Air Force Getting Closer to Testing Hypersonic Weapon, Engineers Say

WaveriderThe U.S. Air Force is making progress in developing a hypersonic weapon based on the success of an experimental scramjet program, engineers said.

The service in 2013 conducted its fourth and longest flight of the so-called X-51 WaveRider. After separating from a rocket launched beneath the wing of a B-52 bomber, the hypersonic vehicle built by Boeing Co. climbed to 60,000 feet, accelerated to Mach 5.1 and flew for about three and a half minutes before running out of fuel and plunging into the Pacific Ocean.

At that speed, which is equivalent to about 3,400 miles per hour, a missile could travel from Washington, D.C., to Atlanta in just several minutes — making it a potentially powerful weapon against enemy air defenses.

“We are the Air Force. What do we want to do with this technology? We want to weaponize it,” Ryan Helbach, an official with the Air Force Research Laboratory, said last week during an exhibition at the Pentagon to showcase various military research projects. “The follow-on program to this is the High Speed Strike Weapon effort. It’s taking a lot of the lessons learned and the technology and moving to a weapons acquisition.”

The hypersonic missile program comes as the U.S. faces increasing competition from China and other countries working to capitalize on the defense technology.

“Certainly, the U.S. is not the only country involved in developing hypersonic weapons,” Mica Endsley, the Air Force’s chief scientist, said in a recent interview with “They (China) are showing a lot of capability in this area. The advantage of hypersonics is not just that something goes very fast but that it can go great distances at those speeds.”

She added, “For example, currently today to get from NY to LA is a five hour flight in a commercial aircraft. With a hypersonic weapon, you could do that same thing in about 30 minutes. You can go great distances at great speeds.”

The nine-year, $300 million X-51 program was designed to demonstrate that the military could build a scramjet capable of accelerating, ingesting hydrocarbon fuel, and actively cooling in flight, Helbach said. Unlike a traditional engine, a scramjet, or supersonic combusting ramjet, has very few moving parts and relies on an air-breathing propulsion system to travel faster than the speed of sound.

But it needs a kick, like a boost from a rocket, to get there. So the WaveRider was first propelled by a solid rocket booster, a surface-to-surface missile called the MGM-140 Army Tactical Missile System, to about Mach 4.5, then separated and activated its scramjet engine built by Aerojet Rocketdyne. (A weaponized version of the vehicle would use another missile, not a ground system design.)

“There are no moving parts in the flow path, so that means there are no compressor blades to suck in the air, so we need something to get us up to above Mach 4 in order to get the compression into the engine,” Helbach said.

The Air Force program, which had a couple of failed tests, came several years after a similar NASA effort called the X-43, which in 2004 shattered speed records when it flew at nearly Mach 9.7, or about 6,600 miles per hour, for 10 seconds. But the engine couldn’t withstand the temperatures involved.

“The engine basically melted because it got so hot,” Helbach said. “They didn’t actively cool it. So for our program, we actively cooled the engine, which means that along the outside of the engine, we cycled the fuel around it to suck out the heat from the engine, heat up that fuel, and then inject it into the combustor for the scramjet engine.”

The X-51 was designed to start its engine using ethylene and transition to a hydrocarbon fuel called JP-7 — the same type of endothermic fuel employed by the SR-71 Blackbird spy plane.

“It basically means you can dump a lot of heat into that fuel,” Helbach said. “When you crack the fuel, it actually makes it more combustible. It increases the amount of combustion you can create from the fuel.”

For the follow-on weapons program, the Air Force has teamed with the Pentagon’s research arm, the Defense Advanced Research Projects Agency, to shrink the technology into a hypersonic weapon that could fit on most of the bomber fleet, according to Kenneth Davidson, manager of the hypersonic materials development at the Air Force Research Laboratory.

“If you look at the X-51, the size is slightly too big to put it on our current bombers,” he said. “It was made as a demonstrator. There’s no weapon in it. There are no sensors on board for controlling the guidance. So we’re looking at making it more durable, getting the guidance control developed so that it can become a weapon system, developing the ordnance.”

Carrying a small, conventional warhead, a hypersonic weapon could be used as a stand-off missile, so the military could strike targets at a safe distance without putting pilots and aircraft at risk.

“You could then attack defensive targets, those heavily defended or the time-critical targets in a very timely manner — if it’s a moving target, before it can move,” Davidson said. “And then ultimately, these would have a sensor so that they can track a moved target — not necessarily something that is moving, but if the target moves or it gets into the area, they can see the target and hit it very, very accurately.”

The High Speed Strike Weapon is affiliated with other demonstration projects being developed by DARPA, including the Hypersonic Air-breathing Weapon Concept and the Tactical Boost Glide, both of which have test flights scheduled for 2018 or 2019.

“Our goal is to make sure the Air Force has the knowledge in 2020 or over the next five years to be able to make acquisition decisions using this technology,” Davidson said. “Our goal is to provide a capability to stand off, launch these vehicles off the aircraft to hit time-critical dependent targets … And ultimately from a manufacturing standpoint, it’s got to be affordable.”

