Soviet Life Support Requirements
LIFE SUPPORT
BASIC METABOLIC REQUIREMENTS IN SPACE
Space beyond the Earth environment is harsh, characterized by a fluctuation of severe temperatures and the absence of a significant atmosphere required to sustain human life. To enable man to survive this environment, a space capsule is necessary which contains the necessities of life. This capsule must provide the proper amount of oxygen required for normal respiration as well as a moderate temperature, between 64 degrees to 81 degrees C, the necessary foods and fluids and the capacity to dispose or recycle human generated waste products such as carbon dioxide, urine, feces, and body perspiration.
Soviet studies have ascertained that the average adult daily requires approximately 800 grams of oxygen, 700 grams of solid food with a total caloric value of 3000-3300 kilo calories, and 2500 grams of drinking water. If the subsequent bodily excretions are not recycled for the production of oxygen, food and water, a three-man crew on a 1-year mission would require 1.5 tons of food, 3.3 tons of bound oxygen, and 5.9 tons of water. This is equivalent to almost one-half the total weight of a space station such as Salyut g 152 153 in order to support life in outer space, the capsule environment and support systems must function properly 24-hours per day for the duration of the mission. The capsule environment must also be sufficiently comfortable to provide the psychological support systems necessary to maintain the mental well-being of the space crew for the duration of the mission.
Since this support system is the only link with Earth, it must contain all those human necessities available on Earth. These include protective equipment to prevent harm to the station from such factors as meteorites and radiation. The capsule must have facilities to serve both recreational as well as exercise functions. For long term space missions it must also provide a means for the regeneration of oxygen, drinking and housekeeping water and food. By the end of 1980, several missions approaching 185 days in space had been completed by the Soviet Union. In those instances, the maintenance of adequate environmental and nutritional supplies has been achieved by resupplying the Salyut space stations with these necessities using primarily "Progress" cargo ships. These efforts as well as the on-board systems have proven very functional. However, as longer and perhaps interstellar space missions are undertaken, it will become necessary to develop systems that will be totally self-contained and capable of regenerating oxygen, water and food. (154)
AIR REGENERATION AND SPACE CABIN ENVIRONMENT
An inherent problem in a sealed environment such as a space capsule is that the human contaminates the spacecraft by micro-mixtures of exhaled air, urine, intestinal gases, and perspiration. The magnitude of this contamination is, of course, all dependent on the temperature, humidity, concentration of carbon dioxide, mobility of the occupants and the character and types of foods consumed.
The waste products of people reaching the external environment via the intestinal tract, kidneys, skin and lungs are composed of more than 400 different chemicals.(155) The emission of volatile components of these waste products may contaminate the space capsule even in the presence of adequate storage areas. The major volatile mixtures generated by the crew from exhaled air, perspiration, urine and intestinal gases consists of the following: ammonia, methylamine, diethylamine, formaldehyde, acetone, methylethylketone, propinic aldehyde, carbon dioxide, formic, propionic, valeric, isovaleric, butyeric and lactic acide, methyl, isopropyi, and propyi alcohol, methane, ethane, propane, hexane as well as trace amounts of other organic compounds. (156) Without effective removal of these substances from the air of a sealed cabin, they could accumulate to toxic levels and thereby reduce the human capacity to work in that environment.
The Soviets employ a series of filtering media for the removal of waste gases and microparticulates. These include activated charcoal filters, high efficiency fiberglass filters and catalytic chemical absorbents.
They are also reported to be experimenting with a variety of techniques for maintaining a purified space cabin environment. Techniques under consideration for removal of carbon dioxide include molecular sieves, synthetic zeolites, as well as freezing of carbon dioxide out of the gas mixtures. A more detailed schematic depicting carbon dioxide removal techniques is shown in figure 48. (157)
The microenvironment aboard the Soviet space station is maintained at values virtually identical to those encountered on Earth. Oxygen is generated by utilizing oxides and superoxides of alkali metals. The generated air in the working and living compartments is usually of a two-gases mixture, nitrogen and oxygen. The air's oxygen and carbon dioxide content is routinely monitored and regulated by means of a gas analyzer. On the Salyut 6 space station the microclimate was as follows: (158)
Total pressure, 700-830 mm Hg; oxygen partial pressure, 154-195 mm Hg; carbon pressure, 1.34-6.64 mm Hg; air temperature, 14.6-24.3 °C; and water vapor partial pressure, 5.37-17.1 mm Hg.
