Editing Project Mercury (section)

=== Background ===
Following the end of [[World War II]], a [[nuclear arms race]] evolved between the US and the [[Soviet Union]] (USSR). Since the USSR did not have bases in the western hemisphere from which to deploy [[bomber|bomber planes]], [[Joseph Stalin]] decided to develop [[intercontinental ballistic missile]]s, which drove a missile race.{{sfn|Catchpole|2001|pp=12–14}} The rocket technology in turn enabled both sides to develop Earth-orbiting satellites for communications, and gathering weather data and [[geospatial intelligence|intelligence]].{{sfn|Catchpole|2001|p=81}} Americans were shocked when the Soviet Union placed the first satellite into orbit in October 1957, leading to a growing fear that the US was falling into a "[[missile gap]]".{{sfn|Alexander & al.|1966|pp=28, 52}}{{sfn|Catchpole|2001|p=81}} A month later, the Soviets launched [[Sputnik 2]], carrying [[Laika|a dog]] into orbit. Though the animal was not recovered alive, it was obvious their goal was human spaceflight.{{sfn|Catchpole|2001|p=55}} Unable to disclose details of military space projects, President Eisenhower ordered the creation of a civilian space agency in charge of civilian and scientific space exploration. Based on the federal research agency [[National Advisory Committee for Aeronautics]] (NACA), it was named the National Aeronautics and Space Administration (NASA).{{sfn|Alexander & al.|1966|p=113}} The agency achieved its first goal of launching a satellite into space, the [[Pioneer 1]], in 1958. The next goal was to put a man there.{{sfn|Catchpole|2001|pp=57, 82}}

The limit of space (also known as the [[Kármán line]]) was defined at the time as a minimum altitude of {{convert|62|mi|abbr=on}}, and the only way to reach it was by using rocket-powered boosters.{{sfn|Catchpole|2001|p=70}}{{sfn|Alexander & al.|1966|p=13}} This created risks for the pilot, including explosion, high [[g-force]]s and vibrations during lift off through a dense atmosphere,{{sfn|Alexander & al.|1966|p=44}} and temperatures of more than {{convert|10000|°F|abbr=on|sigfig=2}} from air compression during reentry.{{sfn|Alexander & al.|1966|p=59}}

In space, pilots would require pressurized chambers or [[space suit]]s to supply fresh air.{{sfn|Catchpole|2001|p=466}} While there, they would experience [[weightlessness]], which could potentially cause disorientation.{{sfn|Alexander & al.|1966|p=357}} Further potential risks included [[space radiation|radiation]] and [[micrometeoroid]] strikes, both of which would normally be absorbed in the atmosphere.{{sfn|Alexander & al.|1966|pp=35, 39–40}} All seemed possible to overcome: experience from satellites suggested micrometeoroid risk was negligible,{{sfn|Alexander & al.|1966|p=49}} and experiments in the early 1950s with simulated weightlessness, high g-forces on humans, and sending animals to the limit of space, all suggested potential problems could be overcome by known technologies.{{sfn|Alexander & al.|1966|pp=37–38}} Finally, reentry was studied using the nuclear warheads of ballistic missiles,{{sfn|Alexander & al.|1966|p=61}} which demonstrated a blunt, forward-facing heat shield could solve the problem of heating.{{sfn|Alexander & al.|1966|p=61}}