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USAF Scramjet Hits Mach 6, Sets Record

Posted by CmdrTaco on from the get-where-yer-going dept.

s122604 writes "The [X-51A Waverider]'s scramjet engine accelerated the vehicle to Mach 6, and it flew autonomously for 200 seconds before losing acceleration. At that point the test was terminated. The Air Force said the previous record for a hypersonic scramjet burn was 12 seconds. Joe Vogel, Boeing's director of hypersonics, said, 'This is a new world record and sets the foundation for several hypersonic applications, including access to space, reconnaissance, strike, global reach and commercial transportation.'"

16 of 326 comments (clear)

  1. Why so short bursts? by Henriok · · Score: 3, Interesting

    Why are these engines burning for such short times? Are these engines so early in development that they really can't get them to be stable and safe for more than 12 seconds? Sounds a lot like fusion: it works but it's not yet useful.

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    1. Re:Why so short bursts? by shadow349 · · Score: 4, Interesting

      Are these engines so early in development that they really can't get them to be stable and safe for more than 12 seconds?

      Are you talking about the scramjet or the events at Kitty Hawk in 1903?

      Because Wilbur already had the first chance, Orville took his turn at the controls. His first flight lasted 12 seconds for a total distance of 120 feet (36.5 m) - shorter than the wingspan of a Boeing 707.

    2. Re:Why so short bursts? by icebrain · · Score: 2, Interesting

      A couple reasons:

      Testing scramjets on the ground is really, really hard, and you can only do it for a very short time (much less than a second).

      Testing scramjets in flight is really, really expensive. And when your funds are limited, you can only build subscale air-dropped missile-sized vehicles instead of full-sized, self-launching, reusable ones (in part because of the "cheaper now and more expensive long-term" being prefereable to "more expensive now and cheaper in the long run" thinking that brought us the Space Shuttle).

      Making things even more difficult is that we pissed away a huge amount of research (from both the US and UK) on scramjets and high-speed flight a couple decades ago. Companies like Marquardt basically specialized in ramjet-style engines, and were hard at work developing scramjets and other neat high-speed propulsion 40+ years ago. They were very close to having flying hardware. But now, all of the hardware, most of the documentation, pretty much all of the institutional/unwritten knowledge, and most of the personnel are gone. We're having to reinvent the high-speed flight wheel almost from scratch, just like we're doing with heavy-lift launch vehicles, manned lunar flight, and ballistic missile defense, all of which we had operational in the 70s.

      It's disgraceful, really, how we piss away useful technology and other exceptional things. There must be some kind of relationship to crabs in the human psyche that's responsible for this self-loathing anti-achievement personality trait.

      --
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    3. Re:Why so short bursts? by bkaul01 · · Score: 3, Interesting

      Scramjets have no moving parts; it's a duct and a fuel injector. That's it. Wear is a non-issue here.

      Figuring out what shape that duct needs to be in order to get stable combustion, however, is far from a trivial problem; it's not just the fluid dynamics of the supersonic flow that must be considered ... thermodynamic losses can be large enough to quench the flame, and where in the duct those losses occur is as important as their magnitude. With most sorts of engines, second-law analysis is only something you look at to refine the efficiency of the technology once it's mature and functional. With scramjets, it's critical to making them work at all. Building one of these, with all our modern computer modeling technology, is kind of akin to building the first rockets with no computers at all.

    4. Re:Why so short bursts? by Ragnarr · · Score: 2, Interesting

      If you think we can't launch aircraft within 24 hours and strike targets around the world, you're gravely mistaken. We have people whose jobs are to plan for missions such as this so that we can go out and do exactly that just by putting bombs on the planes and taking off. Not to mention that now days, with our capacities for SATCOM and other techniques, we're able to pass target information on the fly and build them in the air. As for the child thread below who wonders why we need air refueling; it's critical to all military operations. It's what sets us apart from all other air forces. Most aircraft are designed to take off with a certain weight, and getting that amount of stuff in the air usually is at the extreme end of an aircraft's capabilities. So, by fueling the aircraft just enough to take off and then refueling on the way you're able to take more hate to the bad guys. And, it extends the range of our aircraft. It's usually not comfortable, but most of our aircraft are capable of flying indefinitely if you can get them the gas to keep them there. Refueling is instrumental to our operations around the globe. Cheers!

  2. Re:Interesting... by AdmiralXyz · · Score: 2, Interesting

    How useful is this in the long run? What was the burn ratio compared to other scramjet vehicles of recent design?

    Are there even any other scramjet vehicles in the operational testing phase? I was under the impression that the X-51, and the other vehicles in the Hyper-X program, are the only ones that've actually flown. Scramjets aren't exactly easy to test in the lab.

