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Feature Story

B-52H X-51A

U.S. Air Force Photo

During its first test flight last year, the X-51A Waverider began the 143 second Mach 5 journey attached to the wing of a B-52 Stratofortress.

: The U.S. Air Force elected today not to launch the X-51A Waverider during a planned hypersonic flight test at Edwards Air Force Base, Calif.

An Air Force Flight Test Center B-52 bomber departed Edwards AFB carrying the unmanned X-51A shortly before 9 a.m. (PT) and flew as planned to the designated launch area over the Navy Point Mugu Sea Range. However, according to Air Force officials, test controllers opted to not initiate the test since all required test conditions could not be met.

The next flight test attempt will be rescheduled following a check of the system and when range and test assets can again be aligned.

X-51A Waverider team announces second flight plans

X-51A Waverider

U.S. Air Force Photo

As dawn breaks at Edwards Air Force Base, Calif., the team readies the X-51A Waverider for its first test flight.

The second flight of the X-51A Waverider is tentatively scheduled for March 22, according to the X-51A team, a consortium of the U.S. Air Force, DARPA, NASA, Boeing and Pratt & Whitney Rocketdyne. The team is currently working to complete coordination of all the required ground, air and sea assets. The flight plans were announced at a media bloggers roundtable held on March 15.

Charlie Brink, X-51A program manager for the Air Force Research Laboratory, noted that the vehicle is in a hangar at Edwards Air Force Base in California and is ready to go, pending range availability and other potential last-minute concerns.

Development of X-51A is a joint effort to demonstrate hypersonic technologies in the Mach 4.5 to 6.5 range that will set the foundation for several applications, including but not limited to access to space, reconnaissance and strike, global reach and commercial transportation. Boeing built the air vehicle and performs vehicle integration. Pratt & Whitney Rocketdyne is the engine provider.

X-51A Waverider

U.S. Air Force Photo

The X-51A Waverider uses scramjet technology to reach hypersonic speeds. Scramjets eliminate the need for rockets to carry a supply of liquid oxygen by taking in and isolating the oxygen from the atmosphere being passed through, then introducing that oxygen with a stream of fuel to produce thrust.

On flight day, a B-52H Stratofortress out of Edwards Air Force Base, Calif., will carry the vehicle to the Pacific Test Range. An Army Tactical Missile Systems booster will take the X-51A to approximately Mach 4.5 before the supersonic combustion ramjet engine, or scramjet, accelerates the vehicle to its final flight speed.

In its first flight on May 26, 2010, X-51A flew at approximately Mach 5 for 143 seconds. Although the test was the longest-ever hypersonic flight powered by a scramjet engine, beating the previous record of 10 seconds set by the X-43, an “apparent thermal seal breach” at the engine to vehicle interface allowed hot propulsive gases to escape into the vehicle, reducing the vehicle’s thrust and resulting in early termination of the flight, said Brink.

For this second demonstration flight the team hopes to exceed its earlier success. Brink says the goal is to get past 143 seconds and that a nominal demonstration would be a flight of 240 seconds at Mach 6.

"This technology will manifest itself into all manner of vehicles over the next decade as its utilization is better understood through usage and further testing."

“In an environment where aerospace vehicles are constantly being upgraded with more advanced propulsion systems to further their speed, altitude and range, the development, testing and flight of a practical scramjet engine is an achievement representing the next step in the development of flight propulsion,” said Alex Lopez, vice president of Boeing’s Advanced Network & Space Systems (AN&SS), a division of Boeing Phantom Works. “Many milestones toward the development of an air-breathing hypersonic vehicle were achieved during the first flight. This second flight will continue advancing the technological leap we are achieving.”

The first flight of the X-51A Waverider took place on May 26, 2010. The vehicle was dropped from a B-52H Stratofortress as a booster ignited, bringing the vehicle to approximately Mach 4.5, at which point the scramjet engine took over and accelerated the vehicle to a flight speed of approximately Mach 5.0 for approximately 143 seconds.

“This technology will manifest itself into all manner of vehicles over the next decade as its utilization is better understood through usage and further testing,” said Joseph Vogel, director of Hypersonics and X-51A program manager for Boeing’s AN&SS organization. “As this takes place, we should see a leap in air transportation technology that will allow us to better protect our country and provide for more cost-effective access to space, as the large amounts of oxidizers currently required to boost aircraft into space can be eliminated and/or reduced from future space fairing airships.”