For Gemini IX, the three major questions centered on working procedures rather than technology: tethered versus untethered extravehicular activity, rendezvous in the third spacecraft orbit, and radar versus optical tracking from the spacecraft.
Work on the Astronaut Maneuvering Unit by Chance Vought and the Air Propulsion Laboratory at Wright-Patterson Air Force Base in Ohio set the stage for the tether debates. The manually operated unit was powered by a hot gas, hydrogen peroxide. In a number of tests, the device showed it would be useful to an astronaut in controlling his  attitude and keeping himself stable while he maneuvered in space. When, early in 1963, the Air Force was given a chance to place experiments in the Gemini spacecraft, the AMU was an obvious choice. It could help pilots working in space on many tasks that the Air Force was particularly interested in - maintenance, repair, resupply, crew transfer, rescue, satellite inspection, and assembly of structures. Since none of these was as yet a primary or secondary objective to NASA, the unit would fly in Gemini merely to confirm what it could do.11 The tether entered the picture as a safety factor.
At first, the Air Force had in mind a 60-meter tether. But studies suggested that an astronaut might get tangled up in a weightless tether. Although this might be countered by a reel mechanism that would keep the line taut, the real question soon became whether a tether was needed at all. Could redundant or alternate systems offer the same safety provided by tying an astronaut to an orbiting spacecraft? The Air Force thought they could, and some in NASA agreed. Tether development was canceled.12 Colonel Daniel McKee, head of the Air Force field office in Houston, pointed out that contractors, when they knew the propulsion system would be flown by astronauts not tied to the spacecraft, would be compelled to make highly reliable systems. After all, no one wanted an astronaut floating off into space. But that possibility was exactly what NASA was worried about. Warren J. North, Chief of MSC's Flight Crew Support Division, held that tethers were a spaceman's best friend, "especially if you have oxygen in them."13
The dispute persisted, sometimes heatedly. An MSC and Air Force meeting in July 1965, to consider "EVA possibilities for Gemini 8," included "EVA without tether." But NASA Headquarters soon made its official position quite clear. William Schneider, Deputy Director of Mission Operations, wired MSC Gemini Manager Charles Mathews that "EVA shall be based on the use of a tether on Gemini flights thru Gemini 12."14
McKee was not so easily discouraged. In February 1966, he was still debating the issue. McKee wanted the matter left open until Gemini XII, when the maneuvering unit was scheduled for its second flight. He prepared a position paper, pointing out that all critical systems on the AMU were backed up and that its test programs had been oriented toward free flight, because this was the unit's ultimate purpose.15 MSC Director Robert Gilruth forwarded McKee's case to George Mueller, chief of NASA's manned space flight programs, who was still not convinced. Mueller insisted that all Gemini astronauts would be tethered, but even this experience might be helpful to the Air Force in future untethered flights. A new NASA position paper described spacecraft maneuvers that would maintain tether slackness to simulate free space activity. Although "prudence dictates that a tether be used at all times during Gemini extravehicular activity,"  the door might still be open to untethered flights, "in the event that an operational requirement is identified which cannot be met in [any other] way."16
The spinning flight of Gemini VIII on 16 March gave the Air Force a chance to push that door open: what might have happened had David Scott been outside and fastened to the spacecraft when it went out of control? He could have been wrapped up like a broken window shade. The Air Force suggested adding a safety disconnect device, at least, as long as NASA persisted in a tether, so a crewman could free himself if something like that happened again.
