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Ed White was the first American to perform a space walk. Photo courtesy of NASA
Why do Astronauts wear Spacesuits?
A spacesuit must protect the astronauts
from the harsh environments of space. In space there are very
few air molecules. Note that air pressure is the result of the
movement and collisions of air molecules. This absence of molecules
is referred to as a vacuum.
An astronaut's body fluids would fizz
and bubble if he or she was wearing street clothes and was placed
in a vacuum. Thus, one of the main purposes of the spacesuit
is to provide a leak-proof bladder which stores air pressure
to protect the astronaut's body. This function is so important
that sometimes spacesuits are referred to as pressure suits.
In 1884, a Frenchman named Le Chatelier
noted that: If a stress is applied to a system at equilibrium,
the system tries to readjust itself to reduce the stress, if
possible. The applied stress could be a change in temperature,
a change in pressure, or some other external force. The readjustment
results in a new equilibrium.
The Earth's atmosphere exerts a pressure
against our bodies. This pressure is 14.7 pounds per square inch
at sea level. This pressure helps keep our bodily fluids from
escaping or changing into vapor, although some is lost through
perspiration and other means. This air pressure thus places a
stress on our bodies. Gravity also places a stress on bodies.
When this air pressure is removed, an
astronaut's body changes to release this stress according to
Le Chatelier's principle. This is achieved through the boiling
of bodily fluids. The internal stress in the astronaut's body
drives this change.
Astronaut Michael Collins described the
suits the Gemini astronauts wore as follows.
When fully dressed and ready to go on
a space walk, the astronaut wore the following from the inside
out: (1) long cotton underwear, (2) a nylon comfort liner, (3)
a pressure bladder of neoprene coated nylon, (4) a Link Net restraint
layer, (5) one layer of felt, (6) seven layers of aluminized
mylar superinsulation, and (7) a cover layer of high temperature
nylon.
Reference: Michael Collins, Liftoff, Grove
Press, New York, 1988.
Link Net is a fishnet-like, loosely woven
fabric.
Also, note that some of the spacesuit
layers were changed to be fire-resistant after the Apollo 1 fire
which killed Gus Grissom and two other astronauts.
Space shuttle astronauts wear a launch/entry
suit, as described in the following book:
B. Bondar and R. Bondar, On the Shuttle
Eight Days in Space, Greey de Pencier Books, Toronto, 1993.
The purpose of this launch/entry suit
is to provide the astronauts with protection against the heat
and pressure changes during liftoff. It also provides an extra
layer of protection from cold or fire in case of an emergency.
It consists of an outer suit, long underwear, communications
hat, helmet, parachute, flotation device, gloves, back pad, seat
support, boots, gravity pants, socks, diaper, and diaper belt.
Yes, each astronaut needs to wear a diaper because the liftoff
acceleration puts pressure on the astronaut's bladder. Also,
the astronauts must sit through a long countdown prior to launch,
which may last three hours.
Once in orbit, the shuttle astronauts
wear casual clothes. These clothes have velcro pads to hold items
needed by the astronauts.
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