Although the mobile launch concept would not reach fruition for another year, by July 1961 its four major features were clear:
The Debus-Davis Report represented considerable progress since the Study Office's May report. All aspects of the Saturn concept were described in greater detail, particularly the automated checkout. The flexibility that would characterize LC-39 was evident. The basic concept assumed a launch rate of 26 Saturns per year, but LOD plans allowed for additional pads and assembly bays to accommodate higher launch rates and special missions involving the launch of several vehicles in a brief period. Expediency dictated that rail be the only form of transfer considered. There was not enough time to prepare good cost estimates for canal and road. Further, LOD officials were confident from their LC-34 experience that a rail system would work.49
One of the initial mobile concepts, the horizontal transfer, had been eliminated by mid-1961 and was not mentioned in the Debus-Davis study. In its May report the Study Office had noted "certain operational limits of the horizontal transfer which might prohibit good reliability."50 The statement reflected Albert Zeiler's concern that inspectors would damage wires and tubing during checkout of a horizontal vehicle. (During a vertical checkout workers would stand on platforms extending around the rocket. With the vehicle in a horizontal position, it would be difficult to keep workers from damaging the rocket's thin skin.) Maintenance of umbilical connections during a horizontal transfer was another problem. Fear of the stresses generated in lifting a large launch vehicle from a horizontal to a vertical position was the third and decisive consideration leading to the concept's demise. Huntsville engineers were aware of the strain placed on the 21-meter Redstone's joints and outer skin during this operation. The stress on the 70-meter Saturn might well be excessive.51
Mobile concept as described in the Debus-Davis report of July 1961.
The Saturn C-3 (liquid) launch complex plan comprised a vertical assembly building (VAB), a launcher-transporter, an arming area, and launch pad. The VAB would consist of assembly bay areas for each of the stages, with a high bay unit approximately 110 meters in height for final assembly and checkout of the vehicle. Buildings adjacent to the VAB would house the Apollo spacecraft and the launch control center. The launcher-transporter would incorporate three major facilities: a pedestal for the space vehicle, an umbilical tower to service the upper reaches of the space vehicle, and a rail transporter. An arming tower would stand about midway between the assembly building and the pads. The Apollo Saturn would carry a number of hazardous explosives: the launch escape system (the tower on top of the vehicle that lifted the spacecraft away from the launch vehicle in case of an emergency), retrorockets to separate the stages, ullage rockets to force fuel to the bottom of tanks, and the launch vehicle's destruct system. Launch officials wanted to install these solid-propellant items in an area apart from the rest of the operation.52
By July 1961 LOD engineers had fixed the requirements for the mobile launch concept's electrical checkout. These were fourfold: first, the electrical ground support equipment was to be designed so that checkouts could be conducted simultaneously on vehicles in the VAB and on the pad; second, the electrical systems of the vehicle and launcher-transporter would remain intact after checkout in the VAB; third, the launch control center would be able to launch rockets at a distant pad and check vehicles in the nearby VAB; and fourth, there would be a minimum of connecting cables between the launch pads and the control center because of the distances involved. The plan required the use of two digital computers, one located on the launcher-transporter and the other in the launch control center. The former would be used for checkout of the launch vehicle both at the VAB and on the pad. The performance of the computer on the launcher-transporter would be remotely controlled by the computer in the launch control center. Two firing rooms were necessary - one for control of checkout procedures in the VAB and the other for launch pad operations.53
The significance of the initial mobile launch studies lay more in the timing than in the content. LOD officials would not agree on a final concept for another year. By mid-1961, however, they were confident that some form of vertical transfer would work. Debus's initiative in February 1961 provided LOD time to examine the concept and make some reasonable judgments. When the Kennedy administration announced the lunar landing program in May 1961, LOD officials had a suitable launch concept in mind. Without the three months gained by the February decision, it is doubtful that LOD would have ventured on a new launch concept. The Apollo facilities might well have resembled a larger LC-37.54
49. Debus-Davis Report, passim; Owens interview, 12 Apr. 1972.
50. MSFC, Interim Report on Future Saturn Launch, p. 16.
51. Zeiler interview, 11 July 1972; von Tiesenhausen interview, 29 Mar. 1972.
52. Debus-Davis Report, pp. B-1 through B-7.
53. Ibid., pp. B-9, B-10.
54. The authors are indebted to Rocco Petrone for this idea: interview of 25 May 1972 and remarks delivered by Petrone to Apollo History Workshop, NASA Hq., 19-21 May 1971.