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Annual Report 1991: Appendix Space Studies Board Annual Report—1991 Appendix Prior Year Letter Reports on the Space Station In February 1991, the Board assessed the results of the 1990/1991 redesign of the Space Station and described the results of the study in a letter to NASA Administrator Richard Truly in a letter dated March 14, 1991. This report followed a series of letters on the space station program that began with a request for an assessment of the station's scientific potential by Administrator James Beggs in 1983. This was followed by additional reports on aspects of the program prepared and delivered in 1987, 1989, and 1990. Since the later reports elaborate and extend advice in the previous correspondence, it is helpful to have these earlier documents available for reference. To meet this need, the texts of these forerunner letters are provided here for convenient use. Section A.1 provides the original letter and attachments to Administrator Beggs in 1983 on the general place of the manned orbital laboratory within the space science planning of the time; section A.2 is a letter sent to Space Station REPORT MENU Program Manager Andrew Stofan in 1987 on life sciences requirements; section NOTICE A.3 provides further information on these issues; and section A.4 presents a letter FROM THE CHAIR CHAPTER 1 to Assistant Associate Administrator Joseph Alexander on the subject of cabin CHAPTER 2 atmosphere for the station. CHAPTER 3 CHAPTER 4 These earlier letters furnish the background for the Board's 1991 study CHAPTER 5 and resulting Board advice reproduced in section 4.1. APPENDIX A.1 Report to Administrator Beggs: 1982 Thomas M. Donahue, Chairman of the Space Science Board, sent the following letter to James M. Beggs, NASA Administrator, on September 13, 1982. The Space Science Board appreciates that it had the opportunity to meet with you and to discuss, among other things, the space station concept. We share your view that initiating such a program will require a national commitment file:///C|/SSB_old_web/an91append.htm (1 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix based on considerations that range beyond its use in support of either space science or applications. Nevertheless, we believe that if a station is developed it should be compatible with the objectives of space science to the degree that those requirements do not unreasonably increase the station's cost or substantially limit its ability to meet other national objectives. As you know, the Board has no position with regard to a space station; the Board, however, accepts the opportunity to set forth the technical capabilities required in order to address the objectives of the Board's scientific strategies. We believe that these requirements should be considered during the conceptual definition phase of any space station system. The Board emphasizes, however, that effective utilization of a space station system addressing these objectives will depend on the availability of resources beyond those required for the development of the space station. An adequate capability to support space science objectives for the next two decades already exists in the Space Shuttle augmented with appropriate upper stages. On the other hand, the current level of support for some disciplines is not sufficient for a viable program whether based on the shuttle or a future space station. Under these circumstances, the Space Science Board is apprehensive about the possible adverse consequences of the cost of a space station on the national capability for conducting a vigorous scientific program during the next two decades. The degree to which a space station system would afford opportunities for significant advances in space science depends on the extent to which: 1. Viable space science research is maintained, and important experimental and theoretical endeavors in space science are continued and initiated while the space station system is being developed. If a space station is to have a strong scientific component, financial support for scientific activity must be assured and protected during the course of station development, construction and operation. 2. The operational space station system provides a sufficient number and variety of space science flight opportunities, many involving unmanned spacecraft, on an appropriate time scale. 3. The operational system provides the necessary space platform environments and capabilities, such as low contamination and adequate pointing accuracy, required for space science observations. 4. The necessary capabilities for carrying out space science observations, including achieving the required Earth orbits and reaching extraterrestrial targets, are an integral part of the space station system and not a later or lower priority development. I have asked the Board's Committees to consider the requirements their scientific strategies would impose on a space station system and expect to have file:///C|/SSB_old_web/an91append.htm (2 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix at least a preliminary compilation of those requirements at the time of the Board's next meeting in November 1982. Signed by Thomas M. Donahue Chairman, Space Science Board A.2 Report to Administrator Beggs: 1983 Thomas M. Donahue, Chairman of the Space Science Board, sent the following letter and attachments to James Beggs, NASA Administrator, on September 9, 1983. Last September the Space Science Board agreed to work with NASA in determining the technical capabilities a space station should have in order to address effectively the scientific objectives of the various space science disciplines. During the past year, the Board and its committees have had frequent interactions with the NASA Space Station Task Force, led by John Hodge, in fulfilling that commitment. We have been very favorably impressed by the careful consultation with the community of potential space station users that NASA has