Definition
The term space life sciences refers to the set of sciences that study the biology of living things under conditions of spaceflight. The synonymous term, space biology, coined in 1920 by K. Tsiolkovsky, is more common in Russia (USSR). The origin and development of space life sciences as a discipline are the result of certain advancements in modern science and technology and are associated with the development of jet propelled flight vehicles that can overcome the force of gravity to ascend beyond the bounds of Earth’s atmosphere.
Space biology arose at the intersection of many scientific disciplines: various branches of biology and medicine, physics, chemistry, astronomy, astrophysics, geology, geophysics, geochemistry, radiology, and mathematics. It is indissolubly bound up with cosmonautics and space medicine.
Space medicine is the area of general medicine that studies what happens to human physiological processes under the unique conditions of space flight to develop means and methods for maintaining the health and performance capacity of crews of spacecraft and space station pre-, in- and postflight. As one of the branches of occupational medicine, space medicine attempts to provide the answers to a number of questions confronting humanity as a result of scientific and technological progress. These answers are derived from a very large medical knowledge base relating to various areas of theoretical and clinical medicine such as space physiology and psychophysiology, space hygiene, space radiobiology, and medical expertise.
In the USSR/Russia, space medicine has been seen historically as a composite discipline, encompassing space physiology, which addresses scientific issues involving all of the factors that affect humans in space, and space medicine proper, which addresses the practical issues involved in maintaining cosmonaut health and performance capacity. Thus, in many references in the literature, the term space medicine is used in its broad sense to refer to the combination of space medicine narrowly defined and space physiology.
The mission of space physiology is to find out how much it is possible to decrease comfort and stress human physiological functions, still induce only physiological changes that are merely adaptive rather than pathological and leave performance capacity and job efficiency undiminished. In the light of the high cost of flight time in space, the constant time deficit and the serious potential consequences of human error, it is critical that cosmonauts’ performance capacity be maintained at a high level.
Goals and Objectives
The goals and objectives of the principal space life sciences are presented in Table 1.
Meeting the challenges confronting space life sciences involves efforts in the following major research directions:
• investigation of the effects of weightlessness and other spaceflight factors, including the combined effects on physiology as a whole and on fundamental
• study of the mechanisms by which living things, including human beings, adapt to exposure to spaceflight factors in experiments aboard spacecraft and in ground-based simulations;
• investigation of individual differences in regulating the psychophysiological status of cosmonauts during exposure to the extreme environment of space;
• work on the fundamental problems of space physiology, gravitational biology, ecology, and exobiology.
Table 1. Objectives and Goals of Space Life Sciences
| Space biology | ||
| To conduct fundamental biological | 1. | Study of the biological effects of various |
| research devoted to comprehensive | spaceflight factors on terrestrial life forms | |
| study of space and celestial bodies as | 2. | Investigation of the possibilities for life to |
| a unique living environment and of | exist under extraterrestrial conditions, | |
| the effects of factors of the space | including other planets (exobiology) | |
| environment, including spaceflight | 3. | Study of the mechanisms governing changes |
| factors, on various forms of life | in the physiological functioning of humans | |
| and animals under exposure to spaceflight | ||
| factors (space physiology) | ||
| 4. | Development of life support systems (LSS) | |
| for use by terrestrial life forms under | ||
| spaceflight conditions | ||
| Space medicine | ||
| To support maximum possible physical | 1. | Creation of the requisite conditions to optimize |
| and psychological well-being, high | human vital functions during space flight | |
| performance capacity, job efficiency, | 2. | Monitoring, predicting, and correcting |
| and increased reliability of human | physiological changes that occur as a result | |
| performance under the unique | of the impossibility of fully or partially | |
| conditions of spaceflight and after its | replicating terrestrial conditions | |
| completion | 3. | Maintaining human health during all phases |
| of preparation for flight, flight itself, and | ||
| after flight completion (selection, | ||
| observation, diagnosis, treatment, and | ||
| prevention of pathologies) | ||
| 4. | Ensuring the safety and increasing the | |
| efficiency of spaceflights; providing medical | ||
| and ergonomic measures to increase the | ||
| reliability of human-machine interactions. | ||
processes at the level of individual organs, systems, tissues, cells, and at the subcellular level;
Major Phases in the Evolution of Space life Sciences
Development of the Underlying Knowledge Base and Formulation of the Issues Involved in Preparing for Spaceflight. The scientific goal of preparing for and actually accomplishing a spaceflight was formulated on the basis of an existing scientific knowledge base and previously developed methodological approaches. The knowledge needed to formulate the goal of preparing for spaceflight came from the following sources:
• expeditions to high mountain regions;
• underwater immersion;
* physiological experiments (using centrifuges, barochambers, etc.);
* balloon and, later, aircraft flights.
The sources of the research results that form the knowledge base for space medicine go as far back as the Renaissance. Galileo first described the effects of gravity on living things in 1638. Newton made the first proposal to use rocket-powered vehicles for scientific space travel and suggested methods by which man-made satellites could be inserted into orbit around Earth in 1687. Boyle used a barochamber to conduct experimental investigations of the effects of diminished atmospheric pressure on animal physiology from 1660-1692. A great deal of knowledge was generated by research conducted, without specific consideration of spaceflight, in the eighteenth through twentieth centuries in areas such as pathological physiology, high-altitude physiology, underwater and diving medicine, and aeronautics, and aviation medicine.
Of all of the preexisting biomedical disciplines, aviation medicine had the most important role in making piloted spaceflight possible. At the intersection of medicine and technology, this discipline generated information about the physiological effects of high levels of atmospheric decompression and dynamic flight factors and acquired technical expertise in developing means of preventing the adverse effect of these factors. All of these achievements were subsequently used in preparing for the first spaceflight.
Study of the laws governing physiological reactions to extreme environmental conditions enabled aviation medicine to develop a methodology for analyzing physiological reactivity to the effects of an extreme factor and for preventing this factor from having adverse physiological effects. This methodology was based on the goal of supporting optimal human performance capacity in extreme environmental conditions. Use of this methodology gave researchers a tool that enabled them to solve the analogous problem with regard to spaceflight conditions. This achievement of aviation medicine was one of the most important contributions to the knowledge base for space medicine.
