The astronauts live in a pressurized cabin, whose metal walls act as a barrier to dangerous radiation and to micro meteoroids, the tiny swift particles that stream through space. It is pressurized to atmospheric pressure. They breathe an 80/20, nitrogen/oxygen mixture, much like the air on Earth. The air is circulated through a highly efficient air-conditioning unit, which absorbs odours and the carbon dioxide the astronauts breathe out. The air is kept at a comfortable temperature and humidity.
When the astronauts leave their spacecraft to go spacewalking, they wear a spacesuit that affords them the same level of protection as their pressurized cabin. The early spacesuits, worn by the US Mercury astronauts, for example, were simply modified versions of the pressure suits worn by high-flying jet pilots. When astronauts began spacewalking in the mid-1960s, specialist spacesuits were developed to offer extra protection from the direct exposure to space. They were umbilical suits, which drew oxygen from the life-support system of the spacecraft through a tube.
For the Apollo Moonlanding missions, the astronauts wore a spacesuit that was self-contained so that they were free to roam. The life-support equipment was in a backpack.
The Shuttle suit, properly called the extra vehicular mobility unit (EMU), evolved from it. It is made in two parts - trousers and top; the top part has a rigid aluminium frame and a built-in life-support backpack.
In the early days the whole spacecraft often had to be depressurized before the astronaut could open a hatch and float into space. Modern craft, however, have an airlock, a chamber inside the crew cabin which can be independently depressurized.
Astronauts enter the airlock and breathe pure oxygen for some time before they suit up. This is to clear their blood of nitrogen. Otherwise the nitrogen would bubble out when they wore their suits, which operate at reduced pressure. This would give them dangerous cramp attacks known as "the bends". When the astronauts are suited up, they depressurize the airlock, open the exit hatch and float out into space. They become human satellites.
George
Nelson gets kitted up for the STS-26 Shuttle mission in September 1988.
He is wearing a newlydesigned pressurized flight suit. All Shuttle astronauts
now wear these suits on their journey into orbit. They came Into use following
the Challenger disaster to give astronauts added protection in the event
of a cabin depressurization during lift-off.
An
astronaut puts on the two-part Shuttle spacesuit, or EMU. Next to her skin
she wears water-cooled "long johns". She steps into the trousers first,
then dons the upper torso, which is fitted with a life-support backpack.
Torso and trousers join together by means of an airtight seal at the waist.
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Apollo EVA suit
The spacesuit the Apollo astronauts wore on their daring EVAs on the Moon was multi-layered. Over the astronaut's water-cooled "Iong johns" was a comfort layer, a pressure "bladder" and a restraint layer. On top was a 17-layer outer suit to provide protection against meteoroid particles and sunlight. A backpack carried oxygen, power and communications equipment. |
