As the Titan II program faltered, NASA concerns mounted. The Gemini Program Planning Board persisted in its efforts to resolve the impasse between NASA and BSD. On 28 June, the board asked NASA to state the least it would accept for launch vehicle performance, the Air Force to describe its program in detail. Board co-chairman Robert Seamans, NASA's Associate Administrator, asked MSC Director Robert Gilruth for a precise statement of MSC standards for making Titan II over as the Gemini launch vehicle. The response, on 1 August, was a brief review of "Gemini Launch Vehicle Specifications and Requirements," which pinpointed the three major problem areas that made the Titan II unsafe for manned space flight - longitudinal oscillation (Pogo), dynamic instability of the second-stage engines, and detail design faults of Titan II engines. MSC insisted "that these problems must be satisfactorily solved and the solutions incorporated into the GLV prior to its use in the manned Gemini program."2
Every Titan II so far flown had displayed Pogo, although the level had varied, reaching a low of just over one-third the force of gravity (±0.35g) in the 17th test flight on 13 May 1963. This potential hazard to pilot safety prompted a survey of available data on human tolerance of such vibration, leading MSC to conclude that Pogo should be completely eliminated, or at least not allowed to exceed ±0.25g. A test program on the centrifuge at NASA's Ames Research Center in California, completed in July 1963, tended to confirm the validity of this stand; an MSC astronaut test program conducted immediately after the Ames tests provided even stronger support. Higher levels might be tolerable, but 0.25g still seemed a prudent upper limit. MSC preferred an experimental program to trace Pogo to its source and eliminate it but would settle for this bearable limit if proved on Titan II flights before the vehicle flew in Gemini.3
The second major problem, combustion instability, had not yet occurred in flight, but Aerojet-General's ground tests had revealed incipient instability during second-stage starting - that is, the initial engine-firing pulse could trigger uneven burning in stage-II engines. In a statistical sense, the engine was stable, since Aerojet-General could show that the instability rate was no more than two percent in ground tests. From a physical viewpoint, however, the engine had to be described as dynamically unstable, and that risk could not be accepted when human lives were at stake. Statistical reliability was not enough for a manned booster. Aerojet-General must develop and prove a dynamically stable engine before the first manned Gemini flight.4
The third major area of concern comprised a range of problems, each minor in its own right but significant in the aggregate. Of the 10 full or partial failures in the 20 Titan II test flights to date, Pogo could be blamed for only one, dynamic instability for none at all. The others resulted from small defects - a clogged injector, a failed weld, a broken line.  The central problem seemed to be "a real lack of understanding on the part of Aerojet of procedures and responsiveness to problems that must be associated with the development of engines for use in a manned launch vehicle."5
When several top-ranking MSC officials visited Aerojet's Sacramento plant in July 1963, they were dismayed at what they saw and concerned about a number of questionable practices in design, manufacturing, and quality control, in general, and several components - turbine idler gears, main fuel valves, turbine seals, and turbine manifolds - in particular. The Air Force Space Systems Division (SSD), NASA's agent for launch vehicles, had already spotted 40 engine parts that could be improved. MSC judged that most of these changes had to be made and the results confirmed in flight before the booster was committed to the first manned Gemini mission.6
The Gemini Program Planning Board heard NASA's report on launch vehicle performance standards on 5 August 1963, revised the wording slightly, and accepted it. With this statement as a basis, MSC and SSD were to arrange a formal agreement on the goals of reduced Pogo, a stable second-stage engine, and improved engines. They were also to agree on the programs needed to achieve these goals and the criteria for deciding when the goals had been met.7
Although Titan II itself was still a question mark, the managerial logjam that had so far prevented a concerted attack on its shortcomings as a manned booster now appeared to be breaking up. Major General Ben Funk, SSD Commander, told Gilruth on 8 August that Air Force Headquarters had approved the "augmented engine improvement program." Funk agreed that Aerojet's efforts left something to be desired, then outlined a series of steps he had taken to tighten up the firm's work. He had still another piece of good news. The decision to fly no more Pogo fixes on Titan flights had been reversed. The gas generator clogging problem that had marred the Titan II flight of 20 June seemed to have been solved, and the booster would soon be flying again. Missile N-25, scheduled for a September launch, would carry standpipes and accumulators to suppress Pogo.8
Aerojet-General began work on the improved engine program in September. That same month also saw a start on the Gemini Stability Improvement Program, or Gemsip, an effort to redesign the injector of the second-stage engine to overcome incipient combustion instability.9 When the Gemini Program Planning Board met again, on 6 September, MSC and SSD had agreed on the statement of "Gemini Launch Vehicle Specifications and Requirements for Major Titan II Problems" that the board had requested.10 It fully met NASA's demands. Things seemed to be moving at last.