This contrasts appreciably both in the mode of generating oxygen and in the partial pressure of the gaseous environment employed in the Skylab space station. (159) The latter maintained a partial pressure of 5.0 psi of oxygen (70 percent oxygen, 30 percent nitrogen) supplied from liquid oxygen reservoirs. A regenerated molecular sieve was used to scrub out the carbon dioxide. The space cabin temperature was maintained between 21.2 degrees C and 26.8 degrees C with a relative humidity between 40 and 70 percent. During the more recent U.S. shuttle missions, respiratory gases were supplied at 14.7 psi, a partial pressure, identical to that found on Earth. The gas composition was 20 percent oxygen and 80 percent nitrogen. The carbon dioxide was removed by lithium hydroxide absorption. (160)
There are advantages to the chemical generation of oxygen. These include a reduced weight requirement to that necessary for carrying liquid oxygen. In addition, the Soviet system is much less complicated and therefore less prone to malfunction and the influence by external factors, and provides for a less flammable environment. The disadvantage is that it lacks flexibility in altering the gaseous environment for experimental purposes and in emergencies. A schematic depicting the Soviet life support system is shown in
Cosmonaut Metabolic Balance. Soviet manned spacecraft rely on cartridges of potassium super oxide for an oxygen source, and lithium hydroxide to remove carbon dioxide. A heat exchanger condenses out excess moisture. This figure shows the metabolic balance for a Vostok cosmonaut for 1 day. Approximately 2.5 kg. of regenerator yields about 600 liters of oxygen per day.
There is increasing evidence that under weightless conditions, a modification of proportions of gaseous mixtures differing from those found on Earth might be advantageous. (161, 162, 163) It has been observed that in a space capsule environment, due to weightlessness and hypokinesis, there is a decrease in oxygen uptake and carbon dioxide output. In addition, such other physiological parameters as basal metabolism, blood pressure, and heart stroke as well as the minute volume of the heart, nitrogen balance, muscle mass, plasma and erythrocyte volume are all decreased. Soviet studies have pointed toward the use of altered gas atmospheres to prevent or diminish the effect of deconditioning brought about by hypokinesis and zero gravity.
Additionally, Soviets suggest that the ability to regulate the gaseous atmosphere of a closed environment may effectively be utilized to maintain a high work efficiency with optimum energy expenditure. To these ends it is critical that the space cabin environment be optimum by eliminating toxic substances as well as by regulating on demand the gaseous environment in the capsule. (164)
WATER AND FOOD MANAGEMENT
Metabolic activity of man requires the consumption of such necessities as water, oxygen and solid food. In turn, via bodily functions, he eliminates waste products in the form of urine, feces, carbon dioxide and other gaseous products. He also produces by perspiration and exhalation, organic waste and water vapor. These waste products must either be stored aboard the space capsule, jettisoned into space or recycled for subsequent consumption. The earlier Soviet spacecrafts, being in space for a short duration, primarily brought their water supply from Earth, and stored the waste products and brought them back to Earth. In view of the increased time spent in space and looking forward to even longer missions, it is becoming imperative that these waste products be recycled as efficiently as possible.
Currently, the U.S.S.R. recycles water vapor by condensing it on cooling coils. The condensate as well as water previously used for bathing is passed through ion exchange columns and then through activated charcoal filters, prior to being sterilized by heating. Minerals such as calcium, magnesium, bicarbonate, chloride and sulfate are added to this recycled water. The latter is then stored in water batching units for future use. (165) The water that is brought aboard the spacecraft from Earth is sterilized by a very old technique, ionic silver. This process is bacteriocidal, thereby being an effective sterilant. However, long term storage of water does alter its taste, therefore influencing its acceptability to the cosmonauts.
The Soviets reclaim oxygen from recycled water by electrolysis. Byproducts, such as methane gas, are jettisoned into space. Urine is collected in storage tanks, as is solid waste. When these tanks are filled, they are jettisoned into space. (166)
In summary, the problems associated with water storage for long term space flights prohibit sufficient quantities from being brought aboard the spacecraft at the time of launch. This therefore man-dates the need for a system that can efficiently extract, purify, up-grade, and store water generated by respiration, perspiration and body waste.
Weight penalties and storage difficulties would be too great to use significant quantities of fresh foods, although the Soviets in their Salyut program do provide limited space for refrigeration.
