Extra-vehicular activity

Extra-vehicular activity (EVA) is work done by an astronaut away from the Earth and outside of his or her spacecraft. The term most commonly applies to an EVA made outside a craft orbiting Earth (a spacewalk) but also applies to an EVA made on the surface of the Moon (a moonwalk). In the later lunar landing missions the command module pilot did an EVA to retrieve film canisters on the return trip.

EVA hazards

An EVA is dangerous for a number of different reasons. The primary one is collision with space debris. Orbital velocity at 300 km above the Earth (typical for a Space Shuttle mission) is 7.7 km/s. This is 10 times the speed of a bullet, so the kinetic energy of a small particle (e.g. a fleck of paint or a grain of sand) is equal to that of a bullet with a mass that is 100 times as large. Every space mission creates more orbiting debris, so this problem will continue to become worse.

Related Topics:
Collision - Space debris - Space Shuttle - Bullet - Kinetic energy

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Another reason for danger is that external environments in space are harder to simulate before the mission and that space walks are avoided for routine tasks because of their danger. As a result the EVAs are often planned late in the project development when problems are discovered, or sometimes even during an operational mission. The exceptional danger involved in EVAs inevitably leads to emotional pressures on astronauts who, though selected for exceptional stability under pressure, are still human.

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Other possible problems include a spacewalker becoming separated from their craft or suffering a spacesuit puncture which would depressurize the suit, causing anoxia and rapid death if the spacewalker is not brought into a pressurized spacecraft quickly.

Related Topics:
Anoxia - Death

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One astronaut has suffered a spacesuit puncture. During STS-37, a small rod punctured the glove of one of the astronauts (the name is undisclosed, but it was either Jerry L. Ross or Jay Apt). However, the puncturing object, which stabbed their hand as well, held in place, resulting in no detectable depressurization. In fact, the puncture was not noticed until after the spacewalkers were safely back inside Atlantis. http://www.sff.net/people/Geoffrey.Landis/vacuum.html

Related Topics:
STS-37 - Jerry L. Ross - Jay Apt - Atlantis

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As of 2005, no catastrophic incident has ever occurred during an extra-vehicular activity, and no astronaut or cosmonaut has ever died during one. Still, some scientists are developing tele-operated robots for outside construction work, to potentially eliminate the need for human EVAs.

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