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The Space Suit

The Suit typically made by sewing and cementing various materials together, and then attaching metal parts that let you join the different components together. Suit materials include: ortho-fabric, aluminized mylar, neoprene-coated nylon, dacron, urethane-coated nylon, tricot, nylon/spandex, stainless steel, and high strength composite materials. Modern space suits have several features that make the astronaut work and move comfortably:

• Have a pressurized atmosphere - The spacesuit provides air pressure to keep the fluids in the body in a liquid state, preventing body fluids from boiling.
  
  
• Have sufficient oxygen supply - Most spacesuits provide a pure oxygen atmosphere for breathing as it is not possible to use normal air which consists of 78% nitrogen, 21% oxygen and 1% other gases, as low pressures could cause low oxygen concentrations in the lungs and blood. Spacesuits get the oxygen either from a spacecraft through an umbilical cord or from a backpack life support system that the astronaut wears.
  
  
• Eliminate carbon dioxide - Excess carbon dioxide must be removed from the spacesuit's atmosphere as concentration of carbon dioxide could increase lethal levels, in the limited space of the space suit. Spacesuits use lithium hydroxide canisters to eliminate carbon dioxide, and are accessed through an umbilical cord.
  
  
• Maintain a proper temperature despite of strenuous work and movement into and out of sunlit areas - Most spacesuits are insulated with layers of fabric (Neoprene, Gore-Tex, Dacron) to survive the extremes of temperature and covered with reflective outer layers (Mylar or white fabric) to reflect sunlight. While performing strenuous activities, immense heat is produced from the astronaut's body. It is essential to eliminate this heat, as the sweat produced would fog up the helmet and make the astronaut dehydrated. For removal of this heat, spacesuits either use fans/heat exchangers to blow cool air, or water-cooled garments.
  
  
• Protect from micrometeoroids - Spacesuits have about 11 layers of durable fabrics such as Dacron or Kevlar for protection from collisions with micrometeoroids. These layers also prevent the suit from tearing on exposed surfaces of the spacecraft or a planet or moon.
  
  Protect from radiation to some degree - Spacesuits provide restricted protection from radiation. The reflective coatings of Mylar built into the suits offer some protection, but cannot offer much protection from a solar flare. For this reason space walks are planned during periods of low solar activity.
  
  
• Enable clear vision - Spacesuits have helmets made from clear plastic or durable polycarbonate. Most helmets have coverings to reflect sunlight, and tinted visors to reduce glare. Further, before a space walk, the internal faceplates of the helmet are sprayed with an anti-fog compound. However, modern spacesuit helmet coverings have mounted lights so that the astronauts can see into the shadows.
  
  
• Allow easy movement of the body inside the spacesuit - Movement inside an inflated spacesuit is difficult. To solve this problem, spacesuits are equipped with special joints or tapers in the fabric to help the astronauts bend their hands, arms, legs, knees and ankles.
  
  
• Enable easy conversation with others such as ground controllers, other astronauts etc. - Spacesuits are facilitated with radio transmitters/receivers to enable space walking astronauts to talk with ground controllers and/or other astronauts. The astronauts wear headsets with microphones and earphones. The transmitters/receivers are located in the chest packs/backpacks worn by the astronauts.
  
  
• Facilitate movement around the outside of the spacecraft - Movement in weightlessness is difficult. Therefore, spacecraft are equipped with footholds and hand restraints to help astronauts work in micro gravity.

  
  

  
  Figure 1: Layers in a space suit

  To deal with this dramatic variations in temperature in outer space, spacesuits are heavily insulated with layers of fabric and then covered with reflective outer layers. This minimizes the temperature differences between when the astronaut is in the sunlight and when in shade. Space suits also have internal heaters and cooling systems, and liquid heat exchange pumps that remove excess heat.

  The space suit therefore provides optimal operating atmosphere to the Astronaut as well as the devices he/she carries. Since components of our RFID system would also be a part of the space suit, we need not provide expensive temperature or pressure compensation or use devices with special thermal charateristics.

  
  

  References:

  [1] Space Suit Properties, http://library.thinkquest.org/03oct/02144/travel/

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