The United States human space flight effort has progressed through a series of programs of ever increasing scope and complexity. The first Mercury launch required only a few hundred people. The launch of Apollo 11 for man's first lunar landing engaged thousands. The complex and sophisticated Space Shuttle of today began with this tiny Mercury capsule in 1961.
Project Mercury
• Project Mercury was America's first human space flight program and it proved that human space flight was possible. The greatest challenge to Mercury engineers was to devise a vehicle that would protect a human from the temperature extremes, vacuum, and newly discovered radiation of space.
• This spacecraft that was designed with a volume of only 60 cubic feet, there was barely enough room for its pilot, who sat in a couch facing a panel with 120 controls, 55 electrical switches, 30 fuses, and 35 mechanical levers. The cabin's atmospheric pressure was one-third of that on Earth and contained pure oxygen.
• Project Mercury had taken the critical first step to demonstrate that humans could survive in space, a spacecraft could be designed to launch them into orbit, and that the crew could return safely to Earth.
Project Gemini
• At the near the conclusion of Project Mercury, the Project Gemini was initiated in early 1960s to perfect the techniques required for a lunar mission. Its primary purpose was to demonstrate space rendezvous and docking techniques that would be used during the later Apollo flights to the Moon.
• The Gemini spacecraft was an improvement on the Mercury capsule. But it had only 50 percent more cabin space for twice as many people, and was extremely cramped. Unlike Mercury, which had been able to change only its orientation while in flight, Gemini needed to have the capability to move forward, backward and sideways in its orbital path, and even change orbits to rendezvous with other spacecraft. The complexity of rendezvous demanded two people on board, and more piloting than had been possible with Mercury. It also required the first onboard computers to calculate complicated rendezvous maneuvers.
• During Gemini, ten piloted missions lifted off from Cape Canaveral, Florida, in less than 20 months. By Gemini's end, orbital rendezvous and docking had become routine, and it seemed clear that humans could live, work, and stay healthy in space for days or even weeks at a time. Above all, the program had added nearly 1,000 hours of valuable space flight experience in the years between Mercury and Apollo, which by 1966 NASA was nearing flight readiness.
Project Apollo
• On July 16, 1969, Neil Armstrong, Buzz Aldrin and Michael Collins climbed into Columbia for their 8-day journey. A thrust of 7.6 million pounds took 2.5 minutes to take the rocket to a 40 mile altitude, at a speed of 6,000 mph. After the first stage detached, the second stage took the craft to 115 miles above sea level, with a thrust of one million pounds, at speeds over 15,000 mph.
• After the second stage detached, the third stage brought the craft into a stable Earth orbit. The astronauts performed systems checks. The third stage brought them to the moon. The Apollo Command/Service Module separated from the Saturn third stage, turned around, then reconnected, docking with the Lunar Module. The spacecraft was ejected from the Saturn third stage and the spacecraft traveled to the Moon.
• Three days later, the craft entered a stable orbit. Two of the three astronauts went into the Lunar Module, while one stayed in the Command/Service Module. The Lunar Module detached from the Command/Service Module and descended to the Moon.
• Following their historic landing and exploration of the lunar surface, Neil Armstrong and Buzz Aldrin rejoined Michael Collins aboard the Command Module and headed back to Earth. Three days later, on July 24, they entered Earth's atmosphere at a speed of 25,000 miles per hour and its exterior reached a temperature of 5,000º F. To protect the crew and the priceless cargo, Columbia's exterior was covered with a heat shield.
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