Survey of Soviet Activity in the Use of Active Chemicals for Space Cabin Air Revitalization

A. W. PETROCELLI, PH.D.

The Soviet manned space flights have relied on an "active with the thermodynamics and kinetic studies of the chemical" for the maintenance of a habitable cabin atmosphere. pertinent air revitalization chemistry of these materials. The "active chemical" has not been specifically identified in the available Soviet published literature. However, reasonably de- Numerous publications have appeared dealing with the tailed descriptions of the properties of the "active chemical" nature and the rates of the reactions of these materials have been given and, on the basis of those descriptions, it is con- with carbon dioxide, carbon monoxide, and water cluded that the material employed was an alkali metal super- oxide. vapor. 1-63 Soviet scientists have been active for many years in the study It would be safe to estimate that since the early of inorganic peroxides, superoxides, and ozonides as air revital- 1950's the Russians have outpublished U. S. scientists ization materials. This activity is reviewed and the significance of current Soviet basic chemical studies to future chemical air by about 3:1 in regards to basic research on these ma- revitalization systems is analyzed. terials. At least one of their leading scientists in this area, I. A. Kazarnovskii, 4-1~ who has been active in this field since the early 1930's, has received public acclaim for his work. In an article entitled "Toward New HE AVAILABLE SOVIET popular and technical Achievements in Soviet Chemistry," which appeared in T literature related to the Soviet man in space pro- Pravda, June 25, 1962, Kazarnovskii is praised as a grams has consistently referred to the use of "active major inorganic chemist. His work on superoxides was chemicals" as the prime method of maintaining habit- especially noted and he was credited as being respon- able atmospheres in Soviet space cabins. In this paper sible for the current industrial scale production of the Soviet activity in the area of chemical means of sodium superoxide in Russia. air revitalization is reviewed. The term "chemical Analysis of the Russian literature, both the technical means of air revitalization" is herein defined as the use literature and that prepared for general public con- of multifunctional chemical compounds suitable for use sumption, leads this author to conclude that the great as sources of oxygen and for carbon dioxide removal in attention they have given to active chemical com- manned space cabins. Of particular interest in this re- pounds for air regeneration has been rewarded hand- gard are inorganic peroxide, superoxide, and ozonide somely. The most dramatic reward has been the use compounds. of superoxides by the Russians in the life support sys- In reading this survey, it must be remembered that tems of the Vostok and Voskhod vehicles. Instead of the life support potential of inorganic peroxide, super- using a reduced-pressure, all-oxygen atmosphere, as in oxide and ozonide compounds is not the only im- the case of our Mercury and Gemini vehicles, the p~rtant characteristic of these compounds. They are, Vostoks employed slightly oxygen-rich air at normal in general, strong oxidizing agents and strong bases, pressure, and regenerated the oxygen by means of an and could be useful in a wide number of applications, "active chemical. "44 It must be pointed out that, as far such as high energy oxidizers for propulsion purposes, as can be discovered, nowhere in the Russian literature and in the chemical process industry. Therefore, the describing Russian manned space flights is the source motivation for studying these compounds is not neces- of breathing oxygen employed specifically identified as sarily restricted to life support. a superoxide. However, careful analysis of their avail- The Russian literature in the area of chemical means able published works very clearly points to the use of of air revitalization indicates clearly their willingness unfamiliar oxidation state compounds of the alkali or to invest in long term basic research projects in an alkaline metal superoxide or peroxide, or of the alkali effort to develop chemicals to supply oxygen and/or metal ozonide type. Specifically, it appears that the absorb carbon dioxide and water vapor. One is struck compound of choice was sodium superoxide. Volynkin, by the quality and quantity of published Russian litera- et al., 61 point out that "at the present time, highly ture dealing with basic research investigations con- efficient regeneration substances are able not only to cerned with the chemistry of the synthesis of inorganic give off oxygen to exchange for that used in breathing, superoxide, ozonide, and peroxide compounds, and but also to absorb, simultaneously, great quantities of CO~ and moisture. In addition, these substances, as research has shown, have the ability to oxidize and From General Dynamics/Electric Boat Div., Groton, Con- absorb certain harmful gaseous products formed in the necticut. course of human vital activity." Aerospace Medicine December 1965 1187 SOVIET ACTIVITY IN USE OF ACTIVE CHEMICALS FOR CABIN REVITALIZATION--PETROCELLI

