Space Exposure

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Space exposure is the subjection of a human to the conditions of outer space, without protective clothing and beyond the Earth’s atmosphere in a vacuum. The key concerns for a human without protective clothing beyond Earth’s atmosphere are the following, listed roughly in the descending order of mortal significance: ebullism, hypoxia, hypocapnia, decompression sickness, extreme temperature variations and cellular mutation and destruction from high energy photons and (sub-atomic) particles. A rough estimate is that a human will have about 90 seconds to be recompressed, after which death may be unavoidable. The absence of oxygen outside the body causing rapid de-oxygenation of the blood (hypoxia) is the primary reason for unconsciousness within 14 seconds. If a person is exposed to low pressures more slowly, hypoxia causes gradual loss of cognitive functions starting at about 3 kilometres (10,000 ft) altitude equivalent. Less severe effects include the formation of nitrogen gas bubbles and consequent interference with organ function (decompression sickness), which is less severe in space than in diving. Meanwhile, reduction of blood carbon dioxide levels (hypocapnia) can alter the blood pH and indirectly contribute to nervous system malfunctions. If the person tries to hold his breath during decompression, the lungs may rupture internally. Few humans have experienced these four conditions. Joseph Kittinger experienced localised ebullism during a 31 kilometres (19 mi) ascent in a helium-driven gondola. His right-hand glove failed to pressurise and his hand expanded to roughly twice its normal volume accompanied by disabling pain. His hand took about 3 hours to recover after his return to the ground. Two other people were decompressed accidentally during space mission training programs on the ground, but both incidents were less than 5 minutes in duration, and both victims survived. International Space Station and Space Shuttle astronauts regularly work in Extravehicular Mobility Units (EMUs or space suits) that are at pressures less than 30% of the spacecraft to facilitate mobility, without experiencing noticeable decompression sickness. To date, the only humans to have died of space exposure are the three crew members of the Soyuz 11 spacecraft: Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev. During the re-entry on June 30, 1971, the ship's depressurization resulted in the death of the entire crew. [READ THE REST OF THIS ARTICLE]





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