UPDATED November 21, 2004 NASA's X-43A research vehicle screamed into the record books again, demonstrating an air-breathing engine can fly at nearly 10 times the speed of sound. Preliminary data from the scramjet-powered research vehicle show its revolutionary engine worked successfully at nearly Mach 9.8, or 7,000 mph, as it flew at about 110,000 feet.
The November 16 flight took place in restricted airspace over the Pacific Ocean northwest of Los Angeles. The flight was the last and fastest of three unpiloted tests in NASA's Hyper-X Program. The program's purpose was to explore an alternative to rocket power for space access vehicles.
"This flight is a key milestone and a major step toward the future possibilities for producing boosters for sending large and critical payloads into space in a reliable, safe, inexpensive manner," said NASA Administrator Sean O'Keefe. "These developments will also help us advance the Vision for Space Exploration, while helping to advance commercial aviation technology," Administrator O'Keefe said.
The successful 'Scramjet' test follows a previous "captive carry" dress rehearsal flight from NASA's Dryden Flight Research Center on the 27th September. The September flight involved a full-up replication of all operational functions that will occur on the actual research flight. In the captive carry mission, however, the X-43A and its modified first-stage Pegasus launch rocket were not launched from NASA's B-52B mother ship.
Guinness World Records has recognised the world speed record set by NASA's hypersonic X-43A aircraft in an experimental flight over the Pacific Ocean on March 27 this year. The unpiloted, 12- foot-long aircraft achieved Mach 6.83 -- almost seven times the speed of sound -- or nearly 5,000 mph.
The X-43A flight easily set a world speed record for an air-breathing engine aircraft. The previous known record was held by a ramjet-powered missile, which achieved slightly more than Mach 5.
In achieving Mach 6.83 the vehicle's supersonic-combustion ramjet (scramjet) engine propelled the craft for 11 seconds. The X-43A was boosted to an altitude of 29,000 m (95,000 ft) by a Pegasus rocket launched from beneath a B52-B aircraft.
NASA's Hyper-X program was initiated to demonstrate advanced high-speed propulsion system concepts to overcome one of the greatest aeronautical research challenges - air-breathing hypersonic flight. The advantage of air-breathing flight is that the vehicle -- whether it is aircraft or spacecraft -scoops the air its engines need from the atmosphere rather than carrying heavy, bulky tanks, as rockets do.
A ramjet operates by subsonic combustion of fuel in a stream of air compressed by the forward speed of the aircraft itself, as opposed to a normal jet engine, in which the compressor section (the fan blades) compresses the air. A scramjet (supersonic-combustion ramjet) is a ramjet engine in which the airflow through the whole engine remains supersonic.
The challenge is to introduce fuel, ignite it and produce positive thrust while highly compressed air rushes through the engine in mere milliseconds -- roughly analogous to lighting a match and keeping it burning in a hurricane-force wind.
According to X-43A lead operations engineer David McAllister, who served as test director for the mission, the September 27th flight duplicated all operational functions of the planned 7,000-mph - or Mach 10 - flight and served as a training exercise for staff, except that the X-43A and its modified Pegasus booster were not released from NASA's B-52B launch aircraft and their engines were not ignited.
"We have two primary purposes for doing a captive carry flight," said McAllister. "The first is to make sure that the X-43 and its booster rocket - two highly complex systems - are ready for flight. The second is to make sure we're well trained. It's a very big operation (and) we want to make sure that all those people and all those systems are ready to go."
Compared to rocket-powered vehicles like the Space Shuttle, scramjets promise more airplane-like operations for increased affordability, flexibility and safety for ultra high-speed flights within the atmosphere and into Earth orbit. The highest speed attained by a rocket-powered airplane, NASA's X-15 aircraft, was Mach 6.7.The fastest air-breathing, manned vehicle, the SR-71, achieved slightly more than Mach 3.2. After a review of captive-carry flight data, project engineers are expected to set a tentative date for the final X-43A flight for early November.
The X-43A project is part of the Hyper-X hypersonic research program led by NASA's Aeronautics Research Mission Directorate and operated jointly by NASA's Langley Research Center, Hampton, Va., and Dryden Flight Research Center, Edwards, Calif.