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X-51A Waverider fails to reach full power in second hypersonic test flight


June 16, 2011

Final checks to the X-51A Waverider scramjet, which is affixed to an Edwards B-52H Stratofortress (Image: Boeing)

Final checks to the X-51A Waverider scramjet, which is affixed to an Edwards B-52H Stratofortress (Image: Boeing)

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The second hypersonic test flight of Boeing's X-51A Waverider has ended prematurely with the craft failing to transition to full power. The X-51A Waverider broke the record for the longest ever supersonic combustion scramjet-powered flight on its first autonomous flight in May 2010, flying under scramjet power for just under three and a half minutes at a top speed of Mach 5. For the second hypersonic flight test, the craft was expected to accelerate to about Mach 6, but only managed to accelerate to Mach 5 under solid rocket booster propulsion before the flight had to be terminated.

The second test flight was originally slated for March, 2011, but was cancelled at the last minute because, "all required test conditions could not be met." The X-51A finally took to the air for the second time on June 13, 2011, in the Point Mugu Naval Air Test Range over the Pacific Ocean. After what U.S. Air Force Flight Test Center (AFFTC) officials called a flawless flight from Edwards Air Force Base, the experimental vehicle was released from a U.S. Air Force B-52H Stratofortress at an altitude of approximately 50,000 feet.

The X-51A then accelerated to a speed just over Mach 5 powered by a solid rocket booster, but the vehicle experienced an inlet un-start when the aircraft's air breathing scramjet engine lit on ethylene and attempted to transition to JP7 fuel operation. The X-51A oriented itself to optimize engine start conditions but restart attempts proved unsuccessful and the craft continued a controlled flight orientation until it flew into the ocean within the test range.

Despite the less than successful flight, U.S. Air Force Flight Test officials were trying to put a positive light on things, saying the flight will provide significant hypersonic research data. The Air Force Research Laboratory, Boeing and Pratt-Whitney Rocketdyne engineers are now reviewing the telemetry data collected during the test flight to identify the cause of the problem.

"Obviously we're disappointed and expected better results," said Charlie Brink, the Air Force Research Laboratory's X-51A program manager, "but we are very pleased with the data collected on this flight. I am extremely pleased with the AFFTC and Point Mugu's support and execution of this complex flight test mission, as they provided us every opportunity for success in this endeavor. We have attempted two scramjet experiments now where one successfully lit, and one did not.

"We will continue to examine the data to learn even more about this new technology," said Brink. "Every time we test this new and exciting technology, we get that much closer to success."

Although the first test flight in May, 2010, saw the X-51A achieve scramjet-powered flight for just under three and a half minutes at a top speed of Mach 5, that flight was also cut short when communications with flight controllers was cut off after hot engine gases seeped into the airframe.

Boeing and Pratt-Whitney Rocketdyne have built four X-51A flight test vehicles with the program goal of reaching Mach 6 in hypersonic test flight. The next test flight has been tentatively scheduled for fall 2011.

Source: Air Force Materiel Command

About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

\"which is affixed to an Edwards B-52H Stratofortress\". Edwards B-52H? Not to split hairs but it\'s a Boeing B-52H based at Edwards Air Force Base.


No much in the way of context here. So, this is a rocket? That reaches mach 6 using scramjet right? Could do with a bit more info in the introduction to tell us what this Waverider actually is.

Matthew Hare

Are these scramjets just sunk in the ocean afterwards? Are they recovered? Maybe a Chinese sub is picking up the remains (we know they \"lurk offshore\")? I\'m just sayin\'.


they just junk these into the ocean and I am paying for this? I could accept that if they cost $5000.00 each, and I know no way lsaguy? it is a special edition B-52 like the Eddie Bauer Fords in the 1990\'s ;) Matthew? did you read the article? comprehend it?, one of those queries will be answered with a no

Bill Bennett

Comprehend? Bill Bennett, I\'ve read and re-read your comments, and I still can\'t make any sense of them I\'m afraid. [My apologies if English isn\'t your first language].


Ahhh the joy of the Americans finding new ways to make more enemies - as the corporation based military government - is producing more and more tax payer funded Weapons Systems....

Mr Stiffy

@Matthew Hare: The X-51 is a scramjet, meaning supersonic ramjet, meaning air gets compressed (heated), a bit of fuel injected, and burned, all at supersonic speeds. Because this engine does not work at slower speeds, the X-51 uses a rocket to accelerate to the speed necessary to start the engine (mach 5). In this test, the rocket accelerated the vehicle to Mach 5, the X-51 fired the engine up, but apparently the combustion blew out. (Think of a match in a 3000 mph wind.) What was supposed to happen was the engine would accelerate the X-51 from Mach 5 to Mach 6.

If you could follow a particle of air through the engine at Mach 5, you would see it spends only milliseconds passing through the engine. This does not provide much time to snatch an oxygen from that air particle, use it to burn fuel, heat up, and expand on the way out. Doable, but tricky.

@Mr Stiffy: It\'s odd that this article pressed the \"Play\" button on your never-ending loop of grievances, but I suspect most days it doesn\'t take any outside event to set you off. In the real world, although the AFRL is sponsoring the research and hopes to someday get a weapon out of it, this is pretty foundational hypersonic research. If it pans out, you stand to benefit. No doubt you would still be carping on about the hated Americans even then. Tiresome.


@eclectic_student: I share your sentiments re the repeated negativity amongst the small group of gripers who infest these interesting newsletters, and always relish the prospect of guessing their comments/moans before reading same. Brightens my day!


Think of the SCRAM jet test as trying to light a candle-in-the-(supersonic)-wind....

Anthony Maw
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