DARPA presses on with hypersonics
August failure of Boeing X-51 likely due to fin, resonance
Fourth Hypersonic X-51A To Fly In Mid-2013
"It looks like the second bending node at the stack, the frequency at which that occurs happens at a key frequency that is very close to the lock mechanism that holds the actuator. That's very preliminary," says Brink, but it "looks like we had some cross-coupling between the natural resonance of the stack and the natural resonance of that actuator."
The planned fix is to have flight software activate and unlock the actuators sooner.The fourth and final flight of an X-51 is planned late in the first quarter or early in the second quarter of 2013.
Fourth Hypersonic X-51A To Fly In Mid-2013
A week of tests on a flight actuator assembly will begin on Friday in a bid to confirm the vibration theory. If confirmed, Brink says, the fix to be implemented for flight four will be to power up and unlock the control fins 2-3 sec. into the flight, after the stack is released from the B-52 and before the booster ignites.
Under power, the actuators will then actively hold the fins at zero angle of attack throughout the boost “so we will not have an unlock,” he says. “It’s a pretty simple software change” and there is enough battery capacity and control authority for it to work.
Re: DARPA presses on with hypersonics
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Scramjet Success - AFRL/Boeing X-51A flies at Mach 5.1
Scramjet Success - AFRL/Boeing X-51A flies at Mach 5.1
Published on May 3, 2013
The US Air Force Research Laboratory's Boeing X-51A WaveRider unmanned vehicle achieved the longest air-breathing hypersonic, scramjet-powered flight on its May 1 fourth test flight, flying for 3.5 minutes on supersonic-combustion ramjet power and reaching a maximum speed of Mach 5.1.