For the seventh Gemini mission, NASA had scheduled its longest flight of the program - 14 days. Crew selection was beginning to follow a leap-frog pattern; that is, the backup crew for one mission became the prime crew for a later flight.* On 1 July 1965, NASA picked the Gemini IV backup crew, Frank Borman and James Lovell to fly Gemini VII, with Edward White and Michael Collins as alternates. Collins was the first member of the third astronaut class (selected in October 1963) to be named to a flight.** 2
 NASA officials had been wrestling with the order of flights - which mission was to carry out what major program objectives - for a long time. Slow progress on some systems had forced a shuffling of tasks. A prime example was the pitfall-strewn route of the Agena target vehicle to the launch pad, which affected schedules for both rendezvous and long duration. When Charles Mathews took over the Gemini program, the target vehicle was in real trouble. Thus, flight schedules were changed to fly an Agena mission before the Gemini endurance test. Then, if anything happened, there would be time to work on the vehicle before the next rendezvous flight.3
Although Gemini Agena Target Vehicle (GATV) 5001 had been shipped to Cape Kennedy in May 1965, it was a test vehicle and unqualified for flight. In August, NASA officially assigned GATV 5002 to the first rendezvous mission. It was of better production quality than 5001, but NASA officials still doubted that its main engine could be trusted for docked maneuvers with a manned spacecraft. The Gemini Program Office firmly opposed firing the big engine. This was an old argument. Schirra, in particular, chafed at the limitation and tried hard to get it lifted. When that failed, he was willing to settle for a chance to try out the smaller secondary engines. For a while, Schirra thought he had won his point, but no reference to out-of-plane docked maneuvers appeared in the final flight plan.4
Rendezvous techniques remained largely in the realm of theory. When training for Gemini VI began in the spring of 1965, little had yet been done toward planning crew procedures for making the final maneuvers. Dean F. Grimm of MSC's Flight Crew Support Division joined forces with Astronaut Edwin Aldrin, who had studied the pilot's role in rendezvous for his doctoral dissertation at the Massachusetts Institute of Technology.
In 1963 and 1964, Aldrin worked hard at selling the project office and flight operations on a concentric rendezvous. The target would be launched in a circular orbit 298 kilometers high, the spacecraft in a lower elliptical orbit. Since the spacecraft was closer to Earth, it took less time to circle the globe and could catch up for rendezvous. Aldrin and Grimm worked out the trajectories and maneuvers that would allow the spacecraft to intercept the target.5
A two-week review in April 1965 convinced Grimm and Aldrin that MSC's plans for an active human role in rendezvous were in poor shape. Most work seemed to stress a closed-loop concept that relied more on machines than on men. Radar and computer would make rendezvous nearly automatic. Of course, if either failed, so did the mission. Aldrin and Grimm believed the pilots should have options if the equipment malfunctioned. Grimm went to St. Louis and persuaded McDonnell to rig a device that could simulate trajectories, orbital insertion, and spacecraft-target rendezvous.***  A computer allowed flight profiles to be set up that varied the series of maneuvers leading to target interception. Crewmen learned what to do if any piece of equipment failed, and they profited from merely going through the motions as they tried to decide which procedures were useful and valid. Schirra and Stafford rejected, for example, an early concept for doing rendezvous with the spacecraft inverted - head toward Earth - using the inertial guidance system to judge spacecraft attitude. They both disliked this method because they lost their sense of direction. Overall, the prime crew participated in 50 complete rendezvous simulations. As Schirra and Stafford trained on the simulator, they took notes and discussed with Aldrin and the others the best procedures to use. These were then incorporated into charts that would be carried in flight.6
Aside from concerted efforts to qualify the Agena and to pull together rendezvous plans, Gemini VI preparations were fairly routine. Measures taken to shorten the launch intervals were surprisingly successful, and the 25 October launch date was not hard to meet. In April 1965, GLV-6 became the first Gemini launch vehicle to be erected in the new west cell of the Vertical Test Facility at Martin-Baltimore; tests on GLV-5 were still in progress on the old stand (now called the east cell). GLV-6 reached the Cape early in August and went into storage until Gemini V was launched. Spacecraft 6 arrived in Florida about the same time, but it did not go into storage. Instead, it was hoisted atop a timber tower for electronic compatibility tests with GATV 5002, because the target vehicle's command and communications system had just undergone major modifications. Originally intended as a one-time exercise for the first Agena, these tests became a major part of prelaunch checkout for all Gemini-Agena missions. When they were finished, the test operations group was confident that the Agena would respond reliably to all spacecraft and ground control commands.7
Gemini VI was the last of the program's battery-powered spacecraft, which limited the flight to two days at most. Schirra, in fact, thought the power would be pretty thin for even this amount of time. When the mission directive neared its final version by the end of September, it provided that the "mission may be cut to one day if all objectives are completed." The crew, in other words, could come home as soon as they completed rendezvous and docking with the Agena; everything else was secondary, even experiments. There were seven of these: two depended upon rendezvous with the Agena, one was medical,  three were photographic experiments as carried on all flights and used crew time only when it did not interfere with the major task - rendezvous - and one was passive. "On my mission, we couldn't afford to play with experiments," Schirra later said, "rendezvous [was] significant enough."8
* The pattern was sometimes broken. Neither Grissom nor White flew a second Gemini mission; David R. Scott joined Neil Armstrong on Gemini VIII and Charles A. Bassett II received the prime assignments for Gemini IX.