Piloted flights into the stratosphere (1933-1934) in the pressurized gondola of the USSR and Osoaviakhim high-altitude balloons (reaching an altitude of 18,600 m and 22,000 m, respectively) functioned as a prelude to future piloted flights on spacecraft. These stratospheric balloon flights demonstrated empirically that the problem of operational medical flight support was indeed soluble. Preparing for these flights allowed experts to gain a great deal of practical experience in creating life support systems (LSS) for conditions equivalent to those in space. Stratospheric flights provided the impetus for developing pressure suits and pressurized aircraft cabins for altitudes above 10,000 meters. Moreover, they generated the first information on the biological effects of a previously unstudied factor of the space environment—primary cosmic ionizing radiation. The papers delivered in March 1934 at an All-Union Conference on the Study of the
Stratosphere held in Leningrad formulated a number of biomedical problems related to the study of spaceflight. The goal of human penetration into the upper atmosphere was scientifically formulated for the first time and publicly supported at this conference. Consequently, a scientific center was set up under the aegis of the USSR Academy of Sciences to achieve this goal. Phase One: Creation of an Independent Scientific and Applied Discipline. The technical capacities needed to initiate practical research to prepare for piloted spaceflight began to be developed in the late 1940s. During this period, ground-based experiments; experiments conducted on aircraft, rockets and balloon flights; and the theoretical analysis that preceded them were concentrated in three areas: study of the effects of gravity within the broad range of 0 g to several g’s, study of the biological aspects of the effects of cosmic radiation, and development of a LSS for pressurized cabins. Solving the initial applied problems involved in preparing for piloted spaceflights required efforts to generate absolutely new information on the physiological effects of space environment factors and also a great deal of work to analyze already existing databases in related disciplines. In addition, to guarantee the maximum possible safety of piloted spaceflight, simulations and field experiments had to be conducted to verify empirically whether it was appropriate to extrapolate already established laws to conditions in space.
In 1949, under the direction of A. Blagonravov, the Soviet Union began to implement a program for using the R-1 (V-1) rocket to study physical processes in near-Earth space. In 1950, a group headed by V. Yazdovsky was formed within the Institute of Aviation Medicine to work on the biomedical aspects of high-altitude rocket flights. The first series of experimental tests (1951) involved six launches (of which two failed) of the R-1C rocket that carried dogs to an altitude of approximately 100 km. The first geophysical rocket, R-1C, carrying the dogs Dezik and Tsygan, was launched on 22 July 1951 from the Kapustin Yar Cosmodrome, ascended to an altitude of 100.8 km, and landed successfully. This was the world’s first successful flight of an animal on a rocket. The results of this effort included selection of biological subjects for spaceflight research, development of an animal pressurized cabin LSS, development of sensors and monitoring devices and of methods for studying animals’ physiological functions that could be used under conditions of rocket flight, and study of the nature and severity of the effects of high atmospheric flight on the physiological functioning and behavior of animals.
The second set of experimental trials (1954-1956) involved launching nine R-1E and R-1F rockets carrying a total of 12 dogs to altitudes up to 110 km. This research showed that animals satisfactorily tolerate conditions during powered flight and the subsequent 3-6 minute period of weightlessness and that the LSS and emergency catapult system (for use from a variety of altitudes), as well as the methods for recording physiological functions and the filming system that had been developed, performed adequately.
The next major step was the launch of the second nonrecoverable Earth satellite vehicle (ESV-2) carrying the dog Layka on 3 November 1957. The first orbital flight of a living creature made it possible to test the LSS, the methods that had been used to select and prepare flight animals, and methods for studying a number of physiological functions in flight and for transmitting biomedical information from the flight vehicle to Earth. Biomedical studies conducted on
ESV-2 supplemented material obtained from vertical rocket launches and provided researchers with the essential experimental data to confirm initial hypotheses that exposure of living things, including humans, to space does not cause them any harm. This experiment demonstrated that it is possible, in principle, for a higher animal to complete a spaceflight in near-Earth space.
The results obtained from studies of a broad range of biological subjects on flights of rockets and the first Earth satellite vehicles were meant to be used to prepare for piloted spaceflight (1950-the early 1960s) and indeed demonstrated that there are no biological limits on living under flight conditions in near-Earth orbit.
Getting ready for the first piloted spaceflight entailed solving a number of new problems and developing a number of new research directions. First of all, the physical properties of near-Earth space had to be studied, and a number of issues associated with biomedical, ballistic, and navigational support of piloted spaceflights had to be resolved. It was essential to solve the problem of crew life support (air regeneration, water supply, and maintenance of normal temperature conditions in the crew cabin), ensure their safe return to Earth from orbit, maximize the likelihood of landing in the predetermined region, limit acceleration during powered flight, and provide reliable thermal insulation for the spacecraft’s reentry into the dense layers of the atmosphere.
In the Soviet Union, this research was conducted under the direction of V. Yazdovsky and O. Gazenko during animal flights on the R-2A (five flights) and R-5A (nine flights) geophysical rockets to altitudes from 200 up to 473 km (1957-1960). A total of 14 dogs flew on these missions, some of them two to four times each, as did other animals—rabbits, rats, and mice. These experiments showed that animals do not display any notable disruption ofphysiological status or behavior in the weightlessness induced by geophysical rocket flights.
The successful advance of research in the Soviet Union, as well as the development of a reliable launch vehicle—the R-7—in 1958-1959, made it possible to move on to the final phase of preparation for the first piloted spaceflight, the development of the Vostok piloted spacecraft, and implementation of a cosmonaut selection and training program. These efforts were conducted at virtually the same time and in parallel.