NASA officials, too, had been thinking about the plight of a crewman caught outside a whirling spacecraft. Scott said that he could have spotted the thruster problem and gotten back into the spacecraft to help Armstrong deal with it. But many in the Office of Manned Space Flight were convinced that, if spacecraft troubles arose when a pilot was outside, the best thing for him to do was to get back inside as quickly as he could. There were too many hazards connected with troubleshooting for him to try diagnosing any problem, let alone using a disconnect to discard the security of a lifeline. That ended the active debate,17 but there were still some who thought it was a good idea, one that ought to be tried in future programs.18
The second major issue on the Gemini IX mission - when to rendezvous with the target vehicle - was not so hotly pursued. Planners for Gemini VI, considering possible sources of trouble, had concluded that rendezvous should take place no sooner than the fourth orbit. This was a well researched procedure, which Walter Schirra and Stafford had demonstrated in high style. But some engineers in the Apollo Spacecraft Program Office wanted to tamper with success. Rendezvous in the first, or at least by the third, spacecraft revolution would more closely approximate lunar orbit rendezvous.19 In September 1965, mission planners began working on a tentative M=3 rendezvous (in the third spacecraft orbit) for Gemini IX and X. For the rest of the year, they worked on this new rendezvous scheme.20
NASA, Air Force, and industry representatives met in Houston on 20 January 1966 to review the results of these labors. After the spacecraft had separated from the launch vehicle, the first maneuver - "IVAR" for the unwieldly "insertion velocity adjust routine" - would reduce orbital insertion errors. The crew would use the inertial guidance system to raise or lower spacecraft trajectory immediately. At the apogee of the first circuit, the crew would perform a "phase adjust," to establish the proper phase relation between the spacecraft and the Agena. One and a half orbits later came another change, this time a triple play, to correct phase, height, and out-of-plane errors. The final maneuver was to circularize the flight path two and a quarter revolutions after insertion. This would place the spacecraft about 28 kilometers  below the target and ready to start firings to catch it. The remaining maneuvers were similar to those required for a fourth-orbit rendezvous.21
No one doubted that this sequence would work but some saw no reason for an M=3 at all. Two camps formed. One group insisted that it closely approximated lunar orbit rendezvous; the other maintained that the kinship was so slight that it was not worth doing. The second group also contended that ground tracking and ground computer capabilities for this approach were not as good as they were for rendezvous in the fourth revolution. Schneider believed that the third-circuit concept would be useful to Apollo operations. Mueller agreed with him, and that settled the issue.22
The third Gemini IX debate, radar versus optical tracking, grew from a type of rendezvous clearly applicable to Apollo. This matter first came up when several engineers, looking for ways to keep the spacecraft from getting too heavy, wanted to pull the radar out of both Apollo vehicles. The command module lost its radar in February 1965 when the ASPO Configuration Control Board ruled that the astronaut aboard the mother ship could use an optical sight to help rendezvous with the radar-and-flashing-light equipped lunar module. Later that year, with weight reduction becoming even more pressing, the lunar module's radar was the candidate for removal. This meant that during lunar operations - whether on takeoff from the Moon or at any time the two vehicles were apart - rendezvous of the two ships would depend entirely on astronaut eyes, optical sights, flashing lights, and computers. This was too much for the men who had to fly the machines; they did not entirely trust their eyes or the suggested equipment. They wanted the help of electronic radar signals on one vehicle bouncing back from the transponder of the other. At least, they said, the radar should remain on the lunar module.23
Stafford and Cernan did agree to include a test on Gemini IX to compare optics and radar by performing a rendezvous from above the target vehicle. In this exercise, the Agena would be over the Sahara Desert, which would simulate the lunar surface, and the crew would try to fly down to it, using both radar and optics.24
9 G. Merritt Preston, interview, Cape Kennedy, Fla., 24 May 1967.
10 Memo, Charles W. Mathews to Chief, Gemini Spacecraft Procurement Sec., "Spacecraft inspection requirement," GP-62115, 4 April 1966; memo, Mathews to Chief, Flight Safety Office, "Control system modifications," GP-62154, 22 April 1966; "Gemini Program Mission Report, Gemini IX-A," MSC-G-R-66-6, n.d., p. 3-8.
11 Memo, Col. Daniel D. McKee to MSC, Attn: Paul E. Purser, "DOD/NASA Gemini Experiments," 26 Aug. 1963, with enclosures; Robert B. Voas, exec. sec., "Minutes of In-Flight Scientific Experiments Coordination Panel, September 23, 1963," n.d., p. 7; Stafford memo, 22 May 1970; Col. Wilbur A. Ballentine, interview, Houston, 16 Jan. 1967; "Rendezvous and Extravehicular Systems," Gemini Design Certification Report, February 1966.
12 McKee, interview, Los Angeles, 19 May 1967; Ballentine interview; unsigned draft memo to Mgr., GPO, "Tether and Stabilization Requirements for Extravehicular Mission," n.d.
13 McKee and Ballentine interviews; Warren J. North, interview, Houston, 10 Jan. 1967; "Technical Development Plan for DOD/NASA Gemini Experiments, 631A," SSD, 23 Sept. 1963, pp. 5- 17, -18.
14 [Reginald M. Machell], "EVA Possibilities for Gemini 8," annotated, "10, 11, 12," 9 July 1965; TWX, William C. Schneider to MSC, Attn: Mathews, MG-317, 9 Sept. 1965.
15 Letter, Gilruth to Robert F. Freitag, 2 Feb. 1966, with enclosure, draft, [McKee], "NASA/DOD Position on Untethered Extravehicular Activity," n.d.
16 Letter, Mueller to Gilruth, 17 March 1966, with enclosure, MSF Position Paper, "Tethered Extravehicular Activity in the Gemini Program," n.d.; letter, Mueller to Brig. Gen. Harry L. Evans, 17 March 1966, with enclosure as above.
