Why We Don’t Have an SST

Ask why there was no replacement for the Concorde, which retired in 2003, and people will tell you that supersonic commercial flight is uneconomical. It’s not necessarily true. A supersonic transport (SST) is within the state of the art, but attempts to build one have been misdirected by politics and entrenched business interests, with a dash of class warfare.

In an October 1986 conference on SSTs, FedEx, Northwest Airlines, and McDonnell Douglas all talked as if they were ready to start building a Mach  5 commercial airplane the next day. Four years later, NASA launched its High-Speed Research program, with the focus being a High Speed Civil Transport that could cross the Atlantic or Pacific oceans in less than half the time of subsonic jets. But before any work started, NASA decided the HSCT would not be a premium-price airplane like the Concorde but a 300-seater with fares only 20 percent higher than those for subsonic jets.

This admirably democratic goal ensured that the airplane would be frighteningly big, around 300 feet long. Even though the speed had been cut to Mach 2.4—20 percent faster than the Concorde—the sheer size added challenges to a concept that already had all it could handle. Just building the huge compressor and turbine wheels for the engine was hard, and the noise suppressors (which mixed the jet exhaust with outside air) would have been the size of Winnebagos.

The U.S. commercial airplane industry had by then shrunk to two competitors: dominant Boeing and McDonnell Douglas, the latter being edged into worldwide third place by Europe’s Airbus. A good many people in McDonnell Douglas saw the HSCT as a comeback opportunity. Boeing, which in the 1960s had designed a failed SST (the 2707), saw it as a flashback of a bad memory.

In an upset victory in November 1996, Boeing became one of two finalists (along with Lockheed Martin) in the Joint Strike Fighter program, seen as the future of U.S. combat aircraft, and shut McDonnell Douglas out of the project. Weeks later, McDonnell Douglas agreed to be acquired by Boeing.

Then Boeing produced a study showing that a supersonic airliner would have to be as quiet and economical as the best existing subsonic airplane, goals that were impossible. Without an industry partner, NASA had no choice but to end the program in 1998.

Back at Lockheed Martin’s Skunk Works, aerodynamicists claimed a breakthrough: computer codes that made it possible to design a supersonic airplane with a much reduced sonic boom. The snag was that the craft could not be very large. It would be a corporate jet. Gulfstream saw a market and teamed with the Skunks.

NASA showed no interest, but the Defense Advanced Research Projects Agency paid for tests on an F-5 fighter that validated the low-boom codes. Rolls-Royce and other engine builders schemed engines based on existing hardware, good for almost Mach 2 and acceptably quiet. Nobody ever showed it could not be done.

But there was a huge roadblock. Worldwide, there is no standard for how loud a supersonic boom can be. Overland supersonic flight is banned in the United States and Europe, and if that can’t be changed, a supersonic commercial airplane is an economic non-starter.

The only surviving supersonic project is the decade-old Aerion business jet, designed to fly at supersonic speed over water and just-subsonic—a few knots faster than a Gulfstream—over land. But it’s only a concept. The jet reappeared at a business aviation show in Geneva last May, with its billionaire backer and Aerion’s chairman, Robert Bass, offering to fund any qualified aircraft manufacturer to build it. Nobody yet has bitten on that offer.

Some people will argue that nobody really needs a civilian supersonic aircraft or has the right to impose its noise on others. Nobody needs a Harley-Davidson, but the flatulent cacophony of a rolling column of Harleys rips through the summer evening across many American suburbs. Maybe advocates for supersonics would have more luck if they painted their proposed airplanes black with chrome accents.

Bill Sweetman | READ MORE

Bill Sweetman is senior international defense editor for Aviation Week & Space Technology and has been an Air & Space contributor for 20 years. He is the author of more than 30 books, and has written about almost every aspect of aerospace and military technology.