Astronauts --- Spacesuit --- The Jobs of a Typical Spacesuit
In the main page of this sub-section, we can see that a spacesuit must:
- Provide a pressurized atmosphere
- Give oxygen
- Remove carbon dioxide
- Maintain a comfortable temperature
- Protect an astronaut from micrometeoroids
- Protect an astronaut from radiation to some degree
- Let an astronaut see clearly
- Let an astronaut move his/her body easily inside the spacesuit
- Let an astronaut talk with others
- Let an astronaut move around the outside of the spacecraft
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.
Back
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.
Back
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)
Back
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.
Back
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.
Back
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.
Back
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.
Back
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).
Back
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.
Back
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.
Back
The Jobs of a Typical Spacesuit The Current Spacesuit