Editing Extravehicular activity (section)

===Project Gemini===
[[File:EdWhiteFirstAmericanSpacewalker.1965.ws.jpg|thumb|[[Ed White (astronaut)|Ed White]] performs the first American spacewalk during [[Gemini IV]].]]

The first American spacewalk was performed on June 3, 1965, by [[Ed White (astronaut)|Ed White]] from the second crewed [[Project Gemini|Gemini]] flight, [[Gemini IV]], for 21 minutes. White was tethered to the spacecraft, and his oxygen was supplied through a {{convert|25|ft|adj=on}} [[umbilical cable|umbilical]], which also carried communications and biomedical instrumentation. He was the first to control his motion in space with a [[Hand-Held Maneuvering Unit]], which worked well but only carried enough propellant for 20 seconds. White found his tether useful for limiting his distance from the spacecraft but difficult to use for moving around, contrary to Leonov's claim.<ref name="portree"/> However, a defect in the capsule's hatch latching mechanism caused difficulties opening and closing the hatch, which delayed the start of the EVA and put White and his crewmate at risk of not getting back to Earth alive.<ref name="mcdivittoh">Oral History Transcript / [http://www.jsc.nasa.gov/history/oral_histories/McDivittJA/mcdivittja.pdf James A. McDivitt] / Interviewed by Doug Ward / Elk Lake, Michigan – June 29, 1999.</ref>

No EVAs were planned on the next three Gemini flights. The next EVA was planned to be made by [[David Scott]] on [[Gemini VIII]], but that mission had to be aborted due to a critical spacecraft malfunction before the EVA could be conducted. Astronauts on the next three Gemini flights ([[Eugene Cernan]], [[Michael Collins (astronaut)|Michael Collins]], and [[Richard F. Gordon Jr.|Richard Gordon]]), performed several EVAs, but none was able to successfully work for long periods outside the spacecraft without tiring and overheating. Cernan attempted but failed to test an Air Force [[Astronaut Maneuvering Unit]] which included a self-contained oxygen system.

On November 13, 1966, [[Edwin "Buzz" Aldrin]] became the first to successfully work in space without tiring during [[Gemini XII]], the last Gemini mission. Aldrin worked outside the spacecraft for 2 hours and 6 minutes, in addition to two stand-up EVAs in the spacecraft hatch for an additional 3 hours and 24 minutes. Aldrin's interest in [[scuba diving]] inspired the use of [[Neutral buoyancy simulation as a training aid|underwater EVA training]] to simulate weightlessness, which has been used ever since to allow astronauts to practice techniques of avoiding wasted muscle energy.