Volynkin lists among the important advantages "3.5 and 8 times as heavy," respectively, as a system ascribed to the air revitalization systems of the Vostoks based on the use of these so-called "active chemical the following: compounds." 1. Efficiency of operation at a temperature of 20___ A schematic diagram of the air revitalization system 10~ a relative humidity of 30 to 70 per cent, and a employed in the manned Soviet space flights is shown barometric pressure of 760___ 50 into. of Hg. in Figure 1. The system evolved as a result of labora- 2. Absorption of gaseous products liberated in the tory experiments with animals, dogs weighing 5-7 kg. course of human vital activity. In the early phase of development the number of tests 3. Resistance to the influence of vibration and high conducted appear to be numerous. Seryapin relates overloads; heat and explosion resistance. that in the majority of these early experiments, numer- 4. Simplicity of construction. ous difficulties with the use of the "active chemical" 5. Minimum power consumption. developed and were systematically overcome. 6. High operational reliability. The difficulties spelled out in the Seryapin report 7. Complete automation of process for maintaining are the type of problems known to be associated with the required microclimatic conditions. superoxide systems. The two main problems were In addition to the "active chemical" described above, overproduction of oxygen and non-uniform utilization the Vostoks required an additional chemical for humid- of the "active chemical." They found that they could ity control of the cabin. This fact serves as more evi- overcome these difficulties by breaking up the required dence that the "active chemical" is an unfamiliar oxida- charge of "active chemical" into sections each providing tion state compound since inorganic superoxide, 2-3 days oxygen supply. Thus, as the substance in one peroxide, or ozonide compounds would not be sufficient section became exhausted, it could "automatically" be to maintain the conditions of relative humidity specified switched off and the cabin air allowed to flow through above. In the words of Volynkin, et al., the problems another section. The problems associated with the associated with the use of active compounds were "in "automatic control" of sueh a technique, as well as principle and in practice, solved in preparing and con- weight and volume considerations, eliminated the im- ducting the biological experiments in the two earth plementation of this solution. satellites." Seryapin writes that "the application of The method of utilization finally settled upon was to chemical substances (italics ours), capable of simul- split the "active chemical" charge into two units and to taneous absorption of moisture and carbon dioxide and use a controlling aneroid to switch one of the units on liberation of oxygen is quite economical in comparison or off. Thus the atmospheric pressure in the cabin was with other systems." He goes on to offer that systems used as the controlling variable in the operation of the based on liquid oxygen and gaseous oxygen would be air revitalization unit. Increase of the pressure abo~e 765 mm Hg (the predetermined level) was taken to indicate an increased rate of oxygen production and one of the "active chemical" beds was turned off by F I preventing the cabin air from flowing through it. I I~ / CABIN INSTRUMENT I Conversely, both units were allowed to operate when ~, • PANEL ii the pressure fell below 765 mm Hg. Seryapin reports ', ... that this method of ventilation "works faultlessly and is stable." The use of the cabin pressure for the con- trol of the rate of oxygen production is obviously predicated on the maintenance of a constant cabin air temperature and a very small cabin leak rate. In 1963 a publication in Khimicheskeya promy shlennost' (No. 5, pp. 73-74) described the develop- ment of a glass wool filter for trapping potassium 2vTT? ',,, superoxide dust. The filter was designated as an FS-8.5 filter and is claimed to be very effective. The I significance attached to the development of this filter u I would appear to be that the Russians are making wide ! use of KO2 in cannister type systems. The dusting I_ I problems associated with the use of this material seem Figure I. Schematic Diagram of the Air Regeneration Sys- to have been solved by the use of the FS-8.5 filter. tem used in Vostok Cabins (From Volynkin, Yu. M., et al, This particular article is of further interest in that it is "The First Manned Space Flights," Moscow, (1982)). 