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CELSS technology, composed of various subsystems designed to stabilize the environment in closed space can be used to construct the Closed Ecology Experiment Facility. The Closed Ecology Experiment Facility has the character of an Environmental Time Machine. Many environmental researches of studies will, it is proposed, be conducted using this facility. The concept of Closed Ecology Experiment Facility is described, and several research items related to earth science potentially to be conducted using this facility are indicated. As an example of the application, an improved model of climate estimation is discussed.

In order to determine a required plant cultivation area which can sustain human life in a closed environment, the material circulating measurement system including a Closed-type Plant Cultivation Equipment (CPCE) in which the metabolic data of plants can be accurately measured has been constructed. According to results from cultivation experiments using rice, the harvest index was 29.9% for 110 days, and the required crop area to supply food, oxygen and water for one person was calculated to be about 111m2, 36m2 and 0.9m2, respectively.

A most important problem to creating a CELSS system to be used in space, for example, for a Lunar Base or Manned Mars mission, seems to be how to design and operate the various material recycling system to be used on the missions. Recent studies of a Lunar Base habitat have identified examples of CELSS configurations to be used for the Plant Cultivation Module. Material recycling subsystems to be installed in the Plant Cultivation Modules are proposed to consist of various sub-systems, such as dehumidifier, oxygen separation systems, catalytic wet oxidation systems, nitrogen adjusting systems, including tanks, and so on. The required performances of such various material recycling subsystems are determined based on precise metabolic data of derived from the various species of plants to be selected and investigated. The plant metabolic data, except that for wheat and potato, has not been fully collected at the present time. Therefore, much additional plant cultivation data is required to determine the performances of each material recycling subsystems introduced in Plant Cultivation Modules.

A wet oxidation method is considered to be one of the most effective methods of waste processing and recycling in CELSS (Controlled Ecological Life Support System). The first test using rabbit waste as raw material was conducted under a decomposition temperature of 280 °C for 30 minutes and an initial pure oxygen pressure of 4.9 MPa (50 kgf/cm2) before heating, and the following results were obtained. The value of COD (Chemical Oxygen Demand) was reduced 82.5 % by the wet oxidation. And also the Kjeldahl nitrogen concentration was decreased 98.8%. However, the organic carbon compound in the residual solution was almost acetic acid and ammonia was produced. In order to activate the oxidation more strongly, the second tests using catalysts such as Pd, Ru and Ru+Rh were conducted. As the results of these tests, the effectiveness of catalysts for oxidizing raw material ws shown as follows: COD and the Kjeldahl nitrogen values were drastically decreased 99.65 % and 99.88 %, respectively. Furthermore, the quantity of acetic acid and ammonia were reduced considerably. On the other hand, nitrate was showed a value 30 times as much as without catalytic oxidation.

For the Closed Ecological Life Support System (CELSS) of a manned lunar base which is planned to be built on the moon early in the 21st century, several proposed programs exist to grow vegetables inside a farming module. 1)2)3)4)5) At the 40th IAF (Malaga, 1989) the author et al presented a proposal for supplying food and nutrients to a crew of eight members, a basic concept which is based on growing four kinds of vegetables. 6) This paper describes measures for biohazard protection in farming modules. In this study, biohazard protection means prevention of the dispersion of plant diseases to other plant species or other portions of farming beds.

Many agricultural and other experiments relating to the development of a Controlled Ecological Life Support System (CELSS) were proposed by scientists throughout Japan in the fall of 1982. To develop concrete experimental concepts from these proposals, the engineering feasibility of each proposal was investigated by a CELLS experiment concept study group under the support of the National Aerospace Laboratory. The conclusions of the group were described in two documents, /1/, /2/. Originally, the study group did not clearly define necessary missions leading to the goal of an operational CELSS for spaceflight. Therefore, the CELSS experiment concept study group met again to clarify the goals of CELSS and to determine three phases to achieve the goals. The resulting phases, or missions, and preliminary proposals and studies needed to develop a CELLS are described herein.

In order to reduce the cultivation area required for the growth of higher plants in space adoption of algae, which have a higher photosynthetic ability, seems very suitable for obtaining oxygen and food as a useful source of high quality protein. The preliminary cultivation experiment for determining optimum cultivation conditions and for obtaining the critical design parameters of the cultivator itself was conducted. Spirulina was cultivated in the 6 liter medium containing a sodium hydrogen carbonate solution and a cultivation temperature controlled using a thermostat. Generated oxygen gas was separated using a polypropyrene porous hollow fiber membrane module. Through this experiment, oxygen gas (at a concentration of more than 46 percent) at a rate of 100 to approx. 150 ml per minute could be obtained.

Many research activities regarding Controlled Ecological Life Support System (CELSS) have been conducted and continued all over the world since the 1960's and the concept of CELSS is now changing from Science Fiction to Scientific Reality. Development of CELSS technology is inevitable for future long duration stays of human beings in space, for lunar base construction and for manned mars flight programs. CELSS functions can be divided into two categories, Environment Control and Material Recycling. Temperature, humidity, total atmospheric pressure and partial pressure of oxygen and carbon dioxide, necessary for all living things, are to be controlled by the environment control function. This function can be performed by technologies already developed and used as the Environment Control Life Support System (ECLSS) of Space Shuttle and Space Station. As for material recycling, matured technologies have not yet been established for fully satisfying the specific metabolic requirements of each living thing including human beings. Therefore, research activities for establishing CELSS technology should be focused on material recycling technologies using biological systems such as plants and animals and physico-chemical systems, for example, a gas recycling system, a water purifying and recycling system and a waste management system. Based on these considerations, Japanese research activities have been conducted and will be continued under the tentative guideline of CELSS research activities as shown in documents /1/, /2/. The status of the over all activities are discussed in this paper.

In CELSS (Controlled Ecological Life Support System), utilization of photosynthetic algae is an effective means for obtaining food and oxygen at the same time. We have chosen Spirulina, a blue-green alga, and have studied possibilities of algae utilization. We have developed an advanced algae cultivation system, which is able to produce algae continuously in a closed condition. Major features of the new system are as follows. (1) In order to maintain homogeneous culture conditions, the cultivator was designed so as to cause a swirl on medium circulation. (2) Oxygen gas separation and carbon dioxide supply are conducted by a newly designed membrane module. (3) Algae mass and medium are separated by a specially designed harvester. (4) Cultivation conditions, such as pH, temperature, algae growth rate, light intensity and quantity of generated oxygen gas are controlled by a computer system and the data are automatically recorded. This equipment is a primary model for ground experiments in order to obtain some design data for space use. A feasibility of algae cultivation in a closed condition is discussed on the basis of data obtained by use of this new system.