The previous rocket experiments that established that higher animals can well tolerate short-term exposure to spaceflight factors were merely the starting point for solving a wide range of problems pertaining to selection. This problem was so critical because the overall success and results of spaceflights, in many respects, would depend on cosmonaut physiological status. Incorrect evaluation of an individual’s functional capacities or an undiagnosed disease could have posed a threat to the cosmonaut’s life or resulted in the flight mission’s failure. It was very difficult to conduct an adequate evaluation, primarily because it was impossible to replicate the entire set offactors to which a human being is exposed during spaceflight. Development of the cosmonaut medical selection system used the many years of experience accumulated by aviation medicine in qualifying flight crews for various types of aircraft. Naturally, this system could be used for selecting cosmonauts only if the differences in the professional tasks performed by cosmonauts and the characteristics of their environment were taken into account.
In-depth medical examinations and special tests involving exposure to parabolic aircraft flights, centrifuges, barochambers, thermal chambers, rotating tilt tables, and anechoic chambers resulted, in December 1959, in the selection of the 20 members of the first USSR cosmonaut team. During flight training, a great deal of emphasis was placed on biomedical preparation, including conditioning of the candidates’ muscle, cardiovascular, and vestibular systems. The principal goal was to prepare the cosmonauts physiologically for the combined effects of such unaccustomed factors as acceleration, weightlessness, vibration, motion sickness, and nervous stress. Thermobarochambers, centrifuges, anechoic chambers, training simulators, and vibration benches were used extensively in this conditioning program.
In April 1960, the Soviet Union began a series of (unpiloted) flight tests of the Vostok piloted spacecraft, called a piloted orbital spacecraft (POS). In 19601961, there were a total of seven orbital spacecraft launches, of which only three were complete successes. On 19 August 1960 the third flight of the Vostok orbital spacecraft (receiving the mission designation POS-2) was successfully completed. For the first time ever, the dogs Belka and Strelka and other biological subjects completed a 1-day, 17-pass orbital flight and returned safely to Earth. After this flight, specialists could, for the first time, study the effects of spaceflight conditions on living creatures and conduct meticulous physiological, genetic, and cytological analyses of the animals and other biological subjects after they had been in space for 25 hours. Two more launches of the orbital spacecraft (POS-4 carrying the dog Chernuska and POS-5 carrying Zvezdochka) immediately before the first piloted flight, confirmed that it was feasible for a human being to fly in space. Investigations conducted on these launches showed that the danger from meteors in near-Earth space on the intended flight trajectory was virtually nil and that the level of radiation beyond the radiation belts was not as high as it is during solar flares.
The first piloted space flight took place on 12 April 1961. Yuriy Gagarin completed one pass in near-Earth orbit for a flight of 1.8 hours (108 minutes). Throughout the entire flight, his physiological parameters remained within the limits that could be described as the zone of normal reactions to unusual environmental factors. The results of this flight demonstrated that it is possible, in principle, for human beings to fly in space and that humans can adapt to the unaccustomed state of weightlessness without losing their performance capacity and ability to orient themselves spatially. A meticulous analysis of scientific materials obtained during the flight enabled comprehensive tracking of the cosmonaut’s physiological functions over time and the parallel characteristics of the spacecraft systems’ operations. This made it possible to improve the spacecraft equipment and make the necessary adjustments in the cosmonaut training program. The main result was that the flight demonstrated that, in principle, there are no biological constraints on flights in near-Earth space. This opened the door to a gradual increase in the duration of the human presence in space and in the amount of work performed therein, and thus completed the process of the initial development of space medicine as a science and as an independent branch of medical practice.
Phase Two: Research on Short-Term Piloted Flights in Near-Earth Space.
Yuriy Gagarin’s successful flight was followed by a large number of flights by
Soviet cosmonauts and U.S. astronauts. In August 1961, G. Titov spent more than a day in space on board Vostok-2. The cosmonaut worked, slept, and ate and thus demonstrated that the basic diurnal rhythms of life are maintained in space. During his flight, he made meteorological and geophysical observations, took the first movie from space, and controlled the spacecraft. Extremely valuable scientific material was generated, making it possible to draw conclusions about the effects of spaceflight factors on human physiology during an entire diurnal cycle. Titov also demonstrated that it is possible to perform mental (operator and research) work in space. This was the first flight on which a cosmonaut complained of malaise. G. Titov noted symptoms of motion sickness (dizziness, nausea) when he moved his head, which were more severe during the second pass. The first piloted space flights demonstrated that human beings can live and work in space. However, the issues of how long and how well they could do this required further biomedical research in space.
On these premises, exploration began of the more complex systems and methods required for systematic scientific research on human activities in space. In particular, the following problems were studied: can a human being function in space during a prolonged period; can women tolerate space flight; can mul-timan crews operate in space; can spacecraft rendezvous and dock; is work in open space possible.
In August 1962, the Soviet Union conducted the first multiman space flight (A. Nikolayev, P. Popovich); in June 1963, the first female cosmonaut, V. Tereshkova, spent 3 days in space. The multiman Voskhod spacecraft flew for the first time in October 1964, carrying a crew of three men, including the first physician-cosmonaut, B. Egorov. The first extravehicular activity (EVA) (A. Leonov, 1965) took place during the flight of Voskhod-2.
The next important step was the USSR’s creation of the Soyuz spacecraft in the mid-1960s. Soyuz was intended for further development of processes of autonomous navigation, performance of transport operations (delivery of cosmonauts to space station), conduct of scientific-technical and biomedical experiments in near-Earth space, and for performance of multilevel scientific and applied tasks. The new spacecraft differed from Vostok and Voskhod by virtue of its ability to perform orbital maneuvers and to approach and dock with other spacecraft. The Soyuz cabin was divided into two modules: the reentry module (for returning cosmonauts to Earth) and the orbital module (for conducting scientific research and cosmonaut daily activities and sleep).