maintained during this exercise. In due time, we plan to transmit to you formally the results of the past year exercises by the Board and its committees. Mr. Hodge has briefed the Board concerning the characteristics of the space station now being proposed by NASA. In the reports enclosed with this letter, the Board addresses two separate issues. The first issue is the degree to which the space station now being considered will be required in order to reach the objectives of the Space Science disciplines during the next twenty years. This evaluation, in the Board's opinion, must be made in the light of the adequacy of the presently available space transportation system to meet space science needs without augmentation by the proposed space station capabilities. Our finding is that present systems are adequate to these needs. Therefore, on the issue of meeting the needs of space science, our recommendation would be to use the space shuttle, together with requisite upper stages, maneuvering and propulsion systems for missions to be flown during this century. To meet longer range science objectives, a space station might prove to be very useful in various ways if it were suitably designed. The Board would be happy to work with you to define such a space station if you proceed with plans for it. As we pointed out in our letter of September 13, 1982, the Board agrees with you that the question of whether to go forward with a space station is not apt to be made on the grounds of its usefulness to space science and applications alone. Thus, the report entitled Space Science Board Assessment of the Scientific Value of a Space Station should not be regarded as establishing a file:///C|/SSB_old_web/an91append.htm (3 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix Board position on the question of whether the nation should or should not now or in the future develop such a space station. On the other hand, the Board has considered some additional issues that lie within its competence. These have to do with conditions that should exist as any space station is being developed and after it becomes operational, if a healthy and vigorous space science program is to be maintained concurrently. A discussion of these issues is the content of our second report, Space Science in a Space Station Era, which is also being forwarded to you with this letter. Signed by Thomas M. Donahue Chairman, Space Science Board SPACE SCIENCE BOARD ASSESSMENT OF THE SCIENTIFIC VALUE OF A SPACE STATION During the past year, the Space Science Board has examined the question of what space systems are required to launch and support adequately the space science missions designed to attain the high priority science objectives identified by the Board and its committees. These missions are very numerous, challenging, and exciting. However, the rate at which they are launched would have to increase significantly above the current rate if all of the missions needed to fulfill this program are to be flown during the next two decades. The means of launching and tending them is now available or being developed in the form of expendable launch vehicles and the space shuttle, augmented as required by adequate high energy upper stages. One reason for the present slow pace is the delay in bringing the shuttle and its upper stages to full operational status. Another is that we have not yet learned how to use the shuttle efficiently and effectively as a manned orbiting laboratory. The Space Science Board urges that the present launch systems be fully and flexibly exploited and adequate resources be brought to bear so that the stated objectives of space science can be reached in a timely fashion. The results of following this course should be a rich harvest of discoveries and insights in all disciplines of space science. The Space Science Board has carefully examined the proposal by NASA for a manned space station in low Earth orbit designed to engage in a number of major activities. A significant portion of these activities involves support of space science missions. The Board has also examined the set of specific missions proposed for implementation from the space station system during the years 1991-2000. It has found that few of these missions would acquire significant scientific or technical enhancement by virtue of being implemented from this space station. In view of this and the adequacy of the present space transportation system for the purposes of space science, the Board sees no scientific need for this space station during the next twenty years. In the longer term, the Space Science Board sees the possibility that a suitably designed space station could serve as a very useful facility in support of file:///C|/SSB_old_web/an91append.htm (4 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix future space science activities. Such a space station could provide means for erecting and fabricating large and novel structures in space, and for servicing, fueling, and retrieval of payloads in orbit. If NASA wishes to develop plans for such an ambitious and technically demanding space station for the next century, the Space Science Board would be pleased to work with NASA in defining the properties of such a space station. SPACE SCIENCE IN A SPACE STATION ERA In a recent statement entitled, "Space Science Board Assessment of the Scientific Value of a Space Station," the Space Science Board has addressed the issue of the space science need for a space station. It found no need for a space station to support missions addressing high priority science issues for the next two decades. On the other hand, it found that a suitable space station could offer important services to space science in the more distant future. The Space Science Board realizes that the nation may decide to commit itself to the deployment of a space station in support of needs and objectives other than or in addition to those of space science alone. The characteristics of such a space station should be