1. Fans, one of the few appearing in the open literature that 2. Regulator, 3. Automatic CO~ and O2 Analyzer, 4. "Active deals with a specific engineering problem. As men- Chemical" Regenerator Unit, 5. Dust and Harmful Impurities tioned above, most of their publications are very basic Filters, 6. Dehumidifier Unit, 7. Damper, Manually Controlled, in nature. 7a. Damper, Automatically Controlled (Set to open at 70% R.H. and to close at 35 + 5~ R.H.), 8. Humidity Sensors, A clear insight of Russian activity in the study of in- 9. Temperature Sensor, 10. Pressure Sensor, 11. Remote Control organic superoxide, peroxide, and ozonide compounds Signals to and from Earth. Note: Aneroid control of regenerator can be gained from a study of the published proceed- not depicted. ings of the second conference on the "Chemistry of 1188 Aerospace Medicine December 1965 SOVIET ACTIVITY IN USE OF ACTIVE CHEMICALS FOR CABIN REVITALIZATION--PETROCELLI peroxide Compounds," held in Moscow on November and MzCO4. They have claimed to have prepared 14-18, 1961 and published in 1963. In the introduction potassium and sodium peroxodicarbonate (M2C20~) to these published proceedings, the conference was via the reaction of potassium or sodium superoxide with described as "the first important meeting (on peroxide water and carbon dioxide at O~ They attach two compounds) not only in the USSR, but also abroad." points of significance to this result: The conference was sponsored by the Institute of Gen- (a) Verification of the fact that at low temperatures, eral and Inorganic Chemistry of USSR Academy of -20~ to O~ the reaction of superoxides with water Sciences, by the Scientific Research Institute of Chem- proceeds as follows: istry at the Gorky State University, and by the Scien- 2MO2 + nH20 = M202"xH20 + O_~ + (n-x)H20 tific Research Institute of Basic Chemistry of the State This reaction is significant since it establishes the fact Committee on Chemistry attached to the Council of that in the temperature range indicated, superoxides, Ministers of the USSR. More than 300 representatives upon reaction with water vapor, will form stable per- from 60 scientific research institutes, higher scientific oxide compounds (M20.o'xH~O), thereby diminishing establishments, and industrial enterprises from 29 cities their oxygen yield. This is in marked contrast to the of the Soviet Union participated. In the closing para- results obtained when superoxides are caused to react graph of the introduction to the published proceedings, with water vapor at higher temperatures, i.e., room the following call was made for concentration of the temperature and above. In this case, the reaction pro- research effort: "Research of inorganic chemists should ceeds as follows: be directed toward synthesis of new superoxides and 2MO2 -4- nH~O = 2MOH + 3/2 05 ozonides rich in active oxygen, synthesis of other The Russians reasoned that the presence of the per- peroxide compounds which would enable uncovering oxide compounds in the reaction mixture, at the low regularities of their formation. In this research, it temperature, should be conducive to the formation of would be necessary to apply superhigh pressures of peroxocarbonates, via the reaction: oxygen, ozonized oxygen, concentrated hydrogen per- M20~'nH20 + 2CO,_, = M2C206 +nH20 oxide in anhydrous solutions, and electrochemical Thus, by demonstrating the formation of M2C~O~ via methods." the reaction of MO2 + H20 + CO,_, at O~ they have A nmnber of papers delivered at that conference established the correctness of the mechanism for the along with other published reports serve to confirm the reaction of MO2 and water at low temperatures. continuing Russian interest in the following areas: (b) Their second point is concerned with the dis- 1. Synthesis of alkaline earth superoxides, notably eovery of a new and simple method for the production calcium superoxide. Results to date indicate that the of alkali metal peroxoearbonates. These