The biomedical studies conducted in the 1960s during short-term piloted spaceflights had demonstrated that humans could safely spend 2 or 3 weeks under conditions of weightlessness and perform EVA. After the cosmonauts returned to Earth, certain changes were observed, which, it seemed, increased in severity with increasing duration of space missions. This led to the development of methods to prevent the adverse physiological effects of weightlessness; however, these measures were not actively adopted in space medicine until 1970. The 18-day flight of Soyuz-9 (A. Nikolayev, V. Sevastyanov, 1970) was very significant for the solution of a number of biomedical problems. This flight generated data on the reactions of cardiovascular and musculoskeletal systems to prolonged exposure to weightlessness, studied the role of physical exercise, and investigated the characteristics of the postflight recovery period.
The cosmonauts had problems tolerating what at that point was the longest ever exposure to weightlessness. After the flight, it was found that they exhibited significant atrophic changes in their muscles and orthostatic intolerance, which required medical rehabilitation for a number of days. The experience gained during this flight provided valuable material for studying whether it would be possible for humans to spend longer periods in space. The significant physiological changes noted in the cosmonauts stimulated work to develop systems of targeted preventive measures and enhanced medical examinations and their adoption in operational medical flight support to ensure reliable and safe piloted spaceflights of increasing duration.
Phase Three: Research on Long-Term Piloted Spaceflights in Near-Earth Orbit. The results of short-term piloted flights during the late 1960s suggested that cosmonauts did not undergo any physiological changes that went beyond the bounds of nonspecific responses to extreme environmental conditions or that would be an impediment to further increases in flight duration. This conclusion instilled optimism regarding the planning of future long-term spaceflights and was an impetus to development of a spacecraft of a new type—the piloted orbital space station. The relatively large size of these stations, which could grow by docking with additional modules, made it possible for them to carry equipment for extensive biomedical investigations and for preventing the adverse effects of spaceflight factors. Moreover, these space stations provided comfortable conditions for living and personal hygiene and diminished the physiological effects of severe constraints on motor activity characteristic of smaller spaceflight vehicles.
The strategy developed by Soviet experts involved a sequential, gradual increase in the duration of human exposure to space without damage to health while maintaining satisfactory capacity for performing one or another flight mission. The tactics for implementing this strategy were determined by the results of studies conducted on the flights of piloted orbital spacecraft and unpiloted biosatellites, ground-based experiments, and data from general physiology and the practice of medicine. Continuous accumulation of knowledge on the physiological effects of spaceflight factors made it possible to improve the system for selecting and training cosmonauts, the measures used for medical monitoring and predicting of health status and for preventing the adverse effects of weightlessness, and rehabilitative measures to be used after flights of long duration.
During this phase, each successive piloted spaceflight represented a mean increase in duration of 30-40 days over the previous one. This pattern was dictated by the reliability of medical prediction based on the results of all previous flights. The psychological factor was also considered of major importance in planning increases in piloted flight duration. Thus, increasingly long flights of 96, 140, 175, 185, 211, and 237 days were implemented successively. The work of cosmonaut physician O. Atkov on the 237-day flight in 1984 was of great significance. The presence of a physician on the station made it possible to validate new modes and schedules of physical exercise and to conduct comprehensive studies of the cardiovascular system, which included echographic studies.
The 1-year flight on the Mir Space Station (V. Titov, M. Manarov, 19871988) was a significant milestone. This accomplishment was made possible by implementing an extensive set of planned investigations and successfully solving a number of challenges involved in medical support of long-term flights. New exercise schedules on the bicycle ergometer and treadmill—the major prophylactic countermeasures—were validated, as were new schedules for provocative tests using lower body negative pressure. A whole series of neurophysiological, hematological, and biochemical studies performed by cosmonaut physician, V.V. Polyakov, during the last phase of this flight made it possible to expand significantly the potential for diagnosing and correcting functional disorders arising in cosmonauts during flight.
The culmination of long-term flights on space station Mir was the record-setting super-long-term, 438-day flight of cosmonaut-physician V. Polyakov (1994-1995). The major result of this flight was the demonstration that cosmonauts can retain their health and performance capacity on a flight comparable in duration to a Mars mission, and that the high functional physiological capacities of the crews that worked with him were also retained.
A new chapter was opened, when the International Space Station (ISS) developed through the joint efforts of Russia, the United States, the European Union, Japan, and Canada, went into operation in Earth orbit. Considering the growing demands made on operational medical support of upcoming piloted space flights (see Biomedical Support of Piloted Spaceflight), the following major directions of research will be performed on the ISS:
1. evaluation of the physiological effects of spaceflight factors as a function of their combination, intensity, and duration and the study of individual adaptive and re-adaptive physiological reations;
2. study of the mechanism through which the structure, functions, and behavior of living things change, whether or not they are reversible, and their remote consequences;
3. identification of the most information-rich physiological criteria for ongoing and predictive evaluation of cosmonaut status, pre-, in- and postflight, for use, among other purposes, to optimize prescribed dosages of prophylactic interventions;
4. development of a physiological rationale for techniques to increase specific and nonspecific physiological resistance to a particular combination of spaceflight factors and working and living conditions.
Phase Four: Preparation for Interplanetary Spaceflights. At present, space medicine is at the threshold of the next stage in its evolution, associated with supporting autonomous work by cosmonauts, for example, at a scientific lunar base or on board an interplanetary spacecraft. The novelty of the challenges presented by such flights results from the significantly greater crew autonomy arising, at least in part, from the impossibility of quick or premature return to Earth in cases of emergency or illness and the need to increase significantly the reliability of technical and medical systems. Russia, the United States, and a number of other countries are theoretically analyzing the challenges facing them and are performing experimental work on particular biomedical aspects of autonomous flight. One of the initial phases here involved long-term flights, including the 438-day flight on Mir, which demonstrated that,in principle, there are no biomedical considerations that would prevent a Mars mission. It is assumed that the ISS shall also become a test bed for developing various aspects of interplanetary flights.
The specific aspects of interplanetary spaceflights that require new approaches to the organization of medical support systems are enumerated in Table 2, using a Mars mission as an example.