carefully determined to conform to the principal activity that it is intended to support. For example, it is not obvious that a space station optimized as a transportation node for travel between the Earth and other solar system objects would also be an entirely suitable platform from which to launch and support science and applications missions. Whatever the eventual properties of such a space station, there will probably be a set of high priority science missions that require orbits and operational support for maximum effectiveness other than those available from that station. If a space station program should be undertaken and it is meant to be useful to space science, the Space Science Board urges that the means to initiate and operate space science missions in a timely fashion and in reasonable accord with priority ordering of those missions be maintained. Ordering of missions would then be determined by scientific priority rather than the nature of the launch or support system required. The Board also urges that the scientific program be structured so as to be protected from delay in space station development or changes in its capability. The Board also wishes to make the following specific recommendations and observations. Scientific instruments that can be deployed in orbits compatible with space station orbits should be flown in optimal scientific orbits and on separate platforms if that is necessary to preserve them from contamination, interference, and degradation of pointing stability and control that may be associated with the manned modules. If the space station is designed to provide a servicing capability beyond that provided by the shuttle, that capability should allow retrieval of instruments from a wide variety of orbits. file:///C|/SSB_old_web/an91append.htm (5 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix The deployment of a space station designed in part to support space science implies an increase in the level of space science activity above that presently planned. If such a space station is to be utilized effectively, the space station system should be accessible and affordable for scientific use, and there should be a real increase in the level of support for that activity. A commitment by the nation to long duration human space flight, whether in Earth orbit or beyond, calls for the establishment of a facility for space biological and medical research on the effects on individuals of very long exposure to the "low g" environment. In this sense, the relationship of the life sciences to a space station is a special one. Thus, a manned space station could eventually provide significant opportunities for a number of disciplines in space science provided there is a commensurate increase in the total level of space science activity. Realization of those opportunities would depend on the extent to which the capability to carry out space science research is kept viable, important experimental and theoretical activity is continued, and new endeavors are initiated while the space station is being developed. After the space station becomes operational, realization of those opportunities would depend on the provision of a sufficient number and variety of flight opportunities, many involving unmanned space craft and flight to regions of space near the Earth and further out in the solar system at distances and locations inaccessible to a manned platform. A.3 Report to Space Station Program Manager Stofan: 1987 L. Dennis Smith, Chairman of the Committee on Space Biology and Medicine, sent the following letter to Andrew Stofan, NASA Associate Administrator for the Office of Space Station, on July 21, 1987. The Space Science Board's Committee on Space Biology and Medicine has recently published a report: A Strategy for Space Biology and Medicine for the 1980's and 1990's. In it, we have made two very strong recommendations for the space station: (1) a Variable Force Centrifuge of the largest possible dimensions, and (2) a Dedicated Life Sciences Laboratory. As NASA is actively engaged in planning the design of the space station and making decisions about its initial configuration, we felt compelled to bring these recommendations to your attention while there is still time to affect these decisions and to maximize the station's usefulness to space biology and medical research. Unlike the more traditional space sciences, which are primarily observational with essentially no control of the phenomena under study, space file:///C|/SSB_old_web/an91append.htm (6 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix biology and medicine require interactive experimental approaches. Establishment of new ideas frequently requires intervention in experimental design during the course of experiments, often resulting in modification of hypotheses and generation of new ideas. A permanently occupied Space Station will, for the first time, permit relatively long-term laboratory experiments to be performed in a microgravity environment using the empirical methods so successfully employed in hundreds of laboratories on Earth. In this sense, the necessity of a space station for life sciences research is unique. The field of space biology and medicine is in its infancy. It has been based on ground-based research coupled with limited flight opportunities which, in some disciplines, has allowed the generation of models. They can only be verified by sustained experimental opportunities in space which are also required to create and verify new models. It is safe to say that without dedicated opportunities on the space station, space biology and medicine will not evolve much further as a discipline. That would, in turn, preclude any long term human presence in space. In its report, the Committee on Space Biology and Medicine makes the following recommendation: We have been apprised of the engineering problems involved in the inclusion of a large centrifuge in a freely floating Space Station. The committee still recommends that