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I don’t usually post a middlebrow dismissal, but using an electric compressor is a fairly obvious idea which often gets discussed and immediately dismissed, so

I don’t usually post a middlebrow dismissal, but using an electric compressor is a fairly obvious idea which often gets discussed and immediately dismissed, so there’s not much interesting here until they reveal more of their design. Typical discussion: https://aviation.stackexchange.com/questions/90862/are-there-hybrid-electric-combustion-turbine-engines-where-only-the-compressor-i https://aviation.stackexchange.com/questions/90862/are-there...

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teeray 3y ago
I remember reading somewhere that electric compressor stages are apparently getting used to reduce input lag on automotive turbo chargers.
- JumpCrisscross 3y ago
  > lectric compressor stages are apparently getting used to reduce input lag on automotive turbo chargers Yup, E-Turbo [1]. [1] https://www.motortrend.com/how-to/e-turbo-electric-assist-turbocharger/ https://www.motortrend.com/how-to/e-turbo-electric-assist-tu...
  - silon42 3y ago
    In F1 they also recover energy and charge battery or help power the electric motor (as explained in the article)
    - TrickyRick 3y ago
      Until the new engine rules when it will be removed because it was deemed to expensive, complex and the technology didn't translate to road cars enough for them to justify the R&D.
      - chronogram 3y ago
        Which is a shame because it's the most fun part of the F1 engines to me.
        genman 3y ago
        And the only thing that would justify this kind of global waste.
  - dclowd9901 3y ago
    Even that’s not interesting. It’s just an electric version of an antilag system, first developed in the 80s.
    - wolverine876 3y ago
      Rockets were first developed 1,000 years ago. Nothing is interesting, by your reasoning.
      - jgeada 3y ago
        The liquid fuel rocket motor was only invented 98 years ago (https://www.nasa.gov/history/95-years-ago-goddards-first-liquid-fueled-rocket/ https://www.nasa.gov/history/95-years-ago-goddards-first-liq...) Though borderline possible, it is very hard for solid fuel rockets to make it to orbit, and they have horrible payload to total mass ratios. It all has to do with the specific impulse of the fuels, no solid fuel provides as much as hydrogen/oxygen.
        pfdietz 3y ago
        It's not so much just the Isp -- rockets can easily get to orbit on LOX/RP-1; LOX-LH2 is not needed -- but also dry mass of the stage. Basically the entire solid rocket motor is a thrust chamber, and must be strong enough to withstand that pressure. In a pump fed liquid propellant rocket, this is not the case: the tanks need only withstand a pressure high enough to avoid cavitation in the pumps.
alecco 3y ago
OP engine's goal is "as the first stage of an orbital launch vehicle. [...] get payloads to orbit dramatically cheaper than all-rocket systems". The discussion you linked discards electric compressors because of loss of 20% efficiency due to conversions, but for normal air travel.
- c2h5oh 3y ago
  Twitter thread mentions a combined efficiency of >95% thanks to cryocooling from fuel.
audunw 3y ago
I didn’t see much discussion on potential efficiency gains in that thread. A launcher would aim for higher altitudes than an airplane, so the question of maintaining efficiency the whole way becomes much more important. I suspect this kind of engine would need something like a single-use aluminium air battery to make sense though. You could get really high energy density that way. Power density might be a challenge though.
- Tuna-Fish 3y ago
  I would assume they just use a generator on the shaft? This would be dramatically more weight-efficient than any kind of batteries.
  - vajrabum 3y ago
    Scott Manley in the X thread said "So, is the turbine section driving a generator to make electricity to power the compressor" and Ian Brooke replied "Exactly that. ... The key insight is to use electric motors to drive a compressor. That way we can make it spin at any speed, allowing it to "adapt" to it's airspeed and combustion cycle."
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teeray 3y ago

I remember reading somewhere that electric compressor stages are apparently getting used to reduce input lag on automotive turbo chargers.

JumpCrisscross 3y ago
> lectric compressor stages are apparently getting used to reduce input lag on automotive turbo chargers Yup, E-Turbo [1]. [1] https://www.motortrend.com/how-to/e-turbo-electric-assist-turbocharger/ https://www.motortrend.com/how-to/e-turbo-electric-assist-tu...
- silon42 3y ago
  In F1 they also recover energy and charge battery or help power the electric motor (as explained in the article)
  - TrickyRick 3y ago
    Until the new engine rules when it will be removed because it was deemed to expensive, complex and the technology didn't translate to road cars enough for them to justify the R&D.
    - chronogram 3y ago
      Which is a shame because it's the most fun part of the F1 engines to me.
      - genman 3y ago
        And the only thing that would justify this kind of global waste.
- dclowd9901 3y ago
  Even that’s not interesting. It’s just an electric version of an antilag system, first developed in the 80s.
  - wolverine876 3y ago
    Rockets were first developed 1,000 years ago. Nothing is interesting, by your reasoning.
    - jgeada 3y ago
      The liquid fuel rocket motor was only invented 98 years ago (https://www.nasa.gov/history/95-years-ago-goddards-first-liquid-fueled-rocket/ https://www.nasa.gov/history/95-years-ago-goddards-first-liq...) Though borderline possible, it is very hard for solid fuel rockets to make it to orbit, and they have horrible payload to total mass ratios. It all has to do with the specific impulse of the fuels, no solid fuel provides as much as hydrogen/oxygen.
      - pfdietz 3y ago
        It's not so much just the Isp -- rockets can easily get to orbit on LOX/RP-1; LOX-LH2 is not needed -- but also dry mass of the stage. Basically the entire solid rocket motor is a thrust chamber, and must be strong enough to withstand that pressure. In a pump fed liquid propellant rocket, this is not the case: the tanks need only withstand a pressure high enough to avoid cavitation in the pumps.

alecco 3y ago

OP engine's goal is "as the first stage of an orbital launch vehicle. [...] get payloads to orbit dramatically cheaper than all-rocket systems". The discussion you linked discards electric compressors because of loss of 20% efficiency due to conversions, but for normal air travel.

c2h5oh 3y ago
Twitter thread mentions a combined efficiency of >95% thanks to cryocooling from fuel.

audunw 3y ago

I didn’t see much discussion on potential efficiency gains in that thread. A launcher would aim for higher altitudes than an airplane, so the question of maintaining efficiency the whole way becomes much more important. I suspect this kind of engine would need something like a single-use aluminium air battery to make sense though. You could get really high energy density that way. Power density might be a challenge though.

Tuna-Fish 3y ago
I would assume they just use a generator on the shaft? This would be dramatically more weight-efficient than any kind of batteries.
- vajrabum 3y ago
  Scott Manley in the X thread said "So, is the turbine section driving a generator to make electricity to power the compressor" and Ian Brooke replied "Exactly that. ... The key insight is to use electric motors to drive a compressor. That way we can make it spin at any speed, allowing it to "adapt" to it's airspeed and combustion cycle."

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