Advanced Crew Escape Suit

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An astronaut wearing the ACES suit
Rear view of the suit

The Advanced Crew Escape Suit (ACES) or "pumpkin suit",[1] was a full pressure suit that began to be worn by Space Shuttle crews after STS-65, for the ascent and entry portions of flight. The suit is a direct descendant of the U.S. Air Force high-altitude pressure suits worn by the two-man crews of the SR-71 Blackbird, pilots of the U-2 and X-15, and Gemini pilot-astronauts, and the Launch Entry Suits worn by NASA astronauts starting on the STS-26 flight, the first flight after the Challenger disaster. The suit is manufactured by the David Clark Company of Worcester, Massachusetts. Cosmetically the suit is very similar to the LES (Launch Entry Suit). ACES was first used in 1994.


The ACES was first worn by U.S. Air Force pilots in the mid-1970s[citation needed], replacing a similar suit worn by SR-71 and U-2 pilots, and was identical[citation needed] to the suits worn by X-15 pilots and Gemini astronauts. Unlike the ACES suit, which is a full-pressure suit, the high-altitude suits were partial pressure suits, thus requiring a rubber diaphragm around the wearer's face.

Because of the limitations of protection the LES could offer, NASA and the David Clark Company introduced the current ACES design in 1994, which was the only suit used for Shuttle missions after 1998. Based on the LES, but being a full-pressure suit, the ACES suit now incorporates gloves on disconnecting lock rings on the wrists, liquid cooling and improved ventilation, and an extra layer of insulation. The ACES suit is analogous to the Sokol suits used for Soyuz missions and its functions are virtually the same — the only differences being the ACES suit having a detachable helmet and survival backpack, while the Russian suit has an integrated helmet and no backpack (due to the limitations in space aboard the Soyuz, and that the spacecraft is an entry capsule, not a winged spacecraft or lifting body).


The ACES used by Shuttle astronauts is similar in design to the Gemini spacesuit worn by astronauts from 1965–1966 and by the three Apollo 1 astronauts in 1967.[citation needed] The components of the ACES consists of the following:[citation needed]

  • A one-piece pressure garment assembly with integrated pressure bladders and ventilation system. Oxygen is fed through a connector at the wearer's left thigh and is transmitted to the helmet, via a special connector at the base of the neckring. The helmet and gloves are connected to the suit, via locking rings, a metallic gray in color (Gemini suits featured a gray neck ring and red and blue anodized glove rings). The suit has a Nomex cover layer in international orange color, instead of silver or white as in previous David Clark suits. The orange color allows rescue units to easily spot the astronauts in the case of an Orbiter bailout over the ocean. Underneath the suits, astronauts wear "Maximum Absorbency Garment" (MAGs) urine-containment trunks (resembling "Depends" incontinence shorts) and blue-colored thermal underwear, which has plastic tubing woven into the garments allowing for liquid cooling and ventilation, the latter being handled by a connector located on the astronaut's left waist.
  • A full pressure helmet (the same model used with the LES[2]) with a locking clear visor and a black sunshade worn to reduce any glare from reflected sunlight, especially during the approach and landing phases of the mission. A communications cap (originally white, but since changed to dark brown and identical to those worn by the Russian cosmonauts with the Sokol space suits worn aboard Soyuz missions), is worn underneath the helmet, and connected to a special plug inside the helmet, which is then connected to the intercom system in the Orbiter, via a white-colored plug similar in appearance to the communications "pigtail" on the old Mercury helmets. An anti-suffocation valve at the back of the helmet allows for the passing of carbon dioxide from the helmet. The helmet's clear pressure faceplace is locked into place with a mechanical seal with a prominent "lockdown" bar which can be easily reached with gloved hands.
  • The gloves are also attached via a locking ring and are likewise in international orange color. These can be put on more easily and more quickly than was possible with the launch entry suit, and they allow the wrist to "swivel". When the suit is pressurized, the gloves are also pressurized. The palm of the gloves is textured to allow crews to throw switches, push buttons, turn knobs (especially the "ABORT MODE" knob on the commander's panel), and, for the Commander and Pilot, to operate the flight control stick during the final approach during landing.
  • Heavy black leather "paratrooper" boots with zippers instead of laces. These help prevent foot and ankle injuries and reduce swelling of the feet when the suit is pressurized. No cloth is used on the boot, as a way to prevent injuries in the event of a flash fire (something encountered during the Vietnam War in which aircraft crews wearing jungle boots, with their nylon uppers, were injured when the material literally melted onto the person's skin when an aircraft caught fire).[citation needed]
  • Survival backpack, which includes a personal life raft, that is donned before entering the orbiter.[citation needed]
  • Light sticks, which are tucked into the shoulder pockets on both upper arms. The light sticks are intended as an aid in case of an emergency, and are colored orange to identify the astronaut crew, while technicians in the close-out crew carry green ones.[3]

