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 Outer space, commonly shortened to space, is the expanse that exists beyond Earth and its atmosphere and between celestial bodies. Outer space is not completely empty—it is a near-perfect vacuum containing a low density of particles, pred ...

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. In

human spaceflight Human spaceflight (also referred to as manned spaceflight or crewed spaceflight) is spaceflight with a crew or passengers aboard a spacecraft, often with the spacecraft being operated directly by the onboard human crew. Spacecraft can also be ...

, a life-support system is a group of devices that allow a human being to survive in outer space. US government space agency

NASA The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...

, and

private spaceflight Private spaceflight is spaceflight or the development of spaceflight technology that is conducted and paid for by an entity other than a government agency. In the early decades of the Space Age, the government space agencies of the Soviet Unio ...

companies use the term environmental control and life-support system or the acronym ECLSS when describing these systems. 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 A safety-critical system (SCS) or life-critical system is a system whose failure or malfunction may result in one (or more) of the following outcomes: * death or serious injury to people * loss or severe damage to equipment/property * environme ...

, and are designed and constructed using

safety engineering Safety engineering is an engineering discipline which assures that engineered systems provide acceptable levels of safety. It is strongly related to industrial engineering/systems engineering, and the subset system safety engineering. Safety en ...

techniques. In

underwater diving Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context ...

, 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 technician Professional diving is underwater diving where the divers are paid for their work. The diving procedures, procedures are often regulated by legislation and codes of practice as it is an inherently occupational safety and health, hazardous occupa ...

s. The concept can also be extended to

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s, crewed

submersible A submersible is a small watercraft designed to operate underwater. The term "submersible" is often used to differentiate from other underwater vessels known as submarines, in that a submarine is a fully self-sufficient craft, capable of ind ...

s and

atmospheric diving suit An atmospheric diving suit (ADS) is a small one-person articulated submersible which resembles a suit of armour, with elaborate pressure joints to allow articulation while maintaining an internal pressure of one atmosphere. An ADS can enable di ...

s, where the

breathing gas A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed h ...

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 Cardiopulmonary bypass (CPB) is a technique in which a machine temporarily takes over the function of the heart and lungs during surgery, maintaining the circulation of blood and oxygen to the body. The CPB pump itself is often referred to as a ...

medical ventilator A ventilator is a piece of health technology, medical technology that provides mechanical ventilation by moving breathable air into and out of the lungs, to deliver breaths to a patient who is physically unable to breathe, or breathing insuffici ...

s and dialysis equipment.

Human physiological and metabolic needs

A crewmember of typical size requires approximately of

food Food is any substance consumed by an organism for nutritional support. Food is usually of plant, animal, or fungal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals. The substance is inge ...

water Water (chemical formula ) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living organisms (in which it acts as a ...

, and

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

per day to perform standard activities on a space mission, and outputs a similar amount in the form of waste solids, waste liquids, and

carbon dioxide Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...

. The mass breakdown of these metabolic parameters is as follows: of oxygen, of food, and of water consumed, converted through the body's physiological processes to of solid wastes, of liquid wastes, and of carbon dioxide produced. These levels can vary due to activity level of a specific mission assignment, but must obey the principle of

mass balance In physics, a mass balance, also called a material balance, is an application of conservation of mass to the analysis of physical systems. By accounting for material entering and leaving a system, mass flows can be identified which might have bee ...

. Actual water use during space missions is typically double the given value, mainly due to non-biological use (e.g. showering). Additionally, the volume and variety of waste products varies with mission duration to include hair, finger nails, skin flaking, and other biological wastes in missions exceeding one week in length. Other environmental considerations such as radiation, gravity, noise, vibration, and lighting also factor into human physiological response in outer space, though not with the more immediate effect that the metabolic parameters have.

