A McDonnell group led by Mercury manager Walter F. Burke attended a senior staff meeting at STG on 7 July to outline the company's studies of an advanced Mercury capsule that took three distinct forms. One version, the "minimum change capsule," involved not much more than cutting some hatches in the side of the capsule for better access. Although it could be ready to launch relatively quickly and cheaply (II months, $79.3 million), it had some obvious drawbacks. Better access only accented the capsule's cramped interior, and the hatches themselves weakened the capsule's structure and heat protection. As Chamberlin later remarked, "It was clear that this mod was too little to inspire any additional confidence in the design, and hence make it worth doing. Thus, the merits of the greater modifications became apparent."94 The second McDonnell advanced design, called a "reconfigured Mercury capsule," adhered closely to the Chamberlin Blatz proposal of June. It would take longer to build and cost more than the minimum change capsule (20 months and $91.303 million), but it might very well be worth the expense. And for another two months and $12.248 million, NASA might do even better with McDonnell's third version, a "two-man Mercury capsule."95
The notion of putting more than one man in a modified Mercury capsule was not new, having been suggested at least as early as January 1959.96 That idea had gone nowhere, but Faget revived the possibility at the review board meeting on 9 June 1961. Blatz recalled that, after he and Chamberlin had made their pitch, Faget's comment was, "If we're going to go to all of this trouble to redesign Mercury, why not make it a multiplace spacecraft in the process?"97 Faget's interest in a two-man spacecraft was prompted, in part, by the prospect of extra-vehicular operations. As early as March 1961, he had asked John F. Yardley, McDonnell's manager for Mercury operations at Cape Canaveral, to look into the possibility "of expanding Mercury into a two-man version" for this purpose.98 Others saw reason for a two-man spacecraft in the rigors of long missions. If the Mark II were to be in space for more than a few orbits, then having two men to share the strain  and support each other's activities made good sense.99 There was also a certain compelling logic in building a two-man spacecraft for a program falling between the one-man Mercury and three-man Apollo.100
NASA Headquarters seemed uncertain about the size of the changes STG was thinking about during July 1961. George Low told Associate Administrator Seamans and the Washington program directors on 6 July that McDonnell and STG were working on a minimally modified 18-orbit capsule. He reported that
McDonnell originally looked upon the 18-orbit capsule as a development of a new flight article with substantial increase in size and weight, and incorporating rendezvous capabilities. McDonnell has been advised, however, to proceed on the basis of minimal changes to the existing hardware and to approach design modifications on this basis.101But a master plan for orbital operations, dated 19 July, included, besides four 18-orbit Mercury flights during 1963, eight one-man Mercury Mark II flights to be launched at two-month intervals - from October 1963 through December 1964 - and to perform rendezvous and docking tests in orbit.102
Sketch of the modularised systems in the two-man spacecraft.
Although the ideas for an advanced Mercury presented by the McDonnell study team were much the same as they had been 20 days earlier,104 the audience on 27 July now represented NASA Headquarters as well as STG. Silverstein had long been convinced of the importance of Mercury missions more ambitious than merely circling Earth three times. What he saw in St. Louis was apparently enough to tip the scales toward a decision that many in NASA were ready to welcome. On 28 July, during the second day of the St. Louis meeting, Silverstein directed McDonnell to focus all further effort to improve Mercury solely on the two-man approach.** 105 The choice had been made for a larger, rather than a smaller, follow-on Mercury program.
 In what was to become a familiar pattern, that program had already grown far beyond its original bounds. The McDonnell study contract, the basis for the company's design work on advanced Mercury, had outlined a relatively modest effort. By the time that contract was signed, on 24 April, the work was well along. In just over three weeks, McDonnell requested and received a contract increase from $98,621 to $187,189.106 McDonnell efforts soon far surpassed that limit. By 6 August, the company had assigned 45 engineers to the study, and the original 9,000 engineering manhours called for in the contract had climbed to almost 23,000; added to that figure were 6,000 shop manhours for building and testing models not even mentioned in the contract. The estimated cost now topped $535,000.107
Since STG had agreed that advanced Mercury needed more study, McDonnell had not felt obliged to wait until its contract had been amended to provide the extra funds. The company spent its own money. This was the kind of initiative that earned the firm a good deal of respect in NASA circles. Where others refused to move without money in hand, McDonnell focused on the task and relied on the good faith of its customer to make up the cost. It was seldom disappointed. In this instance, the company proposed a new contract to cover the extra engineering study and shop work done since 19 June, when contract funds had been exhausted, and to pay its projected expenses through the end of September.108 The original contract and the new request together totaled over $670,000, nearly seven times the figure first approved in April. STG did not issue a new contract but, instead, amended the procurement contract to authorize the additional funds.109
* Ironically, Schirra flew in Gemini as spacecraft commander, occupying the left seat and using his right hand for most operations.
