Started with the survival problem in spacecrafts, life support system (LSS) has long been a fascinating and challenging field of research. Basic life-support systems for humans require the supply of food, water, and oxygen, the disposal of human wastes, and the maintenance of temperature. Primary LSSs in spaceships or space stations usually have a low recycling rate of life support materials, most of the food, water and other survival necessities are carried at the beginning of a launch mission, or replenished by cargo spaceships. But for long-distance and long-term interstellar missions, or for the establishment of bases on Moon or Mars, self-sustaining LSSs will be quite essential.
Such self-sustaining LSSs are usually referred as the closed ecological system (CES). From tiny bottle biosphere experiments, which contain only a few fishes, shrimps, and plants, to the Biosphere 2 project, which includes almost all ecosystem types (forests, grasslands, wetlands, ocean, etc.), CESs have been trying to create the long self-sustaining ecosystems independent of the Earth’s biosphere. The vision of CESs is not only to provide the practical basis for interstellar exploration, but also for building shelters when facing catastrophic events on Earth, such as asteroid impacts, nuclear contaminations, or plagues.
However, the long-term stable sustaining of CESs has rarely succeeded. Experiments that try to mimic natural ecosystems, whether a simple bottle biosphere that contains only one type of ecosystem or the Biosphere 2 that includes multiple ecosystem types, usually end in collapse. In contrast, there are many successful cases for CESs with more specific experimental targets and more accurate accountings for biological matter cycle, such as the Lunar Palace 1 (China) and the Biosphere-3 (Russia), which have been succeeded in the experiments of sustaining human occupants for at least one year. But the success of completely closed and real permanent CESs is far from being realized.
In fact, the complex feedbacks of the natural biosphere have not been fully understood yet, the failure of Biosphere 2 indicates that increased complexity does not necessarily mean increased stability. In addition, the impact of energy input on ecosystem function and human survival has not been fully evaluated, the success of CESs such as Lunar Palace 1 depends in part on their sufficient energy input, rather than relying solely on solar energy as in the case of Biosphere 2.
At the theoretical level, the success of LSS or CES requires the innovation and integration of basic ecological principles, such as how the material cycle is driven by energy flow, how the cycles of different elements are coupled, and how to maintain the stable state of ecosystems. At the application level, LSS and CES can provide great opportunities to develop technologies of more efficient material recycling and energy use, which can help to achieve the goals of sustainable development and circular economy.
Just as mankind’s pursuit on space industry has greatly promoted scientific and technological progress in physics, materials, medicine and agriculture, the exploration and investment in LSS and CES will also undoubtedly promote the innovation of ecological sciences and the development of sustainable economy. In this sense, LSS will lead the future of ecology.