B377SG Super Guppy
Even before the Pregnant Guppy had won its first NASA contract, Conroy was writing to von Braun about a successor aircraft equipped with powerful turboprop engines and large enough to transport the S-IVB. NASA did not seriously consider the second-generation Guppy until the original Pregnant Guppy had demonstrated its worth. Robert Freitag, NASA Headquarters' Director, Manned Space Flight Center Development, wrote von Braun in early 1964 noting the "outstanding success we have enjoyed with the Pregnant Guppy." In addition to the Pregnant Guppy's use by MSFC to carry rocket stages, Freitag said the Manned Spacecraft Center in Houston was anxious about having a backup aircraft available. Freitag envisioned three possibilities: acquire a similar Pregnant Guppy and rely on water transport for the S-IVB and S-II stages, acquire a larger type for S-IVB operations and leave the S-II to water transport, and acquire an S-II-size aircraft that could also handle the smaller S-IVB. Any of the three possibilities could meet the logistical requirements of the Houston center, but a decision was needed soon; the timing for production and delivery of Saturn rocket stages to the Cape to meet launch schedules was in question. "Since time is of the essence, Freitag concluded, "I would appreciate receiving your recommendations including advantages and technical funding plan for accomplishing our objectives at the earliest possible date."
Evidence suggests that MSFC gave serious thought to a mammoth aircraft capable of handling a rocket stage the size of the S-II. On 2 February 1964, MSFC drafted a request for quotation titled "Large Booster Carrier Aircraft." The document suggested the development of either an airplane or a lighter-than-air vehicle capable of transporting the S-II (or S-IVB) to test sites in southern Mississippi and the Cape. "In any case, the program is to be characterized by austere funding and early delivery schedules." Several companies proposed various schemes, including the use of modified B-36 bombers or English-built Saunders-Roe Princess flying boats.40 None of these plans ever materialized. NASA concluded that an S-II cargo aircraft would take too long to develop and would cost too much. Also the number of planned Saturn V launches was revised downward, reducing the requirements for S-II transportation. The S-IVB, however, was programmed for frequent launches in both the Saturn IB and Saturn V class of vehicles, so the desire for a backup airplane persisted.41 With its Boeing Stratocruiser inventory, Aero Spacelines proved to be ahead of any competition in supplying a second volumetric air transport.
As before, Aero Spacelines developed the new aircraft with its own resources, although personnel from MSFC came to California to cooperate on the design studies, and a flight-test expert from NASA's Flight Research Center at Edwards, California, worked very closely with the design team. Originally dubbed the B-377 (VPG) for "Very Pregnant Guppy," the second-generation plane finally emerged as the "Super Guppy," or B-377 SG. The larger, heavier cargoes for the Super Guppy required increased horsepower. Although parts of three other B-377 aircraft were incorporated into the Super Guppy, the cockpit, forward fuselage and wing sections, and the engines came from a Boeing C-97J, an Air Force transport version of the commercial Stratocruiser. This aircraft had Pratt & Whitney turboprop engines. Conroy realized that it was imperative for his big new airplane to have the more efficient and powerful turboprop powerplants. Conroy had learned from his contacts in the Air Force that the C-97J airplanes were headed for retirement, and he had hoped to get the airframes as salvage and the engines on a low-priced lease. Conroy succeeded, with NASA lending special assistance in securing the engines. During the spring of 1965, NASA's Office of the Administrator made overtures to the Air Force: "We definitely feel that it would be in the public interest and advantageous to the government if these engines were made available" to transport rocket stages, engines, and other large cargoes. "Under these circumstances," NASA explained, "we would appreciate it if you would approve the proposed lease." Conroy got his engines, and the Super Guppy began acceptance tests before the year was out.
NASA wanted to put the aircraft in service early in 1966, after the plane had proved its flying capabilities, although final FAA certification came later in the spring. John C. Goodrum, chief of MSFC's Project Logistics Office, felt that the utility of the Super Guppy was of such importance that it should be considered operational for "critical cargoes" on a "limited basis" as soon as possible. Although FAA examiners had not yet flown the Super Guppy by March, Goodrum urged operational  service based on the judgment of NASA's own test pilots at Edwards that the plane was satisfactory for transport duties. He advised NASA Headquarters that MSFC planned "immediate utilization" of the airplane to ship a Saturn instrument unit manufactured by IBM in Huntsville. The Super Guppy landed at Huntsville within a week, apparently by special arrangement with the FAA, and flew the IU to the Douglas plant at Huntington Beach for systems testing with an S-IVB stage. The plane made a return trip before the end of the month and delivered another S-IVB test stage to MSFC.
As the Super Guppy became fully operational during 1966, its success reflected the expertise accumulated in missions using its predecessor. The Super Guppy's cargo was loaded from the front, and the entire forward section of the fuselage was built to swing aside on hinges just ahead of the wing's leading edge. This modification added to the ease and swiftness of its operations, and was largely dependent on the ground support techniques and equipment developed for the Pregnant Guppy in the early 1960s. After modification, equipment designed for the S-IV served equally well for the larger S-IVB. The cargo lift trailer (CLT) became a major item in the support equipment developed for handling space hardware as air cargo. The CLT was developed at MSFC and operated on the scissor-lift principle to raise its load for transfer into the cargo hold of the airplane. The CLT could also be used as a transporter over short distances. A movable pallet supported the S-IV on the CLT. The pallet had cradle supports fore and aft that were linked to the pallet with shock mounts of an oil-spring type. The CLT raised the pallet to the loading level of the cargo bay, then the pallet was rolled off and secured inside the aircraft. For aerial shipment, ground crews did not use the shroud that protected the rocket stage during water transport. Instead, engineers designed lightweight covers to fit over the exposed areas fore and aft, and a bank of static desiccators in the propellant tanks comprised the environmental control system while airborne. In a typical delivery sequence, the rocket stage moved eight kilometers overland from the Douglas plant at Huntington Beach to the Los Alamitos Naval Air Station. After loading the stage, the pilots flew north to Mather Air Base, not far from SACTO. When stage tests were completed, the final leg of the airborne logistics sequence concluded with delivery at Cape Kennedy for preflight checkout and launch.
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