The first engineering task was to define the spacecraft as a whole and each major subsystem to conform to the job required by the terms of the NASA contract. Since the basic form and function of the vehicle had already been decided by the time the contract was awarded, the definition phase centered chiefly on refining details and was largely complete by the end of March 1962. The products of this effort were SCDs for each major spacecraft system. The SCD, or Specification Control Drawing, was not the simple document its name implied. Often running to several hundred pages, it set out precisely what McDonnell expected the final system to look like and to do. After each SCD was discussed and cleared with NASA, McDonnell sent it out to potential subcontractors for bids. With minor exceptions, McDonnell developed and built only the spacecraft structural shell and electrical system. All other major spacecraft systems were developed under subcontract, with McDonnell acting as supervisor and integrator.
Like so much else in Gemini, subcontracting plans were well along before the project received formal sanction.  McDonnell had convened a review board early in November 1961, at which procurement and engineering specialists began going over the spacecraft to decide which parts to buy.36 Within a week after James McDonnell signed the contract with NASA, his company was able to present MSC with a list of the major items it planned to procure rather than make and to propose a set of bidders for each item.37
This was the prelude to a January 1962 meeting between Chamberlin, Burke, and Gray to reach an understanding on a standard procedure for securing NASA approval in the company's choice of subcontractors.38 This could become a delicate matter, since a number of Gemini systems were to follow Mercury closely enough to suggest sole-source procurement - that is, asking only one company for a bid instead of seeking competitive proposals from several firms.
McDonnell awarded its first subcontract on a sole-source basis. It was for the development of the spacecraft environmental control system, which supplied the oxygen, regulated the temperature, and disposed of wastes for the crew. In broad terms, it was to be little more than two Mercury systems hooked together, so McDonnell simply selected the company that had developed the Mercury system, AiResearch Manufacturing Company of Los Angeles, California.39 NASA agreed, and McDonnell told AiResearch to go ahead on 19 February 1962.40
McDonnell's second subcontract set the pattern for those systems that had no real Mercury counterpart. The Gemini spacecraft was going to have to maneuver in orbit to achieve rendezvous, and this meant that it had to carry a propulsion system (called OAMS for Orbit Attitude and Maneuvering System). Besides letting a pilot steer the spacecraft, the OAMS also held the ship steady in orbit and, at the start of the mission, provided the power to push the spacecraft away from the spent second stage of the launch vehicle and to insert the craft into orbit - or, in case of trouble, to abort the mission. The complete OAMS had 16 small engines, which burned hypergolic propellants fed under pressure from one fuel (monomethylhydrazine) and one oxidizer (nitrogen tetroxide) tank. All engines were mounted in fixed positions and were run at fixed levels of thrust. Eight of the OAMS engines were rated at 111 newtons (25 pounds of thrust) and fired in pairs, allowing the pilot to pitch, roll, and yaw the spacecraft and so control its attitude. The other eight engines were rated at 444 newtons (100 pounds of thrust); two were oriented to fire forward, two backward, and two to each side. This was the maneuvering part of the system. In July 1962, the rated thrust of the two forward-firing engines was reduced to 378 newtons (85 pounds).
