by Acad. Iosif GITELZON, RAS adviser; RAS Corresponding Member Andrei DEGERMENDZHI, director of the Biophysics Institute (RAS Siberian Branch, Krasnoyarsk); Alexander TIKHOMIROV, Dr. Sc. (Biol.), laboratory head of the Krasnoyarsk Biophysics Institute, executive director of the International Center on Closed Systems

The Biophysics Institute (Siberian Branch of the Russian Academy of Sciences) has developed a unique biotechnological system of life support, BIOS-3. Experiments have shown that a crew of two or three confined within it for 3 to 6 months can satisfy its needs in water and air to 100 percent, and to more than 50 percent in food thanks to a closed system of life support. Similar systems built in other countries cannot boast of a high result like that so far. At present BIOS-3 is being upgraded in keeping with international standards. It will be used for longtime experiments imitating turnover processes to enable man's autonomous survival in lunar and Martian missions.

CLOSED ECOSYSTEM: WHAT IS IT?

Closed ecological systems (CES) provide for a specific mode of biogenic turnover, namely substances consumed at a definite rate by some elements of such systems are regenerated at the same mean rate by other elements from the end products to the original state for a repeat use in the same biological cycles.

The biosphere of the earth is the most striking natural CES vital for survival. In the ideal case such systems can endure infinitely long.

Artificial CES designers seek to realize a turnover of mass-exchange processes with a minimal amount of waste, or substances accumulated within as an extra ballast. Two types of elements-the synthesizers and the destructors--are needed for that. The former are based on photosynthesis for the most part. Therefore they are called phototrophic, coming either from lower plants (microalgae as a rule) or from higher plants. The destructors oxidize substances obtained through photosynthesis as well as products of their vital activity to elements (at best carbon dioxide, CO₂, water, H₂O, and mineral compounds) consumed by phototrophs again.

Man is the all-important component within closed ecosystems. He orchestrates the work of the other components and in fact sets the pace of the turnover so as to meet his needs in oxygen, water and food. For closed ecosystems involving human beings this also means that implicated in the turnover are products of their vital activity, vegetative wastes and other substances. An ecosystem like that with its phototrophic element composed of higher plants is characterized by a greater closedness of turnover processed than that subsisting on algae which are inedible in practical terms, with their biomass accumulating in wastes. A CES/man system can survive for a long time in an autonomous mode. This is an essential factor in manned space missions. Small wonder that the "cosmic boom" of the 1950s and 1960s caused a dramatic rise in space studies when exploration of the Moon and Mars seemed close at hand.

PIONEERING EXPERIMENTS

The world's first operable closed systems of life support were created in the Soviet Union in the early 1960s. The Moscow-based Institute of Aviation and Space Medicine of the Defense Ministry was the focal point of research. Joining in were the Institute of Medicobiological Problems of the USSR Health Ministry (today working under the auspices of the Russian Academy of Sciences), the Krasnoyarsk-based Institute of Physics (IP) of the Siberian Branch of the national Academy of Sciences, and the Institute of Biophysics (IBP) of the RAS Siberian Branch. It so happened the Institute of Medicobiological problems (IMBP) concentrated on life-support systems* in spaceships and orbital stations, with a focus on physicochemical processes, while the Institute of Biophysics (IBP) got involved with closed ecosystems for longtime interplanetary stations, with the emphasis on biological methods. The physicochemical approach cannot give an all-out turnover, for we do not yet know pathways of artificial synthesis of essential nutrients. The other, biological approach, does not have shortfalls like that. Life-support sys-

* See: O. Gazenko, A. Grigoryev, A. Yegorov, "Space Medicine: Yesterday, Today, Tomorrow", Science in Russia, Nos. 3 and 4, 2006; A. Grigoryev, B. Morukov, "Mars: Ever Closer", Science in Russia, No. I, 2011.--Ed.

tems based on it are autonomous, and consequently, more independent in manned longtime missions in deep space.

