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Transportation

A New Type of Jet Engine Could Revive Supersonic Air Travel (yahoo.com) 58

Posted by EditorDavid from the beyond-Concorde dept.
"Since the 1960s engineers around the world have been fiddling with a novel type of jet called a rotating detonation engine (RDE), but it has never got beyond the experimental stage," reports the Economist.

"That could be about to change." GE Aerospace, one of the world's biggest producers of jet engines, recently announced it was developing a working version. Earlier this year America's Defence Advanced Research Projects Agency awarded a $29m contract to Raytheon, part of RTX, another big aerospace group, to develop an RDE called Gambit.

Both engines would be used to propel missiles, overcoming the range and speed limitations of current propulsion systems, including rockets and existing types of jet engines. However, if the companies are successful in getting them to work, RDEs might have a much broader role in aviation — including the possibility of helping revive supersonic air travel.

In a nutshell, an RDE "replaces fire with a controlled explosion", explains Kareem Ahmed, an expert in advanced aerospace engines at the University of Central Florida. In technical terms, this is because a jet engine relies on the combustion of oxygen and fuel, which is a subsonic reaction that scientists call deflagration. Detonation, by comparison, is a high-energy explosion that takes place at supersonic speeds. As a result it is a more powerful and potentially a more efficient way of producing thrust, the force that drives an aircraft forward...

By modifying an aircraft's fuselage and wings, engineers believe they can reduce the boom's impact on the ground below. Such work will help to determine whether or not future supersonic passenger planes will, like Concorde, be restricted to flying beyond the speed of sound only over oceans.
Thanks to long-time Slashdot reader SpzToid for sharing the article.
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A New Type of Jet Engine Could Revive Supersonic Air Travel More

A New Type of Jet Engine Could Revive Supersonic Air Travel

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  • Saudi Arabias Secret Plan To Keep Us Hooked On Oil (Score:3)

    by MrL0G1C ( 867445 ) on Saturday December 30, 2023 @09:05PM (#64118039) Journal

    [Face Palm.]

    I was watching a video recently about Saudis trying to get us to use more oil via more ICE cars and yes, supersonic jets because they use boatloads of oil. https://youtu.be/aT0r_yJafmg?t... [youtu.be]

    • ICE cars and supersonic jets can run on carbon neutral biofuel or hydrogen.

      Battery power can't compete, ever, with energy density per volume or weight.

      And why do you have some kind of fixation on Saudis, this isn't 1970. USA imported 7 percent of their oil from SA last year. USA produces 42 percent more oil than Saudi Arabia.

      • Re: (Score:3)

        by rossdee ( 243626 )

        "supersonic jets can run on carbon neutral biofuel or hydrogen"

        It won't be economical unless you have low cost fusion or something to produce the zero carbon fuel in quantity.
        Concord never made any money even when oil was cheap, there were only a few people rich enough to afford it.

        Of course this new engine will make sense for the military, where cost is not a consideration.

        • Re: (Score:3)

          by PPH ( 736903 )

          It turns out that there might be quite a bit of underground hydrogen. We'll just drill for it. The problem with hydrogen (compared to liquid fuels) is that the in-vehicle storage is expensive and heavy due to the pressures required.

        • Concord never made any money even when oil was cheap,

          That's largely because the route Concorde was designed for (West coast USA to Europe) did not get approval for supersonic travel over the US continent.

        • Re:Saudi Arabias Secret Plan To Keep Us Hooked On (Score:5, Informative)

          by CaptQuark ( 2706165 ) on Sunday December 31, 2023 @01:36AM (#64118477)

          NASA and the US Air Force have been studying the pulse detonation engine for many years and just this year achieved some breakthrough designs using metallic 3D-printed parts. Here is a video showing NASA's work from earlier this year. https://youtu.be/RVxgyz_avQM [youtu.be]

        • Re:Saudi Arabias Secret Plan To Keep Us Hooked On (Score:5, Informative)

          by Richard_at_work ( 517087 ) on Sunday December 31, 2023 @04:38AM (#64118643)

          Concorde not making airlines money was largely a myth - from about 1990 to its retirement, it was one of British Airways best profit centres. Before then, British Airways was still operating under the agreements which carried over from when they were publicly owned, and Concorde was operated as a prestige thing first, revenue source second - when those agreements expired, BA jacked up the prices and found that their customer base didn't really notice, so operating Concorde became profitable.

          • "from about 1990 to its retirement, it was one of British Airways best profit centres."

            Until 1987, the British Concordes were owned by the British government and leased to British Airways. In that year they were sold to BA below cost. They were profitable to BA because they were no longer paying towards the NRE from their development.