–Associate Editor Kris Osborn contributed to this report.

— Brendan McGarry can be reached at

About the Author

Brendan McGarry
Brendan McGarry is the managing editor of He can be reached at Follow him on Twitter at @Brendan_McGarry.
  • Dfens

    Mica Endsley should stick to topics she knows something about, like psychology or human factors. Her statement:

    “today to get from NY to LA is a five hour flight in a commercial aircraft. With a hypersonic weapon, you could do that same thing in about 30 minutes. You can go great distances at great speed.”

    is pure crap. First of all, you don’t get anywhere riding on a hypersonic weapon. That much is obvious. Secondly, a hypersonic vehicle could get you from New York to Los Angeles in 30 minutes if you had a vehicle with sufficient range. The problem is, that drag goes up as the square of velocity, and even faster than that when you get past supersonic speeds, so the probability of the US Air Force coming up with a vehicle that can fly all the way across the US without refueling is ZERO. This is especially true given the fact that the US Air Force relies completely on a bunch of defense contractors to design everything for them, and the defense contractors long ago got rid of any vehicle design engineers fearing that such high profile personnel might not go along with their 30 year weapon development cycles. Hell, the USAF can’t even replicate the success of the SR-71 which was retired for much the same reason the USAF wants to retire the A-10, because operational vehicles take money away from the “welfare for the rich” development programs that keep their defense contractor buddies flush with cash.

    • Big-D

      so true, the air farce is just like those people who go out and have to buy a brand new car every year just to trade it in 12 months later for a even more expensive one

    • Bob

      Hey Dfens! Read Endsley’s statement carefully. She never stated that commercial aircraft would do the same thing in about 30 minutes. She was simply comparing the speed and time factors of a commercial aircraft to the speed and time factors of a hypersonic weapon. She even referenced “weapon” in her statement. Paraphrasing: “Commercial aircraft takes five hours to cross the country, but a hypersonic weapon would only take 30 minutes to do the same thing.” Get it? Sounds like you have anti-military fever. There’s a cure for that: a good healthy dose of patriotism!

  • Guest

    Good job Air Force! We are lucky to have such talented people working for our side. Of course things cost money to research and companies have to make a profit. This project seems to me like money well spent.

  • donbacon

    wiki-On 18 November 2011, the first Advanced Hypersonic Weapon (AHW) glide vehicle was successfully tested by the U.S. Army.
    And now more than 3 years later the USAF is “getting closer” to testing one.
    Point made.

    • Dfens

      It was “successfully tested” if you ignore the part where it disintegrated in flight. Apparently that’s not a failure, it’s a feature.

  • Highguard

    Donbacon, you Sir are sadly mistaken. HTV-1 (which you have conveniently ignored) was the first hypersonic glide vehicle and was developed by the USAF and was the first such vehicle to surpass hypersonic barrier (Mach 5). The fact that it broke up during glide doesn’t detract from that record. That being said, AHW was the first fully successful hypersonic glide test and the Army is to be congradulated. X-51 waverider was the first successful sustained unmanned hypersonic powered flight and was accomplished by USAF (Point made).

    • oblatt23

      any record can be broken if you are willing to lose the aircraft in the process.

    • blight_

      Hypersonic rocketplanes were deployed in the sixties (X-15). Strange that we still have teething problems for PGS when it’s been done at least once. Serious institutional atrophy means we just spend our days rolling the stone up the hill…Sisyphus would laugh.

  • Highguard

    Now, let’s get to the meat and potatoes of what is to be read between the lines in this article. Criticism is spot on that USAF to selling the present to buy the future, and at the expense of national security. We should be agressively fielding today solutions now for PGM capability to deter a major theater war in the next several years. We should also be fully funding the RDT&E of the next gen in PGM, which is clearly hypersonic. If we don’t, then our adversaries will develop them first and we’ll have to play catch-up just like we did in the 60s.

  • Highguard

    Now, for the next gen, Mica, if not careful, is about to make the same mistakes made by so many before in recent history. The solution for a HSSW sooner than later is not a continuing of the DARPA-AFRL program to build a weaponized version of X-51 to fit in a bomber. It is to begin a downselect competition for a 2020 weapon and see which company has the best proposal. LMCO has already self-funded testing and conducted a PDR for an HSSW that fits inside both F-22 and JSF. Let’s see what BA and RMS can come up with. RMS has the edge on high-speed seeker eye tech. AFRL-BA effort has led us into the era of hypersonic Msl tech. Now it’s time to hand it off to industry to compete for an implementable solution before our opponent do it first.

  • eric

    the air force is like a drunken sailor with a credit credit card. they cant even afford the the bills they have now, and they want pie in the sky tech which will cost billions to develop. they need to get their financial house in order before they open their mouths.

  • Roy Edwards

    Who was it that said, “those who do not remember history are bound to repeat it”, or words to that effect? I imagine most of the preceding comments were made by folks who are too young to remember the Bomarc. Are we now seeing Bomarc 2.0?