Chapter V: Part 5

The probability of getting bends is reduced by—

(1) Selection of bends-resistant individuals
(2) Thorough denitrogenation before flight
(3) Limitation of decompressive pressure changes by appropriate choice
of cabin atmosphere pressure and composition
(4) Space-suit pressure setting

In some cases, further improvements might be obtained by using, in the cabin atmosphere, an inert-gas component which has a lower solubility in tissue and body fluids or less tendency than nitrogen to form bubbles.

Fire Hazard

Experience indicates that fires in pure oxygen atmospheres, even at low pressures (e.g., 1/3 atm), are extremely difficult to extinguish. While this phenomenon has nothing to do with respiratory physiology, the risk on flights of long duration may be so serious as to demand special measures. Unless effective countermeasures can be devised, this risk may argue very strongly against the use of such atmospheres in the future. Further experimental investigation is required.

Acceleration Effects on the Lungs and Pulmonary Circulation

Forces produced by high acceleration overdistend one part and compress another part of the lungs. Blood flow diminishes in some parts of the lungs and increases in others. Fluid leaks from the blood into the tissues and into the air sacs in parts of the lungs. These effects cause difficulty in breathing, low arterial oxygen saturation, and impaired consciousness during high sustained acceleration and, to a lesser extent, after its cessation. They must be considered when selecting the best gas to be breathed, since a high partial pressure of oxygen is favorable for consciousness, but a low inert-gas concentration during acceleration is unfavorable for rapid lung recovery afterward.

PHYSIOLOGICAL PROBLEMS

A study of the manned space flights and laboratory observations to date suggests that during long periods of weightlessness, some physiological difficulties may arise which may produce serious effects on human performance. Although recent experience gives no grounds for expecting insuperable difficulties, neither the quantity nor quality of the available observations permits the conclusion that long-term exposure to weightlessness will _not_ have serious consequences. The critical role to be played by the astronaut demands that every effort be made to identify in advance those phenomena which may affect performance, and to study their qualitative and quantitative relationships so that proper precautions can be taken.

Lawton ([ref.197]), in reviewing the literature on prolonged weightlessness, found few instances in which physiological function was truly gravity dependent. He stated that the physiological systems likely to be most affected by weightlessness were the musculoskeletal system, the cardiovascular system, and the equilibrium senses. Subsequent experience proved this to be the case. McCally and Lawton ([ref.198]) analyzed the data from experiments since 1961 and concluded that much more basic laboratory work is necessary. Studies using immobilization, immersion, and cabin-confinement techniques were recommended approaches toward simulating weightlessness.

Much of the difficulty in obtaining precise information of anticipated problems arises from a lack of knowledge of normal mammalian physiology. Many of these deficiencies can be remedied in the laboratory. In space-flight development, however, two distinct investigational approaches can be adopted. The first of these may be characterized as empirical and incremental; that is, the capabilities of the astronaut are explored in successive flights involving relatively modest increases in difficulty or severity of the environmental conditions. In this way it is hoped to ascertain the human limitations without running too great a risk. The second approach can be described as fundamental: determining by a series of controlled experiments the effects of exposure to space-flight conditions upon comparative mammalian physiology, with emphasis on man. A fundamental understanding of the observed effects would be sought so that predictions for new situations and possible ways to control them could be made with confidence.

It is not possible now to predict for flights of 30 days or more—

(1) The effects of sudden reimposition of reentry accelerations and
terrestrial gravity
(2) Changes in body fluid distribution and composition
(3) The effects of violent physical effort on respiratory and
cardiovascular systems in prolonged weightlessness
(4) Central nervous system functions, especially coordination, skilled
motor performance, judgment, and sleep-wakefulness cycles

NASA has emphasized that planning for manned space programs involves a systematic extension from physiological observations in animals to man, and finally the establishment of man as part of the man-vehicle system design. Moreover, these studies require the evaluation of central nervous, cardiovascular, respiratory, gastrointestinal, and other systems as a matrix in mutual interdependence. There is particular interest in the effects of weightlessness on flights exceeding 30 days.

Mammalian flights of about 30 days also merit attention, including the development of the life-support systems which must precede such a program. Development of facilities for biological experiments may well be an important requirement for studies in anticipation of manned flights of longer duration than Apollo. Unless the biological satellite programs of the type mentioned above are successful in providing the necessary data, a manned orbiting laboratory may also be important in studies of shorter range.

General Studies of Biological Rhythmicity

The effects of weightlessness on the organism as a whole may be manifested by important changes in certain integrated behavioral patterns having an inherently rhythmic character. Modifications in basic behavioral patterns and performance may occur as disruptions of rhythmic physiological phenomena, which are themselves the end product of interrelated functional activity in a number of physiological systems, such as the neuroendocrine, cardiovascular, and central nervous systems.

