A brief synopsis of the evolution of the life and physical sciences program at NASA along with a sampling of its accomplishments is provided below. The committee’s intention is not that this synopsis be comprehensive but rather that it set the stage for the chapters that follow by providing a general introduction and overview of the content, purpose, and history of NASA programs. This review is also intended to provide some indications of the potential for a vibrant life and physical sciences program at NASA and of the current status of this research endeavor within the agency.
Since its establishment by Congress in 1958, NASA has recognized broad mandates to (1) extend the presence of humans in space while maintaining their health and safety and (2) provide the necessary platforms and resources to enable scientific inquiry on how the force of gravity affects physical phenomena and living organisms. It was quickly appreciated that the existing environment of space was sufficiently different from that of Earth that the design of spacecraft and space-ready technologies would be a significant challenge. Moreover, it was realized that the near-absence of gravity has a fundamentally unique effect on many biological and physical phenomena that cannot be investigated for any duration of time on Earth. Subsequently, it was understood that space provided opportunities for answering fundamental science questions whose impact would extend far beyond the mission needs of NASA, including results that could enable commercial applications.
One of the major challenges from the outset involved deciding where the organization and management of a microgravity life and physical sciences research mission would reside within the overall NASA administrative infrastructure, which was then being managed by scientists and engineers focused on rocket design and launch capability for space exploration. From the 1980s through 1992, the life and physical sciences were housed in the Office of Space Science and Applications (OSSA) alongside other sciences such as astrophysics and planetary exploration. Rather than maintaining the life and physical sciences research program as a partner to cognate science programs constituting NASA’s research portfolio—e.g., astronomy, Earth science, astrophysics, and planetary science—the senior management at NASA came to view “microgravity sciences” as supportive of, and subordinate to, the agency’s major space programs aimed at developing human spaceflight operations. Thus, the life and physical sciences research program was relocated within the infrastructure of spaceflight operations rather than being an equal partner with NASA’s other science programs.
This decision generated the perception among many scientists outside the agency that, because microgravity life and physical sciences research had no representation at the highest administrative levels within NASA, research in this field was considered unimportant or peripheral to the agency. The acceptance of the life and physical sciences research program waned among many scientists, engineers, physicians, and clinicians working outside NASA. It is noteworthy that these early views of NASA microgravity sciences continue to the present.
By the 1970s, offices for life and microgravity sciences were established at NASA headquarters. In the life sciences, a director position was created and the research mission was formalized as three distinct programs: (1) gravitational biology—understanding the role of gravity in the development and evolution of life; (2) biomedical research—characterizing and removing the primary physiological and psychological obstacles to extending human spaceflight; and (3) operational medicine—developing medical and life support systems to enable human expansion beyond Earth and into the solar system. These three programs had support from specific NASA centers (viz., Johnson Space Center and Ames Research Center), and the three themes articulated by these initial programs continue to define the spaceflight life sciences research missions and focus. In comparison, the development of the microgravity physical sciences program was more diffuse, in part because of its evolution from specific technological research that was related to the development of spaceflight systems. Fluid physics was one of the earliest thrusts because of its relevance to flight systems such as those for propellant control. Broadly, the physical sciences research activities that emerged can be categorized as (1) fluid physics, (2) materials science (crystal growth, metallurgy, soft matter, etc.), (3) biotechnology science (electrophoresis, protein crystallography, etc.), (4) combustion science, and (5) fundamental physics.
While orbital animal life sciences research began with the V2 rocket in 19481—and the Mercury and Gemini missions can be said to have entailed research to answer some very fundamental questions about space environments and our ability to conduct science and exploration missions—it was not until the Apollo Flight Program (1968-1972) that dedicated microgravity life and physical sciences research began within NASA. In total, eleven crew missions were completed: two involved Earth-orbiting; two lunar orbiting; one lunar swing-by; and six Moon-landing missions. Significant information was obtained from these flights, which were conducted within the framework of the Operational Medicine Program. This program was focused primarily on documenting the physiological effects on crew astronauts during varying flight durations and ascertaining whether there were serious deleterious effects. In the physical sciences, early research focused on small “suitcase” experiments. Specifically, to experience microgravity, experiments could be performed only when the spacecraft was in free flight (no thrusters or engines activated) and within the extremely tight constraints on time and crew availability. Experiments on fluid flow, thermal transport, and electrophoresis of biological molecules were performed. In spite of these early milestones, minimal scientific data were obtained that were publishable in a peer-reviewed scientific journal. However, the Apollo microgravity program established a precedent for hypothesis-driven research in the microgravity sciences.
