• TA10: use of boron nitride nanotubes for protection against radiation; and
• TA12: materials and structures for radiation shielding.
In addition, advanced in-space propulsion technologies (TA02) that reduced transit times to distant destination would reduce astronauts’ exposure to radiation.
Launch from Locations Other Than Earth
Launching from locations other than Earth presents a variety of key multidisciplinary challenges. Two major environmental factors must be considered: atmospheric and surface interactions. For bodies with an atmosphere, methodologies for weather and launch load prediction (acoustic, pressure, and thermal) must be established for an unfamiliar atmosphere. Additional uncertainty may be associated with potential chemical interactions between the rocket exhaust, atmospheric constituents, and spacecraft surfaces (e.g., corrosion). Surface interactions such as dust or rock blow-back should be avoided. At the vehicle level, system checkout must also be accomplished without the complex infrastructure and extensive personnel available on Earth. Vehicles that will be fueled in situ, either on another planetary body or in deep space, will require verification of the propellant load and management system, in addition to all other vehicle subsystems. New procedures and technologies will be required to accomplish these tasks and to verify the flight worthiness of space-assembled transport systems. Advances are needed in technologies related to TA02 In-Space Propulsion Technologies, TA04 Robotics, TeleRobotics, and Autonomous Systems, TA07 Human Exploration Destination Systems, TA12 Materials, Structures, Mechanical Systems, and Manufacturing, and TA13 Ground and Launch Systems Processing.
Testing to validate advanced models and simulations is critical to the successful development of level 3 technologies in many roadmaps. As noted in the discussion of technology 11.2.4. Science and Engineering Modeling (in the roadmap for TA11 Modeling, Simulation, Information Technology, and Processing), physics-based analysis tools are a high-priority challenge for NASA aerospace engineering. According to that roadmap, these tools would enable “analytical capabilities that go far beyond existing modeling and simulation capabilities and reduce the use of empirical approaches in vehicle design.” For example, predictive modeling capabilities for many technologies are at a low level of maturity or they are outdated. This is especially true in materials science. To correct this problem over the long term, technology is needed both to develop new models and to maintain, update, and validate existing models with testing. Technology advancements in modeling and simulation are beneficial only if new and updated models can be validated with accurate data, on the ground and in space, as appropriate. In some cases, new testing technologies may be needed to enable adequate assessment of important technologies in a reasonable time and at an affordable cost.
Simulation and modeling are also important to assess the performance of environmental control and life support systems (ECLSSs). This is an exceedingly difficult challenge for an ECLSS or any other system that contains liquids or gases with thermal gradients that are affected by gravity. Available data is insufficient to model accurately how these systems will function in the 1/6 g of the Moon or the 1/3 g of Mars. Data is available for performance in Earth gravity and in (near) zero gravity in Earth orbit, but in most cases performance curves between full gravity and zero gravity are unavailable. Similarly, in some cases, “biological processes that operate properly at 1 g do not in microgravity, but the threshold for restoring proper function is unknown” (NRC, 2011a, p. 4-14). Without appropriate, validated simulation and modeling for various gravity levels of interest, uncertainty regarding the performance of gravity-dependent systems for life support, thermal control, and ISRU processing—and uncertainty about the effects of reduced gravity on human health, will pose a significant risk to the success and safety of many missions. Had the Centrifuge Accommodation Module for ISS not been canceled, it could have addressed some of these issues (NRC, 2011a).
Developing advanced spacecraft systems will require additional flight data to validate many of the models used in design. However, there are few opportunities to collect flight data in relevant environments. Even when a mission opportunity arises, there is an understandable tendency for mission designers and managers to avoid the extra risk, weight, and power demands of instrumentation that does not directly support their mission objectives. It would be worthwhile for NASA to place a higher priority
on adding instruments to missions to collect the flight data to validate engineering models and simulations that could enhance or perhaps enable some future missions. The Mars Science Laboratory Entry, Descent, and Landing Instrumentation (MEDLI) and the Shuttle Boundary Layer Transition Experiment are two prime examples of flight instrumentation added specifically for model validation.
The utility of new technologies can be enhanced if human factors considerations are incorporated throughout the technology development. Developers of space technology could more easily access and understand relevant human factors considerations if (1) consolidated crew comments (on human factors, stowage, psychology, exercise, and so on) from the Apollo, Skylab, space shuttle, and shuttle Spacelab/Spacehab programs were integrated into an existing electronic ISS data base and (2) NASA Standard 3001 and the Apollo-ISS crew databases were made accessible to all U.S. developers of exploration technology. This information could, for example, have a significant impact on spacesuit and habitat design. It might also be worthwhile to integrate human factors requirements and experience into roadmap TA04 Robotics, TeleRobotics, and Autonomous Systems (for human-robot compatible designs), TA06 Human Health, Life Support, and Habitation Systems, and TA07 Human Exploration Destination Systems.
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