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The Space Shuttle/International Space Station Extravehicular Mobility Unit (EMU) is an independent anthropomorphic system that provides environmental protection, mobility, life support, and communications for a Shuttle or ISS crew member to perform extra-vehicular activity (EVA) in earth orbit. It is a two-piece semi-rigid suit and it is currently one of two space suits used by crew members on the ISS, the other being the Russian Orlan space suit. The suits are white to reflect heat and to stand out against to the blackness of space, the red stripes serve to differentiate astronauts. The EMU, like the Apollo/Skylab A7L spacesuit, was a result of years of research and development. It consists of a Hard Upper Torso (HUT) assembly, a Primary Life Support System (PLSS) which incorporates the life support and electrical systems, arms, gloves, Apollo-style "bubble" helmet/Extravehicular Visor Assembly (EVVA), and a soft Lower Torso Assembly (LTA), incorporating the Body Seal Closure (BSC), waist bearing, brief, legs, and boots. Prior to donning the pressure garment, the crew member puts on a Maximum Absorbency Garment (MAG) [basically a modified "Depends" incontinence diaper] (Urine Collection Devices or UCDs are no longer used), possibly a Thermal Control Undergarment (long johns), and then the "Liquid Cooling and Ventilation Garment" (LCVG), that incorporates clear plastic tubing through which chilled liquid water flows for body temperature control, as well as ventilation tubes for waste gas removal. Once the astronaut dons the LCVG, the astronaut then puts on the LTA, similar in nature to a firefighter putting on the pants and boots of a fire protection suit. The astronaut then floats into the airlock, dons the HUT, connects the LCVG umbilical to the umbilical in the HUT, and then the two parts of the suit are locked together using the Body Seal Closure. Once the suit is turned on and checked out, the astronaut then dons a "Snoopy cap," a brown and white fabric communications cap dating back to the Apollo days that incorporates a pair of earphones and microphones, allowing the EVA astronaut to communicate with both the crew members in the Orbiter and ground controllers in Houston. After donning the "Snoopy cap," the gloves and helmet are then locked on, pressurizing the suit. The suit's regulator and fans activate when the servicing umbilicals are removed and the suit reaches an internal pressure of 4.3&_160;psi (30&_160;kPa). A typical EMU can support an astronaut for 8½ hours, with 30 minutes of reserves in the case of primary life support failure. To perform an EVA from the shuttle the cabin pressure is reduced from 14.7 psi to 10.2 psi for 24 hours, then an astronaut must pre-breathe for 45 minutes.[1] EVAs onboard the ISS, the astronaut must pre-breathe for about four hours.[1]
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