In the early 1970s, Skylab became the first U.S. space station. Four Skylab missions were conducted from May 1973 to February 1974, ranging in duration from 28 to 84 days. Much of the research in the physical sciences during those flights was targeted at the effects of low gravity on buoyancy-driven convective flow and on materials processing. The reduction in, or absence of, buoyancy in microgravity transforms combustion processes and is important to solidification and crystallization, among many processes. In the absence of buoyancy, many reactions are limited by diffusion, and not only do they change in dynamical character but the length scale of the process also grows and, overall, becomes simpler to understand. Specifically, combustion can become diffusion-limited, and lack of buoyancy transforms solidification of metals under welding conditions and most scenarios of crystal formation. Containerless processing experiments, which were expected to have potential for commercial application, were included but were not deemed successful. In parallel, a range of life sciences missions were also conducted on Skylab. These covered processes such as cellular development and plant growth, but a key
component was to demonstrate that humans could live in space for relatively long durations while conducting a variety of tasks, including performance of extravehicular activities, and return to Earth without physiological deficits in performance capability. The outcomes of these missions revealed several critical findings, including the following: (1) there were clear-cut deficiencies in cardiovascular functions when exercise was performed by the astronauts at the same absolute intensity before and after the mission; (2) losses in muscle mass and strength as well as in bone density were documented; and (3) loss of movement fidelity, including post-flight balance instabilities, was observed (in the absence of vision abnormalities). It is now known that these alterations were hallmarks of prolonged exposure to the spaceflight environment. Even though the sample size was small, the observations were sufficiently robust to be reported in peer-reviewed scientific journals. Overall, the Skylab program laid the foundation for future microgravity studies of greater breadth and depth.
In 1978, NASA released a formal research announcement calling for research proposals for the laboratory facility of the space shuttle-based space transport system (STS). The unique feature of this announcement was that the research was to be rigidly peer-reviewed by two different panels: one focusing on scientific merit and the other examining the feasibility of conducting the study with the available facility and equipment infrastructure of the STS laboratory. A similar review model was used in the physical sciences. The first life sciences mission was set for the mid-1980s but was postponed until 1991 following the explosion of the space shuttle Challenger, after which shuttle missions were suspended until NASA deemed that it was safe to continue the shuttle program.
The access to space afforded by the STS missions provided for a broad portfolio of life sciences experimentation aimed at assessing the effects of microgravity and spaceflight on biological responses. Of particular note, however, are the three dedicated Space Life Sciences (SLS) missions that were flown in the decade of the 1990s: SLS-1 in 1991 lasted 9 days; SLS-2 in 1993 lasted 14 days; and Neurolab, a dedicated mission for the neurosciences in 1998, lasted 16 days. Within these three missions was a wide scope of experiments, ranging from plant and cell biology studies to complementary human and animal projects. The human studies were enhanced by NASA astronauts and payload scientists, who not only conducted the research as surrogate investigators but also served as the subjects for the composite human science package.
The research topics investigated across the three missions were broad, covering all the physiological systems discussed in this report. A unique feature of these missions was that laboratories for the animal studies were established at both the launch and the landing sites so that ground-based analyses could be conducted in close proximity to take-off and, especially, at landing to minimize physiological alterations occurring during the recovery period. In Neurolab, as with SLS-2, animal subjects were studied in detail during actual spaceflight. Some of the animal specimens were acquired during flight and then compared to animal samples obtained following landing. This was a major accomplishment because all animal studies prior to SLS-2 were performed during varying time intervals after landing, making it impossible to separate in the various experiments the effects of landing from the effects of the spaceflight environment itself.
An additional unique feature of the SLS and Neurolab missions was the synergy established within the international community of investigators and agencies. For example, in the Neurolab mission all of the ground-based research prior to flight was funded by several institutes within the National Institutes of Health, especially the National Institute of Neurological Disorders and Stroke. Investigators from the Japanese Aerospace Exploration Agency and the European Space Agency were also involved.
Although the life sciences program had its roots in issues of crew health and safety, fundamental biology also grew to be a substantive part of the program, particularly in the area of plant biology. For example, research on the effects of loss of convection on root zone hypoxia showed the impact of spaceflight on plant metabolism, and comprehensive gene expression studies revealed genome-wide effects of spaceflight on gene expression patterns.
In many ways, the dedicated flight program in space life sciences served as an important model of how flight-based research can be integrated across (1) project science disciplines, (2) national and international space research programs, and (3) national and international funding agencies. There have been repeated calls within the life sciences community to recapture the synergy that was present in the Neurolab mission.
