Reviews

Issues in Space Hygiene

D. I. Lazarenko, Candidate of Medical Sciences (Moscow)

The launch of the Vostok spacecraft on April 12, 1961, opened a new era in the history of humanity—the era of human conquest of space.

As flight duration increases, the hygienic requirements for life-support systems aboard spacecraft rise rapidly, and the challenges of space hygiene grow to an even greater extent. Research into pressing problems of space hygiene is therefore of particular importance.

The principal problems of space hygiene are: 1. Creating conditions that ensure normal life and a high level of human performance aboard a spacecraft. 2. Protecting humans from the harmful factors of outer space. 3. Studying methods and means of sustaining human life on other planets.

The most important and undoubtedly the most complex problem in space hygiene is that of ensuring normal life and a high level of human performance aboard spacecraft. This encompasses such matters as nutrition, water supply, the development of effective systems for temperature regulation, air conditioning and artificial lighting, special types of sanitary equipment and clothing, the design of a rational schedule of work and rest, and much else.

Providing spacecraft crews with food and water under strict weight and size constraints is a very serious challenge. During the orbital flights of Vostok-1 and Vostok-2, this problem was addressed by carrying the necessary supplies of food and water aboard the spacecraft. Supplies of drinking water treated with special preservatives, together with food concentrates containing all the necessary nutrients and vitamins, sustained flights lasting up to several days. A different approach will be needed for flights to other planets. During a long spaceflight, it does not appear possible to carry substantial reserves of water and food concentrates. Moreover, the food concentrates used aboard Vostok-1 and Vostok-2, while entirely acceptable for flights lasting up to several days, cannot be considered nutritionally adequate for flights lasting months or years.

In considering the problem of nutrition aboard a spacecraft, a number of authors [Briggs (1960); Clark et al. (1960)] propose using dehydrated foods and resynthesizing food from the products of the body’s vital processes, as well as growing plants and animals. They recommend producing food by processing human waste with the aid of various plant organisms (molds, yeasts, algae, and others).

In theory, the problem of nutrition in space could be solved by chemically synthesizing food products from inorganic substances (I. M. Sisakyan, 1961). But that is a path for the future. At the present stage, the most expedient approach would apparently be to establish a cycle of matter within the closed ecological system of the spacecraft cabin.

On Earth, people have grown accustomed to a certain variety of foods which, for readily understandable reasons, they will not have aboard a spacecraft. The closed ecological system will most likely provide cosmonauts with a limited range of foodstuffs from which meals will have to be prepared during many years in space. It is extremely important that, in space, the body receive not only proteins, fats, carbohydrates, water, and vitamins, but also minerals, among which trace elements essential to life—cobalt, copper, manganese, zinc, iodine, and others—are particularly important. Research is needed to determine the quantities of trace elements in the components of the spacecraft’s ecological system and to find ways of supplying them to the human body in the required amounts.

It should be noted that a number of other difficulties will arise in solving the problem of nutrition in space. These include cooking food and developing suitable devices for consuming and storing food and water in weightlessness.

An important task is to find and investigate new principles for supplying water in space. Long-duration human flights to other planets are possible only if a complete water cycle is established aboard the spacecraft [Sendroy (Sendroy, 1959)]. This makes it necessary for humans to use water recovered from the body’s waste products—excretions from the lungs, skin, and kidneys. Various investigators propose using physical and chemical methods of water purification [Clark et al. (Clark a. oth., 1960); Hawkins (Hawkins, 1958); Ingram (Ingram, 1958)]. Methods currently under study include distillation, freezing, ion exchange, and electro-osmosis. The study of freezing and electro-osmosis merits attention because these methods are the most economical in terms of energy consumption (N. A. Dobrotin, 1954; Sendroy, 1959). The most complete purification of water is achieved by distillation and freezing. Evaporation under reduced pressure is a highly efficient approach. Adsorbents and filters will also apparently be indispensable. Water obtained by any of these methods will need to have its taste improved and to be enriched with minerals essential to the body.

A very important issue is the creation of optimal microclimatic conditions in the spacecraft cabin. On the Vostok-1 and Vostok-2 spacecraft, automatic conditioning systems maintained the prescribed microclimate parameters: air temperature (within \(10–25^\circ\)), relative humidity (\(30–70\%\)), normal pressure, and the required concentrations of oxygen and carbon dioxide. The air was regenerated using highly reactive chemical compounds. On future spacecraft, the problem of maintaining air quality could be addressed not only with advanced regenerative systems but also through the use of various plant organisms that, under certain growing conditions, release large quantities of oxygen and absorb carbon dioxide. For a number of years, intensive work abroad has been ...

are investigating the problem of air regeneration by means of photosynthesis [Jackson, 1960].

A place must also be given in scientific research to the regulation of artificial and natural lighting and to the development of hygienic requirements for lighting conditions aboard spacecraft. Above all, the possible adverse effects of solar radiation on the body must be taken into account.

