Armstrong limit

The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and eventually death, unless pressure is restored within 60–90 seconds.[1] Because of this, airplanes usually fly below the Armstrong limit. On Earth, the limit is around 18–19 km (11–12 mi; 59,000–62,000 ft) above sea level,[1][2] above which atmospheric air pressure drops below 0.0618 atm (6.3 kPa, 47 mmHg, or about 1 psi). The U.S. Standard Atmospheric model sets the Armstrong limit at an altitude of 63,000 feet (19,202 m). The Armstrong limit is often used as the lower limit of near-space.

The term is named after United States Air Force General Harry George Armstrong, who was the first to recognize this phenomenon.[3]

  1. ^ a b Cite error: The named reference Landis was invoked but never defined (see the help page).
  2. ^ "NASAexplores Glossary". Archived from the original on 2007-09-27.
  3. ^ "NAHF – Harry Armstrong". November 18, 2007. Archived from the original on 2007-11-18.
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