11 ms·

In the theoretical limit how much improvement in efficiency could such engines provide?

deleted 4y ago
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mdorazio 4y ago
Up to 25% improvement compared to conventional rocket engines according to the Wikipedia page. I haven’t found an actual ISP measurement for this NASA engine, though.
- messe 4y ago
  Is that a 25% improvement in ISP/exhaust velocity or another metric?
  - drtgh 4y ago
    It seems that 25% paragraph on wikipedia cites a non-technical article[1] from 2018: "Theoretical calculations have shown that detonation combustion is 25% more efficient than the isobaric combustion cycle, which corresponds to constant-pressure combustion, which is implemented in the chambers of of modern liquid propulsion engines." From another article[2] of the same year: "Conservatively speaking, a rotating detonation combustor, or RDC, should reduce specific fuel consumption by about 5% compared to a conventional engine. This measure of fuel efficiency is calculated by dividing fuel consumption by power output. A rotating detonation engine generates more power, which drives down specific fuel consumption. A reduction on the order of 5 percent would be a breakthrough, given that designers of conventional engines “try to eke out fractions of a percent,” says Scott Claflin, director of advanced concepts at the Rocket Shop, Aerojet Rocketdyne’s innovation organization." [1] https://rg.ru/2018/01/18/levochkin-vozmozhnost-sozdaniia-detonacionnogo-dvigatelia-podtverdilas.html https://rg.ru/2018/01/18/levochkin-vozmozhnost-sozdaniia-det... [2] https://aerospaceamerica.aiaa.org/departments/increasing-engine-efficiency/ https://aerospaceamerica.aiaa.org/departments/increasing-eng...
    - wolverine876 4y ago
      > that 25% paragraph on wikipedia cites a non-technical article[1] from 2018 The article you footnoted is also in Cyrillic. After all this time, it's amazing to see people trust Wikipedia. It's like they don't care if it's true or not; it's entertainment, pretending to know, not knowledge. A perfect way to spin your wheels forever and go nowhere.
      - messe 4y ago
        > The article you footnoted is also in Cyrillic. And your comment is in Latin, going by your terminology. In the age of decent online translators, do you care to elaborate on why that’s a problem?
      - bobthepanda 4y ago
        I mean, Russia has a fairly large space program, is that surprising?
- kossTKR 4y ago
  25% sounds super disappointing from a laymans perspective and not very "revolutionary" in the grand scheme of time and space. Can't wait until AI will be able to iterate advanced engineering designs in simulation space at incredible speed.
  - grogenaut 4y ago
    From 10% to 35% is a 25% improvement, you're still at 35%... From 70 to 95% is a 25% improvement, but it's a lot more. Going from 98 to 99% is only 1% but also like really a 10x improvment. Rockets are operating at pretty decent efficiency, 25% improvment on an internal combusion engine would be mind blowing and make EVs way less interetsting. There are theoretical maximum efficencies for various types of engines due to thermodynamics. You always lose energy to heat. Entropy is a b**.
    - Lichtso 4y ago
      Technically, from 10% of something to 35% of something is a 350% improvement or a 25 percent point improvement. https://en.wikipedia.org/wiki/Percentage_point https://en.wikipedia.org/wiki/Percentage_point
      - dotancohen 4y ago
        Actually, from 10% of something to 35% of something is a 250% improvement. You already had the first 10%.
      - grogenaut 4y ago
        yes but people often conflate/confuse that... saying the delta in %'s... not % improvement. I agree with you, I'm attempting to point out how a small % increase is a huge actual improvement. This GP was saying that a 25% improvment in the efficiency of a rocket engine was not much to a layman.
  - dotnet00 4y ago
    Simulations aren't really the limiter on engine efficiency, SpaceX etc already lean heavily on simulations. The limiters on engine efficiency at this point are mostly materials and costs, and even the latter are coming down with better fuels (eg Methane, which is extremely popular with rockets debuting this decade) and different design philosophies (eg SpaceX's Raptor engine, which is supposedly under $1M per engine while being the most advanced flight tested rocket engine out there).
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deleted 4y ago