17 Letter, Evans to Mueller, "Tethered vs Untethered Extravehicular Activity," 25 March 1966; memo, LeRoy E. Day to Assoc. Adm., Manned Space Flight, "General Evans letter on untethered EVA," 14 April 1966; letters, Mueller to Gilruth and Evans, 27 April 1966, with enclosures; memo, Mathews to Asst. Dir., Flight Crew Ops., "Gemini IX Extravehicular Flight Plan," GS-64127, 14 April 1966; memo, Alfred P. Alibrando to Scheer, 23 March 1966.
18 McKee and Ballentine interviews.
19 Vearl N. Huff, interview, Washington, 24 Jan. 1967.
20 Memo, Mathews to dist., "Mission Planning," GV-66198, 25 Sept.1965; memo, Mathews to dist., "Mission Planning for Gemini IV through XII," GV-66208, 1 Oct. 1965; Huff interview; memo, Mathews to dist., "Mission Planning for Gemini IX, X, XI, XII," GV-66289, 2 Dec, 1965.
21 "Abstract of Meeting on Trajectories and Orbits, January 20, 1966," 31 Jan. 1966; "Gemini Rendezvous Summary," MSC Internal Note No. 67-FM-128 (TRW Systems Group No. 05952-H281-R0-00), 1 Nov. 1967, pp. 2-2, B-2 through -5, C-2; W. Bernard Evans and Marvin R. Gzarnik, "Summary of Rendezvous Operations," in Gemini Summary Conference, NASA SP-138 (Washington, 1967), pp. 10-ll; P. W. Malik and G. A. Souris, Project Gemini: A Technical Summary, NASA CR-1106 (Langley, Va., 1968), p. 274; memo, Carl R. Huss to MSC Historical Office, Attn: Grimwood, "Comments on draft chapter of Gemini narrative history . . . ," 70-FM-H-29, 3 June 1970; memo, Robert E. Prahl to dist., "Gemini IX Insertion Velocity Adjust Routine (IVAR) Study," 66-FM32-56, 26 April 1966; memo, Ben F. McCreary to Chief, Mission Planning; and Analysis Div., "Gemini IX booster recontact study for overspeed insertions requiring IVAR corrections," 66-FM34-25, 20 April 1966; memo, Mathews to dist., "Gemini IX M=3 differential altitude," GV-66434, 23 May 1966; memo, Mathews to Asst. Dirs., Flight Ops. and Flight Crew Ops., "Gemini IX Mission Activities Priorities," GV-66415, 3 May 1966; letter, Mathews to NASA Hq., Attn: Schneider, "Gemini IX Mission Activities Priorities," GV-66416, 3 May 1966.
22 Note, Schneider to Mueller, 4 Feb. 1966, annotated, "OK if no impact on F.O. [flight operations]. G."
23 A. L. Brady, "Configuration Control Board No. 4 Minutes, February 3, 1965"; memo, Jackson B. Craven to Chief, Apollo Flight Systems Br., "CSM Rendezvous Radar and LEM Weight Study," 9 Feb. 1965; memo, R. Wayne Young to Chief, Guidance and Navigation (G&N) Contract Engineering Br., "G&N Configuration Control Panel Meeting No. 5," 12 Feb. 1965; memo, Owen E. Maynard to Chief, Instrumentation and Electronic Systems Div. (IESD), "Requirement for VHF ranging capability between CSM and LEM," PS6/ 65M182, 15 Feb. 1965; memo, Maynard to Chief, IESD, "Maximum acceptable ambiguity for CSM-LEM VHF ranging system," PS6/ 65M201, 25 Feb. 1965; Cline W. Frasier, "LEM Rendezvous Radar vs. Optical Tracker Study," 16 March 1965; André J. Meyer, Jr., notes on GPO staff meeting, 11 Jan. 1966, p. 1; memo, Robert C. Duncan to Chief, IESD, "Request for support: Evaluation board for LORS [lunar optical rendezvous system] - RR [rendezvous radar] Olympics, " ECA-66-80, 25 Jan. 1966, with enclosure, memo, Wayne Young to Grumman, Attn: Robert S. Mullaney, "Contract NAS 9-1100, Rendezvous Radar Testing," EG4-3-66-70, 25 Jan. 1966; memo, Donald K. Slayton to Chief, Guidance and Control Div., "LORS - RR Olympics, " 1 Feb. 1966; MSC News Release No. 66-38, 2 June 1966; Apollo Spacecraft Program Quarterly Status Report No. 16, for period ending 30 June 1966, p. 53; Quarterly Activity Report for Office of the Assoc. Adm., Manned Space Flight, for period ending 31 July 1966 p. 55.
24 Stafford, interview, Houston, 3 April 1967; NASA News Release No. 66-97, "Project: Gemini 9," press kit, 4 May 1966, pp. 13-14; "Gemini IX-A Mission Report," p. 2-2; "Gemini Program/Mission Directive," NASA Program Gemini working paper No. 5039, 19 Nov. 1965, Appendix A, "Gemini Missions," p. A-9-2.