A second spacecraft rocket system, the reentry control system, was functionally distinct from the OAMS but used the same kind of engines,  so the same contractor would develop them. The reentry control system comprised two rings of eight 111-newton (25-pound) thrusters located forward of the crew cabin. Either of the rings alone could handle the job, but the function was crucial enough - holding the spacecraft attitude steady during its reentry into the atmosphere - to justify complete duplication.41
McDonnell decided that any of four companies might supply the OAMS and the reentry control system and asked each of them to submit a technical proposal. The prime contractor rated the bids and sent a survey team of engineering, quality control, and procurement personnel to grade each of the prospective subcontractors on resources and capabilities. North American Aviation's Rocketdyne Division in Canoga Park, California, won the highest combined rating. Although Rocketdyne's quoted cost was highest, it included an extensive test program unusually early in development, a feature that particularly impressed NASA, which made the choice. McDonnell told Rocketdyne to commence work on 26 February 1962.42
By the end of March, most of the major subcontractors had been instructed to proceed, and all had been selected by the end of May. The Air Force Space Systems Division, acting as NASA's contractor for Gemini launch vehicles, moved just as quickly. SSD set up a Gemini Launch Vehicle Directorate to manage booster development, naming Colonel Richard C. Dineen as director and Colonel Ralph C. Hoewing as deputy.** 43 General systems engineering and technical direction of development, with special stress on man-rating - making sure that Titan II was a safe and reliable booster for manned launches - was contracted to the Aerospace Corporation, which filled much the same role in Mercury for the Atlas booster. Aerospace set up its own Gemini launch vehicle program office under James A. Marsh.44
Gemini launch vehicle development was assigned to Martin's Baltimore plant, although the Titan II missile was developed and built in Denver. Baltimore got the nod chiefly to avoid any conflict between booster and missile work, although the decision did also help to sustain a facility that might otherwise have had to shut down.45 Bastian Hello took over as Gemini Program Manager, reporting directly to Albert Hall, Martin vice-president and general manager of one of the three Martin divisions located in Baltimore.
Martin did not set up a Gemini project organization as such. Rather, each of the nine functional departments in Hall's division  appointed a Gemini manager, who took charge of the program work in his area but remained in the normal departmental chain of command.*** Hello also had the help of a program manager at Denver, where the booster's propellant tanks would be built since the tooling required was too costly to duplicate in Baltimore, and a Martin-Canaveral program manager responsible for launch facilities and operations.**** Subcontracts played a much smaller part in the Martin than in the McDonnell scheme of things, largely because the booster differed much less from the missile than the Gemini spacecraft did from the Mercury capsule. For the most part, Martin could simply buy what it needed.46
Those systems that did need to be developed - engines, airborne guidance, ground computers - were not handled by Martin through subcontracts. Instead, they became the subjects of separate SSD direct contracts. The contract for propulsion systems went to Aerojet-General Corporation's Liquid Rocket Operations plant in Sacramento, California, in March. Two other major contracts followed later, one with General Electric in Syracuse, New York, to furnish the booster radio guidance system (the missile used inertial guidance), the other with the Burroughs Corporation of Paoli, Pennsylvania, to supply ground computers and implement launch vehicle guidance equations.47
The target vehicle for Gemini required even less in the way of special arrangements. Both Atlas and Agena were ongoing programs, already well established, and there seemed little need at the outset for anything more than fitting them to Gemini. The Agena Project Office at Marshall, headed by Friedrich Duerr, bought these vehicles for all NASA programs, and Gemini was simply another customer.# For the target as for the booster, SSD acted as NASA's contractor. Atlas-Agena programs were managed by SSD's SLV-3 Directorate, commanded by Colonel F. E. Brandeberry. The Directorate's Program Integration Division, under Major John G. Albert, took care of NASA Agena programs.## 48 SSD authorized Lockheed to proceed with Gemini Agena development on 19 March 1962, and Lockheed assigned Herbert J. Ballard to manage the Gemini program.49
At the time NASA was arranging to buy Agena for Gemini, the model in use was Agena B. Agena B was essentially hand tailored for  each of its missions, but the Air Force had decided to develop a more advanced Agena D, needing only to have the proper equipment modules installed to carry out any particular mission. On 10 May Brockway McMillan, Assistant Secretary of the Air Force for Research and Development, invited NASA to join in this program. This appealed to the engineers, but the managers hesitated for much the same reasons that had obtained in the case of Titan III. Agena D was a distinctly less ambitious effort than Titan III had been, however, and Duerr wired Albert on 11 June that Gemini would use Agena D.50
The Atlas for Gemini was also to be a standardized vehicle, the SLV-3. This improved version of the Atlas included many mechanical and electrical changes designed to make it more reliable, less troublesome. Its total engine thrust was upped by about 10 percent, mainly to offset the weight added by these changes.51 On 23 July Seamans notified Rubel that NASA would support the SLV-3 program and planned to use the standard booster in all NASA activities that required an Atlas. For its projected role in Gemini, Atlas needed nothing that resembled development. The Air Force bought it from the Convair Division of General Dynamics Corporation right off the production line in its San Diego, California, plant.52
* Three of the six managers handled both Mercury and Gemini: William Dubusker for manufacturing, William D. Eckert for program administration, and John F. Yardley for launch operations. The other three worked only on Gemini: Robert F. Cortinovis for procurement, A.S. Torgerson for reliability and quality assurance, and Robert N. Lindley for engineering. A seventh manager reporting to Burke, Logan T. MacMillan, was assigned solely to Project Mercury.
