4
Considerations Regarding the BR Context

The National Aeronautics and Space Administration’s (NASA’s) human space flight program has attained one of the world’s greatest technological achievements: landing humans on the Moon. In 1966, at the height of the Apollo program, NASA received 4.4 percent of the total federal budget; today NASA receives less than 0.7 percent. Now NASA is poised to attempt missions of even greater visibility and risk. It is in this clash of performance expectations and budgetary constraints that the Bioastronautics Roadmap (BR) was created. This presents unique challenges (and opportunities) for NASA. This chapter considers the BR in the context of the pressures—internal and external to NASA—that generate additional risk for human space flight.

ORGANIZATIONAL CHARACTERISTICS AND RISK

The risks identified in the BR occur in the context of a larger set of risks to the human space flight program and to NASA as an organization. Highly visible failures, such as the loss of the Space Shuttles Challenger and Columbia, have the potential to erode public confidence in—and congressional support for—human space flight and NASA as an agency.

Although the presidential initiative announced in January 2004 (White House, 2004) has added impetus and focus to the goals of NASA, under certain circumstances it could add an additional risk—pressure being applied to achieve the goals of the initiative without sufficient time or re-



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap 4 Considerations Regarding the BR Context The National Aeronautics and Space Administration’s (NASA’s) human space flight program has attained one of the world’s greatest technological achievements: landing humans on the Moon. In 1966, at the height of the Apollo program, NASA received 4.4 percent of the total federal budget; today NASA receives less than 0.7 percent. Now NASA is poised to attempt missions of even greater visibility and risk. It is in this clash of performance expectations and budgetary constraints that the Bioastronautics Roadmap (BR) was created. This presents unique challenges (and opportunities) for NASA. This chapter considers the BR in the context of the pressures—internal and external to NASA—that generate additional risk for human space flight. ORGANIZATIONAL CHARACTERISTICS AND RISK The risks identified in the BR occur in the context of a larger set of risks to the human space flight program and to NASA as an organization. Highly visible failures, such as the loss of the Space Shuttles Challenger and Columbia, have the potential to erode public confidence in—and congressional support for—human space flight and NASA as an agency. Although the presidential initiative announced in January 2004 (White House, 2004) has added impetus and focus to the goals of NASA, under certain circumstances it could add an additional risk—pressure being applied to achieve the goals of the initiative without sufficient time or re-

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap sources for adequate preparation—that could compromise mission safety. Pressure could increase when critical biomedical research is delayed by a disaster-related response, such as the one that occurred after the loss of the Challenger. Thus, to the technical risks of space flight, the President’s initiative has added the organizational risk that elements of the BR might be compromised in an effort to meet a societal goal. The single most substantial organizational risk that NASA faces may be the possibility that a thoughtfully conceived roadmap could be preempted or abandoned as a result of such pressures or of an abrupt change in policy direction. Like the Challenger investigation, the Columbia Accident Investigation Board Report (CAIB, 2003) highlighted an inadequate safety culture within NASA leading to human performance failure. Figure 3.1 was included in this report because it illustrates the remarkable lack of agreement among a knowledgeable group of evaluators who were asked by NASA to address the question, How worried would you be about this risk if we were to go to Mars today? The responses were widely distributed, and mean or median values for such data would appear to be of little or no value. One of the key lessons from the Challenger and Columbia events was the importance of listening to even a single voice, if that voice came from a knowledgeable source, rather than responding to the “group mean” regarding risk. These topics are conspicuously absent from the current version of the BR. Furthermore, differences in the organizational culture, and thus the safety culture, of the international space agencies participating in the International Space Station (ISS) or any of the future Design Reference Missions may exacerbate conflict both within crews and between crews and mission control, increasing the risk of human performance failure (NRC, 1998; Kanas et al., 2000). Support for this thesis is garnered from studies in analog environments, such as submarines (Wilken, 1969; Thomas et al., 2000) and Antarctic expeditions (Wood et al., 1999; Palinkas et al., 2004) that have noted cultural differences in interpersonal relations and adaptation to prolonged isolation and confinement as being relevant to BR Risks 24 and 25 (human performance failure due to poor psychosocial adaptation and human performance failure due to neurobehavioral problems) and, ultimately, to human performance failure. There is a need to ensure close collaboration between NASA researchers, university- and foundation-based researchers, and operational personnel. Successfully implementing the BR will require working through or around this problem, bringing in various stakeholders (Palinkas et al.,