Biological CES allow physicochemistry elements if used as supplementary technologies contributing to higher rates of turnover and greater closedness of mass-exchange processes. Systems making for such integration of biological and physicochemical methods are known as biotechnological closed ecological systems (CES). These are created at IBP.

The beginning was made in the early 1960s as Leonid Kirensky, director of the Physics Institute, and the chief Designer of rocket system Sergei Korolev met to discuss CES for space flights. Kirensky's proposal to build at IBP a closed ecosystem capable of operating autonomously for a long time by using an inner turnover of substances caught Korolev's attention. Then came a number of meetings to look into the matter in greater detail. Taking part were the founders of this new trend in biophysics Ivan Terskov (elected to the national Academy of Sciences in 1981), and one of the authors of the present article Iosif Gitelzon (elected to the Academy of Sciences in 1990). This panel of scientists conceptualized this work in real terms. Korolev set a clear task for the Biophysics Department of the Physics Institute (Siberian Branch of the Academy of Sciences of the USSR): develop within a few years a closed turnover ecosystem capable of longtime operation in an autonomous mode and ensuring man's survival within a hermetic space under conditions close to terrestrial ones. The state set aside funds large enough for attracting experts and purchasing the necessary equipment.

This assignment breaks down into three stages. At first the BIOS-1 project was implemented (1964-1966). It comprised two essential components: a 12 m³ airtight cabin for man and a 20 liter cultivator for growing chlorella, a microalga. An important result was achieved in the course of seven experiments, each taking from 12 hours to 90 days: a completely closed cycle in gas (the exhaled air cleansed from carbon dioxide and impurities, and enriched with oxygen produced by chlorella) and in water (including regeneration of drinking water for cooking and hygienic needs).

Thereupon, in 1966, BIOS-1 was upgraded to BIOS-2 by adding a 8.5 m³ chamber for higher plants--a set of vegetable cultures was grown in it. The plants improved the closedness of mass-exchange processes in the system owing to the partial involvement of plant food in the menu. In addition, higher plants like chlorella were implicated in the regeneration of the atmosphere for respiration. This made it possible to bring down the chlorella biomass essential to vital activity and thus tighten the closedness of mass-exchange processes. An extra volume of oxygen generated through the photosynthesis of higher plants allowed to carry out experiments with a crew

of two testers (two longest experiments took 30 and 73 days and nights each). The work on BIOS-2 continued up to 1970. The pioneering results thus obtained showed the possibility of longtime artificial ecosystem "man/microalgae/higher plants".

Early in 1972 the Krasnoyarsk IBO created an essentially new artificial ecosystem, BIOS-3. In contrast to the two previous ones, it gained quite different structural and functional characteristics. The 300 m³ setup was composed of 4 compartments of identical dimensions: a living module with individual cabins for three testers and another three compartments with plants for food reproduction and regeneration of the atmosphere and water.

Longtime experiments were carried out in BIOS-3 for three months, both to the known scenario "man/chlorella/higher plants" and to the utterly novel one, "man/higher plants". For the first time ever it became possible to obtain a full vegetable diet from plants grown within. As a result, the mass-exchange closedness was brought to 75 percent. In the upshot only BIOS-3--from among all man-made ecosystems both in this and other countries--could sustain a crew of 2-3 in an autonomous mode for 4 to 6 months thanks to the closed water and gas cycle to as good as 100 percent, and to more than 50 percent in food. This result has never been surpassed so far. Thus, the way from BIOS-1 to BIOS-3 was covered within a fantastically short time--seven (!) years.

THE BIRTH OF NEW TECHNOLOGIES

BIOS-3 was created by a galaxy of outstanding scientists. Much credit is due to Leonid Kirensky who kindled Sergei Korolev's interest in the Krasnoyarsk project and organized work on it. Boris Kovrov, Doctor of Biology, played an exceptionally important role in the technological realization of the system. He was capable of making fast, and what was most important, optimal design decisions. He is the author of the "in" servicing idea, that is giving a free hand to the crewmen. In this respect BIOS-3 is superior to all artificial CES abroad. Medical monitoring was an essential part of the experiments. Taking part was a team of space doctors under Oleg Gazenko, with Yuri Okladnikov in charge of direct control. Throughout BIOS-3 experiments over 11 months in all there were no health problems for the crew.

