In
this section
The
Jobs of a Typical Spacesuit
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The Jobs of
a Typical Spacesuit
Providing
Pressurized Atmosphere
Spacesuits provides air pressure to prevent astronauts' body fluids from
boiling (i.e. to keep the fluids in a liquid state). Most spacesuits operate
at pressures below normal atmospheric pressure (1 atm), and the space
shuttle cabin operates at normal atmospheric pressure. The spacesuit used
by shuttle astronauts operates at 0.29 atm. So the cabin pressure of either
the shuttle itself or an airlock must be reduced before an astronaut get
suited up for a spacewalk.
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Providing
Oxygen
Spacesuits must not provide normal air (i.e. 78 percent nitrogen, 21 percent
oxygen and 1 percent other gases) for the reason that the low pressure
will cause dangerously low oxygen concentration in the lungs and blood,
like climbing Mt. Everest does. Therefore, most spacesuits provide a pure
oxygen atmosphere for breathing. Spacesuits get the oxygen either from
a spacecraft through an umbilical cord or from a backpack life support
system that the astronaut wears.
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Removing
Carbon Dioxide
Everybody breathes out carbon dioxide, including astronauts. In the closed
space of the spacesuit, carbon dioxide concentrations will build up to
a high level, which will make astronauts die. So excess carbon dioxide
must be removed from the spacesuit. Lithium hydroxide canisters, which
are located either in the spacesuit's life support backpack or in the
spacecraft in which they are accessed via an umbilical cord, are used
to remove carbon dioxide.
Lithium hydroxide remove carbon dioxide by reacting with it to form lithium
carbonate and water:
2LiOH(s) + CO2(g) -> Li2CO3(s) + H2O(l)
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Maintaining
Temperature
To cope with the extremes of temperature, most spacesuits are heavily
insulated with layers of fabric and covered with reflective outer layers
to reflect sunlight. Everyone produces heat during respiration, so astronauts
produce a lot of heat when doing strenuous activities. If this heat is
not removed, the sweat produced by the astronaut will fog up the helmet
and cause the astronaut to become severely dehydrated.
To remove this excess heat, spacesuits have used either fans or heat exchangers
to blow cool air, or water-cooled garments.
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Protecting
Astronauts From Micrometeroids
To protect the astronauts from collisions with micrometeroids, spacesuits
have multiple layers of durable fabrics. These layers also prevent the
suit from tearing on exposed surfaces of the spacecraft or a planet or
moon.
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Protecting
Astronauts From Radiation
Spacesuits offer only limited protection from radiation. Some protection
is offered by the reflective coatings of Mylar that are built into the
suits, but a spacesuit would not offer much protection from a solar flare.
So, spacewalks are planned during periods of low solar activity.
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Providing
Clear Sight
Spacesuits have helmets that are made of clear plastic or durable polycarbonate.
Most helmets have coverings to reflect sunlight. Also, prior to a spacewalk,
the inside faceplates of the helmet are sprayed with an anti-fog compound.
Moreover, modern spacesuit helmet coverings have mounted lights so that
the astronauts can see into the shadows.
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Providing
Mobility
Spacesuits are equipped with special joints or tapers in the fabric to
help the astronauts bend their hands (gloves), arms (arm assembly), legs,
knees and ankles(boots).
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Allowing
Communication
The astronauts wear headsets with microphones and earphones, and spacesuits
are equipped with radio transmitters/receivers, which are located in the
chestpacks/backpacks worn by the astronauts, so that spacewalking astronauts
can talk with ground controllers and/or other astronauts.
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Providing
Mobility in the Spacecraft and in Space
It is difficult to move around in a condition of weightlessness.
If someone push on somehing, he/she fly off in the opposite direction
(see Newton's Third Law). Spacewalking astronauts in Project Femini
reported great problems with just maintaining their positions; when they
tried to turn a wrench, they spun in the opposite direction. Therefore,
spacecraft are equipped with footholds and hand restraints to help astronauts
work in microgravity. Moreover, before the mission, astronauts practice
spacewalking in big water tanks on Earth. The buoyancy of an inflated
spacesuit in water simulates microgravity.
NASA has developed some gas-powered rocket maneuvering devices to allow
astronauts to move freely in space without being tehered to the spacecraft.
One such device, which was called the Manned Maneuvering Unit (MMU), was
basically a gas-thruster powered chair with a joystick control. When a
astronaut wants to move in some direction, the corresponding part of the
MMU will vent a gas, so the astronaut moves. NASA has also developed a
nitrogen-gas propelled unit that fits on the backpack, called the Simplified
Aid for Extravehicular Activity Rescue (SAFER). The SAFER can help an
astronaut return to the shuttle or station in the event that he/she gets
separated from the spacecraft. The SAFER holds nitrogen propellant and
can change an astronaut's velocity by a maximum of 3 meters/second.
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Photo Courtesy
NASA
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