Measurements of interdependent components of biological rhythmicity are beginning to be analyzed by methods well established in physics—including correlation and spectral analyses, and phase modulation and variance in rhythmic processes. A wide variety of physiological functions can be treated as periodic variables in the analysis, including rhythmicities in cardiac output and blood pressure, respiration, brain waves, and the slower tides of appetite, and sleep-wakefulness. The importance of such investigations argues for their inclusion in forthcoming flight programs. Their experimental simplicity is an additional advantage. Biorhythms have been discussed in more detail in the section on "Environmental Biology."

Effects of Weightlessness on the Cardiovascular System

Earlobe oximetry, indirect measurements of blood flow and of blood pressure by finger plethysmography or impedance plethysmography, and ballistocardiographic techniques have potential application to manned space flight.

Adaptation to prolonged exposure to weightlessness or to lunar gravity may cause difficulties when the astronaut is exposed again to reentry forces and terrestrial gravity. It is possible that these adaptive changes may thus produce unacceptable effects on performance or cause risk to life. It is important to obtain experimental evidence on this subject.

It is common knowledge that following a stay in bed, dizziness, faintness, and weakness characterize arising, and that a feeling of general weakness may persist for several days. The phenomenon has been investigated in a number of laboratories. One approach has been to put healthy young subjects to bed, and even in extensive casts for periods of 2 or 3 weeks or more. Two major findings have emerged from these studies. First, a substantial adjustment in the blood circulatory system occurs, which is termed the "hypodynamic state." Second, there is a large decrease in the skeletal and muscle mass of the body.

There are two kinds of evidence for the hypodynamic state: measurement of parameters of circulatory function, and measurement of the response of the individuals to a quantitatively imposed mild gravitational load. After 3 weeks in bed, otherwise healthy persons exhibit an increase of more than 20 percent in heart rate; a reduction of 10 to 20 percent in total blood volume, primarily as a result of reduction of plasma volume; and a decrease in heart size of about 8 percent. Coupled with these cardiovascular changes is a reduction of 10 percent in the basal metabolic rate. It appears as though the circulation and metabolism are reset to a lower functional level commensurate with the reduced demands placed on the whole organism.

After 3 weeks of bed rest, all of the subjects tested showed pronounced orthostatic hypotension. After tilting, the average heart rate increased by 37 beats per minute, the systolic blood pressure fell some 12-mm Hg, and some of the subjects fainted. The measurements were continued for 16 days after the bed-rest period, and it was round that recovery was not quite complete when the experiment was terminated.

There is little question that in prolonged exposures to the weightless state, there is a fair probability of extensive circulatory adjustments, the seriousness of which cannot yet be foretold. While it is likely that the astronauts will adapt successfully to long periods of weightlessness at some new circulatory functional level, the remote possibility exists that the circulatory changes may be progressive to the point of ultimate failure.

Metabolic Effects of Weightlessness

Without metabolic information, accurate planning of environmental systems for long flights is difficult. Importance is also attached to early evaluation of weightlessness effects on body-fluid equilibria. The results of Earth orbital flights and of terrestrial water-immersion experiments suggest the occurrence of undesirable changes, although no effects leading to operational incapacity have yet arisen.

In both recumbency and immersion, a similar redistribution of body fluids occurs. It has been suggested that recumbency may affect an extracellular fluid-volume receptor mechanism which by decreasing aldosterone secretion by the adrenal gland, would decrease sodium reabsorption by the renal tubules. Aldosterone excretion decreases during recumbency and during standing in water, but increases while standing in air. There is also evidence for cardiac atrial volume receptor mechanisms which respond to increased filling of the left atrium with reflex inhibition of release of pituitary antidiuretic hormone (ADH), resulting in diuresis (Henry-Gauer reflex).

Altered fluid equilibrium in buoyant states is accompanied by shifts in intracellular and extracellular electrolyte distribution, especially sodium and potassium. Evidence from recumbency studies indicates a strong correlation between loss of erect posture or weight bearing and excretion of calcium stores in bone.

A bone X-ray densitometry method has been developed by Mack, at Texas Woman’s University, for accurately determining the loss of bone mineral (±2 percent accuracy) in humans and animals. The heel bone and spine are X-rayed using a calibrated aluminum wedge as a standard. This technique will be used for preflight and postflight analysis of the primate being flown in the 30-day biosatellite. Comparative appraisal of bone mineral behavior in astronauts participating in the Gemini and Apollo programs will be invaluable for future flight missions.

Bed rest and immobilization studies by Mack have shown loss of skeletal mineral and increased calcium in the urine and excreta. Four bed-rest studies, each extending for 2 weeks, compared different levels of calcium intake. Four men were used in each study and served as their own controls during extended ambulatory periods. During 2-week periods, up to 10 percent of calcium mineral was lost from the heel bone. Calcium was also determined in the urine and feces. In other studies, isometric exercises reduced loss of bone mineral during bed rest.

Excretion of calcium in the urine is accompanied by risk of its deposition as calculi or "kidney stones" in the urinary tract. Currently, changes in calcium metabolism resulting from weightlessness over periods up to 2 weeks is not considered a hazard requiring precautionary measures.