** The directorate had four branches: programs, under Major Roland D. Foley; engineering, under Lieutenant Colonel Alfred J. Gardner; safety and test, under Lieutenant Colonel Emmett J. Kelly; and procurement, under William Fried.
*** They were Edward D. Tarmey, Contracts; Lee J. Knight, Finance; George A. Biddle, Planning; Eddie Ball, Sales and Requirements; Jeremie U. LaFrance, Engineering; Martin Barrett, Materiel and Procurement; Francis O. Furman, Manufacturing; Haggai "Guy" Cohen, Quality; and Gordon T. Chambers, Logistic Support.
**** Howard J. Jansen was the Denver manager; O. E. Tibbs had the Cape job.
# Duerr assigned George J. Detko as chief project engineer to monitor the target vehicle program in behalf of MSC.
## Captain Norbert J. Walecka became project engineer for Gemini Agena.
33 Letter, Brown to MSC, Attn: Bailey, "Contract NAS 9-170, Project Gemini, Personnel Assignments," 306-16-488, 26 Feb. 1962, with enclosure, "Project Gemini Management Organization Chart"; Harry W. Oldeg, "Gemini Program Management," AAS paper 66-158, presented at the American Astronautical Society National Conference on the Management of Aerospace Programs, University of Missouri, Columbus, Mo., 16-18 Nov. 1966, pp. 2-3.
34 Robert N. Lindley, "Discussing Gemini: A Flight Interview with Robert Lindley of McDonnell," FLIGHT International, 24 March 1966, pp. 488-89.
35 R[obert] N. Lindley, "Gemini Engineering Program, McDonnell Aircraft Corporation," presented at the Institute of Management Sciences, Dallas, 16-19 Feb. 1966, pp. 4, 6; Lindley, interview, St. Louis, 13 April 1966.
36 Lindley, "Gemini Engineering Program," pp. 7-8, 10; memo, Robert F. Cortinovis, "Procurement Review Board Meeting-MAC Model 133N," 710-587-1, 27 Nov. 1961, with enclosure.
37 Letter, Brown to MSC, Attn: Bailey, "Contract NAS 9-170, Two-Man Spacecraft, Make or Buy Program," 301-16-349, 29 Dec. 1961, with enclosure, "Proposed Buy Listing of Major Equipment."
38 Letter, Walter F. Burke to MSC Field Representative, Attn: Wilbur H. Gray, "Contract NAS 9-170, Procedure for Obtaining NASA Approval of Major Subsystem Source Selection for Project Gemini," 306-101-136, 26 Jan. 1962.
39 Memo, Bailey to GPO, Attn: Chamberlin, "Contract NAS 9-170, Make-or-Buy Supplement," 15 March 1962; memo, Cortinovis for purchase order file, "Environmental Control System - Gemini," 710-041-2, 23 Jan. 1962, with enclosures; letter, Burke to MSC Field Representative, Attn: Gray, "Selection of Equipment, Contract NAS 9-170, Environmental Control System," 306-101-140, 5 Feb. 1962; Project Gemini Quarterly Status Report No. 1, for period ending 31 May 1962, GPO, pp. 15-16.
40 Letter, Gray to Burke, "Selection of Equipment, Contract NAS 9-170, Environmental Control System," NAS/170-252, 13 Feb. 1962; Arthur H. Atkinson, "Gemini - Major Subcontracts, McDonnell Aircraft Corporation," 3 July 1962.
41 Quarterly Status Report No. 1, pp. 12-13, 20; Gemini Press Reference Book, Gemini Spacecraft Number Three, prepared by McDonnell's External Relations Division for news media use at launch [and updated for each mission], ca. March 1965, pp. 45-47; Quarterly Status Report No. 3, for period ending 30 Nov. 1962, p. 15.