Each suit is sized individually, although most suits can be worn by astronauts of different heights. No ACES has failed during normal flight operations. The Columbia investigation found that the crews' ACESs all failed at some point, but also that none of the Columbia crew had sealed their helmets, and also that several were not wearing suit gloves. By comparison, in 1966 an SR-71 pilot in a similar suit, whose helmet and gloves were sealed, survived similar pressure conditions when his aircraft broke up while flying at approximately Mach 3. However, the "thermal and chemical environment of the Columbia accident (the temperature and oxygen concentration) was "much more severe" than in the SR-71 accident, and the report recommended that future crew survival suits be evaluated for thermal and chemical resistance as well as (as USAF suits had been evaluated previously) pressure and windblast.[4]


Name: Advanced Crew Escape Suit (S1035)[5]

Derived from: USAF Model S1034[5]

Manufacturer: David Clark Company[5]

Missions: STS-64[6] to STS-135

Function: Intra-vehicular activity (IVA)[5]

Pressure Type: Full[5]

Operating Pressure: 3.5 psi (24.1 kPa)[5]

Suit Weight: 28 lb (12.7 kg)[5]

Parachute and Survival Systems Weight: 64 lb (29 kg)[5]

Total Weight: 92 lb (41.7 kg)[5]

Useful Altitude: 30 km (100,000 ft)[7]

Primary Life Support: Vehicle Provided[5]

Backup Life Support: 10 minutes[5]

Future use[edit]

Initially, ACES was intended to be retired after the Space Shuttle Program and be replaced by the Constellation Space Suit.[8] The Orion missions are now instead planned to use a modified ACES, this suit would have increased mobility in comparison to its Space Shuttle counterpart and would use a closed-loop system to preserve resources.[9] NASA is also considering using it for contingency and possibly limited capacity EVAs, such as those carried out during the Gemini program.[10] Simulated microgravity testing has occurred on parabolic flights and in the Neutral Buoyancy Laboratory, in order to better characterise the suit's mobility.[10][11]



  1. ^ "Astronaut Candidates 2004 - Training Journals". NASA. 
  2. ^ US Spacesuits. Chichester, UK: Praxis Publishing Ltd. 2006. p. 44. ISBN 0-387-27919-9. 
  3. ^ NASA-TV, Coverage of STS-123 launch preparations, March 11, 2008, and NASA Virtual Launch Countdown retrieved March 11, 2008.
  4. ^ Columbia Crew Survival Investigation Report, pp.3-44–3-46 retrieved September 30, 2013.
  5. ^ a b c d e f g h i j k US Spacesuits. Chichester, UK: Praxis Publishing Ltd. 2006. p. 374. ISBN 0-387-27919-9. 
  6. ^ National Space Society - Space Shuttle Flight 64
  7. ^ ACES Guide - Pg. 15
  8. ^ "Space Shuttle Program Transition and Retirement: Personal Property Disposition Plan". NASA. 2008. Retrieved 10 August 2013. "The ACES pressure suit will no longer be used once Station assembly is completed and the Space Shuttle is retired. For Constellation, NASA has decided to replace the EMU and the ACES pressure suit with the new Constellation Space Suit system." 
  9. ^ "ISS Update: Zero Gravity Suit Tests (Part 1)". NASA. 2 August 2012. Retrieved 5 August 2012. 
  10. ^ a b "Space Station Live: Orion Spacesuits with Dustin Gohmert". NASA. 20 June 2013. Retrieved 10 August 2013. 
  11. ^ "ISS Update: Zero Gravity Suit Tests (Part 2)". NASA. 8 August 2012. Retrieved 10 August 2013. 

US Spacesuits. Chichester, UK: Praxis Publishing Ltd. 2006. ISBN 0-387-27919-9. 

External links[edit]