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The paper discusses the use of methane (generated in the process of oxygen recovery from carbon dioxide released by the crew during its hydrogenation in the Sabatier reaction, with subsequent extraction of 61% of oxygen through electrolysis of the resultant water) in a regenerative life support system for crews on space missions. It demonstrates that the methane resulting from Sabatier reaction can be used both for pyrolysis in order to return the resulting hydrogen into this reaction so as to extract 100% of oxygen from carbon dioxide, and for producing food protein for life support in space. The use of methane pyrolysis was enabled by new technologies which allowed lowering the process temperature down to 500–700°C and obtaining the easy-to-remove carbon. It provides recommendations for designing space systems for methane pyrolysis. The paper makes the case for use of the existing processes for industrial production of protein from methane using methanotrophic bacteria in the production of food protein for space food rations, determines the balance of a closed-loop methanotrophic reaction, provides calculation basis and recommendations for designing space systems for methanotrophic production of food protein. Development of a system for food protein production from methane will enable its use as one of the systems for providing food on the Moon and Mars, as well as a backup system in space transportation missions. Key words: space missions, crew life support, СО2 hydration, methane pyrolysis, methanotrophic bacteria, food protein.

The paper discusses the effect of carbon dioxide (СО2) concentration in the at-mosphere on human health and issues of removing it from the atmosphere under conditions of pressurized modules of space stations. It is shown that, according to respiratory physiology, СО2 is a gas essential for human respiration, which turns into a toxic contaminant, when its concentration exceeds the threshold of 40 mm Hg (5.3 %) in human lung alveoli, and, accordingly, of 46–49 mm Hg (6.0–6.5 %) in arterial blood, what occurs probably when СО2 content in the atmosphere is ≈7.6 mm Hg (1.0 %). These nominal values, which arose at the origin of life, when CO2 content in the Earth's atmosphere was orders of magnitude greater than now, can be observed in all living things that breathe with lungs. Whenever CO2 concentrations in human air vesicles and arterial blood go below these values, the human experiences oxygen deprivation, even when there is a high oxygen concentration in the blood. The use of СО2 for breathing in medicine, aviation, and athletics also does not support the opinion that СО2 content in atmosphere below 7.6 mm Hg affects human health. Data from NASA studies of the link between СО2 levels in the ISS’s atmosphere below 6.0 mm Hg (0.8 %) and astronauts’ headaches does not prove this link. NASA’s unfounded lowering of standards for СО2 content down to 2.0–3.0 mm Hg requires an increase in the number of systems for СО2 scrubbing onboard the space station. At present, according to the minutes of AQS toxicological subpanel of the international ММОР panel, no scientifically proven standards currently exist for СО2 content in the atmosphere of space vehicles; their substantiation requires further scientific studies conducted by testers and cosmonauts.

The paper presents partial analytical solutions for equations describing variation in trace amounts of carbon dioxide in the atmosphere of habitable spaces within pressurized modules (PM) of a space station. The solutions may find practical application in calculations of concentrations for any contaminants, or for air flow through the purification system. It is shown that in a case where low-toxic contaminants are released into the PM atmosphere, it would be enough to cycle 3 volumes of the PM air through the purification system when the system operates without the breakthrough concentration (without the residual concentration of the contaminant at the outlet from the purification system), in order to achieve the 95% purification of the atmosphere. For highly toxic contaminants this value should be significantly increased depending on the maximum allowable concentration of the substance (47 volumes and more — up to 99.9% purification). The paper also considers variation in the concentration of the contaminant in the atmosphere during intermixing of atmospheres between PMs using intermodular ventilation. As a result, new analytical solutions were obtained for practical calculations which make it possible to determine gaseous contaminant concentration at any point in time and the time of the final equalization of the contaminant concentration in the space station atmosphere. It was determined that the time needed for complete mixing of gaseous contaminants through intermodular ventilation between two PMs does not depend on the initial concentrations of the contaminants (and only depends on the PM volumes and the intermodular ventilation flow rate). Key words: space station, pressurized module atmosphere, carbon dioxide, atmosphere purification, variation in concentration, air flow, atmosphere mixing.

The paper presents partial analytical solutions for equations describing variation in trace amounts of carbon dioxide in the atmosphere of habitable spaces within pressurized modules (PM) of a space station. The solutions may find practical application in calculations of concentrations for any contaminants, or for air flow through the purification system. It is shown that in a case where low-toxic contaminants are released into the PM atmosphere, it would be enough to cycle 3 volumes of the PM air through the purification system when the system operates without the breakthrough concentration (without the residual concentration of the contaminant at the outlet from the purification system), in order to achieve the 95% purification of the atmosphere. For highly toxic contaminants this value should be significantly increased depending on the maximum allowable concentration of the substance (47 volumes and more — up to 99.9% purification). The paper also considers variation in the concentration of the contaminant in the atmosphere during intermixing of atmospheres between PMs using intermodular ventilation. As a result, new analytical solutions were obtained for practical calculations which make it possible to determine gaseous contaminant concentration at any point in time and the time of the final equalization of the contaminant concentration in the space station atmosphere. It was determined that the time needed for complete mixing of gaseous contaminants through intermodular ventilation between two PMs does not depend on the initial concentrations of the contaminants (and only depends on the PM volumes and the intermodular ventilation flow rate). Key words: space station, pressurized module atmosphere, carbon dioxide, atmosphere purification, variation in concentration, air flow, atmosphere mixing.

