Civilian Supersonic Cruise: The National SST Effort

The fascination for higher speeds of the 1950s and the new long-range comfortable jet airliners combined to create an interest in a supersonic airliner. The dominance of American aircraft manufacturers designs in the long-range subsonic jet airliner market meant that European man­ufacturers turned their sights on that goal. As early as 1959, when jet traffic was just commencing, Sir Peter Masefield, an influential avia­tion figure, said that a supersonic airliner should be a national goal for Britain. Development of such an airplane would contribute to national
prestige, enhance the national technology skill level, and contribute to a favorable trade balance by foreign sales. He recognized that the under­taking would be expensive and that the government would have to sup­port the development of the aircraft. The possibility was also suggested of a cooperative design effort with the United States. Meanwhile, the French aviation industry was pursuing a similar course. Eventually, in 1962, Britain and France merged their efforts to produce a joint European aircraft cruising at Mach 2.2.16

A Supersonic Transport had also been envisioned in the United States, and low-level studies had been initiated at NACA Langley in 1956, headed by John Stack. But the European initiatives triggered an intensification of American efforts, for essentially the same reasons listed by Masefield. In 1960, Convair proposed a new 52-seat modified-fuselage version of its Mach 2 B-58, preceded by a testbed B-58 with 5 intrepid volunteers in airline seats in the belly pod (windows and a life-support system were to be installed).[1070] The influential magazine Aviation Week reflected the tenor of the American feeling by proposing that the United States make SST a national priority, akin to the response to Sputnik.[1071] Articles appeared outlining the technology for supersonic cruise speeds up to Mach 4 with existing technology. The USAF’s Wright Air Development Division con­vened a conference in late 1960 to discuss the SST for military as well as civilian use.[1072] And in 1961, the newly created Federal Aviation Agency (FAA) began to work with the newly created NASA and the Air Force in Project Horizon to study an American SST program. One of the big questions was whether the design cruise speed should be Mach 2, as the Europeans were striving for, or closer to Mach 3.[1073]

Both Langley and Ames had been engaged in large supersonic air­craft design studies for years and had provided technical support for the Air Force WS-110 program that became the Mach 3 cruise B-70.[1074] Langley had also pioneered work on variable-sweep wings, in part draw­ing upon variable wing sweep technology as explored by the Bell X-5 in NACA testing, to solve the problem of approach speeds for heavy air­planes with highly swept wings for supersonic cruise but also required to operate from existing jet runways. Langley embarked upon develop­ing baseline configurations for a theoretical Supersonic Commercial Air Transport (SCAT), with Ames also participating. Clinton Brown and

F. Edward McLean at Langley developed the so-called arrow wing, with highly swept leading and trailing edges, that promised to produce higher L/D at supersonic cruise speeds. In June 1963, the theoretical research
became more developmental, as President John F. Kennedy announced that the United States would build an SST with Government funding of up to $1 billion provided to industry to aid in the development.

In September 1963, NASA Langley hosted a conference for the air­craft industry presenting independent detailed analyses by Boeing and Lockheed of four NASA-developed configurations known as SCAT 4 (arrow wing), 15 (arrow wing with variable sweep), 16 (variable sweep), and 17 (delta with canard). Langley research had produced the first three, and Ames had produced SCAT 17.[1075] Additionally, papers on NASA research on SST technology were presented. The detailed analyses by both contractors of the baselines concluded that a supersonic transport was technologically feasible, and that the specified maximum range of 3,200 nautical miles would be possible at Mach 3 but not at Mach 2.2. The economic feasibility of an SST was not evaluated directly, although each contractor commented on operating cost comparisons with the Boeing 707. Although the initial FAA SST specification called for Mach 2.2 cruise, the conference baseline was Mach 3, with one of the configu­rations also being evaluated at Mach 2.2. The results and the need to make the American SST more attractive to airlines than the European Concorde shifted the SST baseline to a Mach 2.7 to Mach 3 cruise speed. This speed was similar to that of the XB-70, so the results of its test program could be directly applicable to development of an SST. As the 1963 conference report stated, "Significant research will be required in the areas of aero­dynamic performance, handling qualities, sonic boom, propulsion, and structural fabrication before the supersonic transport will be a success.”[1076]