A Tiny Spacecraft You Wear
A space suit works like a small spacecraft you can wear. Its main job is to protect against the vacuum of space, but it also guards against extreme heat and cold, radiation and tiny fast-moving particles called micrometeoroids. It has to keep a steady pressure, supply oxygen, remove carbon dioxide, and keep the wearer at a comfortable temperature.
That last part is harder than it sounds. On Earth, heat drifts away into the air. In space there is no air, so heat can only escape by radiating away or through direct contact. The outside of a suit swings wildly between sunlight and shadow, so it is heavily insulated. Advanced suits add a cooling garment worn against the skin.
There are suits for inside and suits for outside. Inside suits are lighter and are worn as a backup in case the cabin loses pressure. Suits for extravehicular activity are far more complex. They must protect against everything space can throw at the wearer, while still letting them move and work. They also include a communication system, and even a way to collect bodily waste.
Why Bending an Elbow Is Hard Work
Here is the hidden problem with any pressurized suit. If bending a joint squeezes the suit's volume, the wearer has to push against the air pressure every single time. Even a small force becomes exhausting when you fight it all day, and fine movements get very hard.
So designers try to keep the suit's volume the same no matter how you move. Most suits use layers. Inside is a bladder, a rubbery airtight layer much like a balloon. Outside it is a restraint layer that gives the suit its shape and takes the strain. Because of that, the bladder will not pop like a balloon, even if punctured. Around each joint, pockets of fabric called gores open on the outside while folds close up on the inside, keeping the volume nearly constant.
Hard-shell suits take another route. They use metal or composite parts and ball bearings, a bit like the adjustable elbow of a stove pipe. NASA's experimental AX-5 hard suit let the wearer reach 95% of the positions they could manage without it. Some Russian suits used a simpler trick: strips of cloth wrapped tightly around the arms and legs to stop the suit from ballooning.
Eleven Layers and a Snoopy Cap
The Apollo and Skylab A7L suit had eleven layers in all. There was an inner liner, a cooling garment, the pressure bladder, a restraint layer, another liner, and an outer Thermal Micrometeoroid Garment made of five aluminized insulation layers and a tough white fabric. Together they protected astronauts from minus 156 °C to 121 °C.
The details are full of surprises. Under the helmet, NASA astronauts wear a cap with earphones and a microphone. The Apollo and Skylab version had colours like the comic strip character Snoopy, so everyone called them "Snoopy caps." From Apollo 13 on, the commander's suit got stripes so that two spacewalkers would not look identical on camera.
Gloves have changed a lot too. The first U.S. space suit design, for the Mercury program, had lights at the fingertips. Apollo gloves used a metal fabric to stop punctures, with silicone fingertips for a better sense of touch. Modern spacewalk gloves are heated. And some helmets fix the head facing forward, so the wearer cannot turn to look sideways. Astronauts call this "alligator head."
Breathing Pure Oxygen Before Stepping Out
A space suit does not need to match Earth's air pressure. Nitrogen makes up about 78% of our air, but the body does not use it, so suits can run on pure oxygen at a lower pressure. Many modern suits use about 32.4 kPa. Lower pressure also makes a suit easier to bend.
The catch is decompression sickness. Astronauts living in normal cabin air have nitrogen dissolved in their bodies. Dropping straight into a low-pressure suit could make them ill. So they "pre-breathe" pure oxygen first, which flushes the nitrogen out.
On the Space Shuttle, the cabin pressure was lowered for 24 hours before a spacewalk. After suiting up, astronauts then breathed pure oxygen for 45 minutes before dropping to the suit's working pressure. The International Space Station skips the cabin step and uses a 4-hour oxygen pre-breathe instead. Hard-shell suits could remove this wait, because they can work at higher pressures.
From Gagarin's Suit to Prada
Full-pressure suits for extreme altitudes appeared in the 1930s. Evgeniy Chertovsky created one in 1931, and its Russian name, skafandr, also means diving suit. The first space suit worn in space was the Soviet SK-1, worn by Yuri Gagarin in 1961. In 1965, Alexei Leonov made the first spacewalk in a modified version called Berkut, which means golden eagle.
Early suits were tied to the spacecraft by a cable. With Apollo, life support moved into a removable unit called the Portable Life Support System, letting astronauts explore the Moon without being attached to their spacecraft. Russia's Orlan spacewalk suit, whose name means sea-eagle, has been in use since 1977.
Recent suits have real style. A Hollywood costume designer helped shape the look of the SpaceX suit, and a mannequin named Starman wore one on the first Falcon Heavy launch in 2018. In 2024, the Polaris Dawn mission used a SpaceX suit for the first ever commercial spacewalk. NASA even let the public vote on the design of its Z-2 prototype, and Axiom Space and Prada showed a suit being developed for NASA's Artemis III mission.
