Behaviour of glass
A space suit must perform several functions to allow its occupant to work safely and comfortably, inside or outside of a spacecraft. It must provide:
- A stable internal pressure. This can be less than earth's atmosphere, as there is usually no need for the spacesuit to carry nitrogen (which comprises about 78% of earth's atmosphere and is not used by the body). Lower pressure allows for greater mobility, but requires the suit occupant to breathe pure oxygen for a time before going into this lower pressure, to avoid decompression sickness.
- Mobility. Movement is typically opposed by the pressure of the suit; mobility is achieved by careful joint design. See the Theories of spacesuit design section.
- Supply of breathable oxygen and elimination of carbon dioxide; these gases are exchanged with the spacecraft or a portable life support system (PLSS)
- Temperature regulation. Unlike on Earth, where heat can be transferred by convection to the atmosphere, in space, heat can be lost only by thermal radiation or by conduction to objects in physical contact with the exterior of the suit. Since the temperature on the outside of the suit varies greatly between sunlight and shadow, the suit is heavily insulated, and air temperature is maintained at a comfortable level.
- A communication system, with external electrical connection to the spacecraft or PLSS
- Means of collecting and containing solid and liquid waste