Pressure suit

A pressure suit is a protective suit worn by high-altitude pilots who may fly at altitudes where the air pressure is too low for an unprotected person to survive, even breathing pure oxygen at positive pressure. Such suits may be either full-pressure (i.e. spacesuit) or partial-pressure (as used by air crew). Partial-pressure suits work by providing mechanical counter-pressure to assist breathing at altitude.

Background

The region from sea level to around convert|10000|ft|abbr=on is known as the physiological-efficient zone. Oxygen levels are usually high enough to require no supplementary oxygen and decompression sickness is rare.

The physiological-deficient zone extends from convert|12000|ft|abbr=on to about convert|50000|ft|abbr=on. There is an increased risk of problems such as hypoxia, trapped-gas dysbarism (where gas trapped in the body expands), and evolved-gas dysbarism (where dissolved gases such as nitrogen may form in the tissues, i.e. decompression sickness). Above convert|34000|ft|abbr=on 100% oxygen is required to equal the partial pressure of oxygen in the sea level atmosphere, while above convert|40000|ft|abbr=on oxygen must be under positive pressure to maintain an equivalent altitude of convert|10000|ft|abbr=on.

Body fluids, including blood, boil at around convert|63000|ft|abbr=on (also called Armstong's Line), where due to the reduced pressure the boiling point of water is convert|37|C|lk=on, and the body responds as though it was in the vacuum of space. [cite book | last = Reinhart | first = Richard O. | authorlink = | coauthors = | title = Basic Flight Physiology | publisher = McGraw-Hill Professional | date = 2007 | location = | pages = p. 44 | url = | doi = | id = | isbn = 007149488X]

History

Russia

In Russia, the first full pressure suit was designed by engineer Evgeniy Chertanovskiy in Leningrad in 1931. The CH-1 was a simple pressure-tight suit with a helmet which did not have joints, thus requiring substantial force to move the arms and legs when pressurised. This was remedied in later suits. Work on full pressure suits was carried out during 1936-41 by the Central Aerohydrodynamic Institute (TsAGI), with similar work being carried out by the Gromov Flight Research Institute (LII) after World War II. The LII produced four experimental full pressure suits for aircrews, and in 1959 began work on full pressure suits for spaceflight. [cite book | last = Abramov | first = Isaak Pavlovich | authorlink = | coauthors = | title = Russian Spacesuits | publisher = Springer | date = 2003 | location = | pages = pp. 5-13 | url = | doi = | id = | isbn = 185233732X] Chertanovskiy coined the name skafanders for full pressure suits from the Greek words "skaf" - boat,ship and "andros" - man; "skafander" has since become the term used by Russians to refer to standard diving dresses or space suits.

Haldane-Davis

In 1931, American Mark Ridge became obsessed with breaking the world altitude record in an open gondola balloon. Recognizing that the flight would require specialised protective clothing, he visited the UK in 1933 where he met with Scottish physiologist John Scott Haldane, who had published a concept for a fabric full pressure suit in the 1920s. The two sought the assistance of Robert Henry Davis of Siebe Gorman, the inventor of the Davis Escape Set, and with Haldane's and Davis' resources a prototype suit was constructed. Ridge tested it in a low-pressure chamber to a simulated altitude of 50,000 feet. However, he received no support for further work and never made his attempt on the world record. On 28 September 1936 Squadron Leader F.R.D. Swain of the Royal Air Force set the official world altitude record at 49,967 feet in a Bristol Type 138 wearing a similar suit.cite book | last = Thomas | first = Kenneth S. | authorlink = | coauthors = Harold J. McMann | title = US Spacesuits | publisher = Birkhäuser | date = 2005 | location = | pages = p. 6 | url = | doi = | id = | isbn = 0387279199]

Wiley Post

In 1934, aviator Wiley Post, working with Russell S. Colley of the B.F. Goodrich Company, produced the world's first practical pressure suit. The suit's body had three layers: long underwear, a rubber air pressure bladder, and an outer suit of rubberised parachute fabric which was attached to a frame with arm and leg joints that allowed Post to operate aircraft controls and to walk to and from the aircraft. Attached to the frame were pigskin gloves, rubber boots, and an aluminium and plastic helmet with a removable faceplate that could accommodate earphones and a throat microphone. In the first flight using the suit on September 5, 1934, Post reached an altitude of 40,000 feet above Chicago, and in later flights reached 50,000 feet.

