50 YEARS or more have passed since the first human trip into space, and research and development of Environmental Control and Life Support System, ECLSS, corresponding to various missions have been carried out. Some detailed studies of long duration missions were performed as early as the 1960's and 1970's. Different mission scenarios, such as short term and long term missions, are reflected in the ECLSS design, and the most appropriate ECLSS is different for each mission.
At present, human beings at the International Space Station, ISS, can remain in space for a long term with ECLSS recycling water and oxygen. In the future, examination, research, and development of new life support systems will be required in preparation for exploration of the lunar outpost and manned Mars exploration. As for the development of ECLSS corresponding to these missions, the scale expands and becomes complex, and controlling whole resource recycling becomes more important. A short term mission can use a simple ECLSS that does not perform resource recycling, whereas a long term mission, such as the ISS or a manned Mars exploration, needs resource recycling to reduce resupply, storage requirements and cost.
For supporting these investigations, we are developing new simulation software called SImulator for Closed Life and Ecology, SICLE, which simulates resource recycling and control of the ECLSS. At present, SICLE has operability and expandability, and it is able to help study of closed ecosystem. In addition, we have been improving SICLE to fit for other fields such as logistics.
Resource recycling in the ECLSS is to recycle substances that are needed for human activity and emission matters by utilizing plants and physicochemical devices. Water, oxygen, carbon dioxide and nitrogen are the main component substances. Though some simulators that can simulate resource recycling have been released in the past, we have been developing a simulator with the three following features to accommodate research and development of more diversification and complex life support system.
First, it is important to use a design concept that is based on scientific results. SICLE is a simulator designed based on the scientific results that have supported research of advanced life support system in a real ECLSS research facility, CEEF.
Second, it is important to have an interface that attached importance to direct operability. In a life support system that a large variety of resources and devices cooperate complicatedly, it is important to cognize the detail setting of each device from grasp of system perspective visually and easily. Therefore, SICLE enables a selection operation of the device by icons and making of block diagrams for a designer can design systems easily. In addition, we can grasp and trace the process of simulation visually and change the status such as a device stop and trouble even though SICLE is running.
Finally, it is important to be a software structure including expandability. In order to enable inserting various devices in simulation, SICLE provides a function to easily model various resource recycling systems such as producing and implementing user defined new device and human beings-plant model. Furthermore, SICLE adopts a class structure and algorithm including expandability for applicable to other field.
SICLE provides ECLSS simulations, which can consistently carry out system design, simulation practice and data analysis. It can confirm and grasp a state of simulation anytime. You can easily set up system and change parameters, and can execute and analyze the simulation of various patterns.
The Mars Desert Research Station (MDRS), which is owned and operated by the Mars Society, is a simulated Mars Analogue Research Station in the Utah desert. As the member of the Team NIPPON that consisted of researchers from Japan who conducted a mission at the MDRS as Crew 137 from March 1 to March 15, 2014 and as Crew 165 from March 5 to March 20, 2016, we collected valuable data for further development of SICLE simulations. The crew handled a strong request for conserving water during the MDRS mission through carefully planned cooking and dish washing and reducing showers and toilet flushing. Meanwhile, the measurement of the amount of water supply and drainage was one of the significant research items on this mission, which consequently provided invaluable data of water consumption required for living with a restricted water supply for two weeks.
Inspiration Mars Mission Design Winner Team Kanau
In the summer of 2014, The Mars Society held an international student design competition, Inspiration Mars Student Design Contest. Inspiration Mars is a manned spaceflight mission to Mars driven by Inspiration Mars Foundation. The main concept described in its architecture study report and feasibility analysis paper is sending two Americans, one male and one female, into free-return orbit to Mars in 2018 so that the journey takes only 501 days owning to the special orbital positioning between Earth and Mars. Team Kanau is one of the student competition entry groups that consisted of students and young professionals from Japan and U.S. Team Kanau's mission design won the first prize in the final presentation. Since ECLSS analysis is the key factor of this long duration mission design, we collaborated with Team Kanau to determine an optimal system design, especially to decide the size of recycling tanks, offering SICLE as its simulation software.
宇宙には人間が生きてく上で必要な空気や水、食料などは存在せず、地球から必要な物資を運んでいく必要があります。しかし運搬可能な物資の量には限りがあるため、可能な限り物資や資源の再利用を図ることが重要です。そこで宇宙では環境制御・生命維持システム（Environmental Control and Life Support System, ECLSS）によって、資源の再利用を実現しています。この仕組みは、地球上における人間を中心とした自然界の物質循環サイクルを基にしています。つまりECLSSにおける物質循環とは、人の生活において排出される呼気や排泄物を、植物や物理化学装置を利用して再循環させることで、人が生活する上で必要な空気や水、食料などとして再生し、物資の供給を補おうとする仕組みで、水・酸素・二酸化炭素・窒素が主な構成物質です。
人類が宇宙に進出してから50年以上が経ち，様々なミッションに対応した生命維持システムの研究開発が行われてきました。現在の国際宇宙ステーションにおいては、生命維持システムによって水や二酸化炭素の再生を行いながら、人間が宇宙に長期滞在できるまでになってきています。しかし将来の月面基地や有人火星探査に向けて、新たな生命維持システムの検討や研究開発をより加速していく必要があり、一方で生命維持システムの規模が拡大し、複雑化するにつれ、システム全体の物質循環制御が重要になってきました。また外部からの補給が必要無い、完全な閉鎖生態系における物質循環サイクルを実現した生命維持システムは、制御型生態系生命維持システム（Controlled Ecological Life Support Systems, CELSS）といい、人類が宇宙への移住を果たすためには、ECLSSをミニ地球と呼べるCELSSにまで発展させる必要があります。
ECLSS研究会では、宇宙における生命維持技術の研究を支援するため、ECLSSやCELSSの物質循環と制御を模擬するシミュレータ（SImulator for Closed Life and Ecology, SICLE）の開発に取り組んでいます。また有人宇宙開発研究の一環として、火星砂漠研究基地における模擬居住実験への参加や、有人宇宙飛行計画の設計、学会参加／発表などを行っており、更に地球上での課題解決など地球へのフィードバックとして、他分野へのSICLEの応用なども進めています。