During the flight history of the STS, a range of physical sciences investigations were flown, largely in the context of Spacelab. Among these missions were U.S. Microgravity Laboratory (USML) missions USML-1 and USML-2, as well as Microgravity Science Lab (MSL-1) and several international collaborative missions. The topics of all these experiments mirrored the five physical sciences categories listed above. Among the fluid physics experiments were investigations of surface tension and thermocapillary-driven flow, which generated new insights into instabilities and oscillatory flow excitations. Multiphase fluid flow experiments and investigations of bubbles, droplets, and coalescence were also an active part of the program, as was work on complex fluids. In materials science, crystal growth was an active theme, with one goal being to grow large, homogeneous crystals containing an exceptionally low number of defects in alloys (e.g., ZnCdTe) as well as in organic compounds, most notably in protein crystals. Using the TEMPUS electromagnetic levitator, investigations of undercooled liquids led to the design of glass-forming metal alloys and metallic glasses that had significant commercial impact. Experiments also explored dendrite growth in the absence of convective heat transfer, research that involved materials science and fluid physics. Combustion was an active area driven by fundamental questions and the relevance to fire safety. Central to this research were investigations on flame propagation and extinction, combustion ignition and autoignition, smouldering, and droplet combustion that yielded significant results. Among these were elegant experiments on ball flames. During the Spacelab era, fundamental physics began to emerge as a significant thrust in microgravity research; four experiments were conducted on phase transitions and critical phenomena at both moderate and ultra-low temperatures. Their results included the most precise measurement to date of the superfluid critical point in liquid helium. Collectively, through the shuttle era, research in the physical sciences generated an impressive number of peer-reviewed publications, landmark measurements, and discoveries, all of which could be achieved only through access to space.2
An important element of the STS period of physical sciences research was the rise of discipline working groups. These groups formed advisory committees for NASA and provided an increasingly coherent interface between the scientific community, potential flight opportunities, and NASA’s leadership. They organized conferences and workshops that brought NASA leaders and scientists together with university and industrial scientists and helped to develop a microgravity science community and heritage. Near the latter part of the STS period, the physical sciences research community had grown significantly to include Nobel laureates, members of the National Academies, and some of the best and brightest young scientists of the era. One objective of this report is to present a vision of a program that will recapture for NASA the strength and significance of the research portfolio during the STS period and the excellence of its participants.
From the inception of the International Space Station (ISS) program, elaborate plans were made by NASA and its international partners, especially the Japanese Aerospace Exploration Agency and the European Space Agency, to outfit the ISS as a world-class research laboratory for undertaking cutting-edge research and to provide opportunities that would expand research in microgravity to periods longer than 6 months. This was to be a major leap for the United States, given that the longest missions on Spacelab were less than 20 days. One important goal was to establish a first-class animal facility on the ISS containing Advanced Animal Habitats capable of separately housing 6 rats or 8 to 10 mice that could be utilized for a variety of studies on the effects of long-duration microgravity, while using a centrifuge as a control modality to maintain homeostasis at different gravity loads up to the standard 1 g. Other planned ISS infrastructure goals included shared facilities for combustion and materials research, as well as a flexible low-temperature physics facility. Some of these facilities have been realized and have enabled important scientific milestones such as the achievement of plant growth from seed to seed on orbit. Over the ISS development period, the organization and prioritization of the life and physical sciences changed significantly. These changes included the establishment of the Office of Biological and Physical Research as NASA’s fifth strategic enterprise and an increased focus on the Human Exploration and Development of Space program.
Unfortunately, over only a few years’ time, nearly all non-medical research in this program was canceled owing to a lack of funds and budget reprioritizations focused on the Constellation program. This was a serious blow to the life and physical sciences program within NASA because, since the late 1990s, there had been little or no flight program of substance to expand on the knowledge base established throughout the prior decade. From 2003 to the present time, the budget for biological and fundamental microgravity sciences within NASA has been reduced by more than 90 percent from its prior level, with only modest protection via a congressional mandate, and little opportunity remains (as mandated to NASA) for conducting even ground-based research. This is true for U.S.-led fundamental and applied hypothesis-driven research initiatives, and the committee notes that the only human research being performed on the ISS is agency-sponsored mission operations research. Although the remaining components of the life and physical sciences program are providing important scientific information, as described in subsequent chapters of this report, the extramural research community in these fields of space science is not part of the equation. Potential approaches to addressing these and other organizational issues are discussed in Chapter 12.
1. Grindeland, R.E., Ilyn, E.A., Holley, D.C., and Skidmore, M.G. 2005. International collaboration on Russian spacecraft and the case for free flyer biosatellites. Pp. 41-80 in Experimentation with Animal Models in Space (G. Sonnenfeld, ed.). Advances in Space Biology and Medicine, Volume 10. Elsevier, Amsterdam.
2. National Research Council. 2003. Assessment of Directions in Microgravity and Physical Sciences Research at NASA. The National Academies Press, Washington, D.C.
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