** Others in the third group were Edwin E. Aldrin, Jr., William A. Anders, Charles Bassett, Alan L. Bean, Eugene a. Cernan, Roger B. Chaffee, R. Walter Cunningham, Donn F. Eisele, Theodore C. Freeman, Richard F. Gordon, Jr., Russell L. Schweickart, David Scott, and Clifton C. Williams. This brought the strength of the corps to 30.
** Grimm and Aldrin had help in setting up rendezvous procedures: at MSC, Branch Chiefs Paul C. Kramer (Crew Safety and Procedures) and Edgar C. Lineberry (Rendezvous Analysis); at McDonnell, Charles A. Jacobson, Marvin R. Czarnik, William Murphy, Walter Haufler, and William E. Hayes. Gordon Cooper and Charles Conrad, the Gemini V crew, acted as engineering test pilots until the Gemini VI crews could take over.
1 Walter M. Schirra, Jr., interview, Houston, 4 May 1967; Warren Burkett, "Schirra Expects to Get Flight of His Own after Gemini Test," The Houston Chronicle, 2 Feb. 1965; "Schirra Aiming for 6th Flight," The Sun, Baltimore, 2 Feb. 1965; Jim Maloney, "Goal for Age 46: The Moon," The Houston Post, 2 Feb. 1965; "News Conference, GT-6 Crew Selection," 5 April 1965, p. 2.
2 NASA News Release No. 65-218, "NASA Names Borman, Lovell Gemini 7 Crew, "1 July 1965; MSC News Release No. 65-66, 1 July 1965; Ivan D. Ertel, Gemini XII Flight and Gemini Program Summary, MSC Fact Sheet No. 291-I (Houston, December 1966); MSC News Release No. 66-20, "Gemini and Apollo Crews Selected," 21 March 1965; MSC News Release 180-63, 18 Oct. 1963.
3 Project Gemini Quarterly Status Report No. 7, for period ending 30 Nov. 1963, p. 86; Quarterly Status Report No. 8, for period ending 29 Feb. 1964, pp. 75, 77; "Manned Space Flight Schedules," Vol. I, "Level 1 Schedules and Resources Summaries," April 1964, p. 1-3; André J. Meyer, Jr., interview, Houston, 9 Jan. 1967; Eldon W. Hall, interview, Washington, 24 Jan. 1967; Raymond L. Zavasky, recorder, "Minutes of Senior Staff Meeting, July 10, 1964," pp. 3-4.
4 TWX, Charles W. Mathews to SSD, Attn: Lt. Col. Mark E. Rivers, GV-12088, 27 May 1965; Quarterly Status Report No. 13, for period ending 31 May 1965, p. 20; "GATV Progress Report, May 1965," LMSC-A605200-9, 20 June 1965, pp. 2-1, -3, -4; memo, James E. Powers, Jr., to Mgr., GPO, "Gemini Agena Target Vehicle modified command and communication hardware," GP-61396, 8 June 1965; memo, William C. Schneider to Assoc. Adm., Manned Space Flight, "Use of Agena 5002 for GTA- 6," 9 June 1965; "GATV Progress Report, July 1965," LMSC-A605200-11, 20 Aug. 1965, pp. 2-7, 4-11, -12; Schirra interview; Tommy W. Holloway, "GTA-6 Flight Plan," Preliminary, 2 Aug 1965; "Abstract of Meeting of [sic] Atlas/Agena Coordination, August 11, 1965," 20 Aug. 1965; "Gemini VI Astronaut Prelaunch Press Conference," 11 Sept. 1965; TWX, George E. Mueller to MSC, Attn: Mathews, "Use of Agena Propulsion during Emini [sic] Mission 6," MGS-969, 22 Sept. 1965; Holloway, "Gemini VI Flight Plan," Final, 1 Oct. 1965.
