Outer space holds many dangers. It has extreme temperatures, from highs of more than 200 degrees Fahrenheit to lows of -320 degrees Fahrenheit. Then there's deadly radiation from cosmic rays and hurling particles of space dust. But if an astronaut were to step outside a spacecraft without any protection, none of this would really matter. Since space is a vacuum, without oxygen and air pressure, no one could survive for even two minutes.
Astronaut Franklin R. Chang-Diaz, wearing an EMU, works on the International Space Station.
And that's why astronauts wear space suits when they need to leave their craft. These extravehicular mobility units (EMUs) protect astronauts from the dangers of space and allow them to go on space walks to make repairs, or to help build the International Space Station. A space suit provides air pressure. It does this by surrounding the body with air held in by rubberized fabric. In a way, an astronaut is inside a giant balloon.
Astronauts also carry on their backs a life support system that provides them with pure oxygen. To protect astronauts from the extreme temperatures of space. The outer layer reflects sunlight. The fabric is extra tough to prevent rips from tiny specks of meteoroids whizzing past at high speeds.
A space suit is made up of many layers, 13 in all, from the undergarments that keep an astronaut cool to the outer assembly, helmet, gloves, and life support system. Astronauts mix and match the pieces for a custom fit.
The space suit Neil Armstrong wore to walk on the moon in 1969 weighed 200 pounds on Earth. Today's modern space suit weighs even more. The backpack alone is more than 300 pounds. Designers are working on creating space suits that will weigh much less.
Astronauts in early EMU space suits needed to be tethered, or tied, to the mother ship with 25-foot long cords, hampering their movements. It wasn't until 1984 that astronaut Bruce McCandless became the first person to go on a space walk tether-free. He zipped around wearing a Manned Maneuvering Unit (MMU) jet pack.