World War II

In the US, a large amount of effort was put into the development of pressure suits during World War II. While B.F. Goodrich led the field, other companies involved in such research included the Arrowhead Rubber Co., Goodyear, and US Rubber. The University of Minnesota worked with Bell Aircraft and the US National Bureau of Standards. The Bureau of Standards and the University of California acted as clearing houses to distribute information to all the companies involved. No effective fully mobile pressure suits were produced in World War II but the effort provided a valuable basis for later development.

David Clark Company

Following the war, the Cold War caused continued funding of aviation development, which included high altitude, high speed research such as NACA's X-1. James Henry of the University of Southern California devised a partial pressure suit using a gas mask to provide pressurised oxygen, with gas pressure also inflating rubber tubes called capstans to tighten the suit and provide sufficient mechanical counterpressure to just balance the breathing pressure necessary to prevent hypoxia at a particular altitude. The David Clark Company supplied technical support and resources, and a prototype suit was tested to a simulated 90,000 feet at Wright Field in 1946. Henry's design was subsequently developed by the David Clark Company into the S-1 and T-1 flight suit used by X-1 pilots. The X-1 was succeeded by the Douglas Skyrocket, whose objective was to exceed Mach 2, and an improved pressure suit was required. David Clark won the contract in 1951 with their first full pressure suit, the Model 4 Full Pressure Suit; it was first flown in 1953 by USMC aviator Marion E. Carl who became the first US military aviator to wear a full pressure suit, at the same time setting an unofficial worlds altitude record in the Skyrocket.

Goodrich Mk III & IV

US requirements for high-altitude reconnaissance aircraft such as the U-2, and fighters to intercept high-altitude Soviet aircraft caused the US Navy to be tasked with the development of a full pressure suit in the 1950s. Working with B.F. Goodrich and Arrowhead Rubber, the USN produced a series of designs which culminated in the Goodrich Mk III and IV. While intended for aircraft use, the Mk IV was later used by NASA with minor modifications for Project Mercury as the Navy Mark V. At the same time, David Clark won the contract to produce suits for the X-15 project; its XMC-2 suits qualified as the first US spacesuits. [Thomas, p. 10]

RAF

The RAF Institute of Aviation Medicine and the Royal Aircraft Establishment developed a partial-pressure helmet which was used with a capstan type suit purchased from the US. It was worn by Walter Gibb and his navigator to set a world altitude record on 29 August 1955 in an English Electric Canberra. However, evaluation of the suit showed that it encumbered the wearer and did not integrate well with RAF escape systems. Instead, the RAF IAM proposed a minimal-coverage suit which would provide "get-me-down" protection. The RAF never issued a partial-pressure suit, preferring instead to use anti-g trousers in conjunction with pressure jerkins (which applied mechanical counter-pressure to the wearer's chest).

ACES

The Advanced Crew Escape Suit (ACES), which was first used by USAF pilots in the mid-1970s, replaced the similar David Clark Model 1030 full pressure suits worn by SR-71 pilots, and was identical to the XMC-2 suits worn by X-15 pilots and Gemini astronauts. Modified versions of the suit were adopted by NASA for early Space Shuttle use, the modifications consisting of attachments for a parachute harness, and inflatable bladders in the legs to prevent the crew from passing out during reentry.

Image gallery

ee also

*Spacesuit
*Navy Mark V

Notes

External links

* [http://www.zvezda-npp.ru/english/03.htm Pilot's Protective Gear]
* [http://www.globalsecurity.org/intell/systems/u-2-life-support.htm Pilot Life Support in the U-2 / TR-1 aircraft.]