compounds Russians have not succeeded in synthesizing this com- may be of industrial value. It may also be mentioned pound in greater than 40-50 per cent purity. In this that in addition to the points made above, this work regard, American investigators may have been some- may also be motivated by the intriguing possibility that what more successful. Both R. R. Miller of the Naval if the reaction of CO2 with alkali metal hydroxides and Research Laboratories and Dr. A. W. Petrocelli, carbonates or oxides could be controlled to yield sig- GD/EB, have claimed 50-60 per cent purity. High nificant amounts of the peroxodiearbonates, then it may pm'ity calcium superoxide (85-100 per cent) would be be possible to establish a regenerative CO2 scrubbing superior to both potassium and sodium superoxides as system based on these materials. Differential thermal an air revitalization material. analysis studies of sodium and potassium peroxodiear- 2. Study o[ carbon dioxide-superoxide reaction. The bonates have been reported in the Russian literature. effort in this area appears to be directed to developing These studies establish that at relatively low tempera- a good basic knowledge of this important air regenera- tures, these compounds decompose as follows: tion reaction. The stoichiometric reaction generally M oC20, = M.,CO3 + CO_~ + 1/2 05 written is: 3. Search for and study of new compounds rich in 2MO~ § COs = M2CO8 + 3/2 05 active oxygen. Russian scientists continue to show con- It is known, however, that the reaction is far more com- siderable interest in alkali metal ozonides, MO3. These plex than indicated by the stoichiometry written above. compounds have been shown to react in a manner In addition to alkali metal carbonates, it is known that analogous to the superoxides, i.e., bicarbonates, MHCO3, also form. If the reaction con- 2MO3 + H20 = 2MOH + 5/2 05 ditions favorable for the controlled formation of bicar- The Russians must be considered the leaders in the bonate could be established, then the capacity for COs area of inorganic ozonide chemistry, and it appears, absorption of a superoxide system could be greatly en- h'om the available published literature, that many of hanced. This line of reasoning in part, may explain at the Russian scientists who made major contributions to least, the motivation of Russian workers involved in the superoxide field have also been active in the ozonide detailed basic studies of KOH - COs - H.,O(v) and field, i.e., Kazarnovskii, Makarov, etc. MO 2 - CO~ - H~O(v) reaction systems. In an article appearing in Priroda (Nature) in De- In this same regard the Russians have shown in- cember 1963, entitled "Ozone in the Service of Large- terest in the study of the formation and nature of Scale Chemistry," by Iu. N. Emel'ianov, the claim is alkali metal compounds of the peroxocarbonate type; made that alkali metal ozonides are already finding principally sodium and potassium peroxodicarbonates application in the Soviet Union as "oxidizing agents, (M~C~O~) and the peroxomonocarbonates, MHCO~ bleaching material, as catalysts in certain polymeriza- Aerospace Medicine December 1965 1189 SOVIET ACTIVITY IN USE OF ACTIVE CHEMICALS FOR CABIN REVITALIZATION--PETROCELLI tion reactions, and also as sources of oxygen in in- Their literature demonstrates that they are continuing sulated places where the regeneration of air is required: their efforts to improve on what they have by (a) in the cabins of spacecraft, in autonomous diving suits, search for new compounds suitable for life support etc." (italics ours ). systems, i.e., new superoxides, peroxides, and ozonides, However, we question the implication derived from (b) improving the operation of superoxides systems the above claims which would indicate that such and (c) search for new and better CO2 absorbers. ozonides are being prepared in very large quantities. Examination of publications in this field gives no indica- REFERENCES tion whatever that the Russians have succeeded in adapting, to large scale production, the known method 1. BOGATOV, P. I., et al: Presence of Exhaled Carbon Mon- oxide in Confined Chambers. Voyenno-med. Zhur. 2, 37, of ozonide formation, i.e., the reaction of ozone gas with 1961, Item of Interest prepared by AID, Science and solid alkali metal hydroxides followed by extraction of Technology Section, D.D.C. AD No. 257-922. the prepared ozonide from the greater mass of un- 2. DOBRYNINA, T. A.: Lithium Peroxide. Moscow, 1964. reacted solid hydroxide with liquid ammonia. In the 3. DomaYmNa, T. A.: The 30.5 ~ Isotherm of the Ternary