The proximate cause of the shutdown was the command from the master operations control set, an automatic response to an automatic function - the switchover from primary to secondary flight control during the 3.2 seconds between ignition and liftoff. After the engines ignited, the launch vehicle remained bolted to the stand until thrust built up to 70 percent of maximum. During that time, a switchover in the control system was an automatic shutdown order. The GLV-2 switchover followed automatically when the booster's malfunction detection system sensed the pressure drop in the primary hydraulic system. GLV-2, in other words, spotted its own hydraulic failure, responded by switching over to its secondary system, and then, because it was still on the ground, commanded its engine to shut off.
Having saved itself, GLV-2 stood poised on the pad - a giant question mark. Why had its primary control system failed? The answer was quick in coming. Unexpectedly high pressure in one of the hydraulic lines had burst the aluminum housing of a servovalve, letting the hydraulic fluid leak out. This valve controlled one of the booster's four tandem actuators, the devices that moved the thrust chambers to steer the vehicle in flight. Why the valve housing had failed was a lesson in the folly of unneeded "improvement." At some time during development, someone had decided that the walls of the housing were twice as thick as they needed to be; a third of a centimeter of aluminum was ample to meet design pressures. No one, however, thought to test the actual pressure the housing would have to withstand, nor was any impulse test, as such, included in system qualification. More likely than not, one or another Titan II had suffered the same sort of hard start, but the stouter housings that remained standard in the missile could survive such a pulse while the lighter structural shell in the Gemini booster could not.39
When GLV-2 shut down, Spacecraft 2 posed something of a problem. Launch crews knew what to do with a ready-to-go booster, since they dealt with one after the mock launch that was a regular feature of launch vehicle checkout. There was no comparable background for the spacecraft, however, and that led to some hasty improvisation. Aside from its propellants, the spacecraft fairly bristled with pyrotechnic devices, all armed for flight. Should one of them explode, the results might be catastrophic.
 Draining the booster of propellants took first priority, so Wednesday had passed and Thursday was well along before the main part of spacecraft "safing" was complete. One particularly ticklish operation remained, however - pulling the pyrotechnics from the isolation valves that barred propellants from the spacecraft thrusters until time to fire. The problem was complicated by the fact that the explosive cartridge was not a replaceable unit, and the whole valve assembly had to come out. But this might allow propellants to reach the thrusters or to spill their highly noxious chemicals over the workers. The makeshift answer was to freeze the propellant lines. After one or two false starts - no one was quite sure how to do the freezing - copper tubing was wrapped around the lines (which were packed in dry ice), liquid nitrogen was run through the tubing, and the whole thing was sprayed with CO2.* That worked, and the valve assemblies were replaced over the weekend.40
There was really not much that could be done with the spacecraft over the next few weeks besides making sure it remained in flight status, and nothing much could be done with the launch vehicle until new actuators arrived.** A product of Moog Servocontrols, Inc., the tandem actuators had been taken back to the vendor's plant in East Aurora, New York, for extensive tests. Then the actuators had gone to Martin-Baltimore for further testing. The lightweight servovalves had to be redesigned. Work was further curtailed by the holidays. A messenger reached the Cape with the four new parts on 6 January 1965. They were installed at once and testing resumed, focused mainly on the flight control system. The new round of launch preparations went quickly; by Thursday, 14 January, the last major test was complete. Reviews of spacecraft and launch vehicle gave both a clean bill of health, and launch was set for 9 o'clock Tuesday morning, 19 January.41
The countdown began two hours past midnight. It was almost flawless, although it did produce one disappointment. Spacecraft 2 had been slated to carry six fuel-cell stacks of the old model P2B, left over after the design had been updated early in 1964. Despite their known defects, flight testing them with the reactant supply system seemed like a good idea, but only on a "non-interference with flight" basis and with a dummy load, since electrical power would actually be supplied by battery. The six stacks assigned to Spacecraft 2 had behaved erratically  since they were first installed in St. Louis. When they acted up during the abortive countdown on 9 December and threatened to delay the launch, they were scratched from the mission. Only one stack proved to be still operable; it was activated on 18 December, then shut off and left alone until the next launch attempt. An hour and a half after the countdown started on 19 January, hydrogen intake to the stack was blocked by a stuck valve. Two hours of work left troubleshooters faced with breaking the spacecraft wiring to correct the problem. Since that would have meant a hold in the countdown, the attempt to activate the stack was called off, and the fuel cells were not operated on Gemini 2.42 Aside from the fuel-cell problem, the countdown produced only the most minor anomalies an preplanned two-minute hold.
