The NASA X-43A hypersonic research vehicle and its Pegasus booster rocket, mounted beneath the wing of their B-52 mother ship, had a successful first captive-carry flight on April 28. A dress rehearsal for the subsequent free flight, the captive-carry flight kept the X-43A-and-Pegasus combination attached to the B-52's wing pylon throughout the almost two-hour mission from NASA's Dryden Flight Research Center, Edwards, Calif., over the Pacific Missile Test Range, and back to Dryden.

The NASA X-43A hypersonic research vehicle and its Pegasus booster rocket, mounted beneath the wing of their B-52 mothership take off for a two-hour captive-carry flight. Photo: NASA-DFRC

After taking off from the Dryden Flight Research Center, Edwards, Calif., at 12:33 p.m. PDT, the B-52 soared off the California coast on the predetermined flight path, and returned to Dryden for a 2:19 p.m. PDT landing.

The unpiloted X-43A marks the return to dedicated hypersonic research flights (at least five times the speed of sound) that NASA last pursued with the X-15 program that ended in 1969. Unique to the X-43A is its blending of an integrated airframe with a scramjet (supersonic combustion ramjet) engine, intended to make the X-43A the first air-breathing hypersonic vehicle in free flight. This technology promises significant savings in weight and volume, which could translate into heavier payloads or longer flight duration for future scramjet operational craft. Pending thorough evaluation of all flight data, this captive-carry test could lead to the first flight of the X-43A "stack" as early as mid-May. The first free flight will be air-launched by NASA's B-52 at about 24,000 feet altitude. The booster will accelerate the X-43A to Mach 7 to approximately 95,000 feet altitude. At booster burnout, the X-43 will separate from the booster and fly under its own power on a preprogrammed flight path. The hydrogen-fueled aircraft has a wingspan of approximately 5 feet, measures 12 feet long and weighs about 2,800 pounds.

Close view of Pegasus with X-43A attached to B-52's wing pylon during the flight. Photo: NASA-DFRC

Three X-43A flights are planned; the first two will fly at Mach 7 and the third at Mach 10. Valuable performance data will be relayed electronically to Dryden and Langley. Each experimental aircraft will fly once in the Naval Air Warfare Center Weapons Division Sea Range off the southern coast of California and impact into the Pacific Ocean.

Joel Sitz, Dryden's X-43 project manager, said, "All systems appeared to work great. We are very excited. It's a huge milestone for the program. A lot of people worked hard to get here."

Program officials anticipate that this series of experimental flights will expand knowledge of hypersonic aerodynamics and develop new technologies for safer and more cost effective space access. Today's rocket-powered launch vehicles, including the Space Shuttle, must carry their own oxygen adding considerable weight, complexity and cost to each flight.

B-52/Pegasus with X-43A in flight over Pacific Ocean. Photo: NASA-DFRC

A scramjet-based propulsion system could decrease propellant system weight and increase payload -- or maintain the same payload using a smaller, cheaper vehicle. Scramjet technology could also allow "aircraft-like" operations of launch vehicles with horizontal take-off, landing and servicing that could greatly decrease operations cost and time between flights.

NASA's Dryden Flight Research Center is responsible for X-43A flight-testing and NASA's Langley Research Center, Hampton, Va., manages the program. The vehicle contractor team led by MicroCraft in Tullahoma, Tenn., includes The Boeing Co., Seal Beach, Calif.; and GASL, Inc., Ronkonkoma, N.Y. The booster is a modified Pegasus rocket from Orbital Sciences Corp., Chandler, Ariz.