An immediate question was whether the Atlas launch vehicle could handle the proposed ATDA; it was much lighter in weight than the Agena but lacked an engine to boost it to orbit. A call to General Dynamics in San Diego posed the weight question (without disclosing the as yet unapproved plan) and received an encouraging response.14
By 5 December 1965, Mathews had the case for the alternate vehicle ready. While Day filled in Seamans' staff, Mueller described the plans to the Associate Administrator himself, who approved it. Four days later a statement of work for the ATDA was ready and McDonnell began building the substitute Gemini target.15 This target adapter became something of a sword of Damocles over Lockheed, a weapon that GPO was willing to use at more than one level. Jerome Hammack spurred Lockheed's efforts by sending Smith a picture of the alternate vehicle (often called the "glob"), and Mathews asked Flight Crew Operations for an alternative flight plan, eliminating all Agena maneuvers from Gemini VIII.16
Project Surefire was already running into trouble. The crucial simulated high-altitude tests of the modified engine could only be run at the Air Force's Arnold Engineering Development Center in Tennessee, but it was booked solid. Time was running out for Gemini VIII, scheduled for mid-March 1966. John Hudson flew to Vandenberg Air Force Base, where he persuaded General Bernard Schriever, Air Force Systems Commander, to sign a letter moving Agena to the head of the line at Arnold.17
 The Agena test program also got a priority from NASA, when Mueller decided that Apollo lunar module engine tests at Arnold could be slipped. On 17 December, after Bell had completed the Project Surefire modifications, the Air Force accepted the main engine for GATV-5003. Bell had already begun the series of 48 sea-level firings that the super tiger team had recommended.18
Setting up the test program, however, was only part of the problem. Another source of delay loomed in Mueller's demand that GATV-5003, which had arrived at the Cape on 18 January, undergo a static firing before it was committed to Gemini VIII. A worried Agena team, fearful that this demand would so delay their efforts that the outcome of the Arnold tests would be meaningless, met late into the night of 4 February 1966, the eve of another meeting of the Flight Safety Review Board, to discuss means of getting Mueller to postpone his decision.
The next day, Lockheed's Smith and Aerospace's Hohmann told Mueller that a static firing at this point was just not worth the delay it would entail. Mueller quizzed them closely and asked for a written report on the pros and cons of static firing as well as on everything that had been done to ensure that Agena would not fail again. The pressure was still on, but Mueller had at least not closed the door on Agena - it still had a chance to compete with the ATDA for Gemini VIII.19 February 14 became the deadline for making the choice, while GPO kept working on both the ATDA and Agena.
Late in January, GPO engineers went to St. Louis to conduct a design review of the ATDA, and Gemini procurement received word to put through the final papers for its purchase.20 ATDA development was quick because its parts had already qualified for space flight and good luck held its cost down. A spacecraft rendezvous and recovery  system fished from the sea for postflight examination after the Gemini VI-A mission could be used in building the ATDA. McDonnell put it together by 1 February, and NASA conducted the acceptance review the next day.21 The stand-in was ready to assume the starring role.
Agena was clearly trailing its rival, but its sponsors hoped to regain lost ground when the second act of the test program began at Arnold on 7 February.22 Meanwhile, Hohmann and Smith had sent their written reports on static firing to Mueller. In Hohmann's view, static firing was mainly useful for training launch crews, not for proving rockets. He pointed out that Mercury-Atlas 1 had failed at launch, even though it had been static fired, and that static firing would not have disclosed GATV 5002's problems. Smith stressed the penalties in money and time.23 A quick poll of opinion from NASA Headquarters and the manned space flight centers supported the Hohmann-Smith viewpoint,24 and Mueller dropped the notion of static-firing the Agena.
That was a plus for Agena's prospects, but the test program at Arnold produced less happy results. After the first six tests, problems with mismatched hardware had already compelled GPO to direct McDonnell to speed up its ATDA testing.25 The seventh test, on 12 February 1966, was nearly fatal. Fuel lines contaminated by alcohol and water caused a hard start that badly damaged the engine. Fortunately, Bell had just about finished its series of sea-level tests and could send that engine to replace the damaged one. As Agena's time seemed to be running out, its proponents literally worked around the clock, juggling, cajoling, scheming, begging, and snarling when necessary, to reach what had begun to seem an impossible goal. More than once, Day and Mathews pleaded with Mueller to keep the Agena. Finally he gave them one week to return the vehicle to good health in time for the review board meetings to be held in Washington 6 and 7 March. Day later recalled his feeling, all during Project Surefire, that Mueller was just putting pressure on MSC and Lockheed and never really intended to cancel the Agena. Mueller did object to the cost of the modifications. He was not willing to brook what appeared to be a $15 million overrun and so was studying proposals to cut Agena out of the program, using the ATDA or two spacecraft for rendezvous.26
On 1 March, the new test series began at Arnold. By the end of the fourth day, 22 firings at simulated altitudes of from 83,800 to 114,300 meters had proved the success of the modifications. Meeting as planned, the Design Certification and Air Force Flight Safety Review Boards approved the modified Agena for flight.27 The Agena had been requalified just in time to fly on Gemini VIII, for its rival, too, was ready, having also completed its test program on 4 March. Now the ATDA went into storage at Cape Kennedy, to be called out if the Agena again faltered.28
13 Day, interview, Washington, 25 Jan. 1967; memo, Day to Mueller, "Gemini Augmented Target Docking Adapter," 9 Dec. 1965; R[obert] N. Lindley, "Gemini Engineering Program, McDonnell Aircraft Corporation," presented at the Institute of Management Sciences, Dallas, Tex., 16-19 Feb. 1966, p. 18.