Flights in excess of 2 weeks, however, constitute a problem serious enough to warrant study on the 11-day orbital flights and the 30-day biosatellite primate mission. Therapeutic immobilization, post-poliomyelitis immobility, and experimental restraint in normal subjects lead to a negative calcium balance, with hypercalciuria.

Central Nervous System Functions in Weightlessness

The wide range of individual tolerances to the disturbing effects of vestibular stimulation has emphasized the importance of this factor in astronaut selection. At the same time, vestibular functions must be considered jointly with visual task performance, since both have special significance for such maneuvers as vehicle docking. Vestibular function in the weightless state remains almost completely unknown. Limited evidence from animal and manned space flights suggests that head turning, resulting from vestibular stimulation, may seriously interfere with visuomotor performance, but that susceptibility to these disturbances is significantly different between individuals and that partial adaptation occurs relatively quickly.

NASA is currently collecting extensive baseline electroencephalogram data under controlled conditions in a form suitable for mathematical analysis. Data are being taken from about 200 subjects in major national and overseas centers. It is intended that this study will assist in astronaut selection and monitoring in space.

Studies on many effects of weightlessness on nervous functions require monitoring of the autonomic nervous system, including such autonomic effects as gastrointestinal activity, secretion, lacrimation, salivation, sweating, and the central control of respiration. Urinary estimations of catecholamines and 5-hydroxyindoleacetic acid would provide important data on autonomic system activity if collected in flight and compared with preflight and postflight controls.

Major areas have been outlined in which prolonged weightlessness may be expected to interfere with performance, judgment, and, ultimately, chances of survival. These include cardiovascular, metabolic, central nervous, psychophysiological, and biorhythmic effects. They have been dealt with separately and in sequence, but have not been intended to be viewed as hierarchic. The relative scarcity of data necessarily precludes such an evaluation.

Soviet experience with zero gravity and weightlessness has increased their emphasis on this space-flight factor and was an important topic at the May 1964 COSPAR meeting. Discussion of the postflight medical status of Bykovsky (5-day flight) and Tereshkova (3-day flight) revealed a concern for the significance of prolonged weightlessness and the presence of postflight physical debility and fatigue following Vostok flights 3 through 6. These changes persisted for several days. Among the physiological conditions singled out for mention were—

(1) _Body fluids_— Cosmonauts have shown a postflight weight loss of
1.9 to 2.4 kg apparently resulting from a redistribution of body
fluid in response to elimination of the hydrostatic pressure
gradients caused by Earth gravity. There is the suggestion that
this redistribution is complete within the first 24 hours of
flight. Titov is reported to have been dehydrated alter his flight
with early hemoconcentration. These findings directly support
predictions made from ground-based research.
(2) _Cardiovascular_— Postflight orthostatic tachycardia is reported
for Titov as long as 23 hours after landing; at 48 hours there was
significant residual intolerance to the upright posture.
Cosmonauts have demonstrated a 20- to 35-percent increase in
oxygen consumption during the standard postflight exercise test.

In both of these areas there was a return to normal within the postflight period of study. The Soviets have continued their biological experiments in space with the Vostok/Voshkod series. Fixing of histologic specimens in flight by Bykovsky demonstrated a critical role for man and made possible an expanded experimental program. Biopackages have become more complex with each succeeding flight.

With the exception of postflight orthostatic intolerance after the third and fourth Mercury flights, changes as a result of exposure to a zero-gravity environment have not been noted by U.S. investigations in space. Ground-based research proceeds here at an advanced pace and is supported in large measure by both the USAF and NASA. A study of the relationships among renal and systemic hemodynamics, neurohumoral cardiovascular regulation, and renal excretory function in differently positioned subjects is underway, as are studies of acceleration tolerance.

DEPRESSED METABOLISM

In anticipation of prolonged manned space flights, NASA has sponsored research related to metabolism depression. The daily food requirements, for example, of astronauts during a voyage of several months can constitute a major portion of the weight and storage capacity of the spacecraft. A somewhat promising and fundamental approach to this problem is the reduction of the astronauts’ daily metabolic requirements. It has been suggested that astronauts on prolonged space missions be put in a state of suspended animation until their destination is reached. Though this sounds fantastic, 10 years ago no cell had been frozen to cryogenic temperatures and survived. Today it is commonplace for tissues to be frozen, stored at low temperatures, and thawed and then to maintain their viability and function.

Animal metabolism may be depressed by reducing body temperature, as in hibernation and hypothermia. Other means by which metabolism can be lowered include drugs and electronarcosis. Hibernation is a nonstressful state and results in a great decrease in metabolism. However, human beings are not hibernators, and much research is needed before the mechanism of hibernation is understood, and the possibility of inducing it in humans evaluated. Hypothermia is the direct cooling of the body to temperatures where metabolism is substantially depressed. Extracorporeal circulation systems combined with cooling are in routine use in most medical centers throughout the world. Hypothermia is not an ideal solution, however, since general body hypothermia is a stressful condition. Pharmacologic induction of hypothermia can be accomplished by such drugs as chlorpromazine and harbamil. Other drugs can be used to depress metabolism, but all have some disadvantage.