42 Letter, Burke to MSC Field Office, Attn: Atkinson, "Selection of Equipment, Contract NAS 9-170, Reaction Control and Adapter Propulsion Systems," 306-09-143, 8 March 1962; letter, Gray to Burke, "Selection of Equipment, Contract NAS 9-170, Adapter Propulsion and Reaction Control System," NAS/170-262, 21 Feb.1962; Atkinson, "Gemini Major Subcontracts"; letter, Chamberlin to James M. Grimwood, 26 March 1974, with comments.
43 Harris, "Launch Vehicle Chronology," p. 2; "SSVL: Gemini Launch Vehicle Directorate," 7 May 1962.
44 Harris, "Launch Vehicle Chronology," pp. 5, 6; Sol Levine, "Man-Rating the Gemini Launch Vehicle," presented at the American Institute of Aeronautics and Astronautics 1st Annual Meeting and Technical Display, Washington, 29 June-2 July 1964; "Aerospace Corporation Annual Report, Fiscal 1962-1963," draft, n.d.; letter, Col. Ralph C. Hoewing to MSC, Attn: George F. MacDougall, Jr., "Gemini Launch Vehicle Financial Plan," 4 April 1962, with enclosures.
45 Memo, Bailey for Project Gemini file "Martin-Marietta Company," 4 Jan. 1962; Col Robert R. Hull, interview, Los Angeles, 18 April 1966; Col. Richard C. Dineen, interview Huntington Beach, Calif.,15 May 1967; Bastian Hello, interview, Baltimore, 23 May 1966.
46 "Program Plan," Martin Co. ER 12255, April 1962, pp. 3-8; 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 TOR1001 (2126-80)-3, January 1967, pp. H.A.- 10, -11; trip report, Richard J. Crane, "Trip Report-Modified Titan 11 for Gemini Program," 13 Aug. 1962, with enclosures, esp. Appendix A, "Martin Company Organization for Participation in Gemini Program"; Crane and John H. Boyd, Jr., telephone interviews, 31 Oct. 1972; Hello, telephone interview, 2 Nov. 1972.
47 Harris, "Launch Vehicle Chronology," pp. 6, 9; Wambolt and Anderson, "Launch Systems Final Report," pp. II.A-I, -12, -15, -16, -17.
48 Letter, Detko to Gilruth, "Investigation of the Gemini 6 - Agena Target Vehicle (G6-ATV) Failure," 29 Dec. 1965, with enclosure, memo, Detko to Eberhard F. M. Rees, "Gemini 6 - Agena Target Vehicle (G6-ATV) Failure Investigation," n.d., with "Gemini/Agena Target Vehicle Program Historical Background" attached; Col. John G. Albert, interview, Patrick AFB, Fla., 26 May 1967; memo, Max Rosenberg to NASA Historian, "Comments on Draft Chapter I-V and XIII-XV, Gemini History," 26 June 1970, with enclosure.
49 World Space Directory, I, No.1 (Washington, 1962), p. B-180; "GATV Progress Report, September 1964," LMSC-A605200-1, 20 Oct. 1964; letter, Rockwell Hollands to Sally Gates, 26 June 1969.
50 Chamberlin, "Minutes, February 28, 1962"; letter, Seamans to Brockway McMillan, 29 May 1962; TWX, Friedrich Duerr to SSD, Attn: Albert, 8 June 1962; "Fourth Report on MSFC Activities Covering May 26 to June 25, 1962 to Manned Spacecraft Center"; Quarterly Status Report No. 2, for period ending 31 August 1962, p. 26.
51 "Fourth Report on MSFC Activities"; Quarterly Status Report No. 2, p. 26; memo, Homer E. Newell to Assoc. Adm., "Standard Atlas Space Launch Vehicles," 15 June 1962; letters, Seamans to Rubel, 19 June and 25 July 1962; memo of agreement, "DOD/NASA Standard ATLAS Space Booster Agreement," signed by Seamans, 5 Sept.1962, and by Harold Brown, n.d.
52 Wambolt and Anderson, "Launch Systems Final Report," pp. IV-1, -3.