At four minutes after 9 Tuesday morning, Gemini 2 began the last unmanned flight in the Gemini program. GLV-2 hurled the spacecraft 3,430 kilometers across the South Atlantic through an arc that peaked 160 kilometers above the ocean's surface. The spacecraft endured the most severe heating Gemini was ever likely to meet as it plunged back into the atmosphere, its heat protection proved, its structural integrity uncompromised, and all systems working. It dropped into the South Atlantic on its parachute about 18 minutes after launch, bobbing in the water for an hour and a half until it was picked up by the U.S. Navy's aircraft carrier Lake Champlain.43
Some small question marks dotted the mission, but overall it looked quite good. The postflight news conference was a scene of quiet jubilation, with pats on the back for everyone involved. Nothing earth-shaking turned up in the detailed study of the recovered spacecraft - only minor scratches, chars, corrosion from exposure to sea water, just about what might have been expected - nothing that would in any way militate against the forthcoming launch of Gemini 3, the first to carry men aloft.44
* A motor-operated shutoff valve was installed in later spacecraft to make draining the hypergolics a simpler and safer operation.
** During the lull in Cape activity, NASA realigned its filed center operations on a noninterference-with-Gemini basis. MSC's Florida Operations was transferred to Kennedy Space Center and renamed the Launch Operations Directorate (with Kurt H. Debus as Director and Merritt Preston as Deputy Director) to "place the responsibility for assembly, checkout, and launch of the total Apollo space vehicle with a single organization."
38 "GT-2 Mission Report," pp. 12-17, 13-8, -9,-20.
39 Launch Vehicle Press Handbook (1964 ed.), p. V-5; Mathews, interview, Houston, 12 Dec. 1966; Jerome B. Hammack, interview, Houston, 19 Aug. 1966; Col. John G. Albert, interview, Patrick AFB, Fla., 26 May 1967; Dineen, interview, Huntington Beach, Calif., 15 May 1967; John E. Riley, draft of press release, n.d. [9 Oct. 1964]; Hammack, telephone interview, 2 March 1973.
40 Consolidated Activity Report, December 1964, p.12; Kapryan, interview, Cape Kennedy, Fla., 25 May 1967; "GT-2 Mission Report," p. 12-8; "History of GT-2 at KSC," pp. 85-86; TWX, Kapryan to MSC, Attn: Mathews, daily status report No. 54, 11 Dec. 1964.
41 Memo, Low to dist., "Transfer of MSC Florida Operations to Kennedy Space Center," 23 Dec. 1964, with enclosure, "KSC-MSC Cape Relationships," signed by MSC Director Robert R. Gilruth and KSC Director Kurt H. Debus, 21 Dec. 1964; MSC Announcement No. 64-185, "Reorganization within the Office of Manned Space Flight and Transfer of MSC Florida Operations," 24 Dec. 1964; memo, John W. Smith to Mgr., Gemini, "Actuator modification program," GV-02452, 29 Dec. 1964; "History of GT-2 at KSC," pp. 87-105; "GT-2 Mission Report," pp. 12-8, -9, -18, -21; TWX, Albert to Dineen et al., DWD 39102, 18 Jan. 1965; Albert, Hohmann, Kapryan, and Hammack interviews; Gordon T. Chambers, interview, Baltimore, 23 May 1966; Mathews, "Gemini Summary," p. G-9; memo, Kraft to dist., "GT-2, Flight Readiness and Mission Reviews," GP-01787, 8 Jan. 1965.
42 "GT-2 Mission Report," pp. 6-2, 12-2, 13-6, -7; "History of GT-2 at KSC," p. 106; TWXs, Kapryan to MS-C, Attn: Mathews, daily status reports, No. 53, 10 Dec., No. 55, 14 Dec., No. 59, 18 Dec., and No. 60, 19 Dec. 1964; note, Day to Seamans, "Gemini Spacecraft #2 Fuel Cells," 25 Jan. 1965; TWX, Mitchell to NASA Hq., Attn: James E. Webb, and MSC, Attn: Gilruth, "GT-2 Launch Summary Report," 19 Jan. 1965; Kapryan interview; H. H. Luetjen, interview, Cape Kennedy, 25 May 1967.
43 Edward A. Armstrong and John E. Williams, "Gemini Program Flight Summary Report," MSC-G-R-66-5, July 1966, pp. 6-8; "GT-2 Mission Report," pp. 1-1, 2-1, -2, 4-2, -3; [Ertel], Gemini Program; TWX, Mitchell to NASA Hq., Attn: Webb, and MSC, Attn: Gilruth, "GT-2 Mission Summary Report," 20 Jan. 1965.
44 "News Conference, Gemini-Titan-2," 19 Jan. 1965; "GT-2 Mission Report," pp. 12-31 through -34.