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The Station - Space Walk Trainingliving in space

Why Wear A Spacesuit?

To explore and work in space, human beings must take their environment with them because there is no atmospheric pressure and no oxygen to sustain life. Inside the spacecraft, the atmosphere can be controlled so that special clothing isn't needed, but when outside, humans need the protection of a spacesuit.

Earth's atmosphere is 20 percent oxygen and 80 percent nitrogen from sea level to about 75 miles up, where space begins. At 18,000 feet, the atmosphere is half as dense as it is on the ground, and at altitudes above 40/000 feet, air is so thin and the amount of oxygen so small that pressure oxygen masks no longer do the job. Above the 63,000-foot threshold, humans must wear spacesuits that supply oxygen for breathing and that maintain a pressure around the body to keep body fluids in the liquid state. At this altitude the total air pressure is no longer sufficient to keep body fluids from boiling.

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Spacesuits for the space shuttle era are pressurized at 4.3 pounds per square inch (psi), but because the gas in the suit is 100 percent oxygen instead of 20 percent, the person in a spacesuit actually has more oxygen to breathe than is available at an altitude of 10,000 feet or even at sea level without the spacesuit. Before leaving the space shuttle to perform tasks in space, an astronaut has to spend several hours breathing pure oxygen before proceeding into space. This procedure is necessary to remove nitrogen dissolved in body fluids and thereby to prevent its release as gas bubbles when pressure is reduced, a condition commonly called "the bends."

Spacesuits designed for the space station era will be pressurized to 8.3 psi; therefore, the pre-breathing period will be shortened or diminished.

The spacesuit also shields the astronaut from deadly hazards. Besides providing protection from bombardment by micrometeoroids, the spacesuit insulates the wearer from the temperature extremes of space. Without the Earth's atmosphere to filter the sunlight, the side of the suit facing the Sun may be heated to a temperature as high as 250 degrees Fahrenheit; the other side, exposed to darkness of deep space, may get as cold as -250 degrees Fahrenheit.

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Wardrobe for the Space Shuttle Era

Astronauts of the space shuttle era have more than one wardrobe for space flight and what they wear depends on the job they are doing.

Spacesuit Diagram

During ascent and entry, each crewmember wears special equipment consisting of a partialpressure suit, a parachute harness assembly, and a parachute pack. The suit, consisting of helmet, communication assembly, torso, gloves and boots, provides counterpressure and anti-exposure functions in an emergency situation in which the crew must parachute from the orbiter. The suit has inflatable bladders that fill it with oxygen from the orbiter. These bladders inflate automatically at reduced cabin pressure. They also can be manually inflated during entry to prevent the crewmember from blacking out. Without the suit pressing on the abdomen and the legs, the blood would pool in the lower part of the body and cause a person to black out as the spacecraft returns from microgravity to Earth's gravity. The partial-pressure suit and equipment will support a crewmember for a 24-hour period in a life raft in case of an egress over water.

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*Click on images for captions
Photo credits for all images: NASA.

Additional materials in this section courtesy of NASA.


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