same article, it is mentioned that "As yet, no methods System LiOH-H~O:-H~O and a Study of Hydrated are known for getting these substances (inorganic Lithium Peroxide. Itz. Akad. Nauk. SSSR, Otd. Khim., 961, 1960. ozonides) without the use of ozone." This note indi- 4. KAZAnNOVSKII, I. A., NmoL'sgai, G. P., and ABLETSOVA, cates that they do not have, but are trying to develop T. A.: A New Oxide of Potassium. Doklady Akad. Nauk. better methods for ozonide production. They have not SSSR, 64:69, 1949. as yet, as far as we can discover, reported such at- 5. KAZAnSOVSKn, I. A., and NEYDINC, A. B.: Investigation of tempts in the open technical literature. The major sig- the Mechanism of the Dissociation of Hydrogen Peroxide nificance to be placed on the Soviet claims, however, into Certain Solid Perhydrates. Doklady Akad. Nauk. is that, beyond any question, the Russians do recognize SSSR, 86:717, 1952. the potential of these materials for life support and 6. KAZAnNOVSKII,I. A., et al: Isotopic Exchange of Oxygen Between Free Hydroxyl Radicals and Water. Priroda, other industrial use and are actively pursuing studies 178:100, 1956. on the ozonide compounds. Kazarnovskii was again 7. KAZARNOVSKII,I. A., et al: A Study of the Reaction Mech- given public recognition for his work in this field in the anism for the Spontaneous Decomposition of KO.~ Using a Priroda article. Magnetic Method, Doklady Akad. Nauk. SSSR, 123:475, 1958. The overall conclusion drawn from the Soviet pub- 8. KAZARNOVSKII,I. A., RAIKHSHTEIN, S. I., and BYKOVA, L. N.: lications in this field is that it is very doubtful that Kinetics on the Spontaneous Decomposition of KO::. they have as yet succeeded in advancing the state-of- Koklady Akad. Nauk. SSSR, 108: 641, 1956. the-art to the point that alkali metal ozonide compounds 9. KAZARNOVSKII, I. A.: Structure of Inorganic Peroxides. Zhur. Fiz. Khim., 14:320, 1940. are actually being used for life support purposes, 1O. KAZARNOVSKII, I. A.: Structure of Inorganic Peroxides. Russian literature also reflects an interest in the (Trudy), 4:70, 1940; Khim. Re~. Zhur., 4:30 1941. synthesis and chemistry of peroxide compounds, M20~. 11. KAZARNOVSKII,I. A., and RAIKHSItTEIN,S. I. Karpov Inst. Extensive studies of lithium peroxide, Li20~_, chemistry Phys. Chem., (Moscow) : Inorganic Peroxides. XI. Higher Oxides of Potassium, I. Phys. Chem. (USSR), 21:245 have been carried on at the Institute of General and 1947. Inorganic Chemistry of USSR Academy of Science. In 12. KAZARNOVSKAYA, L. I. (Karpov Inst. of Phys. Chem., 1964, T. A. Dobrynina published a monograph devoted Moscow): The Electrostatic Energy of Lattices of the to Li202 chemistry. Li202 has a particularly attractive Calcium Carbide Type. 1, Phys. Chem. (USSR), 20:1403 1946. life support potential which has certainly not escaped 13. KAZAnNOVSKII,I. A. (Karpov Phys. Chem. Inst., Moscow): the attention of the Russian investigators. The com- Electron Affinity of the Oxygen Molecule, Doklady Akad. pound is known to react with carbon dioxide, i.e., Nauk. SSSR, 59:67 1948. Li20~ + CO2 : Li~CO3 + 1/20~ 14. KAZARNOVSKAYA,L. I., and KAZARNOVSKII, I. A. (Karpov Phys.-Chem. Inst., Moscow): Heat of Formation of KO2. Its potential as a CO~ scrubber and oxygen source is Zhur. Fiz. Khim., 25:293, 1951. apparent. The state-of-the-art with respect to the use 15. KAZARNOVSrm, L A., LIPIKHIN, N. P., and TmHOMmOV, of this compound for life support purposes is not very M.V. (Karpov Phys.-Chem. Inst., Moscow): Isotope Exchange of Oxygen Between Free Hydroxyl Radicals advanced and little that has appeared in the Soviet and Water. Zhur. Fiz. Khim., 30:1429, 1956. open literature would lead us to believe that they are 16. KAZAnNOVSKII, I. A., LI1"IKaIN, N. P., and TmrIOMmOV, very much ahead in the field of peroxide chemistry. M.V.: Oxygen-isotope Exchange Between Free Hydroxyl Lithium peroxide was studied in the U. S. in 1963 under Radicals and Water. Doklady Akad. Nauk. SSSR, 120: a Wright Air Development Center contract by the 1038, 1958. 17. KAZARNOVSKII, I. A., LIPIKItlN, N. P., and KOZLOV, S. V. Foote Mineral Company. (Karpo Phys. Chem. 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Zhurnal Fizicheskoy KhimG 37:922, 1963. 41. RODE, T. V., DOBRXmNA, T. A., and GOLDER, G. A.: 63. YEMEL'YANOV,Yu. M.: Ozone at the Service of Big Chem- Physicochemical Study of Lithium Peroxide. ltzv. Akad. istry. Priroda, 106, 1983. (Note: Claims the use of Nauk., S.S.S.R. OtdeL Khim., 611, I955. ozonides as a source of oxygen in diving equipment, etc. )

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