Atmosphere

Outer space life-support systems maintain atmospheres composed, at a minimum, of oxygen, water vapor and carbon dioxide. The

partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas as if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas ...

of each component gas adds to the overall

barometric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth. The standard atmosphere (symbol: atm) is a unit of pressure defined as , which is equivalent to 1013.25 millibars, 7 ...

. However, the elimination of diluent gases substantially increases fire risks, especially in ground operations when for structural reasons the total cabin pressure must exceed the external atmospheric pressure; see

Apollo 1 Apollo 1, initially designated AS-204, was intended to be the first crewed mission of the Apollo program, the American undertaking to land the first man on the Moon. It was planned to launch on February 21, 1967, as the first low Earth orbita ...

. Furthermore,

oxygen toxicity Oxygen toxicity is a condition resulting from the harmful effects of breathing molecular oxygen () at increased partial pressures. Severe cases can result in cell damage and death, with effects most often seen in the central nervous system, lu ...

becomes a factor at high oxygen concentrations. For this reason, most modern crewed spacecraft use conventional air (nitrogen/oxygen) atmospheres and use pure oxygen only in

pressure suits Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and ...

during

extravehicular activity Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmental support. EVA in ...

where acceptable suit flexibility mandates the lowest inflation pressure possible.

Water

Water is consumed by crew members for drinking, cleaning activities, EVA thermal control, and emergency uses. It must be stored, used, and reclaimed (from waste water) efficiently since no on-site sources currently exist for the environments reached in the course of human space exploration. Future lunar missions may utilize water sourced from polar ices; Mars missions may utilize water from the atmosphere or ice deposits.

Food

All space missions to date have used supplied food. Life-support systems could include a plant cultivation system which allows food to be grown within buildings or vessels. This would also regenerate water and oxygen. However, no such system has flown in outer space as yet. Such a system could be designed so that it reuses most (otherwise lost) nutrients. This is done, for example, by

composting toilet A composting toilet is a type of dry toilet that treats human waste by a biological process called composting. This process leads to the decomposition of organic matter and turns human waste into compost-like material. Composting is carried ou ...

s which reintegrate waste material (excrement) back into the system, allowing the nutrients to be taken up by the food crops. The food coming from the crops is then consumed again by the system's users and the cycle continues. The logistics and area requirements involved however have been prohibitive in implementing such a system to date.

Gravity

Depending on the length of the mission, astronauts may need artificial gravity to reduce the effects of

space adaptation syndrome Space adaptation syndrome (SAS) or space sickness is a condition experienced by as many as half of all space travelers during their adaptation to weightlessness once in orbit. It is the opposite of terrestrial motion sickness since it occurs when ...

, body fluid redistribution, and loss of bone and muscle mass. Two methods of generating artificial weight in outer space exist.

Linear acceleration

If a spacecraft's engines could produce thrust continuously on the outbound trip with a thrust level equal to the mass of the ship, it would continuously accelerate at the rate of per second, and the crew would experience a pull toward the ship's aft bulkhead at normal Earth gravity (one g). The effect is proportional to the rate of acceleration. When the ship reaches the halfway point, it would turn around and produce thrust in the retrograde direction to slow down.

Rotation

Alternatively, if the ship's cabin is designed with a large cylindrical wall, or with a long beam extending another cabin section or counterweight, spinning it at an appropriate speed will cause

centrifugal force In Newtonian mechanics, the centrifugal force is an inertial force (also called a "fictitious" or "pseudo" force) that appears to act on all objects when viewed in a rotating frame of reference. It is directed away from an axis which is paralle ...

to simulate the effect of gravity. If ''ω'' is the

angular velocity In physics, angular velocity or rotational velocity ( or ), also known as angular frequency vector,(UP1) is a pseudovector representation of how fast the angular position or orientation of an object changes with time (i.e. how quickly an objec ...

of the ship's spin, then the acceleration at a radius ''r'' is: Notice the magnitude of this effect varies with the radius of rotation, which crewmembers might find inconvenient depending on the cabin design. Also, the effects of

Coriolis force In physics, the Coriolis force is an inertial or fictitious force that acts on objects in motion within a frame of reference that rotates with respect to an inertial frame. In a reference frame with clockwise rotation, the force acts to the ...

