An overview of Japanese CELSS research activities.

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.     

CELSS transportation analysis

Regenerative life support systems based on the use of biological material have been considered for inclusion in manned spacecraft since the early days of the United States space program. These biological life support systems are currently being developed by NASA in the Controlled Ecological Life Support System (CELSS) program. Because of the progress being achieved in the CELSS program, it is time to determine which space missions may profit from use of the developing technology. This paper presents the results of a study that was conducted to estimate where potential transportation cost savings could be anticipated by using CELSS technology for selected future manned space missions.

Six representative missions were selected for study from those included in NASA planning studies. The selected missions ranged from a low Earth orbit mission to those associated with asteroids and a Mars sortie. The crew sizes considered varied from four persons to five thousand. Other study parameters included mission duration and life support closure percentages, with the latter ranging from complete resupply of consumable life support materials to 97% closure of the life support system. The paper presents the analytical study approach and describes the missions and systems considered, together with the benefits derived from CELSS when applicable.     

Achieving and documenting closure in plant growth facilities.

As NASA proceeds with its effort to develop a Controlled Ecological Life Support System (CELSS) that will provide life support to crews during long duration space missions, it must address the question of facility and system closure. Here we discuss the concept of closure as it pertains to CELSS and describe engineering specifications, construction problems and monitoring procedures used in the development and operation of a closed plant growth facility for the CELSS program. A plant growth facility is one of several modules required for a CELSS. A prototype of this module at Kennedy Space Center is the large (7m tall x 3.5m diameter) Biomass Production Chamber (BPC), the central facility of the CELSS Breadboard Project. The BPC is atmospherically sealed to a leak rate of approximately 5% of its total volume per 24 hours. This paper will discuss the requirements for atmospheric closure in this facility, present CO2 and trace gas data from initial tests of the BPC with and without plants, and describe how the chamber was sealed atmospherically. Implications that research conducted in this type of facility will have for the CELSS program are discussed.     

Performance and reliability of the NASA Biomass Production Chamber.

The Biomass Production Chamber (BPC) at the Kennedy Space Center is part of the Controlled Ecological Life Support System (CELSS) Breadboard Project. Plants are grown in a closed environment in an effort to quantify their contributions to the requirements for life support. Performance of this system is described. Also, in building this system, data from component and subsystem failures are being recorded. These data are used to identify problem areas in the design and implementation. The techniques used to measure the reliability will be useful in the design and construction of future CELSS. Possible methods for determining the reliability of a green plant, the primary component of a CELSS, are discussed.     

Survey of CELSS concepts and preliminary research in Japan

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.     

Object-oriented model-driven control.

A monitoring and control subsystem architecture has been developed that capitalizes on the use of model-driven monitoring and predictive control, knowledge-based data representation, and artificial reasoning in an operator support mode. We have developed an object-oriented model of a Controlled Ecological Life Support System (CELSS). The model, based on the NASA Kennedy Space Center CELSS breadboard data, tracks carbon, hydrogen, and oxygen, carbon dioxide, and water. It estimates and tracks resource-related parameters such as mass, energy, and manpower measurements such as growing area required for balance. We are developing an interface with the breadboard systems that is compatible with artificial reasoning. Initial work is being done on use of expert systems and user interface development. This paper presents our approach to defining universally applicable CELSS monitor and control issues, and implementing appropriate monitor and control capability for a particular instance: the KSC CELSS Breadboard Facility.     

BLSS: A contribution to future life support

For extended duration missions in space the supply of basic life-supporting ingredients represents a formidable logistics problem. Storage volume and launch weight of water, oxygen and food in a conventional non-regenerable life support system are directly proportional to the crew size and the length of the mission. In view of spacecraft payload limitations this will require that the carbon, or food, recycling loop, the third and final part in the life support system, be closed to further reduce logistics cost. This will be practical only if advanced life support systems can be developed in which metabolic waste products are regenerated and food is produced.

Biological Life Support Systems (BLSS) satisfy the space station environmental control functions and close the food cycle. A Biological Life Support System has to be a balanced ecological system, biotechnical in nature and consisting of some combination of human beings, animals, plants and microorganisms integrated with mechanical and physico-chemical hardware.

Numerous scientific space experiments have been delineated in recent years, the results of which are applicable to the support of BLSS concepts. Furthermore ecological life support systems have become subject to intensified studies and experiments both in the U.S. and the U.S.S.R. The Japanese have also conducted detailed preliminary studies.