Titan II, however, had yet to prove itself. Missile problems had already prompted NASA, earlier in 1963, to replace one of Gemini's  manned missions with a second unmanned flight. Still unsolved, they now forced NASA to plan yet another unmanned flight. On 12 July, Mathews told MSC's senior staff that GPO was thinking about backing up the first Gemini flight with an extra unmanned flight (making a total of 13 instead of 12) roughly midway between the first two scheduled missions, or about 1 April 1964. The proposed payload was a boilerplate capsule with instrumentation pallets like those in Spacecraft 1.11
At a meeting on 5 August, the Gemini Program Planning Board agreed to review the plan. The next day, Mathews wired Walter Burke at McDonnell to begin work on the adapter that would attach capsule to launch vehicle. NASA Headquarters approved the new mission and suggested calling it Gemini 1A, or GT- 1A.* Based on data from McDonnell and SSD, the project office figured the cost of the extra flight at around $2 million.12
William C. Schneider, Gemini Project Manager at NASA Headquarters, presented NASA's case for the extra flight to the planning board on 6 September. In essence, NASA wanted to guard against a failure of the first mission by planning a contingent mission, identical to GT-1, to fly before the scheduled GT-2. The board concurred, and Mathews wired Richard Dineen, SSD's Gemini launch vehicle overseer, to make sure that the second launch vehicle would be ready in time to meet the date for GT-1A. The new mission was strictly a backup, however, to be flown only if GT-1 failed to meet its objectives. The decision waited on the outcome of the first mission.13
For GT-1A, MSC diverted a boilerplate spacecraft being built for flotation tests by a local Houston contractor. Named Boilerplate 1A it arrived at the Center on 24 September, where the Technical Services Division began the task of making it flightworthy. Regular biweekly panel meetings started early the next month, and the rebuilt boilerplate was ready in mid-November. It left Houston via flatbed truck on 13 December, reaching Cape Canaveral three days later, there to have its wiring and equipment installed; the work in Houston had been limited to the structure. The adapter, built and instrumented by McDonnell, arrived at the Cape 27 January 1964. By then, however, the threat that had called forth the effort had largely dissipated, and little further work was done before GT-1A was formally canceled on 17 February.14
That cancellation reflected a striking turnaround in Titan II prospects from their lowest ebb during the summer and fall of 1963. BSD resumed the flight test program on 21 August. Although the flight itself was a success, NASA suffered another setback.  This missile was the first of five planned to carry the Gemini malfunction detection system, crucial for Gemini because it was to provide spacecraft pilots with the data they needed on existing or impending booster problems during launch. BSD had agreed to fly the system "piggyback" - installed, working, and reporting to ground receivers and recorders, but not otherwise acting on the missile. The system flown on 21 August suffered a short circuit 81 seconds after liftoff and provided no further data.15
Titan II's next launch, on 23 September, did little to dispel the gloom. A guidance malfunction threw the missile out of its planned trajectory. Since the missile was guided inertially and the Gemini booster used radio guidance, this had no direct bearing on Gemini. That was small consolation, however; Pogo reached plus or minus 0.75g, very nearly the worst since the disastrous flight of Missile N-11 in December 1962.16