A piloted flight to Mars demands solving a number of physiological problems resulting from long-term exposure to weightlessness. The symptoms and mechanisms of the physiological changes occurring under these conditions in prolonged flights have been studied in relatively great detail; however, the prophylactic measures that have been developed require further improvement. In particular, the possibility of using artificial gravity (AG) for this purpose will be investigated, if nongravitational prophylactic measures do not prove effective enough. At the same time, the use of AG could lead to the occurrence of a number of physiological problems from exposure to a rotating system: development of sensory conflicts, difficulty in motor orientation, or adverse effects on the vestibular system. The problem of the combined effects of factors involved in a flight to Mars remains very critical.
On the highly autonomous spaceflights of the future, for example, flights of Mars and other planets of the Solar System, cosmonaut meals will no longer consist solely of stores of food brought from Earth. Instead, the crew’s nutritional system will have to be based on food substances and products produced on board, including those based on nontraditional food sources.
The procedures for crew interactions with ground control services will also have to be revised completely. Because of the delay in radio signals on the Earth-Mars path, it will not be possible for ground-based flight control services to react immediately to events on board, and this will diminish their function mainly to one of consulting and support; the entire responsibility for making moment-to-moment decisions will be borne by the Mars spacecraft crew. Thus, the risk of the Mars mission is significantly higher than that for cosmonauts in near-Earth
Table 2. Specific Features of a Piloted Flight to Mars
* Long-term (no less than 2 years) crew residence in an artificial living environment, which would lead to biological and chemical microcontaminants accumulating in the atmosphere, the formation of an unusual microbial community inside the spacecraft, and the possible deviation of microclimatic parameters from those considered safe
* Possible exposure to galactic cosmic radiation without screening by Earth’s magnetosphere
* Long-term continuous exposure to a hypomagnetic environment and solar ultraviolet radiation
* Diminished possibility for ground control services to respond quickly to what is happening on board as a result of 15-30 minute signal delays
* Impossibility of emergency or premature crew return to Earth or replacement of an ailing crew member
* Cosmonaut exposure to hypergravity during landing, stay on Mars, takeoff from Mars, and landing on Earth
* Need for the crew to live and work together for a long period in isolation, possibly leading to development of psychological incompatibility and psycho emotional stress orbit. Thus, implementation of these missions will have to be preceded by intensive and in-depth investigations in space physiology, psychology, and radio-biology as well as by the development of LSS equipment and other technical spacecraft equipment with significantly higher reliability and maintainability than those in use today.
Major Research Directions
The scientific data needed to solve the problems confronting space medicine have been generated by biomedical experiments conducted on space flights, ground-based simulation studies, and practical experience with operational medical flight support, as well as by advances in general physiology and medicine. Experiments on Board Piloted Spacecraft. The 40-year period during which piloted spacecraft have been flying has made it possible to accumulate unique experience in solving biomedical problems to ensure the safety and efficacy of spaceflights of ever increasing duration. During this period, the duration of piloted space flights has increased to 12-14.5 months for men and up to 6 months for women. The successful implementation of biomedical research programs in space has significantly facilitated this progress. Among those who have spent the most time working in orbit, we should mention S. Avdeyev (750 days on three spaceflights), V. Polyakov (679 days on two spaceflights). A. So-loviev (653 days on five spaceflights), V. Afanasyev (547 days on three spaceflights), and A. Viktorenko (489 days on four spaceflights).
An extensive program of biomedical research and experiments has been implemented on the Salyut-3, -4, and -5 orbital stations that were inserted into orbit between 1974 and 1976. The total duration of work performed by six cosmonaut crews on these stations was 176 days. Much emphasis was placed on developing the optimum physical exercise programs using exercise machines and on improving the work-rest schedule to increase the postflight resistance of the cardiovascular system to the effects of Earth’s gravity.
The flight of Salyut-4 witnessed the first use of the “Chibis” vacuum suit, which applies lower body negative pressure to simulate the effects of Earth’s gravity on the blood system and thus to counteract excess blood flow to the head. The station was also fitted with a rotating chair for studying vestibular function and a bicycle ergometer (in addition to the previously used treadmill). Another innovation was the ”Tonus” apparatus for electric stimulation of separate groups of muscles. Additionally, cosmonauts on Soyuz-18 were fed a diet containing increased levels of salt and additional liquid. This regimen proved very effective in increasing their tolerance for conditions on return to Earth.
The Salyut-6 space station was inserted into orbit in September 1977 and remained in orbit for more than 4.5 years. During this time, it was inhabited by 29 cosmonauts comprising 16 crews (five prime crews and 11 visiting crews), who conducted a large number of scientific and technical investigations, including more than 1600 biomedical and biological studies.
The last station in this series—Salyut-7—was inserted into orbit in April 1982 and remained there for more than 4 years. Ten crews worked on Salyut 7, including five prime crews and five visiting crews, a total of 23 cosmonauts, including the second Soviet cosmonaut physician, O. Atkov, who conducted a large number of ultrasound studies of cosmonauts’ cardiovascular systems, investigated mineral and carbohydrate metabolism, and determined the optimal parameters for physical exercise and loading.
In February 1986, the Soviet Union launched the core module of the third-generation space station, Mir, which formed the basis for a multimodule orbital complex. A total of 44 crews (28 prime and 16 visiting crews), comprising a total of 104 cosmonauts, including 63 foreigners, worked on board this station. A series of international projects were implemented on board with the help of citizens of the United States, France, Germany, the United Kingdom, Austria, Syria, Bulgaria, Slovakia, Afghanistan, and representatives from the European Space Agency (ESA). In addition, nine crews visited Mir on the U.S. Space Shuttle, including citizens of the United States, Canada, France, and representatives from the ESA (a total of 50 people). Mir was the first international piloted space station.
A permanent and important component of Mir flight programs was the broad spectrum of biomedical research studies (a total of 1759) that generated new information on the mechanisms underlying the changes that occur in various human and animal functional systems under conditions of weightlessness and on the characteristics of the processes of physiological adaptation to space flight and of readaptation to conditions on Earth. Mir experiments demonstrated that an entire life cycle could take place in weightlessness. Progress was made in studying the habitability of piloted spacecraft complexes (sanitary/hygienic, mi-crobial, and radiation physics studies); experience was accumulated in the sanitary and hygienic support of crews during long-term habitation of space stations and during contingency modes of LSS operation.