Dornier System has in recent years undertaken an effort to define requirements and concepts and to analyse the feasibility of BLSS for space applications. Analyses of the BLSS energy-mass relation have been performed, and the possibilities to influence it to achieve advantages for the BLSS (compared with physico-chemical systems) have been determined. The major problem areas which need immediate attention have been defined, and a programme for the development of BLSS has been proposed.     

Initial closed operation of the CELSS Test Facility Engineering Development Unit.

As part of the NASA Advanced Life Support Flight Program, a Controlled Ecological Life Support System (CELSS) Test Facility Engineering Development Unit has been constructed and is undergoing initial operational testing at NASA Ames Research Center. The Engineering Development Unit (EDU) is a tightly closed, stringently controlled, ground-based testbed which provides a broad range of environmental conditions under which a variety of CELSS higher plant crops can be grown. Although the EDU was developed primarily to provide near-term engineering data and a realistic determination of the subsystem and system requirements necessary for the fabrication of a comparable flight unit, the EDU has also provided a means to evaluate plant crop productivity and physiology under controlled conditions. This paper describes the initial closed operational testing of the EDU, with emphasis on the hardware performance capabilities. Measured performance data during a 28-day closed operation period are compared with the specified functional requirements, and an example of inferring crop growth parameters from the test data is presented. Plans for future science and technology testing are also discussed.     

Recycling of trace elements required for humans in CELSS.

Recycle of complete nourishment necessary for human should be constructed in CELSS (Controlled Ecological Life Support Systems). Essential elements necessary for human support are categorized as major elements, semi-major elements and trace elements. Recently, trace elements have been identified from considerations of local diseases, food additive problems, pollution problems and adult diseases, consisting of Fe, Zn, Cu, Se, Co, F, Si, Mn, Cr, I, As, Mo, Ni, V, Sn, Li, Br, Cd, Pb, B. A review of the biogeochemical history of the earth's biosphere and the physiological nature of humans and plants explains some of the requirements. A possible route for intake of trace elements is considered that trace elements are dissolved in some chemical form in water, absorbed by plants through their roots and then transfered to human as foods. There may be a possibility that living things absorb some trace elements from atmosphere. Management and recycling of trace elements in CELSS is discussed.     

The Breadboard Project: a functioning CELSS plant growth system.

The primary objective of the Breadboard project for the next 3-4 years is to develop, integrate and operate a Controlled Ecological Life Support System (CELSS) at a one person scale. The focus of this project over the past two years has been the development of the plant growth facility, the first module of the CELSS. The other major modules, food preparation, biomass processing, and resource recovery, have been researched at the laboratory scale during the past two years and facilities are currently under construction to scale-up these modules to an operational state. This paper will outline the design requirements for the Biomass Production Chamber (BPC), the plant growth facility for the project, and the control and monitoring subsystems which operate the chamber and will present results from both engineering and biological tests of the facility. Three production evaluations of wheat, conducted in the BPC during the past year, will be described and the data generated from these tests discussed. Future plans for the BPC will be presented along with future goals for the project as the other modules become active.     

Determining the potential productivity of food crops in controlled environments.

The quest to determine the maximum potential productivity of food crops is greatly benefitted by crop growth models. Many models have been developed to analyze and predict crop growth in the field, but it is difficult to predict biological responses to stress conditions. Crop growth models for the optimal environments of a Controlled Environment Life Support System (CELSS) can be highly predictive. This paper discusses the application of a crop growth model to CELSS; the model is used to evaluate factors limiting growth. The model separately evaluates the following four physiological processes: absorption of PPF by photosynthetic tissue, carbon fixation (photosynthesis), carbon use (respiration), and carbon partitioning (harvest index). These constituent processes determine potentially achievable productivity. An analysis of each process suggests that low harvest index is the factor most limiting to yield. PPF absorption by plant canopies and respiration efficiency are also of major importance. Research concerning productivity in a CELSS should emphasize: 1) the development of gas exchange techniques to continuously monitor plant growth rates and 2) environmental techniques to reduce plant height in communities.     

Closed and continuous algae cultivation system for food production and gas exchange in CELSS.

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.     

The MELISSA pilot plant facility as as integration test-bed for advanced life support systems.

The different advances in the Micro Ecological Life Support System Alternative project (MELISSA), fostered and coordinated by the European Space Agency, as well as in other associated technologies, are integrated and demonstrated in the MELISSA Pilot Plant laboratory. During the first period of operation, the definition of the different compartments at an individual basis has been achieved, and the complete facility is being re-designed to face a new period of integration of all these compartments. The final objective is to demonstrate the potentiality of biological systems such as MELISSA as life support systems. The facility will also serve as a test bed to study the robustness and stability of the continuous operation of a complex biological system. This includes testing of the associated instrumentation and control for a safe operation, characterization of the chemical and microbial safety of the system, as well as tracking the genetic stability of the microbial strains used. The new period is envisaged as a contribution to the further development of more complete biological life support systems for long-term manned missions, that should be better defined from the knowledge to be gained from this integration phase. This contribution summarizes the current status of the Pilot Plant and the planned steps for the new period.     