a Variable Force Centrifuge (VFC) of the largest possible dimensions be designed, built, and included in the initial operating configuration of the Life Sciences Laboratory. It does so because a VFC is an essential instrument for the future of space biology and medicine. The VFC not only provides an onboard 1 g control for experiments concerned with the effects of microgravity on biological processes, it also provides the opportunity to study the effects of varying gravitational forces on such processes. Concerning the deleterious effects of microgravity that have already been documented, a VFC will allow investigators to determine also whether there is a threshold force required for a response to occur or, conversely, to reverse a given response. The centrifuge should be large enough to accommodate experiments on primates, possibly humans, rodents, and larger plants. A VFC is an essential instrument for the future of space biology and medicine. The Space Science Board has documented the need for a centrifuge for space biology and medical research in a number of published reports. Every other group that advises NASA on life sciences issues supports this recommendation. They range from the President's National Commission on Space to the Task Force on Scientific Uses of the Space Station and the NASA Life Science Advisory Committee. To summarize, of the facilities that have been recommended for medical file:///C|/SSB_old_web/an91append.htm (7 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix and biological research on Space Station, there is uniform support in the life sciences community for giving highest priority to inclusion of the VFC in the Initial Operating Configuration. It would be of greatest value when coupled with a dedicated Life Sciences Laboratory. Thus, for maximum advantage, the VFC should be included as part of a Life Sciences Laboratory or a node connected to a dedicated life sciences module. Signed by L. Dennis Smith Chair, Committee on Space Biology and Medicine A.4 Report to Assistant Associate Administrator Alexander: 1990 Louis J. Lanzerotti, Chairman of the Space Studies Board, sent this letter and attachment to Joseph K. Alexander, NASA Assistant Associate Administrator for Science and Applications, on December 12, 1990. Thank you for your letter of November 9, 1990, requesting that the Space Studies Board (SSB) provide its views and recommendations concerning the contemplated reduction in Space Station Freedom's (SSF) pressure to a 10.2 psi/"normoxic" level and the current 90-day study activity. To provide a timely response, the SSB's Committee on Space Biology and Medicine and Committee on Microgravity Research met together on November 28, 1990, to hear briefings from NASA personnel as input to developing the SSB's recommendations.1 The conclusions and recommendations transmitted in this letter report are based on information presented at that meeting as well as on the Board's and its Committees' ongoing interactions with NASA concerning SSF. Attachment A contains illustrative examples of some of the specific relevant materials science issues, both in terms of research and safety, and space biology and medicine issues, both in terms of research requirements and clinical considerations. Because of the very limited time in which the Board has been asked to respond, it does not consider this list exhaustive or complete. The Board has presented its views and recommendations concerning SSF and user considerations on a number of occasions. Most recently in its testimony of May 1990 to the Senate Subcommittee on Science, Technology, and Space, the Board commented on SSF as it was then contemplated. There have been a multitude of recommendations from advisory committees that were created to advise on the scientific requirements for the station. However, current proposals for Space Station Freedom suggest that it may not be of optimum use to the two primary communities for which it is intended-the life sciences and microgravity sciences. The Board and several of its file:///C|/SSB_old_web/an91append.htm (8 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix committees have had an ongoing dialogue with NASA about the space station since its inception. We will continue to do so as it evolves and is eventually deployed . . . . in the context of "responsiveness" [we] feel it is our responsibility to advise the Subcommittee of our continuing concern about the utility of the station if it proceeds as currently planned. This is a multi-billion dollar research effort that must incorporate the requirements of the research it is meant to facilitate, particularly [if] we move forward to research prerequisites for a human exploration program.2 In 1983, in a letter response to a request concerning science use of a space station from then NASA Administrator James Beggs, the Board stated: A commitment by the nation to long duration human space flight, whether in Earth orbit or beyond, calls for the establishment of a facility for space biological and medical research on the effects on individuals of very long exposure to the "low-g" environment. In this sense, the relationship of the life sciences to a space station is a special one . . . a manned space station could eventually provide significant opportunities for a number of disciplines in space science.3 The Board has made recommendations concerning use of a space station in several SSB reports published during the 1980s: Space Science in the Twenty- First Century-Life Sciences and Space Science in the Twenty-First Century- Fundamental Physics and Chemistry (National Academy Press, Washington, D.C., 1988) as well as A Strategy for Space Biology and Medical Science for the 1980s and 1990s (NAP, 1987). The latter report outlines a detailed research strategy for which the availability of a space station is pivotal. It includes specific recommendations for dedicated blocks of time for medical and biological subdisciplines, research questions, and essential