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap 2005). The committee was especially sensitive to the relationships among internal NASA scientists, external investigators, and operations personnel, and these relationships were a prominent theme in many of the deliberations that led to the conclusions and recommendations in this report. Each of these communities feels, to some extent, that the other communities do not adequately appreciate their concerns or viewpoints, but this results in a creative tension that is highly appropriate because it brings advocacy to views that need to be represented in the risk analysis and mitigation approaches that make up the BR specifically, and the overall NASA bioastronautics program in general. The committee concludes that these organizational and cultural factors can have important consequences for crew safety and mission success and thus represent risks that should be considered in the BR. Recommendation 4.1 The committee recommends that an additional risk labeled “human performance failure due to organizational and cultural factors” be added to the BR. It may prove optimal to track this risk in a manner differently from the other risks in the BR (e.g., annual analyses of organizational and cultural risk in a separate report, use of an external standing panel to discuss this issue regularly). The committee’s intent is that a risk-focused analysis of organizational and cultural issues become a visible part of the BR process. ANALYSIS AND PRIORITIZATION TO MEET THE LAUNCH SCHEDULE As a result of the President’s space exploration initiative, NASA has proposed a schedule that requires considerable resources. Prospective funding, up-mass (determined by the type of launch vehicle), power, available equipment, and crew time (both number of crew and their availability to participate in bioastronautics research) are limited resources that directly affect NASA’s ability to utilize the BR to reduce risk. One example of constrained resources concerns the variety of countermeasures that are suggested for the inherent physiologic problems associated with exposure to the space environment for the period of time necessary to support the Design Reference Missions. Life support equipment

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap that functions in microgravity for prolonged periods will have to be designed and tested, medical procedures that can be performed in a microgravity environment have to be created, and regenerative life support systems must be designed and built. For the above technologies, procedures, and capabilities to achieve a Technology Readiness Level (TRL) of 7, by definition these systems must be tested in an “operational environment” (i.e., a microgravity environment). It is almost axiomatic that the efficacy of alternative countermeasures—assuming the crew transits under microgravity conditions—can be tested only in an environment of microgravity. Therefore, the general problem of insufficient microgravity flight time, where such systems are tested and capabilities are validated for exploration class missions, becomes a formidable challenge. A similar concern exists for validation of systems and countermeasures in lunar and martian gravity. Currently, various constraints—created by NASA or external to it, such as the Iran Nonproliferation Act of 2000—limit the International Space Station to a maximum of two (soon to be three) crew members. Routine maintenance of the ISS occupies the vast majority of a crew’s time (NRC, 2002), leaving insufficient time for significant research activities, much less the effort that would be required to achieve a TRL of 7 for needed procedures. Furthermore, the committee is concerned that the planned ISS life span may not be sufficient to accommodate the necessary research or technology development and validation that will be necessary to enable the exploration vision. Finally, even if ISS support is extended and the crew size is augmented, it still may not fully meet the demands for the research that will be needed to support the Design Reference Missions. For example, without a test facility that closely duplicates the ambient pressure and partial pressures of gases to be found in the Crew Exploration Vehicle (CEV), appropriate decompression procedures for extravehicular activity (EVA) and space suit activities cannot be validated in an operational environment. Without a suitable low Earth orbit (LEO) research facility, it is not clear how NASA will be able to accomplish the research studies that are likely to be required to support the Mars initiatives. Projects with extremely long lead times are particularly vulnerable to problems with research prioritization. Consider the derivation and validation of the select-in and select-out criteria for the crew selection process described in Chapter 2. In order to derive such selection criteria, long-duration isolation experiments under conditions of stress—using astronauts or astronaut surrogates as experimental subjects—would have to be per-