In recent years there has been a growing interest in electronarcosis, the induction of sleep by an electric current. Although potentially valuable, this method is far from routine application.

Outstanding advances have been made in metabolism suppression. Recent progress in the biochemistry and physiology of hibernation and hypothermia have shown that the oxygen requirements of individual mammals, organs, and tissues can be reduced. When the chemical composition of the blood and the cardiac output are sufficient to meet cellular requirements, regulatory mechanisms remain effective and animal survival is assured. In contrast, when oxygen transport is interrupted, a reduction in cellular activity occurs and regulation is impaired. In induced hypothermia, the low temperature slows the rates of all processes and modifies the action of metabolites and other substances. This in itself is not harmful, as shown by the true hibernating animal (e.g., ground squirrel), but will become disastrous as soon as anoxia and chemical imbalance begin to develop.

The phenomenon of natural hibernation is being investigated in the laboratory in the hope that the unusual tolerance of hibernating animals to reduced metabolism and low body temperature may some day be produced artificially in ordinary laboratory animals and man. Experiments with the ground squirrel, a typical hibernator, show that the artificially cooled ground squirrel does not tolerate such long periods of low body temperature as does a naturally hibernating animal.

Other studies of the brown adipose tissue (fat), which is present in most hibernating mammals, show it to be essential to hibernation. Indications that brown fat has a thermogenic role in rats exposed to low temperatures suggest that this may be the case in true hibernators ([ref.199]). Arousal of the hibernating animal by cold is triggered by sympathetically activated thermogenesis in areas of brown fat so located, relative to the vasculature, that the heat is transferred to areas of the body concerned with normal metabolic and nervous activity.

Soviet work comparing various depressed metabolic states and resistances to acceleration shows deep winter hibernation to be most effective, followed by deep hypothermia, and drug narcosis as the least effective.

Experimental evidence is being accumulated to show that hibernation and hypothermia somewhat protect animals against radiation. Clinical studies on irradiation of cancer patients indicate that lowering the body temperature reduces cellular metabolism and thus decreases tissue sensitivity to gamma radiation ([ref.200]).

The use of prolonged hypothermia, hibernation, drugs, and electronarcosis appears to hold some potential for reducing astronauts’ metabolic requirements. If one or mote of these methods become practical, human requirements for food and oxygen could be drastically reduced. Simultaneously, these methods may afford radiation protection and acceleration tolerance.

NUTRITION IN SPACE¹⁰

¹⁰ Includes part of [ref.201]. See also [ref.202].

The human body can use food stores so that the nutritional requirements can be reduced for a short time. This will vary widely among individuals and each individual may exhibit characteristic patterns of nutritional behavior. During reduced food intake, muscular efficiency may not change significantly over a period of 4 to 6 days; unfortunately, however, mental activity begins to decline after 24 hours. Feeding requirements can be divided into two categories: short term (for missions of less than 21 days) and long term. Since dehydration can occur in a matter of hours under adverse conditions, water requirements must be considered as a special case.

Water Requirements

Water requirements are extremely critical and the amount supplied should not under any circumstances be kept to a minimum. Rather, a large margin of safety should be allowed.

Present data on water requirements show a very strong dependence upon suit inlet temperatures. In the absence of an accurately controlled suit temperature, water requirements can easily double. If this should occur, the mission would probably have to be aborted, since it is doubtful if electrolyte balance would be maintained at such high rates of water loss. Normal or even extreme conditions of the terrestrial environment usually include diurnal variation in temperature which may modify water needs. These conditions will not be obtained in the spacecraft.

In addition to ground-based experiments, measurements of water intake should be made under actual flight conditions. Data from short-term flights should be used for extrapolation to longer missions.

Formula Diets

The tacit assumption which now prevails, "Astronauts even on short-term missions require a diet of great variety," is apparently not well supported. In many parts of the world, people live on a monotonous diet consisting of only a few types of food with no apparent ill effects, provided their nutritional requirements are satisfied. Experimental evidence from many sources (e.g., the Army Medical Research and Nutrition Laboratory) shows that individuals can be kept on a single disagreeable formula diet for as long as 60 to 90 days without harm. Since highly motivated individuals are chosen for space flights, it is unlikely that they would object to the monotony of a formula diet and would probably prefer its simplicity. Also, there are definite possibilities of developing a much more acceptable formula than present types. There is no reason to anticipate adverse effects from the use of formula diets in short-term flights.