            • Re: (Score:2)

              by mjwx ( 966435 )

              "from about 1990 to its retirement, it was one of British Airways best profit centres."

              Until 1987, the British Concordes were owned by the British government and leased to British Airways. In that year they were sold to BA below cost. They were profitable to BA because they were no longer paying towards the NRE from their development.

              A major problem the Concorde had was that it was never scalable. London/Paris to New York was pretty much the limit of it's range. A modern jet runs LHR-JFK in 8 hours (7.5 on a good run), the Concorde took 3.5.

              Singapore ran a Concorde from London to Singapore, a 14 hour journey by a SQ A380 but because the Concorde required a refuelling stop it took 10 hours. They only ran 3 flights before binning the idea, countries refusing to permit supersonic overflights only made the situation even worse, so the Co

            • British Airways was government owned until 1987, so your dates are quite off.

              Concorde was operated by BA between 1976 and 1983 under an operating cost lease from the British government - however, BA paid full price for the original orders, and received unsold airframes at a reduced cost. When BA was privatised in 1987, no further

              By 1981, Concorde was making a $4Million a year operating profit on the London-New York route - 80% of which was returned to the British government under the lease agreement. So i

        • So what is the theoretical limit of battery energy density? I'm not talking about just lithium ion batteries, but any batteries.

          However, not being able get to places quickly enough is not really any of the main challenges of the humanity. The biggest issue is climate change, and at the moment any usage of biofuel cannot be offset by more biofuel production. So unless we at some point achieve abundance of biofuel, then the supersonic jets might be a good thing. Until then, they are mostly a bad thing on the

        • It won't be economical unless you have low cost fusion or something to produce the zero carbon fuel in quantity. Concord never made any money even when oil was cheap, there were only a few people rich enough to afford it.

          Of course this new engine will make sense for the military, where cost is not a consideration.

          Concord burned most of its fuel on the ground and in subsonic flight. It was very efficient in supercruise.

        • Both Air France and British Airways turned an operational profit flying the Concord over the long haul. Development cost over runs in the 60's and 70's were a definite loser. The forecast looked dismal when it was retired due to the crashes, slump in travel after 9/11, and the fact it was a ~40 year old design by then and would have needed an overhaul if not immediately, very soon. They should have let Branson buy them and have a go at it.

          A great deal has changed in the last 50 years where it may be pos

      • Re: (Score:2)

        by Rei ( 128717 )

        1) "Ever" is a strong statement. Batteries have the potential to use higher energy-density reactions, such as boron + oxygen, lithium + fluorine, etc (both examples are nearly double the energy density of kerosone + oxygen) than those which are practical in open-combustion cycles, due to cost and pollution. Though of course you then kind of blur the boundary between what's a battery, what's a flow battery, and what's a fuel cell.

        2) A vehicle is not just its fuel or its batteries. You can no more drive a

        • Batteries have the potential to use higher energy-density reactions...

          Even if we had a super-battery with ten times the energy density of jet fuel that battery would be powering a propeller and that means subsonic flight. The fastest electric-powered options are maglev trains in partially evacuated tunnels which have huge infrastructure costs but they would be a lot faster than planes.

          • Subsonic works just fine for almost everything now. While supersonic may have its niches, slicing an hour or two off of a domestic flight isn't going to change most uses. Long-distance will differ somewhat, but even then, subsonic is going to be more economical for most uses.

    • Re: (Score:3)

      by Rei ( 128717 )

      Ignore the spin about supersonic passenger jets. Maybe some day, but this is first and foremost a technology that the military will be all over.

  • If only they could find some scientists who have storied m studied detonation in those engines. :)

    Everything is is new again

  • Beautiful solution (Score:3)

    by ThumpBzztZoom ( 6976422 ) on Saturday December 30, 2023 @09:48PM (#64118091)

    "You know what would make this plane quieter? Explosions." - My new engineering hero.

    • Re: (Score:2)

      by dgatwood ( 11270 )

      "You know what would make this plane quieter? Explosions." - My new engineering hero.

      This sounds like a modern version of a pulsejet. What's old is new again.

      • Re: (Score:3)

        by Rei ( 128717 )

        Not exactly. Ignoring that pulsejets involve deflagrations, not detonations, what you're thinking of is a pulse detonation engine (and yes, those are EXTREMELY noisy). This is a rotary detonation engine. It's a "continuous explosion", akin to a continuous flame, but at supersonic velocity inside shockwaves. To the degree that there's noise, it won't be from periodic shockwave surges, like one associates with explosions, but rather, the fact that the combustion wavefront is continuously spiraling around

        • Re: (Score:2)

          by ceoyoyo ( 59147 )

          The noisy thing about detonations, explosions included, is that "supersonic" bit. Supersonic means there's a shockwave. Being continuous doesn't really make it better. Rotation detonation engines are very noisy.