Obviously, the use of dehydrated food requires an adequate water supply. The long term goal of the Soviet space program is the development of methods for growing a portion or all of their food supply aboard the space station. This presumably would also provide a means of carbon dioxide removal from the space cabin and the generation of a portion of the required oxygen. (167)
WASTE MANAGEMENT AND PERSONAL HYGIENE
Extended manned space flights impose special requirements on the general areas of waste management and particularly on personal hygiene. An adult male, as a byproduct of metabolism, produces 1.2 liters of liquid waste and 200 grams of solid waste per day. The earlier Soviet space missions of relative short duration (5 to 18 days) did not require any complex means of either recycling or otherwise disposing of waste. However, as space missions have increased in duration it has become necessary to either dispose of or recycle waste products. Regeneration systems processing fluid waste into potable water as well as recovering of oxygen from such byproducts are now practical and necessary. (168)
The use of solid waste for the production of food and water in closed ecological systems is under intensive investigation. (169) The Soviet publications suggest that waste products in general are still collected and ejected through air locks into space or placed aboard expendable Progress transports that on reentry into the upper atmosphere of Earth are incinerated. (170)
The communal hygiene of the spacecraft inhabitants must be given serious attention in view of the rather confined living quarters aboard a spacecraft. This is necessary not only to provide comfortable living conditions, but also to reduce the risk of transmission of pathogenic microorganisms amongst the inhabitants of the cabin. A high level of personal hygiene also is conducive towards establishing and maintaining a high degree of personal motivation. In order to establish acceptable levels of hygiene, recent Soviet Salyut 6 orbital stations have a shower aboard (see fig. 50). (171) This consists of an elastic cylinder with two capped ends, containing a mechanism for mixing and spraying hot water and hot air and for removing the expanded water vapors. During the earlier Salyut 6 missions, the cosmonauts showered about once a month and supplemented this by using washcloths impregnated with germicidal lotions as well as a deodorant. (172) In the more recent Salyut 6 missions, cosmonauts shower once every 10 days. This latter schedule obviously requires additional water supply. (173) In studies performed both aboard the Soviet orbital station as well as in sealed capsules maintained on Earth, the Soviets observed that there is a marked increase in microbial discharge by the occupants of microorganisms into the space capsule. It has been noted that under normal terrestrial conditions man expells approximately 110 microorganisms per hour from the upper respiratory tract. This discharge accumulates in an airtight space and the concentration becomes 10 times higher when one is confined in a closed environment. Similarly, the microbial flora of the skin is increased by 10 fold in an airtight environ ment, under reduced personal hygiene, restricted by a limited energy and water supply, as well as by the weight and dimensions restrictions posed by the space capsule. (174)
Current personal hygiene practices aboard the Salyut orbital stations include daily sponging with a moist washcloth of the hands, face and mouth. Underwear consisting of a knitted absorbent material is changed once per week. This is preceded by rubbing the skin with moistened and dry towels. The cosmonauts also use a damp washcloth to clean their hands prior to eating and after using toilet facilities. The area of the skin where electrodes had been applied for monitoring of vital functions are also cleansed in this manner. In all instances, a lotion containing antimicrobials is used to dampen the washcloths. (175) Soviets indicate that there occur an average accumulation on the face and hands of 99 mg of chlorides, 105 mg of ammonia and 0.7 mg of nitrites. It is reported that utilizing germicidal lotion did not adversely affect the crew's skin. (176)
Ground based studies by the Soviets have indicated that for long term missions, more novel techniques for cleansing the skin, particularly areas covered with hair, are necessary. The use of showers certainly enhances personal hygiene. However, products must be developed that have sufficient detergent properties to remove lipid accumulation on the skin. These must have selective bacteriocidal properties to maintain relatively normal skin function and microbial flora. Once more, because of the requirement to recycle expended water for subsequent topical and internal consumption, it is mandatory that the detergent and antimicrobial agents be readily removed by the recycling process. (177)
Other components of a comprehensive personal hygiene program consist of the use of tooth brushes with low foaming toothpaste, as well as the use of chewing gum after meals. Shaving as well as hair grooming are accomplished by conventional means, except that hair and shed cornified epidermal cells are removed by a vacuum system. (178)
Communal hygiene aboard the space station must provide conditions that are comfortable and safe in regards to the microclimate, the respiratory gas composition, illumination, vibration levels as well as the microparticulate composition within the space capsule. The microparticulate composition is the summation of the individual's metabolic process as well as the caloric composition of the consumed food. Penetration of microparticulates into the respiratory tract and particularly of potential pathogenic microorganisms may prove to be significantly different under the influence of zero gravity. This factor must be kept in mind when considering the space cabin environment and crew contamination. (179)
The requirement for a comprehensive and effective hygienic program in space is also critical from an aesthetic point of view. The space travelers are confined in a rather small space, thereby being in close proximity to each other, usually over extended time periods. More significantly, from a risk point of view, individuals do shed microorganisms both from their orifices as well as their skin.
As Soviet studies have indicated, there is a transfer of microorganisms from one individual to another, particularly in confined space. Some of the organisms have even shown a modification of their antibiotic sensitivity. (180) In the absence of adequate hygienic protocols, potentials for cross infections are enhanced.
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