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap formed during the derivation phase (Countermeasure Readiness Level, CRL, 1–3). A prospective validation phase would then be necessary (CRL 4–7). Such experiments would then have to be repeated to achieve a meaningful sample size (also requiring long-duration experiments with astronauts or their surrogates). It would be optimistic to believe that the first set of derived criteria would be successfully validated; therefore, several attempts at select-in and select-out criteria would be necessary (CRL 7–9). Similarly, a decision to select a multicultural or mixed-gender crew for long-duration space flight appears likely. The evidence suggests that interpersonal dynamics are influenced substantially by factors such as cultural composition (Lozano and Wong, 1995; Kozerenko et al., 1999; Kring, 2001). Such team dynamics are important factors influencing the success of the expedition. Homogeneous teams appear to work better together than diverse teams (Chatman, 1991; Chatman et. al., 1998). If this experience is considered relevant to crew selection, the ISS or appropriate mission simulations would have to serve as test facilities to validate relevant select-in and select-out criteria for human planetary exploration. It is not clear to the committee that select-in and select-out criteria could be successfully derived, validated, and implemented by the time human exploration beyond LEO commences. Another example of a long-lead-time project concerns the question of whether an artificial gravity environment will be necessary to maintain crew health during a 30-month Mars mission. At issue is the fact that the 0.38g gravitational field of Mars cannot be simulated on Earth for more than a few seconds. Long-term simulations are possible using a centrifuge in the free-fall environment of the ISS. Such a facility—designed to fully support habitats for research rodents—is scheduled to launch in 2008 or later. However, this program is under consideration for cancellation as a result of budgetary constraints. Without this enabling research, it is entirely conceivable that astronauts would land on Mars without any evidence-based assurance that the martian gravitational field would provide sufficient musculoskeletal loading to ameliorate continued bone demineralization. Alternatively, large sums might be spent needlessly on developing a more complex rotating Mars spacecraft. An ambitious and appropriate research program has been proposed by NASA in the BR. In view of the fact that the nation’s most important test facility for human space flight research—the ISS—is constrained by time, up-mass, research facilities, escape capabilities, power, and crew availability

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap (NRC 2002; RAND, 2002), the committee concludes that resources are insufficient to perform the additional work necessary to mitigate the risks identified in the BR to acceptable levels. Recommendation 4.2 The committee recommends that NASA perform regular, detailed assessments of the additional risks to the conduct of the President’s 2004 vision for space exploration posed by the lack of available resources to fully address the issues posed in the BR. This assessment should then be used to make early strategic decisions regarding issues such as, but not limited to, the following: 1. How to provide support for a microgravity research platform that will have the resources (crew time, up-mass, facilities, and power) for the large amount of work necessary to validate countermeasures; achieve Technology Readiness Level 7 for life support systems sufficiently early in the design phase to allow their integration into the overall vehicle; and demonstrate the utility of medical procedures in microgravity. 2. How to support the extensive behavioral research program that would be necessary to validate processes or countermeasures such as select-in–select-out criteria (both for individual crew members and for a composite crew), issues related to cultural diversity, crew interactions, and isolation or stress-induced hazards. These issues may well require long lead times to study adequately. ADDRESSING THE CHALLENGES POSED BY THE SMALL SAMPLE SIZE A number of criteria can be considered in flight crew sizes: (1) resource requirements such as funding, vehicle capacity, and mission objectives; (2) standards for assessing quality control or hardware reliability; and (3) statistical power for performing research. Given the importance that NASA places on each of these criteria, the committee recognizes that NASA must consider all three sets of factors when determining crew sizes. Regardless of which criteria are used to derive crew sizes, achieving