(a force imparted at right angles to motion within the cabin) must be dealt with. And there is concern that rotation could aggravate the effects of vestibular disruption.

Space vehicle systems

Gemini, Mercury, and Apollo

American Mercury, Gemini and Apollo spacecraft contained 100% oxygen atmospheres, suitable for short duration missions, to minimize weight and complexity.

Space Shuttle

The

Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...

was the first American spacecraft to have an Earth-like atmospheric mixture, comprising 22% oxygen and 78% nitrogen. 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 Unit The Extravehicular Mobility Unit (EMU) is an independent anthropomorphic spacesuit that provides environmental protection, mobility, life support, and communications for astronauts performing extravehicular activity (EVA) in Earth orbit. Introduc ...

s, Crew Altitude Protection System, and Radioisotope Thermoelectric Generator Cooling and Gaseous Nitrogen Purge for Payloads.

Soyuz

The life-support system on the

Soyuz spacecraft Soyuz () is a series of spacecraft which has been in service since the 1960s, having made more than 140 flights. It was designed for the Soviet space program by the Korolev Design Bureau (now Energia). The Soyuz succeeded the Voskhod spacecraf ...

is called the Kompleks Sredstv Obespecheniya Zhiznideyatelnosti (KSOZh). Vostok, Voshkod and Soyuz contained air-like mixtures at approx 101kPa (14.7 psi).

Plug and play

The

Paragon Space Development Corporation Paragon Space Development Corporation is an American company headquartered in Tucson, Arizona. Paragon is a provider of environmental controls for extreme and hazardous environments. They design, build, test and operate life-support systems and l ...

is developing a plug and play ECLSS called ''commercial crew transport-air revitalization system'' (CCT-ARS) for future spacecraft partially paid for using NASA's Commercial Crew Development (

CCDev Development of the Commercial Crew Program began in the second round of the Commercial Crew Development (CCDev) program, which was rescoped from a technology development program for human spaceflight to a competitive development program that woul ...

) funding. The CCT-ARS provides seven primary spacecraft life support functions in a highly integrated and reliable system: Air temperature control, Humidity removal, Carbon dioxide removal, Trace contaminant removal, Post-fire atmospheric recovery, Air filtration, and Cabin air circulation.

Space station systems

Space station systems include technology that enables humans to live in outer space for a prolonged period of time. Such technology includes filtration systems for human waste disposal and air production.

Skylab

Skylab used 72% oxygen and 28% nitrogen at a total pressure of 5 psi.

Salyut and Mir

The Salyut and Mir space stations contained an air-like Oxygen and Nitrogen mixture at approximately sea-level pressures of 93.1 kPa (13.5psi) to 129 kPa (18.8 psi) with an Oxygen content of 21% to 40%.

Bigelow commercial space station

The life-support system for the

Bigelow Commercial Space Station The Bigelow Next-Generation Commercial Space Station was a private orbital space station under conceptual development by Bigelow Aerospace in the 2000s and 2010s. Previous concepts of the space station had included multiple modules such as two ...

is being designed by

Bigelow Aerospace Bigelow Aerospace is an American aeronautics and outer space technology company which manufactures and develops expandable space station modules. Bigelow Aerospace was founded by Robert Bigelow in 1998, and is based in North Las Vegas, Nevada. ...

Las Vegas, Nevada Las Vegas (; Spanish for "The Meadows"), often known simply as Vegas, is the 25th-most populous city in the United States, the most populous city in the state of Nevada, and the county seat of Clark County. The city anchors the Las Vegas ...