Formula diets would be extremely desirable for short-term flights. A formula diet (a rehydrated liquid formula could be used) would considerably reduce the number of manipulations and the time required for in-flight preparation, compared to a varied diet. These two improvements could contribute materially to the safety of a flight, since the astronauts would not be preoccupied with food preparation for so long a period, and the food could be dispensed without removing suit components, such as gloves. Storage requirements could be simplified with this type of diet. Weight, however, would not be lowered without the development of more refined formulas than those now available. Formula diets could readily be adapted to the determined metabolic requirements of the individual astronaut. Packaging problems will be simplified by using formula diets, which can easily be given a variety of flavors and colors.

Waste

The problem of waste production is intimately related to nutrition and can be solved or simplified by dietary changes. Any diet should be adjusted for the minimum production of feces, before and during even short flights. Water will be sequestered by accumulation in the feces, and the net loss, under normal conditions, would be approximately 40 to 60 grams per man per day. Flatus can be a serious problem, since considerable concentrations of toxic gases may accumulate. The purification system for the recirculated atmosphere must be able to remove these, although the diet should be planned to minimize the problem. The collection of urine and its storage is of importance, particularly on short-term flights, and individual packaging and labeling of urine specimens will be necessary for the analyses.

Metabolism

An accurately measured intake of nutrients, calories, and water is necessary for determining metabolic demands imposed in any space flight. There is insufficient knowledge to predict total metabolic requirements under the numerous stresses which can be anticipated. Simulator studies are of great importance even for short-duration flights.

The two most important variables to be considered in establishing the minimal diet are protein and energy requirements. NASA is supporting research at the University of California (Berkeley) to determine these requirements and to estimate individual variation in healthy young men. The possibility of minimizing need through biological adaptation is being explored.

It is difficult to estimate the minimum protein requirement of an adult man. The generally accepted criterion of minimum adequate protein nutrition in the adult is the maintenance of nitrogen balance at minimum intake. The minimum protein requirements depend on endogenous nitrogen loss. Analysis of the little data available indicates a best estimate of 2 mg of nitrogen per kilocalorie of basal energy expenditure. However, this figure is higher than that noted in experiments in some human subjects.

After minimum nitrogen requirements and minimum amino acid requirements have been established, studies will be directed toward investigating caloric restriction and adaptation to restriction of calories. It has been suggested that caloric restriction in animals and man results in apparent decreased energy need for the same activity. This apparent paradox has never been explained. It has been shown that there is adaptation to repeated episodes of caloric restriction both in animals and man, so that subsequent periods of caloric restriction result in decreased rate of weight loss, nitrogen loss, and longer survival.

Additional experiments are urgently required to determine the metabolic demands for minerals—in particular, the metabolic balance of calcium, potassium, sodium, and phosphorus. Under conditions of high water consumption, large mineral losses are to be expected. Failure to replace these can cause an imbalance which could impair the efficiency of the individual to the extent of endangering the flight.

Analysis of samples taken in flight, both of urine and feces, should be made. Respiratory quotients can be determined in flight, blood samples should be taken before and immediately after flight for analyzing selected components (in simulator studies these could be taken periodically), and nutritional intakes (which would be facilitated by formula diets) must be measured and analyzed.

Short-Range Technology

There are many practical difficulties in providing for food storage and accessibility in spacecraft. The packaging of food materials, both dehydrated and liquid, has proceeded satisfactorily under the supervision of the Food and Container Institute. If packaging materials are to be made to withstand very high relative humidities and large variations in temperature, additional investigations are required, since such containers are not yet available. In packaging, serious consideration must be given to the ease with which the food may be reached and eaten.

If dehydrated formula foods are to be fed on short-term missions, additional work is required on the rehydration of such formulas. Present methods of water measurement under weightless conditions are not satisfactory, and better methods will have to be contrived.

Long-Term Nutritional Problems

There is a dearth of metabolic information, even for short-duration flights, without which changes in metabolic patterns to longer flights cannot be extrapolated. However, using scattered information, certain changes which may be encountered can be hypothesized. Decalcification of bone and changes in water-holding capacity of the body may be anticipated. It is also possible that changes in proportion of fat to lean body mass could be experienced and should be considered in nutritional planning. Nutritional requirements depend on size, particularly lean body mass, sex, physiological state, and individual metabolic rates. Therefore, individuals for space flight should be screened with these factors in mind if it is desirable to minimize food intake in long flights. The factors which influence the total nutritional requirements of the individual also influence his mental and physical responses to stress.

Synthetic Foods

The development of food materials other than those derived directly from animal or vegetable origin is of interest. Advantages of such diets may be low residue, ease of storage, rehydration, and manipulation. Experiments with chemically defined synthetic diet for humans have been carried out by Medical Sciences Research Foundation, San Mateo, Calif. The complete liquid diet is composed of required amino acids, fat, carbohydrate, vitamins, and minerals. A cubic foot of the diet (50 percent solids in H₂O) supplies 2500 calories per day for 1 month, and has been given a variety of artificial flavors.

