Life Support Systems in Space
by
Gp Capt N Rattan VSM
DPMO (S)
HQ WAC, IAF

Sqn Ldr Anirudh Agrawal
Gd Spl (Av Med)
3 Sqn AF

ABSTRACT
Life support during space travel and exploration has progressed from being a basic survival aid to a more comprehensive system to cater for enhanced crew comfort and mobility. Life support systems in the Mercury Spacecraft had a 5.0 psi oxygen atmosphere with the system having a carbon dioxide absorber. The crew remained in the pressure suit for the complete duration of the flight. Modern spacecraft life support systems are designed to work at sea level pressures (14.7+ 0.2 psi) and provide a 20% oxygen and 80% nitrogen, humidity controlled, environment. They also have water recovery systems to re-use wastewater, a temperature control system and a waste disposal system. The aim is to provide a bio-regenerative system, like the Controlled Ecological Life Support System (CELSS). The International Space Station is to have a "closed-loop" operation of the physicochemical water and air systems. Carbon dioxide will be removed from the atmosphere and electrolysed to produce oxygen for use by the crew by an Air Revitalisation System. It will also have an oxygen generator that will produce water as a by-product. Potable water is to be recovered form hygiene wastewater (shower, hand wash, laundry), urine, and humidity condensate by a Water Recovery System.

For EVA (Extra Vehicular Activity) the astronaut is to be gradually decompressed to a lower pressure before entering the EMU (Extravehicular Mobility Unit). The EMU has a self-contained life support system that contains seven hours of expendables, such as oxygen, a battery for electrical power, water for cooling, lithium hydroxide for carbon dioxide removal and a 30-minute emergency life support system.