The heart of the matter was foot-dragging by BSD on the question of flying Gemini fixes. Once again, the planning board took a hand. It decided to replace the agreement between MSC and SSD of 6 September with a more authoritative Memorandum of Understanding between the co-chairmen of the board, Seamans of NASA and Brockway McMillan, Under Secretary of the Air Force. The board directed NASA to submit another statement of requirements for the Gemini booster and the Air Force to provide a development plan, complete with costs and schedules, for dealing with Pogo, combustion instability, and engine improvement. The board specifically asked the Air Force for a schedule of all remaining Titan II flights, with a plan for flight-testing changes to reduce or eliminate Pogo and unstable burning.17
The meeting of the board took place on 11 October 1963. Four days later, the flight-test question was finally resolved. General Bernard Schriever, a member of the board as well as commander of Air Force Systems Command, called a meeting in Los Angeles of BSD, SSD, and Titan II contractors. Schriever himself firmly supported an active program to clean up launch vehicle problems. Of special concern was whether to follow through with plans to fly Missile N-25 with oxidizer standpipes and fuel accumulators. Aerospace, backed by Space Technology Laboratories, argued strongly for the planned flight, especially since engine ground tests begun in August had confirmed fuel-line resonance as the culprit in the failure of Missile N-11 and shown that fuel accumulators would solve the problem. They carried the day, winning the crucial decision to proceed with the test flight of N-25 as planned. Funk planned to see his BSD counterpart regularly and arranged for meetings between the two project managers, Dineen and McCoy, to make sure that there was no more backsliding.18
Later events were to prove that this time the question had, indeed, been settled.  Meanwhile, however, only the test flights could show that more determined management was the answer to the technological problems. Titan II was still in trouble, and the weekly status reports that Seamans was getting from the Air Force Systems Command after mid-September reflected a promising beginning but little more.19 Some thought was even being given to dropping Titan II from the Gemini project altogether. The Propulsion and Vehicle Engineering Laboratory of NASA's Marshall Space Flight Center began to study the desperate expedient of substituting the Saturn I launch vehicle for both Titan II and Atlas.20
* GT, for Gemini-Titan, had become the standard designation for non-rendezvous missions; GTA, for Gemini-Titan-Agena, for rendezvous missions.
2 "Minutes of the Sixth Meeting, Gemini Program Planning Board [GPPB], Friday, June 28, 1963"; letter, Robert R. Gilruth to NASA Hq., Attn: Robert C. Seamans, Jr., "Gemini Launch Vehicle Specifications and Requirements," GPO-02011-LV, 1 Aug. 1963, with enclosure, subject as above; TWX, Charles W. Mathews to SSD for Col. Richard C. Dineen, GPO-51110, 18 July 1963.
3 L. J. Rose, "Titan II Post Flight Briefing Report," n.d., for Missile N-19, 13 May 1963; MSC Weekly Activity Report for Office of the Dir., Manned Space Flight, 28 July - 3 Aug. 1963, pp. 2-3; memo, W. Fred Boone to Seamans, "August 1, 1963, Meeting on the Gemini Launch Vehicle Specifications," 2 Aug. 1963; memo, Harris F. Scherer, Jr., to GPO, Attn: Willis B. Mitchell, "Interim Report on the physiological tolerance aspects of the Gemini Pogo vibration study conducted at Ames Research Center," 29 Aug. 1963; memo, Scherer to Chief, Crew Systems Div., "History of the Gemini Vibration Study," 13 Sept. 1963, with enclosure; memo, Richard S. Johnston to Dir., "Results of Gemini Pogo vibration tests carried out at Ames Research Laboratory," 1 Oct. 1963; Project Gemini Quarterly Status Report No. 6, for period ending 31 Aug. 1963, p. 78; "Gemini Launch Vehicle Specifications and Requirements."
4 "Gemini Launch Vehicle Specifications and Requirements"; 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.E- 17.