Approaches to resource recovery in Controlled Ecological Life Support Systems.

Recovery of resources from waste streams in a space habitat is essential to minimize the resupply burden and achieve self sufficiency. The ultimate goal of a Controlled Ecological Life Support System (CELSS) is to achieve the greatest practical level of mass recycle and provide self sufficiency and safety for humans. Several mission scenarios leading to the ultimate application could employ CELSS component technologies or subsystems with initial emphasis on recycle of the largest mass components of the waste stream. Candidate physical/chemical and biological processes for resource recovery from liquid and solid waste streams are discussed and the current fundamental recovery potentials are estimated.     

Significance of rhizosphere microorganisms in reclaiming water in a CELSS.

Plant-microbe interactions, such as those of the rhizosphere, may be ideally suited for recycling water in a Controlled Ecological Life Support System (CELSS). The primary contaminant of waste hygiene water will be surfactants or soaps. We identified changes in the microbial ecology in the rhizosphere of hydroponical1y grown lettuce during exposure to surfactant. Six week old lettuce plants were transferred into a chamber with a recirculating hydroponic system. Microbial density and population composition were determined for the nutrient solution prior to introduction of plants and then again with plants prior to surfactant addition. The surfactant Igepon was added to the recirculating nutrient solution to a final concentration of 1.0 g L-1. Bacteria density and species diversity of the solution were monitored over a 72-h period following introduction of Igepon. Nine distinct bacterial types were identified in the rhisosphere; three species accounted for 87% of the normal rhizosphere population. Microbial cell number increased in the presence of Igepon, however species diversity declined. At the point when Igepon was degraded from solution, diversity was reduced to only two species. Igepon was found to be degraded directly by only one species found in the rhizosphere. Since surfactants are degraded from the waste hygiene water within 24 h, the potential for using rhizosphere bacteria as a waste processor in a CELSS is promising.     

红萍湿养栽培供O2装置研制

红萍作为空间站受控生态生命保障系统中的生物部件, 可望为航天员提供O2和新鲜蔬菜并吸收CO2. 研究红萍湿养栽培供O2装置, 旨在建立地面非生物部件, 满足模拟研究的需要. 介绍了所研发装置及关键部件的结构特点和工作原理. 通过红萍湿养板内湿养栽培介质的结构功能设计, 在蓄水保水基质层内部配置具有毛细作用的渗水管路, 介质始终保持整体湿润而表面无明水状态, 为红萍扎根稳固、营养吸收和生长繁殖创造条件. 水压试验确定了渗水管路的主要技术参数和闭合式红萍培养液输配循环系统的间歇循环周期. 整机产出量试验结果表明, 在层间距125 mm, 整机红萍湿养面积6.3 m2, 超高亮度白色LED人工光源能耗152 Wm 2, 红萍表面的光照强度6000~6500 lx, 整机的红萍湿养产量、红萍放O2量和吸收CO2量相应大幅提高, 装置各项性能指标均达到设计要求.      

A study of biohazard protection for farming modules of lunar base CELSS.

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. 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. 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.     

Nostoc sphaeroides Kützing,an excellent candidate producer for CELSS

Some phytoplankton can be regarded as possible candidates in the establishment of Controlled Ecological Life Support System (CELSS) for some intrinsic characteristics, the first characteristic is that they should grow rapidly, secondly, they should be able to endure some stress factors and develop some corresponding adaptive strategies; also it is very important that they could provide food rich in nutritious protein and vitamins for the crew; the last but not the least is they can also fulfill the other main functions of CELSS, including supplying oxygen, removing carbon dioxide and recycling the metabolic waste. According to these characteristics, Nostoc sphaeroides, a potential healthy food in China, was selected as the potential producer in CELSS. It was found that the oxygen average evolution rate of this algae is about 150 μmol O₂ mg⁻¹ h⁻¹, and the size of them are ranged from 2 to 20 mm. Also it can be cultured with high population density, which indicated that the potential productivity of Nostoc sphaeroides is higher than other algae in limited volume. We measured the nutrient contents of the cyanobacterium and concluded it was a good food for the crew. Based on above advantages, Nostoc sphaeroides was assumed to a suitable phytoplankton for the establishment of Controlled Ecological Life Support System. We plan to develop suitable bioreactor with the cyanobacterium for supplying oxygen and food in future space missions.