There is little controversy with respect to the influences that originally led to setting the desired width of the shuttle payload bay at 15 feet. They were both NASA’s space station crew and cargo payloads and a potential new upper rocket stage—a space tug—for moving national security and other payloads from the shuttle’s low Earth orbit to higher altitudes, particularly geosynchronous orbit.
It is also now clear which payload defined the need for a 60-foot long payload bay. In an 1997 interview, Hans Mark, who as both Under Secretary and Secretary of the Air Force during the administration of President Jimmy Carter (1977-1981) had concurrently served from August 1977 to October 1979 as the director of NRO, commented that “the shuttle was in fact sized to launch HEXAGON.” This photo-intelligence satellite, also known as KH(Keyhole)-9 and nicknamed “the Big Bird,” was under development in 1969 as the successor to the Corona satellites, which had been operating since 1960 to provide broad area photographic surveillance of various regions of the world. Hexagon was a very large object, only ten feet in diameter but almost 60 feet long. The satellite would weigh over 30,000 pounds when fully loaded with film for its four entry capsules that would return exposed film to Earth.15
The existence of Hexagon was in 1969 classified at a very high level, above “Top Secret”; thus it could not be mentioned in the DOD/NASA report, which bore only a lower-level “Secret” classification. As Mark suggested, Hexagon was used to “size” the payload bay; originally there were no plans to actually launch it on the shuttle, since the Hexagon program would be reaching the end of its likely service life as the shuttle began operational flights in the late 1970s or early 1980s.16 Air Force and NRO planners judged that whatever system would be the follow-on to Hexagon would likely be equally as large, and Hexagon thus could serve as a surrogate for that future system in determining an appropriate payload bay length.
Less clear is which potential Air Force or NRO missions drove the requirement for a shuttle to have a high cross-range capability. No prior actual national security space system had been required to maneuver to return to Earth, since all were expended after completing their mission. However, the Air Force had pursued from the late 1950s until it was canceled in 1963 a research program called Dyna-Soar, which involved developing a small glider-like winged vehicle that would be launched into orbit on an expendable booster and would have cross-range capability upon its return to Earth. The idea of a piloted space system that could be brought back to a secure base after a one-orbit or short-duration mission remained attractive to national security planners, but that idea had not gone through the typical rigorous review to establish it as a firm national security requirement. Air Force Secretary Robert Seamans suggested that the cross-range requirement was advocated by “operational types,” not the top Department of Defense, Air Force, or NRO leadership.17
The DOD/NASA report had mentioned a “single pass” mission with an unspecified launch location and requiring 1,400 nm of cross-range to return to a location near Washington, DC, presumably so that the intelligence products obtained during the mission could be rushed to top-level decision makers. None of the subsequent discussions of national security shuttle flights discussed such a mission profile; it seemingly reflected the aspirations of those who prepared the 1969 report. Missions taking off and landing at Vandenberg Air Force Base on the California coast (or some other Western launch site18) were much more prominent in later discussions. If the space shuttle were to carry out a one-orbit mission launched from Vandenberg, the shuttle would have to have at least 1,100 nm of cross-range to return to a secure runway at that Air Force base.
A clue to the character of missions that required high cross-range can be found in studies performed by NASA in 1973, after the shuttle entered its development phase. By then, NASA had already done considerable work in designing “reference missions” for two uses of the shuttle—placing a satellite in geosynchronous orbit and resupplying a spacecraft in low Earth orbit. In 1973 NASA developed two new reference mission scenarios for single-orbit shuttle flights from Vandenberg Air Force Base. These reference missions were “representative of Air Force requirements on the shuttle.” One of the two missions, designated 3A, would deploy a satellite into a 104 degree, 100 nm polar orbit; the shuttle would return to Vandenberg after one orbit. The satellite to be deployed would weigh 32,000 pounds and was ten feet in diameter and 60 feet long; it would almost certainly be the follow-on photointelligence satellite to Hexagon. It would be deployed less than 24 minutes after launch. NASA noted that “the mission of the payload is beyond the scope” of the reference mission description, likely referring to its intelligence objectives. The second mission, designated 3B, after carrying out a rendezvous within 25 minutes of launch, would retrieve a similar satellite and return it to Vandenberg after a single orbit.19
So were satellite deployment or retrieval the missions that defined the needed shuttle cross-range capability? Or was it also, or even primarily, the hope of national security planners to be able to fly an on-demand mission in polar orbit to get crisis-related information on what was happening at a flashpoint anywhere in the world, such as the mission landing in Washington, DC, mentioned in the DOD/NASA report? This latter speculation is supported by a letter drafted in late 1971 for then NASA Administrator James Fletcher to send to Deputy Secretary of Defense David Packard as NASA sought DOD support for the shuttle program. The draft letter suggested that “the shuttle could be maintained on ready alert, making possible rapid responses to foreseeable and unexpected situations”; such a mission could examine “unidentified and suspicious orbiting objects”; enable “capture, disablement, or destruction of unfriendly spacecraft”; and make possible “rapid examination of crucial situations developing on earth or in space.”20
The DOD/NASA report also mentioned launches of “self-contained mission modules which possessed their own crews to operate specific mission equipment.” Might these “mission modules” have carried the human – operated KH-10 very high-resolution camera system, code named Dorian, developed during the 1960s for the Manned Orbiting Laboratory (MOL) program? That program was canceled on June 10, 1969, just as the DOD/ NASA shuttle report was being prepared. The MOL combined a capsule based on NASA’s Gemini spacecraft, to be used during launch and reentry, and a two-segment module containing the Dorian camera system and crew quarters. The 1971 NASA draft letter said, “the shuttle could be equipped to perform the MOL mission for seven days on station. . . Alternatively, the shuttle could transport MOL-like equipment in a self-supporting module to the desired orbit for operation over a longer period of time.” Such missions would most likely have been launched into polar orbit so they would overfly all areas of the world, and would return to Vandenberg at their completion, thus requiring cross-range capability.21
The need for high cross-range was throughout the shuttle debate a point of contention between NASA and the national security community. In reality, requirements for national security missions requiring high cross-range were never formalized and more or less evaporated during the 1970s. Well before that time, however, NASA had decided that a shuttle having significant maneuvering capability as it returned from orbit was needed to survive the heat of entry into the atmosphere. So while the national security cross-range requirement initially drove NASA to a particular shuttle orbiter design, one with delta-shaped wings and the thermal protection needed to resist high temperatures during a maneuvering entry, NASA likely would have adopted a similar design even if that requirement had not been levied in 1969. Whether NASA would have gone forward with a shuttle having a 15 x 60 foot payload bay and powerful enough to launch the most heavy national security payloads is not as clear; in the final days of the shuttle debate in December 1971, NASA put forward a somewhat smaller and less powerful shuttle as its proposed design.