14 Richard W. Keehn, interview, San Diego, Calif., 18 May 1967.
15 Day interview; Day memo, 9 Dec. 1965; TWX, Day to MSC, Attn: Mathews, 10 Dec. 1965; memo, Mueller to Assoc. Adm., "Revised Gemini Project Approval Document, Change 4," 9 Dec.1965, with enclosure, "Project Approval Document 91-1, Research and Development," n.d.; memo, Meyer to Chief, Gemini Spacecraft Procurement Sec., "Contract NAS 9-170, Gemini, Statement of Work for the Augmented Target Docking Adapter," GP-61893, 15 Dec. 1965, with enclosure; memo, Meyer to Chief, Gemini Spacecraft Procurement Br., "Statement of work for NASA Defense Purchase Request T-53291- G," GP-61894, 15 Dec. 1965, with enclosure; memo, Mathews to Asst. Dir., Flight Ops., "Augmented Target Docking Adapter for Gemini Rendezvous Missions," GV-66297, 17 Dec. 1965; Hammack interview.
16 Hammack interview; memo, Mathews to Asst. Dir., Flight Crew Ops., "Flight Plan for the Gemini VIII-A Mission," GV-66321, 19 Jan. 1966.
17 Whitacre, "A Development History," p. 12; [Whitacre], notes on "Action Item from MSF Program Review held November 23, 1965 on Agena High Altitude Testing of Bell Engine," n.d.; Gardner memo, 14 Oct.1969; letter, Gen. Bernard A. Schriever to Maj. Gen. Ben I. Funk and Brig. Gen. Lee V. Gossick, 22 Nov. 1965.
18 Memo, William A. Lee to Mgr., ASPO, "An AEDC facility conflict with Gemini," PA/M11-65-261, 16 Nov. 1965, with enclosure, "Derivation of Minimum Time Estimates," n.d.; Walter C. Williams and Bernhard A. Hohmann, interview, El Segundo, Calif., 15 May 1967; TWX, Schriever to NASA, for Mueller, SCG 42245, 15 Nov. 1965; Whitacre, "A Development History," p. 12; "GATV Progress Report, December 1965," LMSC-A605200-16, 20 Jan. 1965, pp. 1-1, 3-4; TWX, L. Eugene Root et al. to Mueller and Gilruth, "Gemini Agena Vehicle 5003 Milestone," LMSC/A781 408/64-60/537, 15 Jan. 1965.
19 Gardner memo, 14 Oct 1969; TWX, Gardner to AFSC et al., "Gemini Agena Target Vehicle Flight Safety Review Board (GATV FSRB)," SSVT 36402, 22 Dec. 1965; "Gemini Agena Target Vehicle Program Status,5 January 1966," LMSC-A777567, 5 Jan. 1966.
20 Meyer, notes on GPO staff meeting, 11 Jan. 1966, p. 1; TWX, Mathews to SSD, Attn: Col. Richard C. Dineen and Gardner, GV-12347, 28 Jan. 1966; memo, Duncan R. Collins to Mgr., GPO, "Augmented target docking adapter," GS-64106, 4 Jan.1966; TWX, Mathews to McDonnell, Attn: Walter F. Burke, "Contract NAS 9-170, Gemini, Monthly NASA MAC Management Meeting," GP- 7449, 11 Jan. 1966; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini, Design and Acceptance Reviews of the Augmented Target Docking Adapter," GP-7450, 11 Jan. 1966; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Augmented Target Docking Adapter A-900-20 Meeting," GV-12319, 12 Jan. 1966; memo, Mathews to Chief, Gemini Spacecraft Procurement Sec., "Implementation of Augmented Target Docking Adapter," GP-61954, 24 Jan. 1966; TWX, Mathews to McDonnell, Attn: Burke, "Augmented Target Docking Adapter, Contract NAS 9-170," GV-12324, 19 Jan. 1966; letter, Mathews to Burke, "Contract NAS 9-170, Gemini, results of Augmented Target Docking Adapter Design Review," GP-61947, 20 Jan. 1966.