The implication of higher plants in the turnover to supply man with oxygen, food and water is an important breakthrough technology. Its author, Dr. Heinrich Lisowski, has validated and in fact realized the procedure of selecting higher plants meant to substitute in full the inedible chlorella. This biologist has raised a new strain of short-stalked wheat expressly for a closed ecosystem, a strain in which grain makes up about 50 percent of the biomass.

BIOS-3 has spurred the birth of new technologies. For one, it has become possible to scientifically substantiate the selection of energy and spectral charac-

Schematic representation of the switch-in of the unit for a physicochemical reprocessing of waste as part of the mass-exchane process in CES, man including.

teristics of visible radiation for the phototrophic component of life-support systems. Furthermore, it has become possible to make use of white light in illuminating plant communities under natural and artificial conditions. And last, it has become possible to formulate the concept of light control relative to the production process in plants with an eye to different levels of photosynthesis.

More than that, our biologists have conceptualized plant-growing procedures at a lunar station. If a station like that is supplied with a life-support biogeneration system, plants (the source of oxygen and food!) can grow there, provided they learn to adjust the lunar day equal to about 14 terrestrial days of continuous sunlight and as many nights of total darkness. Lisowski and his team have coped with this most unusual problem. They have found environmental parameters for growing plants acceptable both in the edible biomass and in the biophysical composition. Thus, solar energy can be used in lunar biogeneration systems of life support.

PRESENT DAY

At present our research institute is tackling two key tasks simultaneously: technical modernization of BIOS-3 and basic technologies for improving the closedness of turnover processes. This work is supported by grants from the RAS Siberian Branch and contracts of the European Space Agency Our research center is drawing upon its own potential as well.

We attach particularly great importance to the second line related to the better closedness of turnover processes. One of the results we have achieved concerns utilization of the inedible plant biomass. To get it involved into turnover within the system we are developing a technology of biological oxidation with the aid of a soil-like substrate. This is a product from wheat straw worked up by worms and microflora, and at the same time it serves as a medium for plant roots. The microflora of the substrate protects the plant roots against mould and rot.

Yet another result relates to the ecologically pure technology of implicating table salt (NaCl) into the internal mass exchange. This salt contained in human liquid excreta may be deadly for plants. So to draw NaCl into the biological turnover it became necessary to resort to the physicochemical method of liquid excreta mineralization. The gist of this method is as follows. A liquid solution of hydrogen peroxide is placed into a variable electric field. Elemental oxygen, a potent oxidant, is detached from the peroxide molecule. It oxi-

View of a small artificial ecosystem:

1-high-intensity light radiation source;

2-phototrophic component (higher plants) within a hermetic chamber;

3-manipulators for work inside the chamber without breakdown of its hermeticity;

4-soil compartment with a soil-like substrate;

5-instrument rack for automatic control over parameters of the medium within the chamber; 6-hermetic chamber case of stainless steel.

dizes plant and animal waste to mineral components used up by plants as a mineral fertilizer. This physico-chemical method is ecologically safe and not energy expensive. Water, the source product for obtaining hydrogen peroxide, is not in short supply in closed ecological systems. This means that actually all stock products that trigger the technological process are drawn in readily. Unlike the conventional physicochemical methods used in space vehicles this one proceeds at temperatures up to 100 ºC and at normal pressure.

True, the mineralized solution obtained in this fashion contains a high concentration of common salt, NaCl. So at first it should be used for growing salicorn (Salicornia europea) edible for man. This annual plant of the amaranth family can grow in media with a high concentration of common salt and accumulate it to 50 percent of the dry weight. Thereafter the NaCl concentration in the nutrient solution drops to values adequate for the cultivation of other plant species.