During the 438-day flight alone, V. Polyakov performed approximately 1000 biomedical analyses and tests in the following areas:
1. use of clinical physiological and laboratory analyses to investigate the mechanisms underlying adaptation of human functional physiological systems to conditions on long-term flights;
2. study of the problems of habitability on long-term space flights and optimization of crew living conditions on board;
3. improvement of medical systems ensuring cosmonaut safety on spaceflights.
The long period during which Mir was used (15 years) made it possible to develop unique expertise in solving biomedical problems to support the safety and efficacy of spaceflights of increasing duration. In particular, the principles governing the evolution of microflora during multiyear use of inhabited facilities with an artificial environment were established, medical and technological risks were defined and classified, means and methods for monitoring and supporting ecological crew safety and for protecting the spacecraft interior and equipment from biodegradation were developed, and other scientific and hygienic problems were solved.
An extensive and multifaceted program of fundamental biological research on plants, birds, and amphibians was conducted on the Salyut and Mir stations.
This program included studying the growth and development of a variety of life forms to develop biological life support systems for future flights. Thus, in the Chlorella experimental program on board Salyut-6, it was first demonstrated that weightlessness had no primary biological effect on an actively growing culture of one-celled algae, either at the level of the organism, or at the level of interactions within the “organism-environment” system. Multiyear studies conducted on Mir (the Oranzherya and Inkubator experiments) first demonstrated that living organisms could undergo a full developmental cycle under conditions of weightlessness; organogenesis was fully demonstrated in mammals and birds, and the full developmental cycle of wheat from seed to mature plants was realized.
Experiments with a model microecosystem (the Aquarium and Aquarium-M experiments) on Mir and on the Bion biosatellites first demonstrated that weightlessness does not affect the functioning of an “algae-bacteria-fish” micro-ecosystem as a whole. All changes in weightlessness that occurred in the system were similar to those it underwent under normal gravity. The growth, development, and reproduction of populations of one-celled algae within the system proceeded normally in space. Spaceflight factors failed to impact algae productivity or their functioning as the autotrophic component of the microecosystem. These results are of important fundamental and applied significance for the development of scientific methodological principles to underlie the design and subsequent implementation of hybrid biological-physical-chemical life support systems (controlled ecological LSS).
As a result of the research conducted on space stations, the major risk factors for piloted spaceflights were defined, and the specific and nonspecific laws of human adaptation to space flight factors were studied. The major physiological systems most subject to changes under conditions of long-term flight were identified, and effective means and methods for preventing undesirable physiological changes in response to spaceflight factors were developed. This research made a significant contribution to solving problems in gravitational biology—the science that studies the effects of gravity on life forms, including human beings. All of this activity culminated in the implementation of comprehensive clinical-physiological studies of the functions, regulation, and structure of various systems pre-, in- and postflight. The results generated are of great importance for the practice of space medicine and also for solving fundamental problems in gravitational physiology and life science as a whole.
Bion Program Research. Between 1973 and 1977, systematic biological and physiological investigations were undertaken as part of the Bion program on flights of 11 Kosmos series biosatellites to deepen understanding of the effects of spaceflight factors, especially weightlessness, on vital processes. These satellites were equipped to conduct flight experiments on various species of animals and plants. All of this research was directed by the Institute of Biomedical Problems and involved extensive domestic and international cooperation. A broad range of scientific disciplines, such as gravitational biology, physiology, developmental biology, cellular and radiation genetics, metabolism, morphology, histology, hematology, and immunology, were involved. Scientists from the United States, France, Canada, Holland, Bulgaria, Hungary, Germany, Poland, Rumania, Czechoslovakia, and China participated in this joint research.
The experimental subjects the biosatellites carried included cell and tissue cultures, one-celled organisms, plants, insects, amphibians, fish, reptiles, bird eggs, and mammals—a total of approximately 40 species of living things at different levels of evolution and ontogenesis. A list of Bion flights is provided in Table 3.
The use of a large number of highly varied biological subjects for research made it possible to obtain statistically significant data on the direct and mediated physiological effects of weightlessness per se (i.e., without social and psychological overlays and without the modulating effects of the prophylactic countermeasures employed on every piloted flight). The investigations performed revealed the universal significance of the gravitational factor in the formation of the structure and functions of living systems and laid the foundations for a new scientific discipline—gravitational biology. It was demonstrated that weightlessness is the major etiological factor that induces physiological changes on spaceflights in near-Earth orbit. The experiments studied the mechanisms underlying the biological effects of weightlessness on the cellular, systemic, and organismic levels, identified the principles governing adaptation of living systems to weightlessness and readaptation to normal gravity, evaluated the effects of artificial gravity, and investigated the biological effects of the heavy components of galactic radiation and the combined effects of cosmic radiation and weightlessness. The flight of biosatellite Kosmos-936 produced data for the first time showing that artificial gravity created by an onboard centrifuge can prevent the adverse effects of weightlessness. This made it possible to consider artificial gravity as a promising method for maintaining the optimal physiological status of human participants in long-term spaceflights.