21 Memo, Mathews to Asst. Dir., Flight Ops., Attn: Chief, Landing and Recovery Div., "Recovery of Gemini Rendezvous and Recovery Section," GV-66187, 15 Sept.1965; "Gemini Program Mission Report, Gemini VI-A," MSC-G-R-66-2, January 1966, p. 6-12; memo, James E. Bost to GPO files, "Contract NAS 9-170, results of negotiations of Contract Change Proposal 100, Augmented Target Docking Adapter . . . ," GP-61936, 13 Jan. 1966; TWX, Mathews to SSD, Attn: Col. B. J. McCarroll, GV-12312, 20 Jan.1966; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini, NASA/McDonnell Management Meeting on Mission Planning," GP-7459, 27 Jan. 1965; TWX, Mathews to SSD, Attn: McCarroll, GV-12346, 27 Jan. 1966; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini, Augmented Target Docking Adapter Acceptance Review, Phase II," GP-7461, 28 Jan.1966; letter, Mathews to Burke, "Contract NAS 9-170, Gemini, results of Augmented Target Docking Adapter Acceptance Review," GP-61988, 10 Feb. 1966; "Gemini Program Mission Report, Gemini IX-A," MSC-G-R-66-6, n.d., p. 12-8.
22 Note, Schneider to Mueller, "Miscellaneous Items," 21 Jan.1966; Whitacre, "A Development History," p. 14; Boorady and Douglass, "Agena Hypergolic Ignition," p. 13.
23 Letter, Hohmann to SSD, Attn: Col. John B. Hudson, "Static Test Firings of GATV," 12 Jan.1966, with enclosures, (1) letter, E. B. Doll to STG, Attn: Gilruth, "Requirements for Flight Readiness Firings on Mercury/Atlas Missiles," 23 March 1960, (2) TWX, Lt. Gen. Howell M. Estes to MSC, Attn: Gilruth, "Atlas Sustainer Engine Turbopump Problems," SSG-13-8-9, 13 Aug. 1962, and (3) "GLV Static Firing Charts;" letter, Lawrence A. Smith to SSD, Attn: Gardner, "Contract AF 04(695)-545, Gemini Program Vehicle 5003 Static Firing Recommendations," 11 Jan. 1966.
24 Letter, Funk to Mueller, "Static-Fire Test," 14 Jan. 1966, with Hohmann and Smith letters; letter, G. Merritt Preston to NASA Hq., Attn: Mueller, "Agena Static Firing," 11 Jan. 1966; memo, Charles W. McGuire to Actg. Dep. Dir., Gemini, "Balance Sheet on Static Firing of GATV-5003," 13 Jan. 1966; memo, Day to Assoc. Adm., Manned Space Flight, "GATV 5003 Static Fire Evaluation," 14 Jan. 1966; memo, Clarence C. Gay, Jr., to dist., "Agena Design Certification," 3 Feb. 1966; letter, Wernher von Braun to Mueller, 17 Feb. 1966; letter, Kurt H. Debus to Mueller, 23 Feb. 1966; letter, Gilruth to NASA Hq., Attn: Mueller, "Agena Design Certification," GV-66369, 12 March 1966, with Smith letter.
25 Whitacre, "A Development History," p. 14; Meyer, notes on NASA MAC management meeting, 11 Feb. 1966, p. 2; Whitacre, telephone interview, 5 March 1971; Day interview; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Augmented Target Docking Adapter," GV-12359, 17 Feb. 1966.
26 Memo, Mathews to dist., "Gemini Design Certification Review, March 6 and 7, 1966," GP-62028, 1 March 1966; TWX, Gardner to NASA et al., "Gemini Agena Target Vehicle 5002 [sic] Flight Safety Review Board and Design Certification Review Board Meeting," SSVT 39094, 1 March 1966; Day interview; letter, Mueller to Gilruth, 2 March 1966.
27 Boorady and Douglass, "Agena Hypergolic Ignition," p. 13; Whitacre, "A Development History," p. 15; TWX, Mathews to SSD, Attn: Gardner, GP-7494, 10 March 1966; memo, Mathews to NASA Hq., Attn: Mueller, "Action items resulting from the Gemini VIII Design Certification Board," GA-60,161, 13 March 1966, with 13 enclosures; memo, Mathews to NASA Hq., "Gemini Agena Target Vehicle action items resulting from the Gemini VIII Design Certification Review," GP-62071, 15 March 1966, with enclosures, (1) memo, Gardner to Mueller and Funk, 15 March 1966, (2) memo, Douglass and Boorady, "Primary Propulsion Subsystem," 14 March 1966, and (3) Reservations, Gerald M. Forslund, 14 March 1966.
28 "Gemini IX-A Mission Report," p. 12-8; TWX, Mathews to McDonnell, Attn: Burke, "Contract NAS 9-170, Gemini Augmented Target Docking Adapter Acceptance Review," GP-7488, 15 March 1966.