instruments and facilities on a space station. SSB ASSUMPTIONS Understanding that your request to the Board arises from a congressionally mandated 90-day study and a set of rapidly changing scenarios and options, the SSB concluded that its advice should be given in some mutually understood context if it is to be both credible and useful. Thus, the Board has agreed on a defined set of assumptions that, in turn, lead to its overall recommendations in response to your request. These assumptions are as follows: 1. The avowed purpose of SSF is to provide a research laboratory, primarily for materials science and space biology and medicine. (This purpose has been stated to the Board itself, to various of its Committees, and to file:///C|/SSB_old_web/an91append.htm (9 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix congressional committees and others on a variety of occasions over the past five years.) 2. A permanent human presence in space and exploration of the Moon and Mars is a national goal of public record. 3. The primary, if not sole, driver behind a desire to lower the pressure of SSF to 10.2 psi/"normoxic" atmosphere during assembly of the facility is the need for extensive extra vehicular activity (EVA) in the shuttle-rated suit currently available. SSB CONCLUSIONS The views and recommendations of the Space Studies Board are based on several fundamental conclusions. Attachment A contains elaborations of some of these points. Space Station Freedom should be designed and operated to maximize accommodation to users, be it the science community, commercial interests, or national security. If SSF is, as has been declared, intended as a means to advance scientific understanding, it must be built to facilitate scientific research. The largest and most extensive data base that exists for biological and medical research was obtained at 14.7 psi-the atmospheric pressure close to that at sea-level. If results obtained in space research on the relatively few available subjects are to be useful and meaningful, they must be compared to the body of scientific knowledge, obtained in ground-based studies, that exists today. While the Board is aware that some ground-based research has been conducted at various high-altitude locations on Earth, most of the extant data is from near-sea- level environments. The Board cannot endorse a decision associated with the descoping activity that would require building new ground-based facilities to conduct additional research in order to create a new set of control data for comparison with data obtained in space-based experiments. This would require significant additional expenditures of both time and public funds that are not readily available. At the same time, optimum long-term atmospheric conditions for the Space Exploration Initiative (SEI) should be identified now and pursued as part of the SSF science objectives and designs. Data must be obtained to support these conditions. A major concern about fire safety is associated with a 10.2 psi/"normoxic" atmosphere: the likelihood of spontaneous ignition increases, and the rate for the spreading of such a flame increases with the increasing fraction of oxygen. (From this perspective, the fraction of oxygen should actually be decreased to improve fire safety, not increased, as would be the case if the SSF pressure were lowered to 10.2 psi/"normoxic".) Providing for SSF fire safety is a tremendous challenge. Anything that might reduce the probability of ignition and/or the spread rate of flame must be fully explored. file:///C|/SSB_old_web/an91append.htm (10 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix SSB RECOMMENDATIONS From both a scientific utilization as well as a fire safety perspective, the Board is convinced that maintaining a 14.7 psi/21% oxygen atmosphere on SSF is much preferred. The Board's primary recommendation is that a high-pressure space suit be designed and procured that would allow for performing EVA without the extensive preparations required with the suit currently available. In addition, because of the serious concerns regarding fire safety, NASA should conduct a study on the potential effects of reducing the oxygen fraction from the normal sea- level value. In particular, the study should address a reduction of the oxygen percentage below 21%. If it ultimately proves necessary to lower the SSF's cabin atmosphere to 10.2 psi/"normoxic" (or other levels lower than 14.7) during SSF assembly, the Space Studies Board strongly recommends the following actions, at a minimum: 1. SSF should be designed from the very beginning to accommodate a range of atmospheric pressures and oxygen ratios from 10.2 psi/"normoxic" to 14.7 psi, and a firm commitment should be made to ultimately operate at 14.7 psi. 2. During the man-tended capability phase (SSF assembly period), the station should be operated at 14.7 psi at all times that EVA is not scheduled, i.e., both for "utilization flights" and the periods between shuttle flights to the station. 3. From the point of permanent manned capability (PMC) forward, the station's pressure should be maintained at 14.7 psi/21% oxygen at all times. 