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap statistically valid results using flight crews will be a daunting problem.1 In general, very small sample sizes make it impossible to state either quality control or research findings with reasonable confidence intervals or to compare alternatives using tests of statistical significance. The committee recognizes that health-related studies based on observations of space mission crews will, for the foreseeable future, suffer from small sample size. Consequently, inferences based on single missions will have inadequate statistical power unless, in the context of reliability analysis, the problem under study is so prevalent that it is detected in the first few subjects (Virzi, 1992; Lewis, 1994). Methods are available to address this problem, including the pooling of data from multiple studies or missions in the manner of sequential clinical trials (IOM, 2001) and Bayesian sequential trials. The committee proposes that rather than rely on data from a single mission for inference, NASA analyze data pooled from several missions. More specifically, the committee proposes that studies be designed to incorporate as many missions as possible, somewhat in the manner of sequential clinical trials, and also that they incorporate prior information from archival data and ground-based studies to the extent practicable. In a Bayesian framework, a prior uncertainty distribution for extent of bone mass loss as a function of age, gender, and time in space, for example, would be incrementally modified by new information gained from—and incidental to—a series of missions. The goal would be to develop a sequence of posterior distributions about the 1   By way of example, managers of NASA’s bioastronautics program have tried to determine whether sufficient astronaut subjects will be available to conduct the forward research needed to successfully mitigate the risks imposed by the Design Reference Missions. A workshop was convened in Houston, Texas, in May 2004 to estimate the requirements for human subjects in exploration research. Representatives of the extramural and intramural research communities, flight surgeons, astronauts, bioastronautics management, and ISS payload planners attempted to derive realistic guesses of the minimum number of subjects that would be needed to mitigate each BR risk to an acceptable level. Without a priori calculation of statistical power, they concluded that at a minimum, 1,025 data points would be required to complete the logistical tasks associated with the current BR, with the majority (71%) derived from in-flight experiments. In the best case (i.e., if each ISS crew member participated in six experiments, the experiments did not interact, and they were performed without loss of data), at least 120 astronaut subjects would be required, nearly double the total number of ISS crew members expected for the rest of its useful life. (This assumes a three-person crew rotating every six months; this estimate and the utility of the resultant data would be further affected by changes in the size of the crew or the length of their sortie.)

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap quantity of interest, the last of which would always summarize the current accumulated information (see Appendix E for more details). Recommendation 4.3 Drawing on the findings of the Institute of Medicine report Small Clinical Trials: Issues and Challenges (IOM, 2001), the committee recommends the use of pooled data from Bayesian sequential trials techniques and hierarchical random or fixed effects methods to compensate for the small sample sizes associated with individual flights. EFFICIENCY AND TECHNOLOGY ISSUES Bioastronautics is a focused effort to enable human exploration of space through effective risk management solutions and innovative science and technology discoveries (NASA, 2003). The BR states that the roadmap is the framework used to identify and assess the risks of crew exposure to the hazardous environments of space (NASA, 2005, p. 1). Later, risk is defined more broadly as the conditional probability of an adverse event from exposure to the space flight environment (NASA, 2005, p. 12). The lack of specific reference to crew exposure in this second definition has the potential to produce confusion and misinterpretation of the BR. The BR states that it “guides the prioritized research and technology development that, coupled with operational space medicine, will inform: (1) the development of medical standards and policies; (2) the specification of requirements for the human system; and (3) the implementation of medical operations. The BR provides information that helps (1) establish tolerances (i.e. operating bands or exposure limits) for humans exposed to the effects of space travel and develop countermeasures to maintain crew health and function within those limits, and (2) develop technologies that make human space flight safe and productive.” In this context, it is inappropriate to have the BR address any other aspect of technology development that is not directly tied to crew exposure to the hazardous environments of space. The committee concludes that evaluating “efficiency risks” is relevant to the BR only when it relates specifically to crew exposure to the hazardous environments of space. A more precise definition of “efficiency” may clarify the problem. Often, the BR uses the term “efficiency” ambiguously. Generically speaking, efficiency represents “the ratio of the effective or useful output to the total