A difficult task is the development and construction of waste collection devices and a system for the disposal of fecal matter that meet sanitary and hygienic requirements and the distinctive conditions of spaceflight. These two problems are closely related, although it is difficult to incorporate their solutions into the design of a spacecraft without violating hygienic requirements. Human excreta must pass into sealed collection containers through special receiving devices that ensure their immediate and complete isolation. The prolonged stay of cosmonauts in sealed spacesuits will create additional difficulties in solving this problem.

At present, there are several views on the disposal of fecal matter. One possible approach is to use human and animal excreta to grow plants [Ebbs, 1959; Nakamura, 1959; Taylor, 1958] for human consumption. Human and animal excreta would thus enter the cycle of matter in the closed system of the spacecraft. Weightlessness makes it necessary to develop a set of special hygienic measures and to create “unearthly” devices for maintaining personal hygiene. Crew members and all unsecured objects around them will move freely within the sealed cabin. Water not contained in sealed vessels will likewise move freely through the cabin air. These difficulties could be overcome much more easily if artificial gravity were created in the living compartments of spacecraft.

It has been suggested that the existence of bacterial forms under space conditions cannot be ruled out (I. M. Sisakyan, 1961), giving rise to a number of new problems.

Flights to other planets greatly expand and complicate the requirements for cosmonauts’ clothing. Various types of spacesuits will have to be developed. In the event of cabin depressurization or a cosmonaut’s exit from the spacecraft, a suit equipped with a number of life-support systems is needed: heating and cooling, ventilation, oxygen supply, water-vapor absorption, and so on. Naturally, cosmonauts’ clothing must be convenient to use, lightweight, and unrestrictive of movement, and must meet a number of other requirements arising from the particular conditions of the space environment. Questions such as the provision of underwear for spacecraft crews also require study.

A person’s prolonged stay in an isolated cabin of limited volume calls for serious research and the development of the most rational schedule of work and rest. The effects of work processes and working conditions on cosmonauts must be studied in order to establish hygienic standards, create the most favorable conditions for work, eliminate possible harmful effects of environmental factors, and improve cosmonauts’ working capacity.

Flights of manned spacecraft have shown that coordination of movement does not undergo substantial changes under these conditions. The cosmonauts operated a telegraph key, made entries in onboard logs, and performed similar tasks with considerable accuracy. This gives grounds to believe that…

…regard the maintenance of human working capacity under conditions of prolonged weightlessness as possible and suggests specific ways of solving this problem.

An extremely important question in the exploration of outer space is the need for further study of the effects of ultraviolet radiation, cosmic rays, and other forms of ionizing radiation on the cosmonaut’s body, as well as the development of reliable measures to protect humans against them.

Satellite flights have established that space near the Earth is characterized by intense radiation (A. A. Blagonravov, 1961). It has also been established that explosive events occur periodically on the Sun—on average, once a month—producing enormous numbers of particles with energies of tens or hundreds of thousands, and sometimes billions, of electron volts. This radiation may pose a serious danger to cosmonauts who are in interplanetary space at the time.

The effects of cosmic radiation on the human body have not yet been sufficiently studied. During the flights of Vostok-1 and Vostok-2, no signs of an effect of ionizing radiation on the cosmonauts were detected. This can apparently be explained by the favorable radiological conditions under which the flights took place (A. A. Blagonravov, 1961): the spacecraft orbits lay below the radiation belts, and there were no explosive events on the Sun.

The extent of the harmful effects of cosmic radiation on food and water has likewise not been studied. The concern here is that cosmic radiation possesses enormous energy and can induce radioactivity in foodstuffs and water.

Computing equipment and telemetry devices transmit information to Earth on the operation of all the cosmonaut’s life-support systems. Modern teleradiometric equipment is used as the principal means of monitoring hygienic conditions aboard the spacecraft. This calls for further, more detailed development of specialized research methods and equipment, with extensive use of precise mathematical methods.

All this shows that the successful exploration of space is closely bound up with the further development of scientific research in space hygiene.

References

Blagonravov, A. A. Vestn. AMN SSSR, 1961, no. 6, p. 19. — Dobrotin, N. A. Cosmic Rays. Moscow, 1954. — Sisakyan, N. M. Vestn. AN SSSR, 1961, no. 6, p. 31. — Briggs, M. H., J. Brit. Interpl. Soc., 1960, vol. 17, p. 325. — Clark, R. T., Clamann, H. G., Balke, B., et al., Aerospace Med., 1960, vol. 31, p. 553. — Ebbs, I. C., J. Am. Diet. Ass., 1959, vol. 35, p. 13. — Hawkins, W. R., J. Aviat. Med., 1958, vol. 29, p. 525. — Jackson, C. B., Roush, G. R., Bovard, R. M., Aerospace Engng., 1960, vol. 19, no. 5, p. 40. — Ingram, W. T., Air research a development command. Office of scientific research. Report N. 58–148. Dec. 1958. Curr. list med. literature, 1959, vol. 36, no. 10287. — Sendroy, J., et al., Aerospace Med., 1959, vol. 30, p. 640. — Taylor, A. A., Food Technol., 1958, vol. 12, p. 442.

Received November 15, 1961.