Don’t Give Up on Hypersonic Technology, Experts Say in Wake of X-51 Test Failure

The loss of the third X-51 hypersonic test vehicle Aug. 14 was “painful,” two aerospace experts said, but it shouldn’t prevent the promising technology from moving forward.
 
“The whole idea of a flight test is that it’s a test. You have to be allowed to fail,” said Mark Lewis, former chief scientist of the Air Force, and now a professor of aerospace engineering at the University of Maryland. Hypersonic vehicles — defined as flying at Mach 5 and above — have the promise to be a game changer just as stealth aircraft were, he said.
 
The Air Force had four of the Waverider test vehicles; it is now down to one. With the current budget crunch, and the high-profile failure, the question is whether the program will move forward. What made this test particularly painful was that the experimental scramjet engine never had a chance to prove itself. A fin caused it to lose control after 16 seconds and the engine never ignited.
 
“It is unfortunate that a problem with this subsystem caused a termination before we could light the scramjet engine,” said Charlie Brink, X-51A program manager for Air Force Research Laboratory in a statement. "All our data showed we had created the right conditions for engine ignition and we were very hopeful to meet our test objectives.”
“This particular control subsystem had proven reliable in the previous two flights of the X-51A, including the historic May 2010 flight when the Waverider flew for more than three minutes at Mach 4.88 under scramjet power — nearly five times the speed of sound,” the statement published by the Air Force News Service said. Program officials will now begin the process of determining the exact cause of the failure. Lab officials have not decided when or if the fourth vehicle will fly, the statement said.
Lewis likened it to a an experimental heart surgery, where the wheel falls off a gurney as the patient is wheeled into the operating room, and the procedure is called a failure.
“Hopefully, they will continue it,” said Richard Aboulafia, an analyst with the Teal Group. “It benefitted from the defense spending upturn and hopefully it won’t get too crushed by the downturn,” he said.
 
Both Aboulafia and Lewis said the technology holds a lot of promise. The mainstream press made a lot of the fact that passengers using the technology could one day fly from New York to London in an hour, but that is not the military’s vision. It wants the capability of delivering a “prompt global strike weapon” or an aircraft that could penetrate contested airspace to gather overhead intelligence.
“From the standpoint of a strike weapon, it still holds a lot of promise, it is just taking a while for it to mature,” Aboulafia said. “Obviously, the more advanced and capable you make your strike munitions, the less you have to worry about your platform.”
Lewis said: “It is pretty clear to me that the way forward is to fly that fourth vehicle and make sure we solve whatever that problem is, and get to the point where we can light off the engine and learn about the hypersonic engine that we set off to learn about in the first place.”
 
In modern warfare, speed is absolutely the critical issue, he said. To be able to reach out and touch something quickly, to gather intelligence quickly, to strike quickly, and penetrate effectively is paramount. “I would argue that hypersonics brings all that to bear,” he said.
 
Stealth technology has given the U.S. Air Force an edge for decades, Lewis said, but other nations are developing those capabilities. “We have to look for the next thing beyond stealth. One of those things is high speed. Even if they can see me, there is not a lot they can do to stop me.”
 
Making the leap from the X-51 to a prompt global strike weapon is not that far off if there were a concerted effort to move ahead, Lewis said. The first two tests did successfully fire the experimental engine, he noted. “It is not a really big leap to go from something like that to … something that is more weapon-like.”
The Air Force and the Defense Department are clearly still interested in the technology. They have a high-speed strike weapon program just getting under way, which would take it to the next level. Assistant Secretary of Defense for Research and Engineering Zachary Lemnios and his deputy Alan Shaffer are championing hypersonics, Lewis said.
 
Aboulafia added: “Hypersonics have been proceeding at a trickle over the past few decades. It won’t go away. It will just be a long time before it receives the kind of funding you associate with a firm development program.”
Photo Credit: Air Force

Topics: Aviation, Science and Engineering Technology, Test and Evaluation