Table 3. Flights in the Bion Program
| Biosatellite | Year | Duration (days) | Biological subjects |
| Kosmos-605 | 1973 | 22 | 45 male rats, tortoises, fruit flies, meal worms, crown galls of carrot plants |
| Kosmos-690 | 1974 | 20.5 | 35 male rats, tortoises, fruit flies, pine seeds, fungi, bacteria |
| Kosmos-782 | 1975 | 21 | 45 male rats, fruit flies, fish roe, yeast, carrot crown galls |
| Kosmos-936 | 1977 | 18.5 | 30 rats (male and female), fruit flies, higher and lower plants |
| Kosmos-1129 | 1979 | 18.5 | 37 male rats, eggs of the Japanese quail, higher and lower plants, cultures of mammalian cells, carrot crown galls |
| Kosmos-1514 | 1983 | 5 | 2 monkeys, 10 male rats, guppies, crocus, corn seed sprouts |
| Kosmos-1667 | 1985 | 7 | 2 monkeys, 10 male rats, fruit flies, guppies, newts, higher plants |
| Kosmos-1887 | 1987 | 14 | 2 monkeys, 10 male rats, insects, guppies, newts, planaria, higher plants |
| Kosmos-2044 | 1989 | 14 | 2 monkeys, 10 male rats, guppies, crocus, corn seed sprouts |
| Kosmos-2229 | 1992-93 | 12.5 | 2 monkeys, frogs, newts, insects, cell and tissue cultures, planaria, seeds, plant sprouts |
| Bion-11 | 1996-97 | 12 | 2 monkeys, newts, crustaceans, insects, French snails, one-celled animals, seed sprouts |
Ground-Based Simulation Experiments. It is well known that the reverse side of scientific and technological progress is an increase in the extreme factors to which humans are exposed. Thus, it is natural that various different scientific experiments have had to be performed to assess the possible adverse consequences of such exposure to enable the development of the necessary preventive or protective countermeasures. Possibly, this need has been especially critical in aviation, space, and underwater medicine, which must confront the most complex and extreme external conditions that can have a significant effect on the health and occupational performance of humans.
To resolve these issues, of course, experts have used the experience accumulated in many areas of medicine and the results of initial studies on laboratory animals. However, in many instances, experiments or tests have had to be performed on humans if problems are to be solved once and for all. In 40 years, several hundred such investigations were undertaken in ground-based laboratories creating simulations of the effects of various spaceflight factors (isolation in a pressurized chamber, hypokinesia with head-down tilt, and water immersion) on living things. These tests have lasted from several days to a year. The centrifuge made it possible to study the effect of acceleration across a broad range of values, the barochamber—the significance and role of the barometric factor and altered atmospheric gas composition; and apparatus producing various types of ionizing radiation—the effects of the radiation factor. Water immersion made it possible to replicate certain biological effects of weightlessness.
A medical-technical experiment of a year’s duration involving three test subjects, which was conducted in the Soviet Union in 1967-1968, was important for the development of advanced LSS. This experiment investigated the possibility of long-term (up to 1 year) retention of normal human performance capacity under conditions of isolation in a pressurized chamber of limited size using water and oxygen regenerated from wastes and virtually totally dehydrated food. It addressed the characteristics of human interactions with the environment under these conditions, methods of medical monitoring, technological methods for designing the various modules, and other issues. During the experiment, the test subjects lived in an isolation chamber consisting of a living module and an experimental greenhouse connected to each other. This test of a closed-cycle LSS demonstrated that it is possible to live and work for a long period of time within such systems.
A 182-day experiment involving hypokinesia that was conducted at the Institute of Biomedical Problems in 1976-1977 in many respects was a prologue to the phase of long-term flights. The research methods and prophylactic coun-termeasures used in this experiment generated data, which, along with results of examinations of cosmonauts who at that time had participated in flights of moderate duration, allowed medical personnel to predict that it would be possible to increase flight duration further systematically.
The results of another experiment conducted in the same Institute in 19861987 made a significant contribution to the realization of the 327-day flight and the succeeding 1-year flight. This unique experiment involved long-term (370 day) hypokinesia for nine volunteer subjects. In many respects, this experiment made it possible to deepen and expand our understanding of the mechanisms by which weightlessness affects human physiology. Moreover, the procedure, schedules of physical exercise, and certain drugs whose efficacy it validated were subsequently used by cosmonauts on long-term flights.
In 1994, before the first long-term flight of female cosmonaut Ye. Kondak-ova, a 120-day hypokinesia test was conducted on female subjects, which made it possible to develop the recommendations necessary for her flight.
In 1999-2000, before the ISS went into full operation, the Institute of Biomedical Problems conducted a 240-day multifactor experiment, SFINCSS (Simulation of Flight of International Crew on the Space Station), involving participation by space agencies of Russia, the European Union, Canada and Japan, and also researchers from Austria, Germany, Norway, the United States, Sweden, and the Czech Republic. Twenty-seven volunteers from Austria, Germany, Canada, Russia, France, and Japan conducted more than 27,000 experimental trials and tested routine medical monitoring procedures. This experiment generated unique expertise in studying the interactions of an international crew and the long-term performance of a female crew member under conditions maximally approximating actual spaceflight conditions. Ground-based simulation experiments have generally preceded studies conducted on board unpiloted and piloted spaceflights, and their results have proven extremely useful in analyzing the data produced on spaceflights.
Research in Exobiology. Exobiology is the component of space biology that studies the presence, extent, and evolutionary characteristics of life in the Universe. Thus, exobiology asks such questions as, Where else in the Universe might life be found, and how would it be possible to establish its existence?
The awareness of the evolutionary interaction between the Universe and life led to extensive scientific search for such interactions in natural history. The issues addressed by exobiology may be divided into four areas; each corresponds to one of the major periods in the development of living systems:
• cosmic evolution, biogenic compounds;
• prebiological evolution;
• origin and early development of life;
• evolution of advanced life forms.
In its study of these areas, exobiology traces the paths leading from the beginning of the Universe to the major periods in the history of life. Additional aspects of exobiology address the study of compounds related to life and the search for life elsewhere in the Universe. Thus, exobiology develops through studying the occurrence and development of life on Earth, directly studying other planets and smaller celestial bodies of the solar system, and studying the rest of the Universe through observations from ground-based and orbital observatories.
The possibility of comparing biogenic products or extraterrestrial life forms with terrestrial forms is of enormous interest to biology. The problem of the existence of life beyond Earth is a component of one of the most important biological and philosophical problems—the origin and development of life in the Universe.