[deleted]

Up to 25% improvement compared to conventional rocket engines according to the Wikipedia page. I haven’t found an actual ISP measurement for this NASA engine, though.

messe 4y ago
Is that a 25% improvement in ISP/exhaust velocity or another metric?
- drtgh 4y ago
  It seems that 25% paragraph on wikipedia cites a non-technical article[1] from 2018: "Theoretical calculations have shown that detonation combustion is 25% more efficient than the isobaric combustion cycle, which corresponds to constant-pressure combustion, which is implemented in the chambers of of modern liquid propulsion engines." From another article[2] of the same year: "Conservatively speaking, a rotating detonation combustor, or RDC, should reduce specific fuel consumption by about 5% compared to a conventional engine. This measure of fuel efficiency is calculated by dividing fuel consumption by power output. A rotating detonation engine generates more power, which drives down specific fuel consumption. A reduction on the order of 5 percent would be a breakthrough, given that designers of conventional engines “try to eke out fractions of a percent,” says Scott Claflin, director of advanced concepts at the Rocket Shop, Aerojet Rocketdyne’s innovation organization." [1] https://rg.ru/2018/01/18/levochkin-vozmozhnost-sozdaniia-detonacionnogo-dvigatelia-podtverdilas.html https://rg.ru/2018/01/18/levochkin-vozmozhnost-sozdaniia-det... [2] https://aerospaceamerica.aiaa.org/departments/increasing-engine-efficiency/ https://aerospaceamerica.aiaa.org/departments/increasing-eng...
  - wolverine876 4y ago
    > that 25% paragraph on wikipedia cites a non-technical article[1] from 2018 The article you footnoted is also in Cyrillic. After all this time, it's amazing to see people trust Wikipedia. It's like they don't care if it's true or not; it's entertainment, pretending to know, not knowledge. A perfect way to spin your wheels forever and go nowhere.
    - messe 4y ago
      > The article you footnoted is also in Cyrillic. And your comment is in Latin, going by your terminology. In the age of decent online translators, do you care to elaborate on why that’s a problem?
    - bobthepanda 4y ago
      I mean, Russia has a fairly large space program, is that surprising?
kossTKR 4y ago
25% sounds super disappointing from a laymans perspective and not very "revolutionary" in the grand scheme of time and space. Can't wait until AI will be able to iterate advanced engineering designs in simulation space at incredible speed.
- grogenaut 4y ago
  From 10% to 35% is a 25% improvement, you're still at 35%... From 70 to 95% is a 25% improvement, but it's a lot more. Going from 98 to 99% is only 1% but also like really a 10x improvment. Rockets are operating at pretty decent efficiency, 25% improvment on an internal combusion engine would be mind blowing and make EVs way less interetsting. There are theoretical maximum efficencies for various types of engines due to thermodynamics. You always lose energy to heat. Entropy is a b**.
  - Lichtso 4y ago
    Technically, from 10% of something to 35% of something is a 350% improvement or a 25 percent point improvement. https://en.wikipedia.org/wiki/Percentage_point https://en.wikipedia.org/wiki/Percentage_point
    - dotancohen 4y ago
      Actually, from 10% of something to 35% of something is a 250% improvement. You already had the first 10%.
    - grogenaut 4y ago
      yes but people often conflate/confuse that... saying the delta in %'s... not % improvement. I agree with you, I'm attempting to point out how a small % increase is a huge actual improvement. This GP was saying that a 25% improvment in the efficiency of a rocket engine was not much to a layman.
- dotnet00 4y ago
  Simulations aren't really the limiter on engine efficiency, SpaceX etc already lean heavily on simulations. The limiters on engine efficiency at this point are mostly materials and costs, and even the latter are coming down with better fuels (eg Methane, which is extremely popular with rockets debuting this decade) and different design philosophies (eg SpaceX's Raptor engine, which is supposedly under $1M per engine while being the most advanced flight tested rocket engine out there).

deleted 4y ago

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