Extravehicular Mobility Unit
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The Extravehicular Mobility Unit (EMU) is an independent anthropomorphic spacesuit that provides environmental protection, mobility, life support, and communications for astronauts performing extra-vehicular activity (EVA) in Earth orbit. Introduced in 1982, it is a two-piece semi-rigid suit, and is currently one of two spacesuits used by crew members on the International Space Station (ISS), the other being the Russian Orlan space suit. It was used by NASA's Space Shuttle astronauts prior to the end of the Shuttle program in 2011.
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.[1] For EVAs on board the ISS, the astronaut must pre-breathe for about four hours.[1]
Specifications
Baseline Extravehicular Mobility Unit Spacesuit
Manufacturer: International Latex Corporation (ILC) Dover and Hamilton Standard (primary life support systems)[1]
Missions: STS-6 (1983) to STS-110 (2002)[1]
Function: orbital extra-vehicular activity[1]
Operating Pressure: 4.3 psi (29.6 kPa)[1]
EVA Suit Weight: 109 lb (49.4 kg)[1]
Total Shuttle EVA Suit Weight 254 lb (115 kg)[1]
Primary Life Support: 8 hours (480 minutes)[1]
Backup Life Support: 30 minutes[1]
Enhanced Extravehicular Mobility Unit Spacesuit
Manufacturer: International Latex Corporation (ILC) Dover, Hamilton Standard (primary life support systems) and NASA (SAFER)[1]
Missions: 1998 to present[1]
Function: orbital extra-vehicular activity[1]
Operating Pressure: 4.3 psi (29.6 kPa)[1]
EVA Suit Weight: 122 lb (55.3 kg)[1]
Total Shuttle EVA Suit Weight 275 lb (124.7 kg)[1]
Total ISS EVA Suit Weight 319 lb (145 kg)[1]
Primary Life Support: 8 hours (480 minutes)[1]
Backup Life Support: 30 minutes[1]
Manufacturer
The EMU hardware and accessories (PLSS, helmet, communications cap, and locking rings for the helmet and gloves), is manufactured by the Hamilton Sundstrand division of United Technologies out of Windsor Locks, Connecticut, while the suit's soft components (the arms of the HUT and the entire LTU) are produced by ILC Dover out of Frederica, Delaware. The two companies, who were rivals during the early days of Apollo for the contract to build the "Block II" (moonwalking) space suit, teamed up in 1974 against the David Clark Company and Garrett AiResearch for the EMU development and construction. During Apollo, the ILC Dover-produced A7L used the life support backpack, helmet, and locking rings supplied by Hamilton United, but originally, ILC Dover was to just supply the arms and legs of the suit, a similar process that is still going on today.
History
Upon receiving the contract to build the EMU in 1974, Hamilton United and ILC Dover delivered the first EMU units to NASA in 1982. During the research and development phase (1975–1980), a suit being tested caught fire, injuring a technician and forcing a redesign on the regulator and circulation fan. On STS-4 in July 1982, the astronauts practiced donning and doffing the suit in the Shuttle's airlock. The first Shuttle EVA was to occur on STS-5, but an electrical failure on the circulation fan forced the EVA to be cancelled. The first EVA of the new EMU finally occurred on STS-6 when Story Musgrave and Donald Peterson went out in the payload bay of the Space Shuttle Challenger and tested techniques to lower the launch cradle of a solid-fuel upper stage used to boost a Tracking and Data Relay Satellite (TDRS-A) into a geo-stationary orbit.
Other EVAs followed on the Shuttle, notably those on STS-41-B (the first Manned Maneuvering Unit flight), STS-41-C (the Solar Max repair mission), and STS-51-A (where two stranded satellites were retrieved and returned to Earth), but the majority of EMU uses occurred on the servicing missions of the Hubble Space Telescope. For those flights, two sets of EVA astronauts would venture out of the orbiter, thus requiring NASA to fly four sets of suits (along with repair parts). 41 EVAs using EMUs had been conducted out of the Space Shuttle airlock prior to the start of ISS assembly in November 1998.[2]
With the building of the ISS, Hamilton Sundstrand and ILC Dover refined the existing Shuttle EMU by making the suit modular. This allowed the EMU to be left on the ISS for up to 2 years and resized on-orbit to fit various crew members. They also made provisions for increased battery capacity, the Simplified Aid for EVA Rescue (SAFER), improved cameras and radios, and a new caution and warning system. Another feature incorporated into the ISS suits included an additional battery to power heaters built into the glove, allowing astronauts to keep their hands warm during nighttime passages on each 95-minute orbit.
Currently, the ISS EMU and the Russian ORLAN are used by crews of all nationalities on the International Space Station. The two EMUs are stored within the Quest Joint Airlock.
Future use and proposed replacement
NASA continues to use the EMU in the wake of the retirement of the Space Shuttle in 2011. When preparing for the Constellation Program, a now-cancelled series of missions to the ISS, Moon, and Mars which was planned to commence in 2015, NASA planned to replace the EMU and the ACES pressure suit with a new Constellation Space Suit system, derived from the ACES suit and the ILC Dover-developed Mark III and I-Suit space suit systems.
The new suit would have been designed, depending upon the configration, to protect the astronaut during launch, in-flight emergencies, reentry and landing, and both microgravity and lunar EVAs. It was planned to feature common hardware and the modular features used in the ACES and EMU suits.
On June 11, 2008, NASA awarded a contract for Oceaneering International for the development and manufacturing of the new suits, with the David Clark Company and United Space Alliance being two of seven contractors in the new endeavor. Oceaneering beat out the Hamilton Sundstrand/ILC Dover partnership in the manufacturing of the new space suit.
However, an August 15, 2008 NASA press release stated that a compliance issue required the termination of Oceaneering's contract for the Constellation suit for the convenience of the government.[3] Later, NASA announced that effective March 2, 2009 "NASA has awarded an interim letter contract to Oceaneering International Inc. of Houston to begin work on the design, development and production of a new spacesuit system for the Constellation Program.[4] The new contract featured a Hamilton Sundstrand/ILC Dover partnership. The cancellation of the Constellation Program in 2010 leaves the suit's current status uncertain.
Images
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EMU without Extravehicular Visor Assembly -
EMU without television camera and SAFER
See also
References
- ^ a b c d e f g h i j k l m n o p q r s US Spacesuits. Chichester, UK: Praxis Publishing Ltd. 2006. ISBN 0-387-27919-9.
{{cite book}}: Unknown parameter|coauthors=ignored (|author=suggested) (help) Cite error: The named reference "us" was defined multiple times with different content (see the help page). - ^ W. West, V. Witt, C. Chullen. "EVA 2010: Preparing for International Space Station EVA Operations Post-Space Shuttle Retirement" (PDF). American Institute of Aeronautics and Astronautics.
{{cite web}}: CS1 maint: multiple names: authors list (link) - ^ "NASA To Take Corrective Action In Spacesuit Contract Protest". Retrieved September 12, 2011.
- ^ "NASA awards spacesuit contract---again". Retrieved September 12, 2011.
US Spacesuits. Chichester, UK: Praxis Publishing Ltd. 2006. ISBN 0-387-27919-9. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)