When the X-51A Waverider program was established, the test team set out to demonstrate the viability of air-breathing scramjet propulsion. The goal of the $300 million concept-demonstrator program became reality May 1 when the test team achieved a record- setting 210 seconds of air-breathing hypersonic flight.
“This mission was a full success. We boosted for roughly 26 seconds and then we were on powered scramjet for three and a half minutes. We flew the mission until we exhausted the fuel. We took aerodynamic data on the cruiser from unpowered all the way until we flew it in the ocean,” said Charlie Brink, X-51A program manager, from the Air Force Research Laboratory’s Aerospace Systems Directorate.
The test team gathered 370 seconds of telemetry data as the Waverider traveled 230 nautical miles and reached maximum Mach at 5.1, with a peak altitude of approximately 60,000 feet. The test was executed over the Point Mugu Naval Air Warfare Center Sea Range.
It was the fourth and final flight for the X-51A Waverider program, the culmination of knowledge gained and lessons learned from previous flights.
“The first flight was in May of 2010, which was a partial success; total flight time on scramjet power was 143 seconds. The second was in June of 2011 and the scramjet engine started and stalled due to excessive pressure in the combustor. This failed flight produced the most amount of learning, it was kind of an aha moment,” said Brink. “During the third flight in August 2012, we had an unexpected fin failure on the cruiser. It was a hardware failure, which had nothing to do with scramjets. May 1 was our last and most successful flight.”
While lessons learned from previous flights and more recent advancements in hypersonic technologies contributed to the success of the final mission, according to Lt. Col. Jason Wierzbanowski, 419th Flight Test Squadron commander, ultimately it was the test team’s ingenuity and flawless execution that can be attributed to Waverider’s record-breaking achievement.
“The highly complex mission required coordination between multiple government agencies and branches of military service,” said Wierzbanowski. “It required flawless execution of the aircraft maintenance unit, aircrew members, support aircraft, and the control room members. The test mission was a unique challenge for the entire test team and required countless hours of planning and rehearsal.”
The X-51A departed Edwards attached to the wing of a B-52H, flown by aircraft commander Maj. Andrew Murphy and pilot Capt. Thomas Meagher.
Additional 419th FLTS crew members included navigator Maj. Jonathan Beich, radar navigator John Kirk and flight test engineer Capt. Christopher Rondeau.
They faced a takeoff with the minimum amount of fuel and once airborne, crewmembers were challenged with strict timelines, constant coordination with the control room and chase aircraft, while operating the B-52H on the edge of its flight envelope at 50,000 feet.
“We took the B-52 to the very top of its envelope and we just barely reached the bottom of the X-51 envelope. There is minimal overlap there,” said Murphy.
The 2nd Bomb Wing at Barksdale AFB, La. provided the B-52H flown during the final X-51A mission. The aircraft along with crew chiefs and maintenance personnel were sent to support the mission because the two B-52s at Edwards were assigned to other test programs.
“We want to thank Global Strike Command and the Barksdale maintainers, those guys have been here for a month and half getting the airplane ready to support the mission, they were exceptional,” said Murphy.
In addition to the support from the 419 FLTS, 912th Aircraft Maintenance Squadron and 419th Aircraft Maintenance Unit; the Hypersonics Combined Test Force was an integral component of the test team, serving as a liaison between AFRL and the operations community.
“AFRL needed a test agency, so they came to us. We brought the flight test expertise to the program and the hypersonics knowledge to identify what was going to be needed; from identifying the launch platform, securing chase aircraft, coordinating support for Edwards and Point Mugu ranges and working with the ground crew, Boeing and Pratt and Whitney Rocketdyne. Really it’s a coordinated effort of understanding AFRL and operations community; we were the liaison between the two,” said Lt. Col. Timothy Jorris, Hypersonics CTF director.
One of the biggest challenges for Jorris was securing a chase aircraft for the final X-51 flight. They needed an aircraft that performed well at 50,000 feet, so the Hypersonics CTF coordinated with the NASA Dryden Flight Research Center, which provided an F-15 chase, flown by their chief pilot, David Nils Larson for the historic mission.
An additional F-16 chase aircraft was provided by the 445th Flight Test Squadron.
While the success of the final mission was cause for celebration, Jorris is already looking forward to using all that was learned from the X-51A Waverider to further develop hypersonic capabilities.
“Our Hypersonics CTF ends up getting lots of different test programs from a variety of sources; AFRL, DARPA, the Air Force Rapid Capabilities Office, even NASA. And what the X-51 program just did is open up multiple hypersonic research projects and demonstrations. What’s great is that it’s more than just the success of the X-51; it’s all the future projects that will now be moving forward,” said Jorris.
The X-51A Waverider’s demonstration of sustained hypersonic, air-breathing propulsion was a major breakthrough that will lay the foundation for future development of hypersonic weapons and vehicles, providing a more efficient alternative to rocket propulsion.
“Air-breathing scramjet propulsion is eventually going to have a place beside rocket propulsion. Think of the space shuttle; to get something into orbit you have to strap a huge tank of liquid oxygen and liquid hydrogen and solid rocket boosters to get it into space. If you could fly along at high speeds and capture the air; you’re not carrying the oxidizer up with you,” said Brink. “Scramjets have the potential to become a much more efficient propulsion cycle for portions of the spacelift mission.”
The Air Force Research Laboratory’s X-51A Waverider program leveraged expertise from not only the 412th Test Wing and 412th Operations Group; but Boeing, Pratt and Whitney Rocketdyne, NASA and included a prominent role from the Defense Advanced Research Projects Agency.