5 "Gemini Launch Vehicle Specifications and Requirements"; Quarterly Status Report No. 5, for period ending 3-I May 1963, pp. 41-42; letter, Gilruth to Maj. Gen. Ben I. Funk, 26 July 1963.
6 Gilruth letter, 26 July 1963; "Gemini Launch Vehicle Specifications and Requirements"; Walter C. Williams, interview, El Segundo, Calif., 15 May 1967; Ray C. Stiff, Jr., interview, Sacramento, Calif., 10 May 1967.
7 "Minutes of the Seventh Meeting, Gemini Program Planning Board, Monday, August 5, 1963"; letter, Seamans to Brockway McMillan, 29 Aug. 1963, with enclosure, "Gemini Launch Vehicle Specifications and Requirements," 21 Aug. 1963.
8 Letter, Funk to Gilruth, "NASA Manned Spacecraft Center Tour," 8 Aug. 1963; Donald T. Gregory, recorder, "Minutes of Senior Staff Meeting, August 9, 1963,"p. 5.
9 Letter, Lt. Gen. Howell M. Estes, Jr., to Seamans, "Titan II/Gemini Program Status Summary," 18 Sept.1963, with enclosures; letter, Brig. Gen. W. E. Leonhard to Hq. NASA (Seamans), "Titan II/ Gemini Program Status Summary," 8 Oct. 1963, with enclosure; letter, Lt. Col. John J. Anderson to Seamans, 21 Oct. 1963, with enclosure, "Statement of Work, Titan II Augmented Engine Improvement Program," 3 Oct. 1963; memo, George E. Mueller to Adm., "Development of the Gemini Launch Vehicle," 6 Dec. 1965, with enclosure, "The Gemini Launch Vehicle Story," n.d.
10 "Minutes of the Eighth Meeting, Gemini Program Planning Board, Friday, September 6, 1963."
11 Raymond L. Zavasky, recorder, "Minutes of Senior Staff Meeting, July 12, 1963,"p. 6; Weekly Activity Report, 28 July-3 Aug. 1963, p.3; memo, William C. Schneider to MSC, Attn: Mathews, "Project Gemini Action Items from OMSF Status Review of June 20, 1963," I July 1963; TWX, Mathews to NASA Hq., Attn: Schneider, "Backup Boilerplate Spacecraft for Gemini Mission Number One," GPO-54022-A, 26 July 1963; memo, Mathews to Asst. Dirs., Engineering and Development and Administration, "Request for Engineering and Procurement Support in Preparing a Boilerplate Spacecraft as a Gemini Flight Article," GPO-04013-S, 14 Aug. 1963.
12 "Minutes of the Seventh GPPB Meeting"; TWX, Mathews to Walter F. Burke, GPO-5301 1-S, 6 Aug. 1963; Gregory, "Senior Staff Meeting, August 9, 1963,"p. 4; letter, Col. Ralph C. Hoewing to MSC, Attn: Richard E. Lindeman, "Budget for Gemini Launch Vehicle," 11 Sept. 1963, with enclosures; memo, Lindeman to Gemini Cost Files, no subject, 9 Aug. 1963; Glenn F. Bailey to McDonnell, "Change Notice No. 2," 21 Aug. 1963; Bailey to McDonnell, "Change Notice No. 5," 11 Sept. 1963; Bailey to McDonnell, "Change Notice No. 6," 16 Sept. 1963; memo, Mathews to Gemini Procurement Office, Attn: Robert L. Kline, "Contract NAS 9-170, Change Notice No. 2," GPO-03082-A, 3 Sept. 1963.
13 "Minutes of the Eighth GPPB Meeting"; TWX, Mathews to Dineen, GPO-54150-A, 6 Sept. 1963; Zavasky, "Minutes of Senior Staff Meeting, September 13, 1963," p. 5; memo, Williams to Goddard Space Flight Center, Attn: Harry G. Gross, "Manned space projects," [25 Sept. 1963]; TWX, Williams to Maj. Gen. Leighton I. Davis, "NASA-MSC mission flight schedule," MFS 001, 8 Oct. 1963; Quarterly Status Report No. 7, for period ending 30 Nov. 1963, p. 3.
