When NASA planning had first focused on flight around the Moon rather than landing on it, rendezvous lacked any urgency. Orbital operations seemed a matter of expedience, a way of making do with smaller boosters than direct ascent demanded. Circumlunar flight, too, could be launched with smaller boosters, but without any need for rendezvous, and a lunar landing appeared to be a long way off. Nobody denied that larger launch vehicles would be an asset to the American space program,  and nothing suggested that building such vehicles would pose any special problem other than time and money. Rendezvous, on the other hand, was an unknown. How hard it might be, how dangerous, could not be predicted. Nobody denied that rendezvous could be a useful and important technique, but planning the lunar mission around it appeared unnecessarily risky. Under the circumstances, direct ascent could be defended as more prudent.
Kennedy's decision changed all that. Gone were the long stretches of time that had allowed the choice between rendezvous and direct ascent to seem less than urgent. NASA now had to select the method that offered the best prospect for meeting the deadline. Even before it was announced, but knowing that a decision was imminent, NASA began seeking the answer.
On 2 May, Associate Administrator Seamans formed a task group to explore "for NASA in detail a feasible and complete approach to the accomplishment of an early manned lunar mission."40 Most members of the ad hoc group came from NASA Headquarters, as did its chairman, William A. Fleming, then acting as Assistant Administrator for Programs.* 41 Fleming had been working closely with Seamans for several months and had, in fact, drafted the Seamans memorandum that created the task group.
The Fleming Committee had four weeks to size up the scope of the task that NASA faced. This was a tall order for so short a time, and the committee felt compelled to limit itself to one approach.42 It elected direct ascent as "the simplest possible approach - the approach of least assumptions and least unknowns."43 Rendezvous, much the biggest unknown, had no place in the lunar landing program, although it was "an essential program in its own right."44 Having dismissed rendezvous, the Fleming group devoted most of its effort to choosing between solid and liquid propellants for the first stages of Nova-class boosters.45 While this did permit the group to pinpoint some crucial decisions that needed to be made quickly - especially the importance of an early choice of sites for the large ground facilities the lunar mission required46 - it merely avoided the question of rendezvous versus direct ascent. Convinced, as Fleming later remarked, "that it was always possible to 'build something bigger and make it work,'"47 his committee saw no reason to base its study on a risky and untried alternative.
 Others in NASA were not so sure. On 19 May, while the Fleming Committee was still meeting, John Houbolt wrote Seamans from Langley deploring the state of the launch vehicle program and urging more serious attention to rendezvous. He denied any wish to argue for rendezvous against direct ascent but insisted that, "because of the lag in launch vehicle development, it would appear that the only way that will be available to us in the next few years is the rendezvous way. For this very reason I feel it mandatory that rendezvous be as much in future plans as any item, and that it be attacked vigorously."48
This was a viewpoint that Seamans, long a student of orbital rendezvous and openly receptive to such ideas since joining NASA, must have shared. On 25 May, he called on Don R. Ostrander, Director of Launch Vehicle Programs, and Ira H. A. Abbott, Director of Advanced Research Programs, to name "a group of qualified people . . . to assess a wide variety of possible ways for executing a manned lunar landing." Seamans wanted their report quickly, "at about the same time as the one under way by the Ad Hoc Task Group on Manned Lunar Landing." NASA Headquarters furnished none of the six members of this committee, led by Bruce T. Lundin of Lewis Research Center.** 49 Lundin regarded his committee as speaking for the field centers, in contrast to the Headquarters viewpoint expressed by the Fleming group.50 The Lundin report was ready by 10 June, a week before the Fleming report.
Although Lundin's committee discussed other matters, its main concern was to compare the several rendezvous schemes with each other. It pointedly excluded any specific comparison of rendezvous with direct ascent but noted two inherent advantages in rendezvous that promised an earlier manned lunar landing. One was the relative capacity of a rendezvous-based program to absorb increases in a payload weight, which meant that early decisions on booster design and development might not so critically affect the program. The other was the smaller size of launch vehicles required by a rendezvous mission, a size which would not call for the development of large new engines.51
Time limited the Lundin Committee to a brief qualitative survey, which could not compare in scope or detail to the elaborate quantitative assessment provided by the Fleming Committee.*** 52 Clearly, however, the choice between solid or liquid propellants in the first stage or  two of a Nova booster was too restricted; the proper alternative to direct ascent was some form of rendezvous. This proposition won unanimous agreement at a meeting between Seamans and the program directors.**** On 18 June, though only after considerable discussion, they decided to pursue two courses. Ostrander would form a team from NASA Headquarters and Marshall to define an overall plan for using orbital operations to achieve manned lunar landing. At the same time, the Fleming Committee study of direct ascent would be paralleled by an equally intensive investigation of the rendezvous and orbital operations approach.53
The first line of action under Ostrander produced a preliminary project development plan for orbital operations by mid-September.54 For the second, Seamans formed still another ad hoc group that was "to establish program plans and supporting resources necessary to accomplish the manned lunar landing mission by the use of rendezvous techniques" with as much rigor as the Fleming report. He named Donald H. Heaton, his former assistant who had become Assistant Director for Vehicles in Ostrander's office, as chairman of the new group.55
Heaton's group was about the same size as Fleming's, but its members were more evenly divided between Headquarters and the field centers.# Its findings, issued late in August, concluded that "rendezvous offers the earliest possibility for a successful manned lunar landing."56 Despite this parade of studies, as future events were to show, the issue had only been joined, not settled. But the view that rendezvous techniques were important enough to pursue "whether or not rendezvous is selected as an operating mode" for the lunar mission57 was clearly gaining strength. And this viewpoint was crucial to the fate of Mercury Mark II, which had in the meantime taken on a much more sharply defined form.