** McDonnell was also told to go ahead with work on the 18-orbit Mark I; this directive became official on 25 October 1961. The 18-orbit Mercury was no longer deemed an improved version. As Faith 7, it eventually carried L. Gordon Cooper. Jr., through the 22-orbit Mercury-Atlas 9 mission in May 1963.
92 Purser notes on discussion between himself, Gilruth, Faget, Chamberlin, and Charles W. Mathews on MK2 Hermes and MK1, 3 July 1961; "Spacecraft Comparisons: (1) Mark 2 Capsule-Hermes Plan, Extensive Redesign; (2) Mercury - with 18 Orbit Capability, Minimum Redesign - Part of a Program with Specialized Vehicles for Each Mission," prepared by Scheduling Section, Contracts and Scheduling Branch, ca. 1 July 1961 (see memo, Nicholas Jevas to Grimwood, 21 March 1968).
93 Purser notes, 3 July 1961.
94 Chamberlin comments, 26 March 1974.
95 Ibid.; Purser notes on senior staff meeting, 7 July 1961; Jack C. Heberlig, "Notes on Senior Staff Meeting, July 7, 1961," 11 July 1961, with enclosure; "Mark II Mercury Spacecraft," McDonnell C-57342, 6 July 1961.
96 Memo, Robert B. Voas to Meyer, "Request for feasibility study of dual seating for Redstone flights," 23 Jan. 1959.
97 Blatz and Nold interviews.
98 John F. Yardley, interview, St. Louis, 13 April 1966.
99 Walter C. Williams, interview, El Segundo, Calif.,15 May 1967; Low, interview, Houston, 7 Feb. 1967.
100 Walter F. Burke, interview, St. Louis, 15 April 1966.
101 Discussion notes, "First Meeting of Manned Lunar Landing Steering Committee, July 6, 1961," 11 July 1961, p. 2.
102 "Earth Orbital Rendezvous for Early Manned Lunar Landing," Part I, Fig. 4 - "Master Flight Plan-Orbital Ops." pp. 17, 58.
103 Brown letter, 18 Aug., enclosure 2, "NAS 9-119 (MAC Job 832), Estimated Tooling Manhour Expenditures by Element," C-58497, ca. 6 Aug.1961; Low and Sanders interviews.
104 Cf. "Mark II Mercury Spacecraft," C-57342, and "Mercury Spacecraft: Advanced Versions," McDonnell C-57978, ca. 27 July 1961.
105 "Estimated Engineering Manhour Expenditures by Element"; memo, James I. Brownlee for record, "Negotiation of Definitive Contract NAS 9-170, Project Gemini Two-Man Spacecraft Development Program," 13 March 1963; Low and Burke interviews; Project Mercury Status Report No. 13, for period ending 31 January 1962, p. 2.
106 Contract NAS 9-119, Amendment No. 1, 17 May 1961; Change order, Bailey to McDonnell, "Additional Engineering ManHour Requirements," 17 May 1961.
107 Letter, Bailey to Brown, "Contract NAS 9-119, Design Engineering Study for Mercury MK-II Spacecraft," PASO-B-2791, 9 Aug. 1961; "Estimated Engineering Manhour Expenditures by Elements."
108 Letter, Brown to Bailey, "Proposed Contract, MK-II Mercury Engineering Studies," 832-16-67, 25 Aug. 1961, with enclosure, "MK-II Mercury Engineering Studies," 8185-4, 25 Aug. 1961.
109 Bailey to McDonnell, "Amendment Nr. 1 to Letter Contract Nr. 6," NAS 5-59, 30 Aug. 1961.