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap input in any system.”2 However, the efficiency risks described in the BR are described better by the term “economy,”3 which represents savings realized by optimizing resource utilization. In the context of the BR—like many other space systems engineering problems—resources can be defined by six metrics: mass, volume, power, reliability (time), complexity, and consumables. These are legitimate system-level considerations, but the types of risks associated with thinking about these questions are quite different from those associated with crew exposures to hazards. The systems engineering approach required for exploration results in a solution that is economical in each of these dimensions. However, several of these dimensions are pre-defined for the human system. Thus, the risk management principles applied to such technology development will be different. For example, project risk management principles typically drive system engineering (Royer, 2002), and safety risk management principles typically drive the development of hardware and infrastructure in which and with which humans will interact. The committee does not support the notion that risks associated with crew exposure to the hazardous environments of space and resource risks and constraints can credibly be addressed in parallel in the same management process. The proper time sequence is to address risks associated with crew exposure to the hazardous environments of space and continuously update the data available to a higher-level risk management process that makes more and more informed decisions about the value of accepting or further mitigating a risk. Resource constraints are appropriately addressed at this higher (programmatic) level, and these decisions feed back into overall systems designs, which are adjusted as needed to accommodate the total acceptable programmatic risk. This may well involve substantial engineering research and development to produce more effective or efficient system components, which is a key element of the spiral design concept that NASA has adopted for its exploration vision. However, the fundamental difference between the technology systems (e.g., vehicles; equipment; food preparation and delivery systems; clothing; air production, purification, conditioning, and distribution) and the human system is that the human system cannot be “reengineered” or redesigned in the same manner as mechanical components. In this sense, human risks drive all other systems development, with little room for adjustment. 2   http://dictionary.reference.com. 3   http://dictionary.reference.com.

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap The committee concludes that system efficiency concepts in the BR must focus on risks of adverse crew health events associated with technology and system failures. Recommendation 4.4 The committee recommends that the current definition of risk be altered to clearly identify at least two types of risks: (1) health and medical risk, defined as the conditional probability of an adverse event to the human system (i.e., crew health or medical event) resulting from exposure to the space flight environment, and (2) engineering technology and system performance risk, defined as the conditional probability of an adverse event resulting from the space flight supersystem that affects crew health or mission success. THE CASE OF ADVANCED HUMAN LIFE SUPPORT The engineering and system technology risks found in the advanced human life support category are linked clearly to human health risks. Advanced human life support comprises food and life support systems, environmental monitoring and control systems, and EVA technologies and the human factors related to these technologies. In the area of Advanced Human Support Technologies, NASA faces challenges that may be divided into two areas: (1) determination of the optimal technology and (2) engineering development and qualification of the hardware, software, and operational procedures required to realize the system’s performance. Neither of these challenges is associated directly with crew health risks, except through the development of medical and toxicological requirements that advanced human life support technologies must meet. Notwithstanding the recommendation above (i.e., that the BR should be focused only on engineering technology and system performance risks related to the conditional probability of an adverse crew health or medical event resulting from the space flight supersystem), the committee provides some discussion here of the two challenges. Determining the optimal technology involves interrelated studies of the medical and toxicological, physical, chemical, and biological sciences and to date has built on accumulated experience. In the context of long-duration missions, ensuring highly reliable performance of technologies will depend on two principal means of verification: stress testing and full-

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap duration life testing. In the former approach, relevant environmental factors are made more stressful (e.g., hotter or colder than normal) to permit evaluation of long-term performance in a short period of time. The “full-duration” approach is to build the apparatus and operate it within normal limits for an extended period of time, preferably several times the actual requirement. (As mentioned previously, in order to achieve a TRL of 7, this testing should be performed in a relevant environment.) Coupled with failure analysis and remediation, the full-duration approach gives the greatest confidence. To accomplish this sort of qualification with advanced life support systems, accumulated operational experience with such systems or their immediate predecessors is necessary.4 With regard to the underlying requirements for human health and performance that drive the operating parameters of advanced human life support systems, the committee believes that more attention must be paid to risks related to environmental factors associated with long-term missions, such as analyses of air and water quality, and factors related to crew cabin and EVA (e.g., suit, rover) atmospheric composition and pressure. Current operating parameters are derived from terrestrial standards and ground- and space-based operational testing environments available to date (including the ISS). The committee found neither sufficient analysis of the research required to fully determine the operational characteristics for advanced life support system technologies for the Design Reference Missions nor evidence within the BR that justifies the use of terrestrial parameters for these missions. REFERENCES CAIB (Columbia Accident Investigation Board). 2003. Columbia Accident Investigation Board Report. On-line [available: http://www.caib.us]. Accessed 4/18/05. Chatman JA. 1991. Matching people and organizations: selection and socialization in public accounting firms. Administrative Science Quarterly 36(3): 459–484. 4   The Russian-built Elektron oxygen generator is a case in point. A U.S.-designed and built system using more advanced technology awaits launch in mid-2008. The United States is engaged in adapting the Russian system rather than using the intervening time to qualify the U.S. apparatus.

