Suit Components
The EMU, like the Apollo/Skylab A7L spacesuit, was the 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, arm sections, gloves, an Apollo-style "bubble" helmet, the 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 incontinence diaper – Urine Collection Devices (UCDs) are no longer used), and possibly a Thermal Control Undergarment (long johns). The final item donned before putting on the pressure suit is the "Liquid Cooling and Ventilation Garment" (LCVG), which incorporates clear plastic tubing through which chilled liquid water flows for body temperature control, as well as ventilation tubes for waste gas removal.
After donning the LCVG, the astronaut then puts on the LTA, before entering the airlock. The astronaut then dons the HUT, connects the LCVG umbilical to the umbilical in the HUT, and then locks the two parts of the suit together using the Body Seal Closure. Once the suit is turned on and checked out, the astronaut dons a "Snoopy cap," a brown and white fabric communications cap dating back to the Apollo days, which 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 psi (30 kPa). A typical EMU can support an astronaut for 8.5 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, after which an astronaut must pre-breathe for 45 minutes. For EVAs on board the ISS, the astronaut must pre-breathe for about four hours.
Read more about this topic: Extravehicular Mobility Unit
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