Over autumn last year a US company called Aerion strapped a scale model to the underside of NASA’s F-15B research aircraft and flew it at twice the speed of sound. The results from the experiment proved in fact what Aerion had until then only worked out in theory: that by shaping the body of an aircraft in certain, patented ways, drag can be drastically reduced at high speeds. Indeed, reducing drag allows very high speeds to be achieved. And that is just as well because Aerion claims some US$4 billion worth of letters of intent to buy the new, 2.0 version of its proposed private jet, expected to be in the air by the end of the decade and each costing in the region of an eye-watering US$100 million.

That price, to those for whom, as the cliché has it, time is money, could be money well spent because Aerion’s jet, known as the Supersonic Business Jet (SBJ), will be the first of its kind. It will fly at supersonic speeds, crossing the Atlantic in just a couple of hours. “Our belief is that the demand for supersonic passenger flight is there now as it ever was. The market is impatient for more speed,” says Aerion’s CEO Doug Nichols. “The commercial aircraft industry has largely been locked at sub-supersonic speeds for decades now but it’s never really lost sight of the desire for supersonic flight; it’s always been a question more of economics and operating costs. But new technology is making overcoming those obstacles a reality. And there are a lot of people who value time above all else: the time to recreate, or tend to business, or even tend to some emergency.”

Nor is Aerion alone. While it is focused on using conventional engines with revolutionary fuselage and wing design, Britain’s Reaction Engines sees radical new power plants as the way to achieve supersonic speeds. For some years the technology company — which recently won a £60 million (US$100 million) grant from the British government to develop its Sabre jet-cum-rocket for use on a potential space plane — has been part of a European Union and European Space Agency-initiated project called LAPCAT (or Long-Term Advanced Propulsion Concepts and Technologies). That saw it develop the concept for the A2, an aircraft capable of flying non-stop to the other side of the planet at a cruising speed of around Mach 5, or five times the speed of sound, around 3,500mph.

Crucially, the project has shown that such an aircraft is technically feasible, a first for an aircraft of that range. Its secret? An engine fuelled not by conventional kerosene but by liquid hydrogen. That, naturally, would lead to some problems. There is currently no infrastructure to supply the fuel, which is in itself expensive, and servicing aircraft with it at certain airports would be expensive too. Indeed, operating costs of such an aircraft would be an estimated three times that of subsonic flight.

“In the end it all depends on how much people are prepared to pay to fly on such an aircraft,” says Reaction Engine’s technical director Richard Varvill. “The problem with supersonic flight as we understand it is that it can be done with conventional engines, but then you can’t fly very far and the whole objective is to reduce the time of long journeys. Even conventional airliners have to refuel on the longer-haul flights. So I think you have to address the engines.”

There are other hurdles too: the sonic boom, for example, was why Concorde (not an economic failure at all, as myth has it) could not fly at supersonic speeds over land mass. Were this to be cracked (NASA’s Quiet Spike technology is one proposed solution) and a small supersonic private aircraft was to become a reality, uptake would undoubtedly initially be the preserve of ultra-high-net-worth individuals.

Yet they would, as Robbie Cowart, director of Gulfstream Aerospace’s Supersonic Research Programme, says, nevertheless be an important stepping stone on the road to its becoming commonplace in commercial flight: “Mobile phones started as an expensive item for the minority and similarly it took a few people who could see its value early on and who could afford to make it feasible for everyone else.” In fact, Gulfstream is still pondering the issues: last year it released new drawings of an advanced supersonic business jet design in patent application forms.
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