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap Chatman JA, Polzer JT, Barsade SG, Neale MA. 1998. Being different yet feeling similar: the influence of demographic composition and organizational culture on work processes and outcomes. Administrative Science Quarterly 43(4): 749–780. IOM (Institute of Medicine). 2001. Small Clinical Trials: Issues and Challenges. Washington, DC: National Academy Press. Kanas N, Salnitskiy V, Grund EM, Gushin V, Weiss DS, Kozerenko O, Sled AD, Marmar CR. 2000. Interpersonal and cultural issues involving crews and ground personnel during Shuttle/Mir space missions. Aviat. Space Environ. Med. 71(9 Suppl): A11–A16. Kozerenko OP, Gushin VI, Sled AD, Efimov VA, Pystinnikova JM. 1999. Some problems of group interactions in prolonged space flights. Hum. Perf. Extreme Environ. 4(1): 123–127. Kring JP. 2001. Multicultural factors for international spaceflight. Hum. Perf. Extreme Environ. 5(2): 11–32. Lewis JR. 1994. Sample sizes for usability studies: additional considerations. Human Factors 36(2): 368–378. Lozano ML, Wong CK. 1995. Human factors concerns for international partners in a Space Station environment. American Institute of Aeronautics and Astronautics Space Programs and Technologies Conference, Huntsville, AL, September 26-28. Herndon, VA: AIAA Publications Customer Service. NASA (National Aeronautics and Space Administration). 2003. Bioastronautics Strategy. On-line [available: http://spaceresearch.nasa.gov/docs/BioastronauticsStrategy.pdf]. Accessed 5/18/05. NASA. 2005. Bioastronautics Roadmap—a risk reduction strategy for human space exploration. On-line [available: http://ston.jsc.nasa.gov/collections/TRS/-techrep/Sp-2005-6113.pdf]. Accessed 1/6/2006. NRC (National Research Council). 1998. A Strategy for Research in Space Biology and Medicine into the Next Century. Washington, DC: National Academy Press. NRC. 2002. Factors Affecting the Utilization of the Insternational Space Station for Research in the Biological and Physical Sciences (TGRISS Phase II). Washington, DC: National Academy Press. Palinkas LA, Glogower F, Dembert M, Hansen K, Smullen R. 2004. Incidence of psychiatric disorders after extended residence in Antarctica. Int. J. Circumpolar Health 63(2): 157–168. Palinkas L, Lawrence A, Allred CA, Landsverk JA. 2005. Models of research—operational collaboration for behavioral health in space. Aviat. Space Environ. Med. 76 (1 Supp.): B52–B60. RAND. 2002. RAND Perspectives on ISS Budget Issues. Arlington, VA: RAND Science and Technology Policy Institute. Royer PS. 2002. Project Risk Management Principles: A Proactive Approach. Vienna, VA: Management Concepts, Inc. Thomas TL, Hooper TI, Camarca M, Murray J, Sack D, Mole D, Spiro RT, Horn WG, Garland FC. 2000. A method for monitoring the health of U.S. Navy submarine crewmembers during periods of isolation. Aviat. Space Environ. Med. 71(7): 699–705. Virzi RA. 1992. Refining the test phase of usability evaluation: How many subjects is enough? Human Factors 34(4): 457–468.

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap White House. 2004. President Bush announces new vision for space exploration program. Remarks by the President on U.S. space policy. On-line [available: http://www.whitehouse.gov/news/releases/2004/01/20040114-3.html]. Accessed 5/26/05. Wilken DD. 1969. Significant Medical Experiences Aboard Polaris Submarines: A Review of 360 Patrols During the Period 1963–1967. Report No. 560. Washington, DC: Naval Submarine Medical Research Library. Wood JA, Lugg DJ, Eksuzian DJ, Hysong SJ, Harm DL. 1999. Psychological changes in 100-day remote Antarctic field groups. Environment and Behavior 31: 299–337.

OCR for page 73
A Risk Reduction Strategy for Human Exploration of Space: A Review of NASA’s Bioastronautics Roadmap This page intentionally left blank.