14 "Abstract of Meeting on Boilerplate Flight Article, September 24, 1963," 26 Sept. 1963; TWX, Mathews to Burke, GPO-54223-A, 30 Sept. 1963; "Abstract of Meeting on Boilerplate Flight Article Scheduling, October 8, 1963," 11 Oct. 1963; "Abstract of Meeting on Boilerplate Flight Article, November 20, 1963," 27 Nov. 1963; Weekly Activity Report, 8-14 Dec. 1963, p. 1; TWXs, Walter J. Kapryan to MSC for Mathews, AMR 01-15-74, 15 Jan., AMR 01-28-83, 28 Jan., and AMR 02-17-94, 17 Feb. 1964.
15 "The Gemini Launch Vehicle Story," p. 2; Weekly Activity Report, 18-24 Aug. 1963, p. 2; memo, Scott H. Simpkinson to Mgr. GPO, "Final MDS Piggyback Inspection on Titan #N-29, at Denver, Colo.," GPO-00749, 8 April 1963; memo, Christopher C. Kraft, Jr., to Chief, MSC Operations Support Office, "Titan II Malfunction Detection System Piggyback Program," 10 April 1963, with enclosures; memo, David B. Pendley to Chief, Flight Operations Div. (FOD), "Titan II Coordination Meeting of June 14, 1963," 17 June 1963; MSC Consolidated Activity Report for Office of the Dir., Manned Space Flight, 19 May - 15 June 1963, p. 27; Howard T. Harris, "Gemini Launch Vehicle Chronology, 1961 - 1966," AFSC Historical Publications Series 6622-l, December 1966, p. 40; Pendley to Chief, FOD, "N- 24 Malfunction Detection System (MDS) Titan II Piggyback Test," 30 Aug. 1963; Quarterly Status Report No. 6, p. 69.
16 "GLV Analysis of Titan II Launches," Martin, n.d., for Missile N-23, 23 Sept. 1963; Quarterly Status Report No.8, for period ending 29 Feb. 1964, p. 52.
17 "Minutes of the Ninth Meeting, Gemini Program Planning Board, Friday, October 11, 1963."
18 Paul E. Purser, recorder, "Minutes of Project Gemini Management Panel Meeting . . . , November 13, 1963," p. 10; Dineen, interview, Huntington Beach, Calif., 15 May 1967; Funk, interview, Sunnyvale, Calif., 12 May 1967, and telephone interview, 5 Jan. 1973; memo, Sheldon Rubin to Dineen, "Results of Analysis of N-25 Configuration on Aerospace Analog Model of POGO," Aerospace 63-1944- 51, 15 Oct. 1963.
19 Estes letter, 18 Sept.1963; letter, Leonhard to NASA Hq. (Seamans), "Titan II/Gemini Program Status Summary," 27 Sept. 1963; letter, Maj. Gen. Marcus F. Cooper to NASA Hq. (Seamans), "Titan II/ Gemini Program Status Summary," 4 Oct.1963; Leonhard letter, 8 Oct. 1963; letters, Estes to Seamans, "Titan II/Gemini Program Status Summary," 16, 24, and 30 Oct. 1963.
20 Memo, Billy A. Neighbors to dist., "Saturn I/Agena/Gemini Vehicle Feasibility Study Initiation Meeting," R-P&VE-AV-530, 17 Oct. 1963; memo, Neighbors to dist., "Design Data, Saturn I/Agena/Gemini Vehicle Feasibility Study," R-P&VE-AV-558, 18 Nov. 1963; memo, Neighbors to dist., "Conclusions, Saturn I/Agena/Gemini Vehicle Feasibility Study," R-P&VE-AV-576, 18 Dec. 1963.