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Getting ready to go outside

For spacewalking astronauts, getting dressed for work is an intricate, time-consuming task. They have to don a bulky suit consisting of many components and any mistake in the procedure could have life-threatening consequences.

The undergarments come first—and these are more unusual than most. They include a device to collect and store urine (later transferred to the Space Shuttle’s waste management system) and a long-john known as the liquid cooling and ventilation garment. Made of spandex, it contains many small tubes that allow cooling water to circulate over the astronaut’s body.

Next comes a drink bag filled with water, which is velcroed to the inside of the suit with a tube sticking up within easy reach of the astronaut’s mouth. The astronaut then dons a "Snoopy" cap, a cloth headpiece with headphones and microphones for two-way communications.

Then it’s time to pull on the "lower torso assembly"—the pants with attached boots. This item has several layers of fabric that protect the astronaut from extreme temperatures, which can span more than 200 degrees Celsius between direct sunlight and shade. These fabrics also prevent penetration by micrometeoroids, which could cause a loss of pressure in the suit.

The top half of the suit—known as the hard upper torso or HUT—is trickier to get into. A hard shell of fibreglass, it’s attached to the wall of the Shuttle’s airlock and the astronaut wriggles into it from below. American astronaut Jerry Ross, a veteran spacewalker, compares it to being "hung like a coat on the wall."

Helped by crewmates, the spacewalker then dons the helmet with its adjustable visor and the heavy, rubber-tipped gloves. Finally, any tools needed for the spacewalk are attached to the suit.

The dressing process takes about an hour and a half.

After spending time breathing pure oxygen, the spacewalkers, who work in pairs, are ready to go outside. Leaving the airlock is a careful and deliberate process. First, the airlock pressure is gradually reduced while the suits are checked for leaks. Then the pressure drops to zero and the astronauts prepare to exit the hatch.

They switch the suits to battery power, turn on the communications system and the cooling water supply. Then they tether themselves to each other and one connects a tether to the inside of the airlock—a precaution against accidentally floating away when they emerge from the airlock.

One astronaut goes out the hatch, attaches himself to safety line on the outside and hands in a second tether to his crewmate. Then they disconnect the line between them and the one to the inside of the airlock and emerge into the Shuttle’s cargo bay to begin work.