          • Yes, RDEs *are* extremely noisy -- they have a very distinctive screech... somewhat like afterburner screech.

            Any kind of aircraft using them for commercial service would almost certainly have to be a hybrid of some kind, using a far quieter engine to get them to altitude before engaging the RDE so that the noise was less of a factor. Of course all high-speed flight needs to be done at high altitude anyway because the air is simply too dense at lower altitudes.

            The hybrid configuration would add weight and c

      • Pulse jets were still using conventional combustion, not detonation. Detonation waves travel much faster than flame fronts - faster than ambient temperature sonic.

        Detonation waves have higher temperature and potentially higher efficiency, but lots of engineering challenges

        • Yes, there are *many* challenges... not the least of which is that of reliably sustaining the detonation. Think of it as trying to keep a candle lit in a hurricane.

          It took a long time for researchers to produce an RDE that would run for more than a few short seconds without stopping, due to the precarious nature of the rotating shock wave and its sensitivity to pressure/density, temperature and other factors.

          Going from "we got it working" to "we have a commercially viable product in production" is a huge s

    • "You know what would make this plane quieter? Explosions." - My new engineering hero.

      It only takes one.

  • Defence? (Score:3, Funny)

    by alleycat0 ( 232486 ) on Saturday December 30, 2023 @10:16PM (#64118133) Homepage
    America doesn't have a Defence Advanced Research Projects Agency - it has a *Defense* Advanced Research Projects Agency. /pedant

  • - This is interesting to the science nerd in me, with or without any practical application

    - They've talked about modifying wing design to reduce sonic boom with conventional jet engines as well - that's nothing new

    - I'd thought the primary reason supersonic flight never took off was the cost - and, while this may make it relatively cheaper, I expect it'll still be expensive enough that most people won't be willing to pay for the flights

    - It seems like there are always a small group of people beating the dru

    • Re: (Score:2)

      by Rei ( 128717 )

      Yeah, but missile-, fighter-, and UCAV designers are drooling over getting their hands on a mature RDE ;)

      That said, engines were at least one of the reasons that supersonic passenger aircraft were expensive to design and operate relative to their passenger capacity. It's always been hard to design an engine that's efficient at both low-speeds and supersonic speeds (though technology has been advancing). I'm not sure that RDEs help that, but engines definitely are one area that needs work.

    • - I'd thought the primary reason supersonic flight never took off was the cost

      You are mostly right. When you exceed the speed of sound, the aerodynamic drag rises significantly. This costs more fuel and limits the range of the aircraft.

      But the Concorde took off because it was designed to be more fuel efficient. The point is that jet engines become more efficient when the air is accelerated as little as possible. For a given thrust and engine diameter, this means flying as fast as possible.

      You can imagine how much engineering went into the design of the Concorde to minimize the drag r

  • Aiming the sound makes sense, but wouldn't smaller more frequent pulses help lower the sonic boom too?

    And what are they using? I kept thinking of a solid explosive but dissolved into solution. Like put C4 into gasoline or whatever can dissolve it. Then explode the mixture (solvent and solute).

    • The sonic boom is from the shock wave formed at the leading edges of the fuselage and wings. It is not from the engine.

  • There's always classified patents around jet engines, specifically because they are used in missles. This won't see the light of day for decades.

  • Over the ocean, uninhabited land is one thing, but that was part of the issue with the SST's. No one wants to hear the sonic booms over their homes daily, which is why (in the USA anyway) they were restricted to the coasts.

    • Over the ocean, uninhabited land is one thing, but that was part of the issue with the SST's. No one wants to hear the sonic booms over their homes daily, which is why (in the USA anyway) they were restricted to the coasts.

      Some European countries also banned supersonic flight over land for teh same reasons the US did.

  • >"A New Type of Jet Engine Could Revive Supersonic Air Travel"

    Perhaps they should work or reviving AIRPORTS first. As long as the nightmare security theater and poor on-time track record continue, I think I will just stay at home. I don't know a SINGLE person who has taken a trip in years that hasn't had to deal with a late arrival/departure or missed connection or canceled flight, often multiple ones in one trip. One of my employees got stranded and had to spend the night somewhere AT HER OWN EXPENSE

  • there are POC engines that start as rde and switch to oblique at higher speeds.

    kinda reminds me of how the sr-71 engines used an adjustable engine where that cone in front of the intake slid in and out.

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