Primary life support system
A primary life support system (PLSS), is a device connected to an astronaut or cosmonaut's spacesuit, which allows extra-vehicular activity with maximum freedom, independent of a spacecraft's life support system. A PLSS is generally worn like a backpack. The functions performed by the PLSS include:Regulating suit pressure
Providing breathable oxygen
Removing carbon dioxide, humidity, odors, and contaminants from breathing oxygen
Cooling and recirculating oxygen through the pressure garment, and water through a Liquid Cooling and Ventilation Garment or Liquid Cooling Garment.
Two-way voice communication
Display or telemetry of suit health parameters
Telemetry of an indicator of the wearer's immediate health
A portable life support system from the Apollo A7L suit, with its outer cover removed
The interior of the Apollo PLSS
Diagram of the A7L PLSS and OPS, with interfaces to the astronaut and the Lunar Module cabin
James P. Lucas testing the PLSS at Houston Flight Center
A space suit or spacesuit is a garment worn to keep a human alive in the harsh environment of outer space, vacuum and temperature extremes. Space suits are often worn inside spacecraft as a safety precaution in case of loss of cabin pressure, and are necessary for extravehicular activity (EVA), work done outside spacecraft. Space suits have been worn for such work in Earth orbit, on the surface of the Moon, and en route back to Earth from the Moon. Modern space suits augment the basic pressure garment with a complex system of equipment and environmental systems designed to keep the wearer comfortable, and to minimize the effort required to bend the limbs, resisting a soft pressure garment's natural tendency to stiffen against the vacuum. A self-contained oxygen supply and environmental control system is frequently employed to allow complete freedom of movement, independent of the spacecraft.
Apollo spacesuit worn by astronaut Buzz Aldrin on Apollo 11
Orlan space suit worn by astronaut Michael Fincke outside the International Space Station
Feitian space suit being displayed at the National Museum of China
Space suits being used to work on the International Space Station.