NASA scientists are delighted - and doubtless relieved - at the successful launch and testing of their X-43A scramjet vehicle on Saturday.

The X-43A and its Pegasus booster rocket were released from a B-52 at 40,000ft. The booster carried the rocket to 95,000ft and, after successful separation of the two, the scramjet operated independently for over 15 miles at speeds around Mach 7 (c.5,000mph).

Larry Huebner, scramjet propulsion research engineer on NASA's Hyper-X program, said the scramjet experienced "positive acceleration" during its short flight. "Our vehicle under airbreathing power went over 15 miles," he enthused. "The flight today was the first-ever airframe integrated scramjet engine experiment. We can claim an air-breathing powered record today... no doubt about it."

Huebner's reference to the "first-ever airframe integrated scramjet" is certainly a nod to the Australian team who in 2002 fired up its own rocket-propelled HyShot scramjet. That had no integrated vehicle, but hit around Mach 7.6 with its projectile host's assistance. The HyShot site notes that: "Supersonic combustion was achieved on the second flight".

Which is what it's all about. To qualify for the title, a successful scramjet must mix atmospheric air with hydrogen and ignite it while flow throughout the engine remains at supersonic speeds.

The advantages of the technology are clear: the scramjet contains relatively few moving parts compared to a conventional turbine jet engine. NASA hopes that hypersonic passenger transports will be one benefit of the technology.

However, the scramjet may still have some way to go before becoming a viable transportation technology. NASA's success on Saturday comes almost three years after the X-43A's first flight ended in self-destruction provoked by a booster rocket malfunction. ®

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