. The

space station A space station is a spacecraft capable of supporting a human crew in orbit for an extended period of time, and is therefore a type of space habitat. It lacks major propulsion or landing systems. An orbital station or an orbital space station i ...

will be constructed of habitable Sundancer and

BA 330 The B330 (previously known as the Nautilus space complex module and BA 330) was an inflatable space habitat being privately developed by Bigelow Aerospace from 2010 until 2020. The design was evolved from NASA's TransHab habitat concept. B330 wi ...

expandable spacecraft modules. " human-in-the-loop testing of the environmental control and life-support system (ECLSS)" for ''Sundancer'' has begun. Bigelow Volunteers

Natural systems

Natural LSS like the

Biosphere 2 Biosphere 2 is an American Earth system science research facility located in Oracle, Arizona. Its mission is to serve as a center for research, outreach, teaching, and lifelong learning about Earth, its living systems, and its place in the univers ...

in Arizona have been tested for future space travel or colonization. These systems are also known as

closed ecological systems Closed ecological systems (CES) are ecosystems that do not rely on matter exchange with any part outside the system. The term is most often used to describe small, wikt:manmade, manmade ecosystems. Such systems are scientifically interesting and ...

. 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 and saturation diving habitats

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: Underwater habitats differ in that the ambient external pressure is the same as internal pressure, so some engineering problems are simplified. *Gas compression, mixing and storage facilities *Chamber climate control system - control of temperature and humidity, and filtration of gas *Instrumentation, control, monitoring and communications equipment *Fire suppression systems *Sanitation systems 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 A diving bell is a rigid chamber used to transport divers from the surface to depth and back in open water, usually for the purpose of performing underwater work. The most common types are the open-bottomed wet bell and the closed bell, which c ...

The life support system for the bell provides and monitors the main supply of

, 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. This is extended to the divers through the diver umbilicals. 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.

Experimental life-support systems

MELiSSA

Micro-Ecological Life Support System Alternative (

MELiSSA Melissa is a female given name. The name comes from the Greek word μέλισσα (''mélissa''), "bee", which in turn comes from μέλι (''meli''), "honey". In Hittite, ''melit'' signifies "honey". ''Melissa'' also refers to the plant ''Me ...

) is a

European Space Agency , owners = , headquarters = Paris, Île-de-France, France , coordinates = , spaceport = Guiana Space Centre , seal = File:ESA emblem seal.png , seal_size = 130px , image = Views in the Main Control Room (1205 ...

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

CyBLiSS ("Cyanobacterium-Based Life Support Systems") is a concept developed by researchers from several space agencies (

, the

German Aerospace Center The German Aerospace Center (german: Deutsches Zentrum für Luft- und Raumfahrt e.V., abbreviated DLR, literally ''German Center for Air- and Space-flight'') is the national center for aerospace, energy and transportation research of Germany ...

and the

Italian Space Agency The Italian Space Agency ( it, Agenzia Spaziale Italiana; ASI) is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy. The agency cooperates with numerous national and international entit ...

) which would use

cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blu ...

to process resources available on Mars directly into useful products, and into substrates for other key organisms of

Bioregenerative life support system Bioregenerative life support systems (BLSS) are artificial ecosystems consisting of many complex symbiotic relationships among higher plants, animals, and microorganisms. As the most advanced life support technology, BLSS can provide a habitation e ...

(BLSS). 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.

Footnotes

References

* * * * * * * * * *

External links

* [http://ocw.mit.edu/courses/aeronautics-and-astronautics/16-423j-aerospace-biomedical-and-life-support-engineering-spring-2006/ Aerospace Biomedical and Life Support Engineering (MIT OpenCourseWare page – Spring 2006)]
Space Advanced Life Support (Purdue course page – Spring 2004)

Advanced Life support for missions to Mars

Mars Advanced Life Support

Mars Life Support Systems

Personal Hygiene in Space
(Canadian Space Agency)
Plants will Be Critical for Human Life Support Systems in Space
{{DEFAULTSORT:Life Support System Spacecraft design