"The S-IVB is a UNIQUE people-carrying rocket."
- Max Hunter "It is the only rocket ever used to project humans away from the earth to another celestial body with the means to get them back."
The Saturn Rocket Family
The Saturn family of American rocket boosters was developed by a team of mostly German rocket scientists led by Wernher von Braun to launch heavy payloads to Earth orbit and beyond. Originally proposed as a military satellite launcher, they were adopted as the launch vehicles for the Apollo moon program. Three versions were built and flown: Saturn I, Saturn IB, and Saturn V. Saturn rockets were used in support of the Apollo lunar missions, the launch of the Skylab space station, Ferrying crews to and from Skylab, and to launch the American half of the Apollo-Soyuz Test Project.
NASA awarded Douglas Aircraft Company in Santa Monica one of few outside contracts to build a major part of the Saturn rocket. In his capacity of Chief Engineer of Space Systems at Douglas Aircraft Company, Max Hunter was responsible for the engineering for all Douglas space efforts, which included the Saturn rocket's I-VB stage (third stage).
32 Saturn rockets were; launched between 1961 and 1975. The Saturn family of rockets included the Saturn I (10 launches), Saturn IB (9 launches), the three-stage Saturn V (12 launches), and the two-stage Saturn V (1 launch). Although some flights experienced significant problems, no Saturn rocket failed catastrophically in flight.
Douglas awarded one of few outside contracts to build a major part of the Saturn.
At Huntsville, Alabama, on 6 January 1960, Abraham Hyatt, Deputy Director of Launch Vehicle Programs at NASA Headquarters, met with von Braun, Eberhard Rees (von Braun's technical adviser), and ABMA staff to ensure that S-IV contract procedures met NASA expectations. Hyatt got the ABMA team to loosen up a little on strict constraints that would limit the number of potential applicants; it was agreed that at least 20 companies would get specific invitations to submit proposals. Any other company could request to participate, although Hyatt felt that "most companies will realize that this is a 'big league' competition and I doubt that there will be any companies aside from those selected who would seriously consider submitting a full scale proposal."
During the all-day session at Huntsville, ABMA agreed to set up a technical evaluation team and a business evaluation team to analyze proposals from the various contractors. A source selection board, staffed by ABMA and NASA Headquarters representatives, would then review the findings of the evaluation teams and make a final recommendation to the Administrator. A calendar called for a bidders' conference at Huntsville, 26-27 January, contractor proposals submitted 29 February, and source selection board recommendations by 1 April. ABMA was also directed to submit second-stage specifications, a funding plan, and a management plan to Headquarters.
By the time of the bidders' conference, not all the S-IV specifications had been established. Rather than delay the conference, NASA and ABMA agreed to have bidders submit proposals for a stage to load 54 500 kilograms. Within a month, ABMA promised to determine the precise loading and use this figure in negotiating final details with the winning contractor. Von Braun explained this situation to the first session of the bidders' conference on 26 January. The prospective contractors got an extensive briefing from top NASA and ABMA managers and received a bulky packet of materials to use as guidelines in submitting proposals. The next day was spent answering questions. Following that, the prospective contractors had one month to prepare their detailed proposals; NASA and ABMA had the following month to evaluate them.3 After considering the scope of the project and the guidelines laid down by ABMA, only 11 contractors submitted proposals
The source selection board made its presentation to NASA Administrator T. Keith Glennan on 19 April 1960. By 26 May, Glennan had reviewed all the relevant materials, and NASA announced that Douglas Aircraft Company had been selected for further discussions leading to a  final contract for the S-IV stage.5 Douglas** and Convair had been the leading contenders, and Glennan finally based his decision on certain subjective factors. The findings of the Source Selection Board tended to give Convair a slight edge in technical competence, although Glennan remarked that "the Douglas proposal, in some ways, seemed more imaginative." Convair, however, scored lower in the business and management areas. No matter who was chosen, Glennan said, minor shortcomings in either the business or the technical areas could be easily corrected. Other reasons, therefore, favored Douglas.
Glennan pointed out that Convair would have a continuing business in liquid hydrogen rockets because of its own Centaur program. Moreover, the Centaur was ticketed for use in proposed Saturn vehicles as an upper stage called the S-V. Glennan apparently had a strong reservation about giving Convair the S-IV stage as well, because "a monopolistic position in this field seems possible." In short, Glennan chose Douglas because "broadening the industrial base in hydrogen technology is in the best national interest.
