Life-support system
A life-support system is the combination of equipment that allows survival in an environment or situation that would not support that life in its absence. It is generally applied to systems supporting human life in situations where the outside environment is hostile, such as outer space or underwater, or medical situations where the health of the person is compromised to the extent that the risk of death would be high without the function of the equipment.[1]
For other uses of "Life support", see Life support (disambiguation).
In human spaceflight, a life-support system is a group of devices that allow a human being to survive in outer space.
US government space agency NASA,[2] and private spaceflight companies
use the phrase "environmental control and life-support system" or the acronym "ECLSS" when describing these systems.[3] The life-support system may supply air, water and food. It must also maintain the correct body temperature, an acceptable pressure on the body and deal with the body's waste products. Shielding against harmful external influences such as radiation and micro-meteorites may also be necessary. Components of the life-support system are life-critical, and are designed and constructed using safety engineering techniques.
In underwater diving, the breathing apparatus is considered to be life support equipment, and a saturation diving system is considered a life-support system – the personnel who are responsible for operating it are called life support technicians. The concept can also be extended to submarines, crewed submersibles and atmospheric diving suits, where the breathing gas requires treatment to remain respirable, and the occupants are isolated from the outside ambient pressure and temperature.
Medical life-support systems include heart-lung machines, medical ventilators and dialysis equipment.
Space vehicle systems[edit]
Space Shuttle[edit]
The Space Shuttle was the first American spacecraft to have an Earth-like atmospheric mixture, comprising 22% oxygen and 78% nitrogen.[5] For the Space Shuttle, NASA includes in the ECLSS category systems that provide both life support for the crew and environmental control for payloads. The Shuttle Reference Manual contains ECLSS sections on: Crew Compartment Cabin Pressurization, Cabin Air Revitalization, Water Coolant Loop System, Active Thermal Control System, Supply and Waste Water, Waste Collection System, Waste Water Tank, Airlock Support, Extravehicular Mobility Units, Crew Altitude Protection System, and Radioisotope Thermoelectric Generator Cooling and Gaseous Nitrogen Purge for Payloads.[6]
Soyuz[edit]
The life-support system on the Soyuz spacecraft is called the Kompleks Sredstv Obespecheniya Zhiznideyatelnosti (KSOZh) (Russian: Комплекс Средств Обеспечения Жизнедеятельности (KCOЖ)). Vostok, Voshkod and Soyuz contained air-like mixtures at approximately 101kPa (14.7 psi).[5] The life support system provides a nitrogen/oxygen atmosphere at sea level partial pressures. The atmosphere is then regenerated through KO2 cylinders, which absorb most of the CO2 and water produced by the crew biologically and regenerates the oxygen, the LiOH cylinders then absorb the leftover CO2.[7]
Natural systems[edit]
Natural LSS like the Biosphere 2 in Arizona have been tested for future space travel or colonization. These systems are also known as closed ecological systems. They have the advantage of using solar energy as primary energy only and being independent from logistical support with fuel. Natural systems have the highest degree of efficiency due to integration of multiple functions. They also provide the proper ambience for humans which is necessary for a longer stay in outer space.
Underwater habitats and surface saturation accommodation facilities provide life-support for their occupants over periods of days to weeks. The occupants are constrained from immediate return to surface atmospheric pressure by decompression obligations of up to several weeks.
The life support system of a surface saturation accommodation facility provides breathing gas and other services to support life for the personnel under pressure. It includes the following components:[12] Underwater habitats differ in that the ambient external pressure is the same as internal pressure, so some engineering problems are simplified.
Underwater habitats balance internal pressure with the ambient external pressure, allowing the occupants free access to the ambient environment within a specific depth range, while saturation divers accommodated in surface systems are transferred under pressure to the working depth in a closed diving bell
The life support system for the bell provides and monitors the main supply of breathing gas, and the control station monitors the deployment and communications with the divers. Primary gas supply, power and communications to the bell are through a bell umbilical, made up from a number of hoses and electrical cables twisted together and deployed as a unit.[13] This is extended to the divers through the diver umbilicals.[12]
The accommodation life support system maintains the chamber environment within the acceptable range for health and comfort of the occupants. Temperature, humidity, breathing gas quality sanitation systems and equipment function are monitored and controlled.[13]
Experimental life-support systems[edit]
MELiSSA[edit]
Micro-Ecological Life Support System Alternative (MELiSSA) is a European Space Agency led initiative, conceived as a micro-organisms and higher plants based ecosystem intended as a tool to gain understanding of the behaviour of artificial ecosystems, and for the development of the technology for a future regenerative life-support system for long term crewed space missions.
CyBLiSS[edit]
CyBLiSS ("Cyanobacterium-Based Life Support Systems") is a concept developed by researchers from several space agencies (NASA, the German Aerospace Center and the Italian Space Agency) which would use cyanobacteria to process resources available on Mars directly into useful products, and into substrates for other key organisms of Bioregenerative life support system (BLSS).[14] The goal is to make future human-occupied outposts on Mars as independent of Earth as possible (explorers living "off the land"), to reduce mission costs and increase safety. Even though developed independently, CyBLiSS would be complementary to other BLSS projects (such as MELiSSA) as it can connect them to materials found on Mars, thereby making them sustainable and expandable there. Instead of relying on a closed loop, new elements found on site can be brought into the system.