Experimental Scramjet Aircraft Set for Test Flight

The X-51A Waverider hypersonic scramjet project is set for its second test flight today, and the U.S. Air Force hopes it will demonstrate technology that can eventually be used for more efficient transport of payloads into orbit. The craft will be carried to 15,240 meters (50,000 ft.) by a B-52 from Edwards Air Force Base in California, and be dropped over the Pacific Ocean. A booster rocket will fire, getting the Waverider to Mach 4.5; then the scramjet will kick in, and designers hope it will reach Mach 6 or more.

The X-51 Waverider program is a cooperative effort of the Air Force, DARPA, NASA, Boeing and Pratt & Whitney Rocketdyne.

In May 2010, the first test of the vehicle had sort of a “successful” flight of 200 seconds of autonomous flight, which set a duration record for an aircraft powered by a scramjet (short for “supersonic combustion ramjet”) engine. However, it was hoped that the X-51A would fly for as long as 300 seconds (or 5 minutes) and reach Mach 6. But during that flight, the Waverider suddenly lost acceleration, and the vehicle was “terminated” (destroyed – as planned, the Air Force said) while moving at Mach 5. The loss of acceleration was attributed to a design flaw, which led to hot exhaust gas leaking from the engine into electronics bays.


The scramjet is an air-breathing engine, where intake air blows through its combustion chamber at supersonic speeds. This has been compared to lighting a match in a hurricane, and the concept has had limited success. The engine has no moving parts, and the oxygen needed by the engine to combust is taken from the atmosphere passing through the vehicle, instead of from a tank onboard, making the craft smaller, lighter and faster. Designers say it could reach speeds of anywhere from Mach 12 to Mach 24. Mach 24 is more than 29,000 km/hour (18,000 miles per hour.) This could cut an 18-hour trip to Tokyo from New York City to less than 2 hours.

Sources: NASA, The Register, Spaceports

11 Replies to “Experimental Scramjet Aircraft Set for Test Flight”

  1. *Marginally* lighter, AFAIU, at least in boosters, the weight of the engine is not a trifle. Expensive, more things that can go wrong, … Nah.

    But it is a fun thing to play with, so … ride on! (Also, I believe the proverbial waverider was the idea to have the skin as part of the engine, the air the rest. If that can be worked, it could be a future contender in the light weight division!)

  2. Can someone explain how and why the X51 does a roll before and after booster separation?

    If I’m not mistaken, the shuttle does this in case an abort is needed? Though I don’t think that’s applicable here.

    1. Look at the angle of the exhaust on the Shuttle’s triple engine cluster. If the Shuttle was ‘on top’ the engine thrust angle would be pushing the combined vehicle ‘downward’ and working with gravity. With the Shuttle ‘underneath’ the thrust angle is pushing ‘up’, and more in line with the flight trajectory desired.

  3. One reason the Shuttle does a partial roll is to align the Inertial Guidance system to help prevent a possible “Gimbal Lock” condition (nice Wiki article). There may be other reasons for the partial roll but this is one of them.

    I used to work on sub launched missiles (Poseidon) and it was programmed to do a roll orientation upon launch to get the IMU on the down-leg side of the trajectory. The Shuttle uses a similar guidance system.

  4. Wow, the US is finally catching up.

    Let’s see. Australia at Woomera has been doing research into this for ages… I.e July 2002 – HyShot scramjet – now almost nine years ago.

    I.e See Successful Hypersonic Scramjet flight tests in Australia of June 18, 2007

    How quickly American seem to forget, nor wonder where some of their original experimentation actually came from. I thought “Imitation is better than art”, is is it the other way round? Ta.

      1. And I understand your enthusiasm as it’s not frequent that you get to “toot”. Ta.
        Btw, did Russia peek too?

  5. Better than that, Waverider (which is actually a wing shape, or in this case the nose cone) was invented by Prof. Terence Nonweiler in March 1967, and he won the Royal Aeronautical Society Gold Medal for the underlying theory in 1962. Since 1977 it’s been the flagship and logo of the Scottish spaceflight society ASTRA, who did the first Waverider free flight, rocket launch to free flight and radio-controlled flight(1985-89). Terence was a pacificist and would have hated the Mach 6 cruise missiles it’s turning into, so ASTRA has restarted its project to push Waverider’s peaceful applications (see ‘Flight in non-terrestrial atmospheres’ by Gordon Dick and myself, Analog, January 1993.)

    1. “a wing shape”

      Ah, thanks! I guess all the g’s & mach’s scrambled and swept my brain clean.

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