Carbon dioxide (СО2) scrubbing from pressurized volumes of long-term space stations is one of the most critical aspects of crew life support, since each person, on average, releases 480 liters of СО2 (~ 1kg) per day. Meanwhile, СО2 is one of the gases required for human breathing, but at the same time its content in the atmosphere of the pressurized cabin must be kept below established standards, exceedance of which makes СО2 a contaminant harmful to humans. It should also be taken into account that at present the established standards for СО2 content in the space station atmosphere are not based on scientific research. The key parameter of the scrubbing system, which determines the СО2 content in the atmosphere of the space station pressurized cabin, is the effective flow rate of the scrubbed air through the system. It was established that in order to scrub the atmosphere, two requirements must be met: 1) supply the required air flow rate to the scrubbing system (this requirement applies to all types of the system), 2) provide the required efficiency of the scrubbing system for the contaminant removal. A formula has been derived for calculating the effective flow rate through the air scrubbing system, allowing not only to calculate the necessary charge through system of clearing, but also which makes it possible to compare performances of various types of systems. It was established that the most efficient system for scrubbing СО2 from the air is the sorption system, since it has the largest absorption surface, all other conditions being equal, and, therefore, it has the highest efficiency factor Key words Space station, carbon dioxide, air scrubbing, standards for СО2 content, effective airflow rate, calculation formula, efficiency factor, absorption system for scrubbing СО2 from air.

Life support for first manned spaceflights was based on supplies of consumables. Crew life support systems based on supplies of water and oxygen, in spite of their simplicity, are extremely inefficient in orbital space missions and are unfeasible in deep space missions because of mass and volume constraints. Therefore, there are currently developed and are to be used on space stations the life support systems that are based on chemical and physical regeneration of water and oxygen extracted from human waste. In view of further advances in long-duration orbital stations, and the prospects of establishment of planetary outposts and deep space exploration, the problem of constructing an automated system for controlling a suite of regenerative LSS becomes urgent. The complexity of solving the problem of constructing an efficient control system in this case owes to the existence of a large number of effectiveness criteria. The paper proposes a system of consolidated global efficiency criteria, which allows to break up this problem into a series of sub-problems of optimization in order to solve this problem. The proposed criteria are longevity, cost, comfort. The paper presents a series of specific examples of using the proposed principles with necessary generalizations. Key words: space life support systems, atmosphere revitalization equipment, automated control system, global generalized efficiency criteria, longevity, cost, comfort.

It is planned to include greenhouses in the suite of regenerative life support systems for crews of manned long-duration space vehicles to improve their habitability. Space greenhouses will provide crew members with green vegetables containing digestible vitamins and dietary fibers, as well as psychophysiological support during long space missions. The paper presents an analytical review of designs of a number of greenhouses in our country and abroad, both existing and under construction that are capable of operating in spaceflight environment. It describes their key design and operational properties, analyses problems standing in the way of developing more productive space greenhouses. It explains the advantages of our country’s conveyor-type space greenhouse with cylindrical planting surface for continuous production of vitamin-rich greens and other vegetables onboard a manned spacecraft. It points out the need to construct our country’s ground prototype for a full-scale space greenhouse to develop the process for growing plants in orbital station, transportation vehicles, in lunar and Martian outposts. Key words: regenerative life support systems, habitat, space greenhouse, cylindrical planting surface.

Based on the multiyear experience of hygienic control of the orbital stations, there are three causes of contingent air pollution: leakage of service system pipeline with chemical working bodies, spills of reagents used in biochemical and technological experiments, and air pollution by products of thermal oxidative degradation of nonmetallic materials. The authors describe their experience in successful elimination and prevention of hazardous consequences of fire aboard the space stations. Analysis of air pollution dynamics after actual fire events in the space station modules showed that it approximates a two-chamber air flow model with two phases of pollutant equilibration: first a rapid fall of concentration in the module on fire till air in the modules gets completely mixed, and then slow elimination of harmful pollutant from air. Identified were markers,--propylene and methylmetacrilate,--reacting to first signs of fire. Carbonic acid nitriles were recognized as toxic products of destruction. The positive effect of intermodular ventilation on dilution of toxic products of thermal oxidative destruction of materials was demonstrated. Satisfactory agreement of calculated and factual pollutant concentrations on board Mir permitted conclusion on applicability of the theoretical model to prediction of levels of air pollution due to contingency.

The problem of environmental compatibility of the ISS Russian and U.S. segments arises from chemical and biological inequality of their atmospheres and is attested by the data of observations during operation of Russian orbital stations Salyut and Mir. Efforts must be made to develop unified limits, and common procedures and requirements for evaluation of ISS materials and equipment by experts of the international partners.