The X-43 is a scramjet—as different from a jet engine as a rocket was from the steam engine—and this will be its first flight. If all goes to plan, it should smash every world airplane record. It will make the fastest aircraft, the rocket-powered X-15 (Mach 6.7), look turgid, and leave the fastest jet, the SR-71 Blackbird (Mach 3.2), in its stratospheric dust. Says Vince Rausch, director of the Hyper-X project: "It's the future. We're convinced of that. What we've not done yet is demonstrate to the people it's real. And that's what we have to do in May."
Scramjet is short for supersonic combustion ramjet. It uses the rush of air at high speed to ignite fuel and produce thrust, rather than relying on compressed air from a jet engine's fan blades. As well as being capable of hypersonic speeds (greater than Mach 4), scramjets get their oxygen from the air rather than tanks (as rockets do), reducing cost and freeing up space for cargo or passengers. They are also currently environmentally friendly: all three models under test run on pollution-free hydrogen.
To Allan Paull, leader of the Australian HyShot project, which will test its own and a British model on July 2 and 9, the logic of hypersonics is undeniable. "If you had the money and the will, you're probably talking about five to 10 years before you have hypersonic aircraft," he says. "Once you have demonstrated something, if someone wants to run with it, it's just a matter of money."
Plenty of money is needed. Paull's team built a scramjet for just $750,000 but it has no body attached and hitches a ride on a former U.S. Navy rocket. The American version is also unready for boarding: the X-43 is only 4 m long, 1.6 m wide and 60 cm thick. But the leaders of world aeronautics seem to believe the future is hypersonic. nasa has invested $185 million in Hyper-X and partly funds Paull's work at the University of Queensland.
The next stage, says Rausch, will be a 13-m long, recoverable and reusable aircraft. Ideas circulating at nasa include a plane that uses jet engines to take off and land and scramjets for hypersonic flight in between. Rausch predicts manned flights around 2010-15 and hypersonic passenger planes around 2025. "We will have the capability to go after this in a big way. We're real excited." Paull is similarly bullish: "The applications are likely to initially be more for space or military. But scramjets have the essentials for a passenger plane." Rausch says FedEx have also expressed an interest in using the technology for a priority package service. As for turning the lights out on the in-flight films and food fiascos that define modern air travel, Rausch says killing off killing time "would be fine with me." Bye-bye economy class syndrome—hello instant jet lag.