Douglas selection raises some eyebrows
The choice of Douglas, and the reasons for that choice, stirred a minor controversy. On 12 May, the Committee on Science and Astronautics, House of Representatives, asked the General Accounting Office to investigate NASA's selection of Douglas. The report of the General Accounting Office, dated 22 June 1960, generally sustained Glennan's statements on the matter and noted that his decision "was consistent with the written presentation of the Source Selection Board and other related documents." The report also supported the NASA position on problems concerning logistics and other questions.
During May and June, NASA, Huntsville, and Douglas went ahead with the negotiations that preceded the signing of a final contract. Meeting two or three times a week on the West Coast, conferees hammered out details of costs for planning, tooling, engineering, testing, and manufacturing. A second group worked out details of technical design and engineering and set up continuing working panels that included both government and contractor counterparts. This combination of close collaboration and monitoring by NASA set the pattern for future relationships with Douglas, as well as other stage contractors. During the succeeding months, decisions on engines, configurations, and missions influenced the evolution of the S-IV and led to two versions of its successor, the S-IVB.
S-IV significance and the influence of Thor
The special significance of the S-IV extended very quickly into the heart of the Apollo program. As noted earlier, the upper stage of the Saturn V played the final, truly critical role of the Saturn vehicle's job:  Earth orbit of the vital payload; then, a second burn for the translunar trajectory. This was the role of the eventual Saturn V third stage, the S-IVB, whose technology sprang from the recent technological past. "Just as Thor technology led us to the S-IV," Hal Bauer wrote, "the S-IV led to the S-IVB."
In the evolution of the hydrogen-fueled S-IV and S-IVB, Douglas drafted its designs against the mission profile and general requirements established by the Marshall Space Flight Center. Douglas engineers were not always happy with the close technical monitoring from Huntsville, a strong characteristic of the Marshall team. Differences were inevitable, given the pride and confidence of personnel on both the contractor's side and the customer's side. In retrospect, Douglas personnel emphasized their role in pushing ahead in many technical areas, apart from contributions by their counterparts in MSFC's well-equipped laboratories. Douglas people also emphasized their independence from Convair in the development and production of liquid- hydrogen-fueled upper stages, though Douglas did learn from Convair's experience. Contractor research carried out under the aegis of NASA was not proprietary; under NASA cognizance, Douglas and Convair held a number of technical discussions.
The S-IV was much more akin to Douglas's earlier experience with the Thor vehicle in terms of structural design materials and fabrication of the tankage. Moreover, the Centaur was a comparatively small vehicle. The S-IV was rather large, for its time, and the tankage concept was extrapolated from the Thor development.
The size of the original S-IV was significant but largely overshadowed in light of subsequent evolution of the Saturn V stages, the S-IC and the S-II. It should be remembered that the Saturn I and Saturn IB, with the S-I and S-IB first stages, respectively, relied on the somewhat makeshift design approach of clustered tanks to supply the requisite volume of propellant. The S-IV tankage was unique. Nothing that size had previously been attempted for any American rocket, and the liquid hydrogen fuel created unique design challenges. In many respects, then, the S-IV emerged as the first really definitive rocket stage of the Saturn program. It did not begin with a feasibility study; it was not a case of joining together existing tankage components and proven engines. The S-IV evolved as a result of requirements established by a comparatively elaborate mission profile, an untried engine design and exotic propellant combination, and unusual size. Its success, so early in the program, was a notable achievement of the manned space program and a credit to NASA, MSFC, Pratt & Whitney, and Douglas Aircraft Company.
In comparing the S-IV to the S-IVB, there was a strong consensus among those who worked on both that the `more advanced' S-IVB was, nevertheless, simpler. The earlier upper stage, with its cluster of six engines, created more design tangles than the single-engine S-IVB, even though the latter had to have the capability to restart in space. Some of the instrumentation for the S-IVB was more sophisticated, but aside from the engine, there were no major differences between the two. The electronics, including the circuitry and design for the propellant utilization probe, for example, passed easily from the S-IV to the S-IVB.
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