This synthetic diet has been fed to human volunteers for 6 months in a pilot study at the California Medical Facility, Vacaville, Calif., and the results are being reviewed. Schwarz Bioresearch, Inc., is studying the storage, stability, and packaging of chemically defined synthetic diets for human and animal flights.

Food Production in Space

Long-term feeding in space depends upon a payload of stored food unless food is produced during flight. If sufficient propulsive energy is available, the duration of missions using stored food may be quite long. However, in emergencies in which a mission lasts longer than planned, survival may depend on the ability to produce food extraterrestrially. Eventually it will be desirable or necessary to produce food beyond the confines of Earth.

The nutritional requirements of the crew will be influenced by such factors as activity, physical and psychological stress, individual size of the members, and individual metabolic rates. The food intake will have to be adjusted to meet these requirements. It is necessary to know the nutritional requirements of each astronaut and the way in which these are altered by the conditions of space flight in order to estimate needs on long missions. Without this information, the food supplies for the longer flights may be too much, too little, or improperly balanced. Where dependence would not be on stored food alone, but on food produced en route, more exact information on requirements is needed to determine the capacity of food production units.

In the discussion of bioregenerative systems, it was suggested that food materials could be produced by photosynthetic organisms (e.g., algae, duckweed, and other higher plants) or by nonphotosynthetic organisms (e.g., _Hydrogenomonas_). In contrast to the use of living organisms, reprocessing waste materials by chemical treatment or the actual synthesis of high-energy compounds has been suggested. No chemical system has yet been demonstrated as workable for the economical production of food in space, and the systems considered produce materials which may be converted to food, but are not food as such.

Algal cultures have had the most extensive investigation as food in space, but the technical problems of using this material as a food source have not yet been solved. It is apparent from the investigations to date that algae will require treatment before they can be used as food. In limited trials, difficulties have been experienced with amino acid deficiencies, digestibility, high residues, and gastric distress. Processing methods which would be applicable in space travel and the possibility of secondary conversion by other animals or plants should be systematically investigated.

chapter 8

_Significance of the Achievements_

SIGNIFICANCE TO SCIENCE

One of the most critical research areas of the space program is bioscience. Of both practical and philosophical significance in exploring the origins of life and the possibilities of life on other planets, bioscience also promises much in medical aspects. Space offers biologists completely new environmental factors, such as the effects of zero gravity and of removal from Earth’s rotation. These effects have been studied in attempts to advance understanding of basic mechanisms of physiology and biological rhythms. These studies can be of great value in dealing with problems of disease and metabolic disorders.

Biological research is fundamental to the problem of successfully protecting and sustaining man in the peculiar and hostile space environment. Understanding human requirements and variations in their response to various environmental factors offers value in medical research for human survival and comfort. The many technological discoveries and advancements in electronic and engineering equipment greatly enhance medical diagnosis, treatment of disease, and the extension of human life.

The life sciences, biology and medicine, are fundamental to the success of manned exploration of space, which marks a unique and significant development in the long history of man’s conquest of new frontiers. Those who pioneered other frontiers on land and sea and in the air were not forced to await biological and medical research. Even the pioneers of aerial flight began their efforts without first seeking biomedical data. The search for such data followed flight experience and, indeed, was made only after problems arose.

Project Mercury, NASA’s first program for manned space flight, stimulated immediate and extensive studies in the life sciences to sustain man in space. Before a vehicle could be designed to carry an astronaut into space, anticipated biomedical problems associated with space flight were studied. Life-support systems were designed to offer adequate protection from environmental stresses peculiar to space, such as zero gravity, removal from Earth’s rotation, and high-energy cosmic radiation. These life-support systems used knowledge already gained from research for manned space flight by the U.S. Air Force.

Our entry into space has put us at the threshold of fundamental and far-reaching discoveries in the biological realm which have profound implications for other areas of human thought and endeavor. As man goes farther into space, the hazards increase; but past accomplishments indicate that the road ahead holds more promise than peril and that the vistas of knowledge that may be foreseen are as vast as space itself.

Almost everything which now can be said about the effects of extraterrestrial environments and about life on the Moon or the planets lies in the realm of pure speculation. There is one prediction, however, that can be made with considerable certainty by reason of historical precedent—the opportunity to investigate a totally new area, such as is offered by space exploration, is certain to produce a burst of scientific interest as soon as the path is charted by a few pioneers. Over the next few decades a progressively larger proportion of biological interest will turn to space. We may well expect that the discoveries made here will revolutionize some of our concepts of biology.

It should be fully realized that the accumulation and dissemination of biological and other scientific information is not only of great value to science and humanity but is of tremendous import to the prestige of the Nation.

SIGNIFICANCE FOR PRACTICAL APPLICATIONS

It can be predicted as confidently for space biology as for other space sciences that the economic costs will be amply repaid in the long run by applications of space-oriented biotechnology to other fields of biology and medicine. There are inevitable substantial, though indirect, contributions of NASA’s continuing efforts in space biology.

