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Boeing 2707 SST

The Boeing 2707 SST was to be the first American supersonic airliner. It would have been built at the Boeing plant in Renton, Washington. President John F. Kennedy committed the government to subsidizing the development of a commercial airliner to compete with the Concorde & Russia's TU-144. Ultimately, Boeing's swing-wing design was selected as the winner of the US SST competition. They called their SST the Model 2707. Whereas the Concorde and TU-144 cruised at M = 2.2 to 2.4, and the Boeing design cruised at M = 2.7, hence 2707.

In the early 1960s, the Bristol Aeroplane Company (which later became part of the British Aircraft Corporation (BAC)) in England and Sud-Aviation (which later became Aerospatiale) in France were both working on designs for a supersonic passenger airliner. They both came up with very similar designs for a delta-wing aircraft which could carry about 100 passengers and fly at about Mach 2.2 (1,400 mph). They also both discovered that the development costs of such an aircraft would be so high that neither nation could afford to build it. In November 1962, an international agreement was signed which would allow BAC and Sud-Aviation to jointly build the aircraft, and the governments of Britain and France would share the development costs. Thus, the Concorde was born.

At that time, unknown to anyone in the Western World, the Soviet Union was also working on a supersonic transport (SST) known as the TU-144. The TU-144 was very similar to the Concorde in size and shape, but was designed to fly a little faster at Mach 2.35 (1,500 mph).

The SST took shape as a response to the joint Anglo-French venture, the Concorde. Like the 747, the push for supersonic commercial flight demanded heavy dollops of advanced technology. The Concorde and SST programs were marked by politics. The politics featured international agreements, competing centers of influence in Washington, congressional hearings, and the rise of environmentalism as a major popular movement.

This challenge was too serious for President Kennedy to ignore. The United States, not to be outdone, decided to enter the SST competition. America's planebuilders had nothing like Concorde in the offing. Moreover, there was never any prospect that an American SST would go forward as a purely commercial venture, with corporations raising the needed funds through bank loans and sales of securities. The costs of an SST would be too great, as were the technical uncertainties. In addition to this, airline executives, busily purchasing the current generation of jets, were far from thrilled at the thought of being stampeded into a supersonic era.

The Concorde and the TU-144 already had a head start. The program launched in 1963, and the Federal Aviation Administration estimated that by 1990 there would be a market for 500 of the craft. Due to its late start, it was evident that the 2707 could not beat either the British or the Russian SST into service and lost both public and government support.

The project was eventually canceled before the 2707 ever flew. Political, economic, and environmental factors led the United States to cancel the project. In March 1971, the US Senate rejected further funding and the project was cancelled 20 May 1971. At the time, there were 122 unfilled orders by 26 airlines, including PanAm, Continental, American Airlines and TWA. The two prototypes were never completed.

The B2707-300 mockup was disassembled and shipped to Central Florida, where it sat in a scrapyard on Merritt Island near Kennedy Space Center for 19 years. The owner of the mockup, Mr. Bell, died suddenly and his aerospace relics and treasures were auctioned off. The translating nose and forward fuselage was purchased and partially reassembled for display at the Hiller Aviation Museum in San Carlos, California. The remainder of the mockup was destroyed. The details of the demise of the B2707-200 mockup are unknown.

Future SST

As envisioned by NASA's High-Speed Research (HSR) program, the next-generation High-Speed Civil Transport (HSCT) would fly 300 passengers at 2.4 times the speed of sound - crossing the Pacific or Atlantic in less than half the time presently required on modern subsonic, wide-bodied jets - at an affordable ticket price, estimated at less than 20 percent above comparable subsonic flights. The technology to make the this HSCT possible is being developed by an unprecedented teaming of major U.S. aerospace companies in the multi-year HSR program. Although actual development of such an advanced supersonic transport (SST) is currently on hold, commercial aviation experts estimate that a market for up to 500 such aircraft could develop by the third decade of the 21st Century.

Phase I of the HSR program, which began in 1990 and continued through 1995, focused on environmental challenges: engine emission effects on the atmosphere, airport noise and the sonic boom. Much research remains to be accomplished in these and other areas, but Phase I established some clear lines of approach to major problems and spawned confidence among team members that environmental concerns can be satisfied.

Phase II, initiated in 1994, focused on the technology advances needed for economic viability, principally weight reductions in every aspect of the baseline configuration, because weight affects not only the aircraft's performance but its acquisition cost, operating costs and environmental compatibility. In materials and structures, the HSR team is developing, analyzing and verifying the technology for trimming the baseline airframe by 30-40 percent; in aerodynamics, a major goal is to minimize air drag to enable a substantial increase in range; propulsion research looks for environment-related and general efficiency improvements in critical engine components, such as inlet systems. Phase II includes computational and wind tunnel analyses of the baseline HSCT and alternative designs. Other research involves ground and flight simulations aimed at development of advanced control systems, flight deck instrumentation and displays.

In December 1995, a single aircraft concept was chosen to focus the intensive technological development planned for the next three years of the HSR program. This aircraft, the Technology Concept Aircraft (TCA), is not an actual design or airplane that will be built, but rather serves as a common reference point for HSR technology development. The TCA evolved from separate Boeing and McDonnell Douglas HSCT designs. Computer modeling and wind tunnel tests were used to produce a single concept with superior aerodynamic performance and operational characteristics, which also satisfied environmental goals. The technology focus also was significantly narrowed in the areas of propulsion and airframe structural components. Technical challenges remain in each area, however, though significant progress has been made.

Improvements in materials, structural, and systems technology that are available or currently being developed could make a second generation of supersonic aircraft more widely affordable. Studies have concluded that an aircraft with between 250 and 300 seats cruising at Mach 2 to 2.4 (at altitudes between 16 and 20 km) is most likely to be successful. To make such aircraft effective for the long overseas routes that benefit most from the increased speed and maintain viability with regard to viewpoint of sonic booms, the projected range must be at least 8000 km (and possibly 10400 km).

The Concorde has already demonstrated the practicality of Mach 2.05 as an achievable cruise speed with aluminum alloys for the basic structure. For speeds above Mach 2.2, more exotic materials would be required including titanium alloys and organic composites for structural items and more complex air intakes. At speeds between Mach 2 and 2.4, airframe characteristics currently dictate cruise altitudes between 16 and 20 km. Optimization studies are planned to investigate lower cruise altitudes, recognizing the potential benefit of minimized ozone impact. To enable the inclusion of route segments over populated areas without sonic booms, an advanced supersonic airliner must also be capable of cruising efficiently in an environmentally acceptable manner at subsonic speeds and lower cruise altitudes.

Studies have examined a wide range of speeds and concluded that speeds higher than Mach 2.4 offer little gain in block time, whereas they exacerbate airframe materials and propulsion problems, hence increase technical risk. Prior projections concluded that aircraft with a cruise speed of Mach 2.0 to 2.4 were feasible for entry into service in 2005, and a hypersonic vehicle cruising at Mach 5 might enter service by about 2030. Events have shown that these projections were optimistic, and it is unlikely that a new Mach 2 to 2.4 vehicle will enter service much before 2020. By the same token, required research for the hypersonic vehicle and its economics would make entry into service of a hypersonic vehicle unlikely before 2050 - and possibly later unless scheduling and airport curfews could be accommodated to demonstrate higher cruise speed benefits. Therefore, the focus of the remaining discussion is on vehicles cruising at speeds up to Mach 2.4.

The NASA High-Speed Research (HSR) Program was phased out in fiscal year 1999.

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