Involving liquid excreta into the turnover opens up the possibility of eliminating dead-end substances in CES, that is no good for further use. Exometabolites (excreted products of metabolism), for one, will be rendered harmless and drawin into the turnover. The Biophysics Institute has come up with a set technologies toward this end. The problem of solid exometabolites is much easier to handle, for they contain no NaCl, and their implication in mass exchange after sterilization poses no great difficulties.

PROSPECTS

Closed ecosystems have two explicit application domains: in other space and on earth. The former is connected with physical models of stable turnover processes for lunar and Martian stations.* The make-

* See: E. Galimov, "Prospects of Planetary Studies", Science in Russia, No. 6, 2004; N. Trukhanov, N. Krivova, "Geomagnetic Field to Mars?", Science in Russia, No. 3. 2010.--Ed.

up of such systems, their specific functions and basic design characteristics are determined first of all by the type of a particular planetary station, its objectives, the time of physical confinement, the number of crew members, the weight and energy constraints, and other requirements (medical, operational, and so forth).

The literature offers a variety of different life-support systems predicated both on the available stocks and on the physicochemical methods of atmosphere and water regeneration, and also on drawing in corresponding biological components (microalgae, higher plants, fish, among other things). Our experience at IBP makes it possible to focus on an integrated bio-logical-physicochemical system of life support with the biological component playing a dominating role. In a planetary biogenerative CES (say, in a hypothetical Martian mission), regeneration of the atmosphere based on higher plants alone will have one essential drawback, namely great sluggishness, a lag due to their long cycle of growth. The stationary performance of a system like this is possible only month after its commissioning: for instance, full supply of water and oxygen will be a real thing in two months, and that of the plant part of the diet, in three or four months. At this stage only an algal cultivator can cater to the crew's needs in water and oxygen: producing 600 grams of dry matter daily, it will solve the problems of air normalization in full.

The higher plant conveyer has to be switched in at the very start, simultaneously with the algal cultivator. In time the load on the algal conveyer will be going down, and it could be switched off in the end. Consequently, in the long run a planetary station's biogenerator should rely only on higher plants supplying man with oxygen and plant food.

Now what concerns the terrestrial spin-offs from closed ecological systems: they are possible in most different fields. For example, illumination technologies designed for CES may provide a basis for energy-saving lamps with physiologically adequate spectral and power characteristics. Such bulbs can be used for obtaining ecologically pure plant foods in regions with unfavorable climate and weather conditions. The homes making use of such closed-cycle technologies could enable residents to live on autonomously for a long time (for instance, during harsh frosts and poor weather up in the north, or in mountain regions hard of access). This could be combined with a partially closed cycle in the reproduction of plant food, waste disinfection and utilization, and regeneration of the atmosphere as well. An ecological home like that will consume less energy than standard housing.

Yet another terrestrial application domain, a biosphere turnover model. Possible climate changes on our planet are being widely discussed in the scientific community. However, there is still no adequate understanding of the causes and mechanisms involved. Their modeling will help answer many questions bearing on the key, essential parameters vital for the performance of the biosphere as a system. Such approaches apply not only at the level of the biosphere, but also in what we call "biosphere-like systems".* Proceeding from the results obtained this way, it will become possible to create imitation models providing for an essentially new understanding of global atmospheric processes.

For this purpose we should create simplified biosphere-like artificial ecosystems with highly closed turnover of substances and a relatively small exchange mass related to some extent to natural biotas. We at IBP are designing such systems that may prove to be an effective tool for modeling biosphere processes, including research into their resistance to anthropogenic (man-caused) effects. A heretic artificially illuminated system like this keeps up a turnover process between two basic components, the photosyn-thesizing (higher plants) and the heterotrophic (soillike substrate) one. The gas composition of the air as well as its temperature and humidity is maintained in an automatic mode. By designing different factors of action on the system (temperature and CO₂ concentration changes, etc.), we can assess its response and test different scenarios of climate changes.

* Artificial closed ecosystems characterized by mass-exchange cycles much similar to those in the global biosphere.--Auth.