NASA-supported biological research has many practical applications and "spinoffs" which contribute to the fields of health and medicine, food and agriculture, and industry and manufacturing. Some of these are presented to show the range and value of applications which have resulted from basic and applied biological research. In addition to those listed are many others from the biosatellite program, particularly in the fields of bioengineering and miniaturization.

Health and Medicine

Solar cells, which have powered space systems, are now being used as a power source in studies on brain function. A miniaturized solar cell developed by General Electric provides enough power, under ordinary house lights, to stimulate an animal’s brain and to telemeter respiratory, cardiovascular, and brain-wave data while the animal is allowed to move about freely. Such a system is now used by the National Institute of Mental Health Laboratory at Rethesda, Md.

Scientists at the Ames Research Center have devised a new technique for studying organic compounds, whether synthesized in the laboratory or produced by a living system. This technique is based on a property of matter called optical activity. Previous methods of measuring optical activity have been plagued by low sensitivity. The new method is many tunes more sensitive and represents a real contribution to modern analytical instrumentation.

Studies on calcium metabolism and bed rest simulating weightlessness are adding knowledge on the prevention of demineralization of the skeleton; treatment of Paget’s disease and osteoporosis prevention of muscular atrophy; the cause and treatment of renal calculi (kidney stones); optimal calcium for the human diet; and the factors influencing calcium absorption, metabolism, and excretion. The results will have great importance in bone healing and repair, care and treatment of fracture cases, treatment of paraplegics, and treatment of polio patients and similar cases. These grant studies at Texas Woman’s University have also proven that the X-ray bone densitometry method can accurately detect changes in the skeleton.

A primary objective of the planetary exploration program is the detection of possible extraterrestrial life. The study of the fundamental properties of living things on Earth is restricted to the type of life which has evolved and survived here. Life which has been exposed to totally different environmental conditions may have markedly different physiological characteristics. The impact of the new information obtainable from the study of extraterrestrial life upon the sciences of medicine and biology will unquestionably be of fundamental and far-reaching importance. Advancement in the treatment of disease and the problems of aging are among the many possible consequences.

New developments in such techniques as ultraviolet spectrophotometry, polarimetry, and gas chromatography will find use in the detection of biochemicals and other compounds in hospitals and in toxicology and pathology laboratories. They will also be useful in studies of atmospheric pollutants such as smog.

Studies of the chemistry of living systems, molecular biology, and biophysics of cellular processes will create a better understanding of the basic mechanisms of life, leading to an understanding of both inherited and acquired disease, especially neoplastic conditions and chemical disturbances incident to mental disease.

The University of Pittsburgh is conducting a study to increase the availability of cytological technique in research and as a monitoring procedure by developing an automatic electronic scanning device using computer analysis for recording, counting, and sorting chromosomes. Structural changes in blood cell chromosomes can indicate the degree of radiation damage as well as damage resulting from various environmental stresses. Accordingly, this instrument, when developed, can be used as a radiation dosimeter in civil defense by swiftly detecting the degree and type of chromosomal aberrations in blood cells. Thus, casualties in nuclear attack could be quickly detected and treated. This system would also be useful for nuclear industrial plants and for military maneuvers. In medicine, various disease trends could be monitored. (Chromosomes exhibit anomalies in leukemia and mental retardation as well as in other states.) In space exploration and experimentation, the device can spot monitor radiation dose levels as well as changes resulting from any of the environmental stresses experienced in space. This apparatus can be modified for use as an extraterrestrial-life-detecting instrument by scanning the growth of cells (or cellular inclusions), computing rates, and telemetering changes to the researcher.

Investigations of rhythmic phenomena of various physiological systems can result in knowledge of the utmost importance to medicine. Rhythmic phenomena are found in the cardiovascular system of normal humans. Changes in these rhythms have the potential of foretelling abnormalities (heart disease, arteriosclerosis) before outward signs are manifested, allowing for earlier diagnosis, treatment, and control or cure.

The spacecraft sterilization program requires the use of rooms having the lowest attainable level of bacterial contamination. The rate of dissemination of bacteria from the humans in the room is basic to the problem. Data on this matter are being obtained through support of the Communicable Disease Center of the U.S. Public Health Service. The findings are affecting the measures used in surgical practice to lower infection rates.

Studies on the physiology of hibernation in mammals are important to understand temperature regulation and the mechanism of survival at low body temperatures. The purpose of this type of research is to understand and use reduced metabolic activity in astronauts on future extended space flight. Other applications involve studies of the mechanisms of injury and freezing biological organisms, for improving techniques in hypothermic surgery, pathology, and preservation of tissue for human grafting.

