SPACE SUIT

SPACE SUITS To work outside of a shuttle or station in space where there is no atmospheric pressure and no oxygen to sustain life, humans must take their environment with them. Inside a spacecraft, the atmosphere can be controlled so that special clothing isn't needed, but humans on the outside need the protection of a spacesuit. Above the altitude of 63,000 feet, 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. The first American spacesuit, for Project Mercury, was a modified version of a U.S. Navy high-altitude jet aircraft pressure suit worn "soft" or unpressurized. It served only as a backup for possible spacecraft cabin pressure loss, which never happened. Spacesuit designers followed the U.S. Air Force approach for greater mobility when they developed the spacesuit for the two-man Gemini spacecraft. The Gemini spacesuit was flexible when pressurized. To walk on the Moon's surface a quarter million miles from Earth, spacesuits had to protect astronauts from jagged rocks and the searing heat of the lunar day. They had to be flexible enough to permit stooping to pick up rocks, setting up scientific data stations at each landing site, and riding in the lunar rover buggy. The moon suit had a backpack that provided oxygen for breathing, suit pressurization, and ventilation for Moon walks lasting up to seven hours. The nine Skylab crewmen who manned America's first space station for 171 days during 1973 and 1974 wore simplified versions of the Apollo spacesuit. Apollo spacesuits were used again in July 1975 when American astronauts and Soviet cosmonauts rendezvoused and docked in Earth orbit in the joint Apollo-Soyuz Test Project (ASTP) flight. Shuttle spacesuits are pressurized. Before going outside to perform tasks in space, an astronaut has to spend hours breathing pure oxygen. That's necessary to remove nitrogen dissolved in body fluids to prevent its release as gas bubbles when pressure is reduced, a condition known as the "bends." Spacesuits for the space station era will be pressurized to shorten the pre-breathing period. The suit will shield an astronaut from deadly hazards such as bombardment by micrometeorites and the extreme temperatures. Without the Earth's atmosphere to filter sunlight, the side of the spacesuit facing the Sun may be heated to as high as 250 degrees Fahrenheit. The other side, exposed to the darkness of deep space, may get as cold as minus-250 degrees Fahrenheit. Today's shuttle spacesuits have built-in communications radios and gas-jet fly-around backpacks. There also is a urine-collection device that receives and stores urine for transfer later to the orbiter waste-management system. The spacesuit includes a liquid cooling and ventilation garment-a one-piece mesh suit made of Spandex, zippered for front entry and weighing 6.5 pounds dry. The garment has water-cooling tubes running through it to keep the wearer comfortable during active work periods. There also is an in-suit drink bag containing 21 ounces of water, and a "Snoopy Cap" radio holder with headphones and microphones for two-way communications and caution-and-warning tones, and a biomedical instrumentation subsystem. The maximum total weight of the largest-size spacesuit is 107 pounds. The suit's backpack, with a control display on the suit chest, supplies oxygen for breathing, suit pressurization, and ventilation. It also cools and circulates water used in the liquid cooling ventilation garment, controls ventilation gas temperature, absorbs carbon dioxide, and removes odors from the suit atmosphere. To fly around space, astronauts wear a nitrogen-propelled backpack known as the Manned Maneuvering Unit (MMU), which latches to the spacesuit.