5 Edwin E. Aldrin, Jr., "Line of Sight Guidance Techniques for Men in Orbital Rendezvous" (Ph.D. dissertation, Massachusetts Institute of Technology,1964); Schirra interview; Dean F. Grimm, interview, Houston, 13 April 1967; Aldrin, interview, Houston, 4 April 1967.
6 Grimm interview (additional information from telephone interview, 12 Feb. 1969); Schirra interview; Marvin R. Czarnik, interview, St. Louis, 15 April 1966; "Preflight Training Plan for Fourth Manned Gemini Flight Crew (GTA-6)," NASA Program Gemini working paper No. 5031, 23 Aug. 1965.
7 "Manned Space Flight Schedules," Vol. I, June 1965, p. 1-7; J[oseph] F Wambolt and S[ally] F. Anderson, coordinators, "Gemini Program Launch Systems Final Report: Gemini/Titan Launch Vehicle; Gemini/Agena Target Vehicle; Atlas SLV-3," Aerospace TOR-1001(2126-80)-3, January 1967, p. II.G-5; MSC Weekly Activity Report for Office of Assoc. Adm., Manned Space Flight, 1-7 Aug. 1965, p. 1; "Gemini Program Mission Report, Gemini VI-A [sic]," MSC-G-R-65-5, October 1965, p. 12-3; James M. Grimwood and Barton C. Hacker, Project Gemini Technology and Operations: A Chronology, NASA SP-4002 (Washington, 1969), pp. 279, 281; "Medium Space Vehicles Programs Monthly Progress Report, August 1963," LMSC-447186-38, 20 Sept. 1963, p. 2-2; "Abstract[s] of Meeting[s] on Atlas Agena, March 20, 1963," 27 March 1963; "April 3, 1963," 9 April 1963; "June 6 and 7 1963," 12 June 1963; "July 2, 1963," 8 July 1963; "August 7, 1963," 20 Aug.1963; "September 4, 1963," 10 Sept. 1963; "October 2, 1963," 8 Oct. 1963; memo, G. Merritt Preston to GPO, Attn: William R. Wakeland and Walter J. Kapryan, "Gemini/Agena Combined RE Compatibility and Functional Compatibility Test, Plan X," 28 Oct. 1963; TWX, Mathews to SSD, Attn: Rivers, GT-55349, 8 Jan. 1965; TWXs, Mathews to Dep. Dir., Launch Ops., KSC, Attn: Preston, SSD, Attn: Rivers, and McDonnell, Attn: Walter F. Burke, "Definition of Responsibilities for Cape GATV Testing," GT-55395, 12 March, and "Plan-X Test Objectives," GT-55394, 17 March 1965; letter, Mathews to Col. Alfred J. Gardner, GP-61612, 20 Aug. 1965; memo, Scott H. Simpkinson to Mgr., GPO, "Plan X testing of Spacecraft 6 and GATV 5002," GT-65374, 13 Sept. 1965.
8 "Gemini VI Mission Directive," NASA Program Gemini working paper No. 5037, 20 Sept. 1965, p. 3-2; Schirra interview; NASA Release No. 65-327, "Project: Gemini 6," press kit, n.d. (for release 20 Oct.1965), p. 1; Meyer, notes on GPO staff meeting, 25 Aug. 1965, p. 1; MSC News Release No. 65-85, 25 Sept. 1965; memo, Mathews to Thomas P. Stafford, "Experiments scheduled for Spacecraft 6," GP- 61135, 9 April 1965; memo, Mathews to Chief, Flight Crew Support Div., Attn: Chief, Spacecraft Ops. Br., "Gemini Experiment MSC-4, Optical Communication," GP-61324, 26 May 1965; letter, Robert R. Gilruth to Ames Research Center, Attn: Smith J. DeFrance, "Request for training of GTA-6 flight crews," EG27-65-626, 18 Aug. 1965; letter, Mueller to Gilruth, 13 Oct. 1965.