NASA achieved the fastest flight of an air-breathing aircraft March 27 with the second flight attempt of its unmanned X-43A "Hyper-X" demonstrator, which reached speeds above Mach 7, according to the agency.

"We can claim an air-breathing powered record today, no doubt about it," NASA Langley Hyper-X propulsion lead Larry Huebner said in a press conference March 27. "Bottom line is, it's time to roll up our sleeves and start looking at some data."

The 12-foot X-43A is a scramjet-powered demonstrator designed to advance hypersonic (faster than Mach 5) engine technology. The Hyper-X Launch Vehicle (HXLV), based on Orbital Sciences' Pegasus XL, boosts the X-43A to its release altitude of 95,000 feet after being dropped from the wing of a B-52.

The flight, which originated at NASA's Dryden Flight Research Center in California, began at 12:40 p.m. Pacific time March 29, when NASA's B-52B launch aircraft carrying the HXLV lifted off the runway. The HXLV was dropped from the B-52B just before 2 p.m. PST, then boosted the X-43A to 95,000 feet over the Pacific Ocean.

Approximately 90 seconds after HXLV ignition, the X-43A separated and ignited its scramjet for roughly 10 seconds, reaching a maximum speed of just over Mach 7. The vehicle achieved positive acceleration while climbing and demonstrated "outstanding vehicle control" during the flight, according to Huebner.

After running out of hydrogen fuel, the X-43A glided unpowered for eight minutes and executed a number of aerodynamic maneuvers before crashing into the ocean at a pre-determined point. It will not be recovered.

"What we demonstrated today is something that we've been working on on the ground for over 40 years," NASA Dryden X-43A Project Manager Joel Sitz said at the press conference. "Flight is reality."

Supersonic combustion ramjets, or scramjets, have fewer moving parts than traditional turbojet engines and draw their oxygen for combustion from the atmosphere rather than carrying it, which allows more weight for payload. NASA has been pursuing scramjet technology with an eye toward future reusable launch vehicles that would feature scramjet-powered initial stages.

"The ramjet/scramjet is the holy grail of aeronautics, in my mind," Sitz said. "If you go from ground to space, you need to use a ramjet/scramjet if you're going to do it in the most efficient way you can. So I think this technology will find its way into future vehicles and integrate nicely."

The first flight attempt for the X-43A in 2001 ended in failure when its modified Pegasus booster veered off course while the two vehicles were mated, forcing flight controllers to destroy both. The failure was attributed to the high dynamic pressures experienced by the Pegasus, which normally is launched at a higher altitude where the air is thinner (DAILY, Oct. 14, 2002).

The future of hypersonics at NASA has been in doubt following the announcement of President Bush's new vision for space exploration, which will require the realignment of $11 billion in NASA funding over the next few years. A follow-on to the X-43A, the larger X-43C, already has been canceled by NASA's new Office of Exploration Systems, which inherited the agency's hypersonics programs when it was formed in January (DAILY, March 19).

Three expendable X-43A demonstrators were built by prime contractor ATK GASL, based on a design by Boeing Phantom Works. With a successful flight under its belt, the program now will be funded by NASA's exploration office to conduct a third flight at Mach 10 in the fall, using the last demonstrator, according to NASA spokesman Michael Braukus.