Because of the heavy workload in Gemini and the upcoming missions in Apollo, Robert Gilruth had convinced George Mueller the previous year that he needed more astronauts. On 4 April 1966, NASA announced that 19 new flight candidates had been selected, bringing the roster up to 50.* Donald Slayton presided over the corps, selecting and training the crews that were flying Gemini missions almost bimonthly.
Preparations for Gemini IX, the second mission scheduled for 1966, began the year in tragedy when its prime crew, Elliot See and Charles Bassett, crashed their aircraft into the building at McDonnell Aircraft Corporation that housed the mission spacecraft. Both were killed. Thomas Stafford and Eugene Cernan took over their duties. On 17 May, an Atlas booster attempted to put an Agena target vehicle into orbit for Gemini and failed. NASA launched a substitute vehicle, called the augmented target docking adapter, on 1 June. Stafford and Cernan were ready to follow, but problems with their guidance system and computer forced them to wait two days before Gemini IX-A was launched to start the chase. Once they caught up, they found that the launch shroud had stuck to the substitute target, making it look, as Stafford said, "like an angry alligator." Although hopes for a second docking in space were dashed, Stafford and Cernan carried out rendezvous maneuvers in a variety of ways and Cernan spent two strenuous hours outside of the spacecraft, trying in vain to ride an astronaut maneuvering unit. Apollo mission planners examined these flight results closely, looking for better operations and training procedures, especially for extravehicular activity.45
Six weeks after the Stafford-Cernan flight, on 18 July, John Young and Michael Collins pushed off aboard Gemini X to rendezvous with a pair of Agenas, one launched for their own mission and the other left in orbit by Gemini VIII. They had trouble making the initial rendezvous and used too much fuel; but, once hooked up to their Agena, they found both high-altitude flight, to 763 kilometers, and a meeting with the second Agena fairly simple. Using a hand gun, Collins had such a successful period outside the spacecraft that some NASA officials believed most of the extravehicular problems had been overcome.46
But on 12 September, with Charles Conrad at the helm of Gemini XI, Richard Gordon found that moving about in space was as difficult as Cernan had said. Gordon became totally exhausted trying to hook a line between the spacecraft and target vehicle so the two craft could separate, spin, and produce a small amount of artificial gravity. He managed to finish the job, but at great physical cost. Nevertheless, Gemini XI expanded manned space exploration to a distance of nearly 1,400 kilometers above the earth to demonstrate that Apollo spacecraft could travel safely through the trapped radiation zones on their way to the moon. More importantly, perhaps, the crew carried out a first-orbit rendezvous, to simulate the lunar module lifting off the moon to meet the command module in lunar orbit, and made the first computer-controlled reentry. Conrad checked his onboard data with mission control, cut in his computer, and flew in on what amounted to an automatic pilot - much as Apollo crews would have to do to hit the narrow reentry corridor on their return to earth.47
In the Gemini finale, NASA was intent on eliminating some of the mystery of why man's work outside his spacecraft was so difficult. In preparation for this, the astronauts began underwater training, which simulated extravehicular activity more closely than the few seconds of weightlessness that could be obtained during Keplerian trajectories in aircraft. The pilot-controlled maneuvering unit was canceled after Gordon's difficulties, so the Gemini XII crew could concentrate on the "fundamentals" of extravehicular movements. When James Lovell and Edwin Aldrin left the ground on 11 November, this was really the chief objective of their mission. By this time, crew systems personnel had attached enough rails and handholds here and there about the spacecraft to give Aldrin a relatively easy five hours of work outside the spacecraft.48
Gemini made major contributions to Apollo and to the astronauts. Flight control and tracking network personnel learned to conduct complex missions with a variety of problems, and mission planners understood more about what it would take to land men on the moon. Rendezvous was demonstrated in so many ways that few engineers remembered they had ever thought it might be difficult. Perhaps the biggest gain for the astronauts was that 16 of the 50 had flown, operated controls, and performed experiments in the weightlessness of space.
Apollo astronauts, however, would rely more on simulators than on Gemini experience. There were, or soon would be, three sets of these trainers - two at Cape Kennedy and one in Houston - modeled after the command module and the lunar module. The simulators, constantly being changed to match the cabin of each individual spacecraft, were engineered to provide their riders with all the sights, sounds, and movements they would encounter in actual flight. Slayton had told George Mueller that the crews would need 180 training hours in the command module simulator and the flight commander and lunar module pilot an additional 140 hours in the lunar module trainer - about 80 percent more training time than the pilots of the early Gemini flights had required.49
* The 19 candidates were Vance D. Brand, John S. Bull, Gerald P. Carr, Charles M. Duke, Jr., Joe H. Engle, Ronald E. Evans, Edward G. Givens, Jr., Fred W. Haise, Jr., James B. Irwin, Don L. Lind, John R. Lousma, Thomas K. Mattingly II, Bruce McCandless II, Edgar D. Mitchell, William R. Pogue, Stuart A. Roosa, John L. Swigert, Jr., Paul J. Weitz, and Alfred M. Worden. Actually this fifth set brought the total selected to 55, but the number on active status had been reduced for a variety of reasons: John Glenn had resigned to pursue a political and business career; Scott Carpenter had returned to duty in the Navy; and Charles Bassett, Theodore Freeman, and Elliot See had been killed in aircraft accidents.
45. MSC news release 66-22, 4 April 1966; MSC, "Gemini Program Mission Report, Gemini IX-A," MSC-G-R-66-6, n.d., pp. 1-1 through 1-3, 4-1; [Ertel], Gemini IX-A: Rendezvous Mission, MSC Fact Sheet 291-F (Houston, August 1966); Hacker and Grimwood, On the Shoulders of Titans, chap. XIV.
46. MSC, "Gemini Program Mission Report, Gemini X," MSC-G-R-66-7, August 1966, pp. 4-1 through 4-11; [Ertel], Gemini X: Multiple Rendezvous, EVA Mission, MSC Fact Sheet 291-G (Houston, September 1966); Hacker and Grimwood, On the Shoulders of Titans. chap. XIV.
47. MSC, "Gemini Program Mission Report, Gemini XI," MSC-G-R-66-8, October 1966, pp. 4-1 through 4-3; [Ertel], Gemini VI Mission: High Altitude, Tethered Flight, MSC Fact Sheet 291-H (Houston, October 1966); Hacker and Grimwood, On the Shoulders of Titans, chap. XV.
48. Shea to R. E. Newgood, 24 Oct. 1966; MSC, "Gemini Program Mission Report, Gemini XII," MSC-G-R-67-1, January 1967, pp. 4-1 through 4-5; Ertel, Gemini XII Flight and Gemini Program Summary, MSC Fact Sheet 291-I (Houston, December 1966); Hacker and Grimwood, On the Shoulders of Titans, chap. XV.
49. Mueller to Gilruth, 26 March 1966.