4. NASA should provide a control chamber at 14.7 psi/21% oxygen in which to conduct plant and animal experiments. Accommodation of scientific requirements for SSF must be fully considered and reviewed. Briefings at the November 18, 1990, meeting suggest that many options being considered as part of the 90-day SSF study could have a major impact on the availability of other resources-power, experiment operation time, data communications bandwidth, and inertial/rotational acceleration characterization and control during the early man-tended phase. The Board recommends that great care and consideration be taken to ensure that the man- tended phase of SSF is the most cost-effective way to achieve the scientific objectives of the microgravity and life sciences research programs. For example, would an extension of Spacelab capability through SSF assembly be of greater value than relying on the Space Station during that period? In conclusion, the Board understands that Space Station Freedom has been, and likely will continue for some time to be, the subject of debate. The Board believes this is healthy and appropriate, both because of the SSF's file:///C|/SSB_old_web/an91append.htm (11 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix potential as a major national resource and its associated significant costs. At the same time, the Board takes the position that at some point in the discussion and decision process, agreement as to the station's purpose and function must be reached by all concerned-the SSF's supporters and critics-with NASA, the user community, Congress, industry, and the public. If the decision is made to proceed with the project, all involved should do so honestly and with a common sense of purpose. The Board supports the position taken in a 1988 report to President- Elect Bush, that . . . some form of space station is essential to establish the feasibility of extended human space flight. It is the only way to properly research the need for artificial gravity in extended manned missions and to develop the necessary technology for these missions.4 The Board looks forward to assisting NASA in whatever ways are possible as plans and decisions concerning Space Station Freedom are finalized. Signed by Louis J. Lanzerotti Chairman, Space Studies Board ATTACHMENT A Illustrative Examples of Microgravity Science Issues and Space Biology and Medicine Issues Associated with Space Station Freedom Cabin Atmosphere Microgravity Science 1. The Space Studies Board concludes that the 10.2 psi/"normoxic" atmosphere being considered for Space Station Freedom (SSF) will have no effect on microgravity experiments that will be conducted in closed containers. Experiments requiring other than 10.2 psi/"normoxic" ambient pressures can be contained in gloveboxes or with appropriate gas-handling systems that are planned for SSF experiment hardware as of this time. 2. If the SSF cabin pressure were lowered to 10.2 psi/"normoxic", it might be necessary because of potential fire hazard, to eliminate certain materials (virtually all nonmetals), a likely source of additional costs. Fire-extinguishing and air filtration systems would be required to mitigate additional risks. These issues require further study. 3. Potential impacts of a reduced pressure on control of the thermal file:///C|/SSB_old_web/an91append.htm (12 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix environment should be studied in greater detail. Much of the avionics on SSF will be performed by forced gas circulation, at reduced pressures; increased linear flow velocities may be required to manage avionics and payload heat loads. Space Biology and Medicine 1. The major argument against lowering the SSF cabin pressure to 10.2 psi/"normoxic" is the extensive ground-based data base that exists as a control for data obtained in space-based experiments. 2. A variety of experimental data from studies on hypobaric physiology have demonstrated that low pressure per se has major effects. These include a shift of fluid from the lower part of the body toward the head and thorax, increased excretion of water and salt, orthostatic hypotension, muscle atrophy (particularly of antigravity muscles), bone demineralization, a reduced glomerular filtration rate as measured by creatinine clearance, a reduction of vital capacity (e.g., reduced levels of aldosterone, glucorcortocoids, and angiotension), and increased body temperature and associated thermal discomfort. These all represent changes observed in microgravity. Unfortunately, there is a perception that since experiments in space have been performed under a variety of atmospheric conditions, ranging from 5 psi to 14.7 psi (oxygen ranging from 21% to 100%) with no dramatic difference in physiological changes, variable atmospheres are not of concern. There are no conclusive data that support this conclusion. 3. As the construction and maintenance of the SSF will involve much greater EVA time than has ever been undertaken, the risk of astronauts being subjected to bends must be minimized. 4. A lower cabin pressure would have an unfavorable effect on plant research. Although plants could probably survive under conditions of lower pressure, the consequences of forcing photosynthetic organisms to perform under such conditions could produce undesired results both in terms of research return and goals associated with food production in space. Examples of some of the deleterious effects are significant reductions in photosynthesis, and the effects of reduced pressure on critical processes such as transpiration. Developmental processes mediated by volatile plant hormones might also be affected, resulting in alterations in growth and such parameters as seed set and fruit ripening. 1November 28, 1990, briefings: OSSA Space Station Freedom restructure study guidelines, R. Rhome; presentation to the National Academy of Sciences CMGR/CSBM, A. Nicogossian; atmosphere and hypoxia, J. Kerwin; Space Station Freedom presentation, W. Taylor; letter from CMGR member W. Sirignano to R. Sekerka re fire safety and combustion (with attachment); and file:///C|/SSB_old_web/an91append.htm (13 of 15) [6/18/2004 10:27:25 AM]

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Annual Report 1991: Appendix letter from Lewis Research Center re fire safety and materials science issues. 2Space Studies Board testimony to the Senate Subcommittee on Science, Technology, and Space, May 10, 1990. 3SpaceScience Board letter report to NASA Administrator James Beggs, September 9, 1983. 4NationalAcademy of Sciences and National Academy of Engineering, Toward a New Era in Space: Realigning Policies to New Realities (National Academy Press, Washington, D.C., 1988). Last update 3/3/00 at 10:03 am Site managed by Anne Simmons, Space Studies Board file:///C|/SSB_old_web/an91append.htm (14 of 15) [6/18/2004 10:27:25 AM]