* Of the 23 members of the Fleming Committee, 18 were from NASA Headquarters: Fleming, Addison M. Rothrock, Albert J. Kelley, Berg Paraghamian, Walter W. Haase, John Disher, Merle G. Waugh, Eldon Hall, Melvyn Savage, William L. Lovejoy, Norman Rafel, Alfred Nelson, Samuel Snyder, Robert D. Briskman, Secrest L. Berry, James P. Nolan, Jr., Ernest Pearson, and Robert Fellows. Remaining members were Koelle, Marshall; Kleinknecht and Alan Kehlet, STG; A. H. Schwichtenberg, Lovelace Foundation; and William S. Shipley, Jet Propulsion Laboratory.
** Lundin's Committee consisted of Walter J. Downhower (Jet Propulsion Laboratory), Alfred Eggers (Ames Research Center), Laurence Loftin (Langley), Harry O. Ruppe (Marshall), and Lt. Cot. George W. S. Johnson (Air Force).
*** The Lundin Committee met during the week of 5 June 1961. Most of its sessions were devoted to presentations by Ames, Langley, Lewis, and Marshall on Earth orbit rendezvous, by Langley and Marshall on lunar orbit rendezvous, and to a general discussion of rendezvous proposals.
**** The meeting was attended by Seamans, Silverstein, Abbott, Ostrander, Siepert, DeMarquis D. Wyatt, and Charles H. Roadman (who had replaced Clark Randt as Director of Life Sciences Programs).
# The members were Heaton, Richard B. Canright, L.I. Baird, Rafel, McGolrick, Louis H. Glassman, John L. Hammersmith, Briskman, Nolan, Warren J. North, and William H. Woodward, from NASA Headquarters; Wilson B. Schramm, R. Voss, Koelle, Peter J. deFries, and Harry Ruppe, of Marshall; John Houbolt and Hewitt Phillips, from Langley; Hubert M. Drake, from Flight Research Center; and J. Yolles, Air Force System Command.
40 Memo, Seamans to Dirs., Offices of Space Flight, Launch Vehicles, Advanced Research, and Life Sciences Programs, "Establishment of Ad Hoc Task Group for Manned Lunar Landing Study," 2 May 1961.
41 [William A. Fleming et al.], "A Feasible Approach for an Early Manned Lunar Landing," Report of the Ad Hoc Study Group, 16 June 1961, p. i.
42 Memo, Fleming to Eugene M. Emme, "Comments on Gemini History, Draft Chapters I and II," 5 Aug. 1969, with enclosure, subject as above, pp. 2, 5.
43 Fleming, interview, 6 Aug. 1968, as quoted in John M. Logsdon, "NASA's Implementation of the Lunar Landing Decision," NASA HHN-81, September 1968, p. 9.
44 "A Feasible Approach," Part I, "Summary Report of Ad Hoc Task Group Study," p. 2.
45 Ibid., pp. 32-47.
46 Letter, Seamans to Emme, 8 Jan. 1969.
47 Logsdon, "NASA's Implementation," p. 9.
48 Letter, John C. Houbolt to Seamans, 19 May 1961; Houbolt, interview, Princeton, N.J., 5 Dec. 1966.
49 Memo, Seamans to Dirs., Launch Vehicle and Advanced Research Programs, "Broad Study of Feasible Ways for Accomplishing Manned Lunar Landing Mission," 25 May 1961; Bruce T. Lundin et al., "A Survey of Various Vehicle Systems for the Manned Lunar Landing Mission," 10 June 1961.
50 Letter, Lundin to Seamans, 12 June 1961.
51 Lundin et al., "A Survey," pp. 26-27; Lundin letter, 12 June 1961.
52 Memo, H. Kurt Strass to Dir., "Visit to NASA Headquarters, June 6, 1961, by H. Kurt Strass, Apollo Projects Office," 8 June 1961; Logsdon, "NASA's Implementation," p. 12.
53 Memo, D. D. Wyatt for record, "Discussions with the Associate Administrator on June 15, 1961," 20 June 1961.
54 "Orbital Operations Preliminary Project Development Plan," compiled by MSFC Committee for Orbital Operations, P. J. deFries, chairman, 15 Sept. 1961.
55 Memo, Seamans to Dirs., Launch Vehicle, Space Flight, and Advanced Research Programs, and Acting Dir., Life Science Programs, "Establishment of Ad Hoc Task Group for Manned Lunar Landing by Rendezvous Techniques," 20 June 1961.
56 [Donald H. Heaton et al.], "Earth Orbital Rendezvous for an Early Manned Lunar Landing," Part I, "Summary Report of Ad Hoc Task Group Study," Ad Hoc Task Group for Study of Manned Lunar Landing by Rendezvous Techniques, August 1961, pp. i, 3, 89 (emphasis in original).
57 Ibid., pp. 8 (emphasis in original), 89.