Apollo Expeditions to the Moon



The Gemini program was designed to investigate in actual flight many of the critical situations which we would face later in the voyage of Apollo. The spacecraft carried an onboard propulsion system for maneuvering in Earth orbit. A guidance and navigation system and a rendezvous radar were provided to permit astronauts to try out various techniques of rendezvous and docking with an Agena target vehicle. After docking, the astronauts could light off the Agena rocket for large changes in orbit, simulating the entry-into-lunar-orbit and the return-to-Earth burns of Apollo. Gemini was the first to use the controlled reentry system that was required for Apollo in returning from the Moon. It had latches that could be opened and closed in space to permit extravehicular activity by astronauts, and fuel cells similar in purpose to those of Apollo to permit flights of long duration. The spacecraft was small by Apollo standards, carrying only two men in close quarters. However, the Titan II launch vehicle, which was the best available at that time, could not manage a larger payload.

A picture diagrams of early manned space vehicle design
Early proposals for manned space vehicles varied greatly in configuration and weight. In some, the men within faced one way during launch and another during reentry; in others, the vehicle was turned around, not the seats. Different approaches to the problem of escape from launching disaster were shown in these six industrial proposals. Environmental control, thermal and radiation shielding, and protection against meteorite impact were all unknowns facing early spacecraft designers.

A picture diagram of a one-man lunar lander
A one-man lunar lander weighing 5000 pounds was envisioned as early as 1961 by a pair of Space Task Group engineers, James A. Chamberlin and James T. Ross, and here drawn by Harry A. Shoaf. It was seen as part of a 35,000-pound payload that might be carried by a post-Mercury spacecraft. The other extreme in early ideas to send men to the Moon called for a direct-ascent manned lunar vehicle weighing some 150,000 pounds. It would have been launched by Nova, a giant booster capable (on paper) of approximately 12 million pounds of thrust.

A total of 10 manned flights were made in the Gemini program between March 1965 and November 1966. They gave us nearly 2000 man-hours in space and developed the rendezvous and docking techniques essential to Apollo. By burning the Agena rockets after docking, we were able to go to altitudes of more than 800 nautical miles and prove the feasibility of the precise space maneuvers essential to Apollo. Our first experience in EVA was obtained with Gemini and difficulties here early in the program paved the way for the smoothly working EVA systems used later on the Moon. The Borman and Lovell flight, Gemini VII, showed us that durations up to two weeks were possible without serious medical problems, and the later flights showed the importance of neutral buoyancy training in preparation of zero-gravity operations outside the spacecraft.

Gemini gave us the confidence we needed in complex space operations, and it was during this period that Chris Kraft and his team really made spaceflight operational. They devised superb techniques for flight management, and Mission Control developed to where it was really ready for the complex Apollo missions. Chris Kraft, Deke Slayton, head of the astronauts, and Dr. Berry, our head of Medical Operations, learned to work together as a team. Finally, the success of these operations and the high spaceflight activity kept public interest at a peak, giving our national leaders the broad supporting interest and general approval that made it possible to press ahead with a program of the scale of Apollo.

A photo of Gemini spacecraft This Gemini spacecraft, in preparation in the Pyrotechnical Installation Building at the Cape, was to climb to a record altitude of 853 miles in September 1966. It docked in space with an Agena, and then used the big Agena rocket for the energy needed to reach the larger orbit. Gemini flights provided priceless experience in the tricky business of rendezvousing two craft in space with the minimum expenditure of energy. They also supplied practice at docking and in extravehicular activity, both needed for future Moon voyages. Finally, they helped build up experience with the mission-control system developing on the ground to support manned spaceflight.

A picture of a interior-section of the two-man Gemini spacecraft
The two-man Gemini seemed capacious after tiny Mercury but it was actually very cramped. The astronauts rubbed elbows, and the man in the right seat, returning after EVA with his bulky spacesuit and tether, had to jam himself in to close the hatch over his head.

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