How does a spacesuit act like a tiny spacecraft?

A spacewalk suit carries a small controlled environment around its wearer. The pressure garment contains gas around the body, while strong supporting layers help it hold its shape and still bend at joints. A regulator manages the gas pressure. Holding pressure and supplying oxygen are linked jobs, but they are not the same idea.

Oxygen supports breathing, while a fan circulates gas through the suit and backpack. Breathing also adds carbon dioxide to that gas. Removal equipment takes carbon dioxide out of the circulating stream, so providing fresh oxygen alone is not the whole air-management system. The backpack also supplies electrical power for its equipment.

The body continually produces heat, and the suit must carry excess energy away. Beneath the pressure garment, small tubes in a cooling garment carry water near the skin. The circulating water takes up body heat and carries it to equipment that transfers energy outside the suit. Protective layers also affect energy exchange with sunlight and the surroundings.

The suit's layers perform different jobs, including containing gas, limiting heat exchange and resisting small impacts. Its joints must also allow movement while the inside is pressurized. A spacesuit works as a connected system: the pressure garment surrounds the wearer, while powered equipment continually manages the gas and energy moving through it.