CELSS

CELSS stands for Closed Ecological Life Support System, also called Controlled Ecological Life Support System. It refers to a class of life-support concepts and hardware intended to sustain humans in space by recycling air, water, and biomass within a closed environment. A CELSS integrates atmosphere management, water reclamation, food production, and waste processing to reduce resupply needs.

Development began during the early spaceflight era and progressed through ground tests and spaceflight analogs. NASA and other researchers explored combining physical-chemical systems with bioregenerative elements such as crops and microorganisms. Notable programs include the Soviet BIOS-3 project, later studies in Biosphere 2, and NASA breadboard and integrated life-support experiments. The International Space Station has supported ongoing bioregenerative research as part of its life-support portfolio.

Core components include air revitalization (CO2 removal and O2 generation), water recovery (condensate collection and urine and wastewater treatment), and food production (crop cultivation via hydroponics or aeroponics). Waste processing, nutrient management, and energy supply with redundancy are also essential. Systems rely on sensors and automated controls to maintain stable atmosphere, humidity, crop health, and resource balance, often requiring substantial energy input.

Status and outlook: A fully closed, long-duration CELSS has not yet been demonstrated in practice. Today, CELSS concepts remain part of bioregenerative and advanced life-support research within space agencies, with the aim of enabling future missions to the Moon, Mars, or deep space through more efficient, reliable closed-loop systems.