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  3. Jet - Scramjet - And Questions! by Anonymous Coward · · Score: 4, Interesting
    • Jet engines still have propellers to compress air, into which the propellant is injected where this mixture then ignites.
    • Scramjets just use their immense speeds to do the compression with a funnel, but that also means they need more conventional means to reach these high speeds (such as getting a ride on a B52 plus gravity)

    Questions

    • What is the fuel efficiency per kilometer traveled?
    • Can a scramjet reach escape velocity, or get close enough so that additional oxygen for the fuel doesn't make up more than half the payload?
    • Did they find a new way to lose heat at supersonic speeds? Otherwise these rides will remain short ones.
    1. Re:Jet - Scramjet - And Questions! by MartinSchou · · Score: 3, Interesting

      Can a scramjet reach escape velocity

      If it is capable of propelling whatever it's carrying to 11.2 km/s (just under Mach 33 at the Earth's surface). Since this one only goes to 6, there's still a ways to go.

      Just as a foot note - if you're travelling at 11.2 km/s in a circle with a 6,378 km radius (Earth's equator), you will experience an acceleration opposite to gravity of 19.67 m/s^2 (aka 2 g). Just slightly slower if you do it at an altitude of 10 km (19.64 m/s^2). At the altitude this one reached, you'd hit 19.6 m/s^2

    2. Re:Jet - Scramjet - And Questions! by BJ_Covert_Action · · Score: 5, Interesting
      With regards to question 3, they have developed some pretty tricky ways to help cool the engines and the body of the vehicle. For instance, they cool the engines by circulating the JP-7 fuel through the body to absorb some of the heat to help bring it to the combustion point. This is very similar to how rocket nozzles are currently cooled to slow melting/failure:

      The scramjet will circulate the fuel behind engine walls to cool the structures. Without such active cooling, the temperatures in a scramjet could reach 5,000 deg. Fahrenheit, high enough to melt virtually any metal on Earth. Solving the cooling challenge is a major AFRL/Pratt & Whitney achievement.

      Source

      My wager is that the entire vehicle took thermal control into its design considerations and it uses a combination of geometry, aerodynamics, and fuel management to help sink heat at an appropriately high rate to prevent too much for a build up. However, since I don't have the design specs, and I doubt anyone outside of the military will, for awhile at least, I can only speculate. You also have to understand that at those speeds, your gas dynamics become a problem of rarified gasses and heat management becomes a very tricky problem indeed, one that can't be approached by traditional cooling means. So in summation I would guess yes, they have probably found some very cool new ways to sink heat at hypersonic speeds.

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  4. Re:Interesting... by Pojut · · Score: 5, Interesting

    Scramjets aren't exactly easy to test in the lab.

    Hell, even normal jet engines are tough to test. Have you seen the equipment used to keep those things stationary while testing them? Holy fuck .

    --
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  5. Amazing by maillemaker · · Score: 4, Interesting

    It's amazing to me that they can make a machine who's parts are GLOWING they are so hot and the metal still functions without failing.

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    1. Re:Amazing by BobZee1 · · Score: 2, Interesting

      The company I work for makes the parts in what "they call" the hot section of the engine. These are some really awesome materials. I fly a desk so I don't get to play with the goodies.

      --
      dumber people are doing harder things everyday
  6. Re:For those of you who don't know how fast Mach 6 by vlueboy · · Score: 5, Interesting

    Mac 5 melts aluminum steadily
    Mac 6 melts steel

    And don't forget that keeping this friction heat down also requires a good deal of power.

  7. Re:Interesting... by stjobe · · Score: 2, Interesting

    I agree that using the J58 as an example of a typical jet engine is rather like using an atom bomb as an example of an explosion.
    At the same time, since the J58 is essentially a turbojet/ramjet hybrid, it might be said to be the distant forefather of the X51 engine.

    Oh, and anything that makes me go look at pictures of the most beautiful aircraft in the world, the SR-71, is a good thing.

    --
    "Total destruction the only solution" - Bob Marley
  8. Re:Didn't hit mach 6, just mach 5! by slaad · · Score: 2, Interesting

    Most sources seem to be reporting mach 5, but that msnbc article is rather funny. The caption by the picture says mach 6 and then the article itself says mach 5.

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  9. Re:Interesting... by fahrbot-bot · · Score: 2, Interesting

    How useful is this in the long run?

    The usefulness, overlooked in the summary and (brief) article, but reported in The Register (longer article), is that this vehicle used jet fuel (JP-7) instead of Hydrogen. Additionally, it apparently flamed out at Mach 5, not 6.

    The hypersonic X-51A ignited, burning a mixture of ethylene and JP-7 jet fuel, and once well alight switched over to all jet fuel operation.

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