How does a spacesuit work?

Key facts

Agency: National Aeronautics and Space Administration (NASA)

#explainer

Contents · 8

01Overview
02Pressure and movement
03A compact life-support system
04What happens to exhaled gas
05Why the body needs preparation too
06Key points
07Sources
08Connections

A spacesuit maintains pressure around the body, supplies oxygen, removes carbon dioxide and carries away excess heat. During a spacewalk it takes over some functions of a spacecraft cabin. Connecting an oxygen cylinder alone would not suffice: breathing safely also requires pressure.

Pressure and movement

A gas-tight bladder retains the breathing atmosphere, while a stronger restraint layer limits expansion. Joints, bearings and shaped components allow movement against internal pressure. Outer layers protect against abrasion, small particles and thermal radiation. The helmet provides visibility and eye protection.

A compact life-support system

For self-contained EVA suits, a backpack carries supplies and life-support equipment. A fan circulates gas, and an undergarment containing water tubes removes body heat. A launch survival suit has a different purpose and may not support independent outdoor work. Equipment therefore depends on the suit type and mission.

What happens to exhaled gas

The entire oxygen supply is not dumped into space after each breath. Gas circulates through a loop that removes carbon dioxide and replenishes consumed oxygen. Circulation also helps remove moisture. A fan or carbon-dioxide-removal failure can therefore be serious even while oxygen remains in the supply tank.

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Why the body needs preparation too

Suit pressure and gas composition can differ from the station atmosphere. Spacewalk preparation therefore includes prescribed procedures, including oxygen prebreathing as required by the system. An airlock progressively separates the cabin from vacuum. Donning a helmet is not the whole process: seals, communications, supplies and life-support functions also need checks.

Key points

A gas-tight bladder retains the breathing atmosphere, while a stronger restraint layer limits expansion.
For self-contained EVA suits, a backpack carries supplies and life-support equipment.
The entire oxygen supply is not dumped into space after each breath.
Suit pressure and gas composition can differ from the station atmosphere.