Food and Agriculture

Gathering agricultural information by remote sensing of Earth’s surface from aircraft, balloons, and satellites has a potential application in research and development. Current needs for data gathered in this way include crop and livestock surveys for marketing planning; soil mapping; crop disease, insect, and weed surveys; soil conservation management and research; and crop acreage control programs. As population and world trade increase, the needs will become even more intense for regularly scheduled synoptic surveys of the world’s agricultural lands for crop plantings and harvests; determining the condition of crops as affected by drought, disease, or insect outbreaks; and studies of the lands suitable for agricultural development in underdeveloped countries. The only way that worldwide synoptic surveys can be made is by using orbiting platforms.

The NASA nutrition program for developing diets for prolonged manned and animal space flight lends itself to civil defense purposes; military maneuvers where space and weight are prime considerations; polar and desert exploration; reducing hunger in underdeveloped countries; and detecting metabolic diseases as well as diseases of infancy and old age. For space research such a diet can be used on prolonged manned space flights, animal experiments in space, manned orbiting laboratories, and space and planetary stations. Studies on the packaging and stability of foods under various conditions of humidity, temperature, and radiation will lead to better processing and storage.

Learning how microbial spores are transported by air is important to biology, agriculture, and medicine. Besides spreading crop destruction, microbial spores produce allergic responses in some human beings. To obtain the facts, not only the biology of micro-organisms but also the weather factors that induce the flight of mature spores must be known. Thus, both biological and meteorological problems are involved. Data obtained under a NASA contract with the General Mills Electronic Division (now part of Litton Industries, Inc.) indicate that spores of fungi are present in low numbers in the stratosphere. A reservoir of spores exists which cannot be brought down by the normal scrubbing mechanisms of rainfall and other meteorological disturbances in the troposphere. This finding has important implications for reducing the spread of agricultural crop diseases and for protecting persons suffering from allergies. This project has indicated the necessity for designing novel biological samplers for use in the stratosphere. Such samplers will aid in determining various pollutants of the atmosphere.

The NASA program for developing sterile spacecraft for the biological exploration of Mars will contribute improved methods of sterilization that can be applied to the canning industry. Studies on sterilization at low temperatures for long periods of time are being supported by NASA at the Massachusetts Institute of Technology and the Communicable Disease Center and the Sanitary Engineering Center of the Public Health Service. The developing capability is making possible the heat sterilization of products that never before could be thoroughly sterilized.

In preparing for missions to search for extraterrestrial life, research on the psychrophilic or cold bacteria, on halophytic or salt bacteria, and on specialized bacteria and other organisms growing in extreme environments is defining the extremes under which life can exist. Increased knowledge about organisms that can grow in or on refrigerated, dried, or salted foods and other materials should have practical applications for food storage and preservation. Research on psychrophilic bacteria is being conducted by Whirlpool Corp. and the NASA Ames Research Center.

Theoretical studies of Martian life involve investigations of plant and bacterial spores. Many of these forms are spoilage organisms and some produce lethal toxins. This work has potential importance for food processing and for obtaining more precise knowledge of how wounds become infected. The program for investigating possible forms of life on Mars includes a thorough study of anaerobic micro-organisms. This research has led to the discovery of new types of nitrogen-fixing bacteria other than the familiar types found in the root nodules of leguminous plants. Thus, it may be possible to use these microorganisms, or the principles involved, in the incorporation of vital atmospheric nitrogen into terrestrial soils which are now unproductive.

Industry and Manufacturing

Batteries that have been developed in the space program to endure high sterilization temperatures for extended times will have greatly increased shelf life at normal storage temperatures and will be serviceable after many hours of baking at high temperatures.

Currently, the highest quality tape recorders are subject to imperfect reproduction because the tapes are heat labile; i.e., they soften and stretch when warm. The development of high-quality magnetic tapes for space-data recorders is an outgrowth of the materials developed to meet spacecraft sterilization requirements. These improved tapes will be useful for all types of recording—industry, automation controls, home, and studio.

OUTLOOK FOR BIOSCIENCE—MAJOR PROBLEMS

The problems undertaken are among the most challenging, if not _the_ most challenging, man faces on the space frontier. These include the quest for the origin of life, the explanation of life and life processes, the elucidation of the environment’s role in establishing and maintaining normal organization in living organisms, the possibility of extraterrestrial life on other planets—the concern of exobiology. The greatest promise for their solution lies in advances in biological theory rather than other avenues of research; therefore, it is fortunate that the need to solve them has come at a time when developments in experimental biology are at a high level. In addition, technological developments in electronics and engineering are providing new and wonderful instruments for this great exploration into the sources of life. Many of these have had practical application that has made possible important advances in medical diagnosis and treatment.

The broad national space goals initially charted by NASA have gone beyond space flight in near-Earth orbit to lunar and interplanetary exploration by man and machine. For such missions, more intensive and comprehensive research in the life sciences is needed. Before manned voyages for extended periods into deep space will be possible, solutions must be found for problems such as the development of bioregenerative life-support systems, communication with nonhuman species, and the development of new methods for transferring knowledge to the human brain.

The problems are all of the type that could perhaps be solved by truly great advances in biological theory, and probably not by any other avenue.

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