Studies in exobiology are conducted in two major areas: simulation of conditions in space or on certain planets and studies using robotic spacecraft. Vertebrates and higher plants are relatively sensitive to extreme factors, but microbial forms colonize virtually all possible ecological niches on Earth. There are organisms that can survive in a vacuum and those that can multiply under pressures up to 1300 bar and survive at pressures up to 20,000 bar. Some organisms can survive under exposure to ultraviolet radiation at a dose of 50,000 erg/mm2 and ionizing radiation in does of 2-4Mrad. Many microbes can survive for long periods without access to external energy sources, without food, and with virtually no water.
As for the presence of extraterrestrial life forms (for example, on Venus or Mars), investigations conducted from robotic spacecraft have not yet yielded positive results. Nevertheless, all human activity in space occurs under conditions of biological quarantine. Safeguards must be taken to ensure that terrestrial life will not be exported to other celestial bodies and that possible extraterrestrial organisms are not brought back to Earth. The development of space biology and its accomplishments do not merely serve the goals of interplanetary travel and the human conquest of space. In the future, space biology will facilitate the construction of the most general biological concepts pertaining to the problem of life in its most general sense and the paths of evolution of life in the Universe.
Major Results. Biomedical experiments conducted on 85 crew missions ranging in duration from 23 to 438 days on space stations Salyut and Mir (USSR/ Russia, 1971-2000), studies made on the Kosmos-110 specialized unpiloted biosatellites (USSR, 1966) and the 11 launches within the Bion research program (USSR, Russia, 1973-1997), and ground-based simulation experiments and investigations in general physiology and medicine have expanded our knowledge of the effects of spaceflight factors on living things, and in particular, on human beings. This has made it possible to improve continually the cosmonaut selection and training system and the means for medical monitoring of health to prevent the adverse effects of weightlessness and to provide postflight rehabilitation.
The major product of these efforts has been the creation of a unique system for preventing the adverse physiological effects of weightlessness, whose efficacy was convincingly demonstrated during space-station flights up to 1 year and longer (see Biomedical Support of Piloted Space Flight). On future spaceflights, requirements for maintaining cosmonaut health and supporting job efficiency and performance capacity will become more stringent as a result of increased space mission duration, requirements for enhanced EVA and assembly work, and the heightened complexity of research programs.
Understanding how living things react to extreme environmental factors and data on the limits of tolerance and endurance will make it possible to solve practical problems involved in designing and perfecting biotechnical systems and developing means and methods for increasing physiological tolerance to spaceflights, which is especially critical for supporting flights of human beings and their potential terrestrial fellow passengers (animals and plants).
Table 4. Results of Studies in Space Life Sciences
| Space biology | Space physiology |
| Demonstration that weightlessness does | Definition of the major risk factors for |
| not damage intracellular processes, cells, | piloted spaceflights |
| tissues, organs, or the organism as a | |
| whole | |
| Demonstration that the development and | Identification of the human functional |
| growth of living things in weightlessness | systems most subject to alteration in |
| is generally normal without anomalous | space |
| manifestations | |
| Comprehensive study of the mechanism by | Establishment of the main principles and |
| which changes occur in various portions | stages of nonspecific and specific |
| of the musculoskeletal system as a | adaptive physiological changes in |
| function of duration of exposure to | response to various extreme factors |
| weightlessness | |
| Failure to identify any remote biological | Expansion of the understanding of the role |
| effects of space flight | of the gravitational factor |
| Identification of the time course of changes | Study of the major mechanisms underlying |
| in vestibular functions in flight and | regulation offunctions and the formation |
| quantitative description of the | and maintenance of homeostasis |
| mechanisms of its adaptation to | |
| weightlessness | |
| Experimental demonstration that creation | Development of a rationale for approaches |
| of artificial gravity on a spaceflight, | to predicting human tolerance and |
| through use of an onboard centrifuge, | controlling defense reactions and reserve |
| can prevent the development of a | capacities under altered living conditions |
| number of adverse physiological changes | |
| during spaceflight | |
| Study of important mechanisms underlying | Development of a system of medical |
| the adaptation by various life forms to | measures and self-contained mobile |
| the effects of weightlessness and other | devices for providing medical care under |
| spaceflight factors | extreme conditions |
| Study of the combined biological effects of | Design of means of rapid assessment of |
| weightlessness, radiation, and other | sanitary and hygienic conditions and |
| spaceflight factors | ecological monitoring |
| Identification of the forms and limits of the | Refinement of requirements (including, |
| dependence of living things on gravity | toxicological ones) for an artificial living |
| environment | |
| Discovery of the principles underlying the | Formation of a concept of the norm |
| evolution of microflora during long-term | pertaining to various groups of healthy |
| use of a space station, making it possible | humans (profession, gender, age) |
| to evaluate medical, technological, and | |
| biospheric risks | |
| Study of the effects of heavy ions from | Development of techniques for appropriate |
| galactic cosmic radiation on living things | and corrective nutrition |
| Experimental demonstration during | Expansion of the knowledge of human |
| spaceflight of the utility of an | reserve capacities and human reactions |
| electrostatic spacecraft shield against | to extreme situations |
| ionizing radiation |
One of the challenges faced by space biology is the study of the biological principles and methods for creating an artificial living environment in a spacecraft. Particular issues that need to be addressed, if this problem is to be solved, include finding living things that are promising components (subsystems) of a closed ecological system, identifying the combination of environmental factors and methods that will support the optimal population productivity and stability of such organisms, and simulating experimental biocenoses and investigating their functional characteristics and potential for use on spaceflights. The creation of an artificial closed ecological system—a living environment for humans on a spacecraft—would enable analysis and revision of the general biological significance and acceptability of traditional terrestrial living conditions and means of satisfying basic human needs. The main results of scientific studies conducted in space life sciences are provided in Table 4.
Among the important factors that have enabled human conquest of space, we can cite extensive coverage of the relevant problems, combining of traditional and innovative approaches to their solution, a close relationship between scientific exploration and the solution of applied problems, and collaboration between medical personnel and designers of space technology. All this has contributed to making space biology, physiology and space medicine sciences worthy of the twenty-first century.
