7 ms·

New jet engine enables efficiency at every speed for cheaper orbital launches

164 points by thoughtpeddler 3y ago

MilStdJunkie 3y ago
Rotating Detonation Engine of some kind? I've had a bit of a thrust-crush on that configuration since I heard they were working on the fluid dynamics to make them work. Pulse Detonation Engines are cool and all, but no one wants a kilometer of tailpipe hanging off the ass end of their vehicle. That fluid problem really is the Achille's heel of RDE, because it requires such a clean airflow in the thing, in order to synchronize the blast waves. The longest burns to date, so far as I know, have been with LOX.
- ethbr1 3y ago
  They look otherworldly too. Recent NASA test: https://m.youtube.com/watch?v=UShD03eG9IU https://m.youtube.com/watch?v=UShD03eG9IU
  - nielsbot 3y ago
    Was this a destructive test? Thing looks like it destroyed itself. (What's with the foil just flying all over the place?)
    - ridgeguy 3y ago
      Some of the instrumentation wire harnesses were wrapped in foil, which got ripped off by air currents driven by the exhaust plume. Foil wraps shield against heating by IR radiation from the plume. It's cheap but effective.
    - MilStdJunkie 3y ago
      The sound from these things can literally tear other nearby assemblies apart. Aside from the "clean flow" problem, this is another gigantic engineering hurdle to scaling these things up to a larger size. There's such a thing as too powerful.
- nielsbot 3y ago
  > no one wants a kilometer of tailpipe hanging off the ass end of their vehicle speak for yourself
- JumpCrisscross 3y ago
  > Rotating Detonation Engine of some kind? No, if only by the sound. By the way, what happened to SABRE [1]. Slowly plugging along, or a victim of Brexit? [1] https://en.wikipedia.org/wiki/SABRE_(rocket_engine)#History https://en.wikipedia.org/wiki/SABRE_(rocket_engine)#History
  - mattashii 3y ago
    Most "news articles" on the company website over the past year were joint projects from spinoff technologies and corporate rewards, with the most exciting things being them raising 40 million last year. In the meantime, I've noticed that another company "Hermeus" is building on similar concept engines to be used on their hypersonic planes, though currently they seem to be targeting modified versions of existing jet engines (changing the compressor while keeping combustion chamber intact), not a whole new model of jet engine.
jacknews 3y ago
"The key insight is to use electric motors to drive a compressor." Is this for the air intake? There must be a speed limit to this surely, and then you have to close intake and switch to rocket mode or something? And then there's the weight of the batteries and motors - I guess you could re-purpose those as oxidizer pump or whatever maybe. And is that an aerospike? A nice idea, but problematic for thermals. I mean I assume they have something working, but I'm skeptical of the concept.
- JumpCrisscross 3y ago
  > must be a speed limit to this surely, Why? Scramjets combust supersonic flows [1]. > aerospike If this is a jet engine, as described, that's the back of the turbine. [1] https://en.wikipedia.org/wiki/Scramjet https://en.wikipedia.org/wiki/Scramjet
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  - jacknews 3y ago
    I don't think scramjets have turbines?
    - JumpCrisscross 3y ago
      This isn’t a scramjet. We watched it cold start and it has a compressor.
      - jacknews 3y ago
        Exactly, so why are you posting a link to scramjets, in relation to supersonic combustion? I don't think a turbine engine can handle hypersonic speeds, and so this will only work in the first phase of flight, as a booster. Or if it's intended for SSO, the intake will have to close at higher speeds, or the very least the turbine stopped, and the engine switch to rocket mode, with oxidizer pumped in somehow. And then the 'back of the turbine' will likely have thermal issues.
PBnFlash 3y ago
This seems to not have consideration for hypersonic air flow. If this is just a lifting engine it can only provide a small fraction of delta v.
- inamberclad 3y ago
  I asked this of the Stratolaunch people several years ago. They said there's an advantage to simply lifting the vehicle that high, it's already starting with more potential energy than it would at sea level. However, it hasn't seem to have made them competitive...
  - JumpCrisscross 3y ago
    > there's an advantage to simply lifting the vehicle that high, it's already starting with more potential energy than it would at sea level This implies dropping to presumably start a scramjet? Otherwise, all you're getting is a bit of altitude and softer max Q. The surprise advantage of air-launched vehicles is you can launch from any airfield. The surprise disadvantage is you need strength two directions; vertically, when it's thrusting, and horizontally, when it's hung underwing.
  - powderpig 3y ago
    Virgin Orbit anyone?
akamaka 3y ago
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.
thot_experiment 3y ago
Press X to doubt. I'll believe it when I see it. "The key insight is to use electric motors to drive a compressor" Uhhhh what? This just does not seem like a good approach, admittedly most of my aerospace knowledge comes from KSP and Scott Manley videos, but the atmosphere thins out pretty damn quick and if they're saying that they can get a benefit on a first stage by getting their oxidizer from atmo in exchange for a bunch of hardware and batteries color me extremely skeptical. This is a field that has had it's problems attacked by a lot of very smart people and the even if this made sense (to my amateur eye it doesn't) the devil is in the details. Hope I'm wrong though!
- SkyMarshal 3y ago
  Are they really using batteries, or do they have constant electrical generation via a turbine or something? Seems batteries for this thing would add a lot of weight.
  - JumpCrisscross 3y ago
    > batteries for this thing would add a lot of weight The only reason I can think they would choose launch over e.g. drones is that it's powerful but doesn't last long. That implies supercapacitors.
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  - cobbal 3y ago
    The electron rocket used batteries to drive the fuel pumps for a liquid engine that could get into orbit. It used a lot of LiPo batteries, which it jettisoned as they were used up.
- powderpig 3y ago
  Conventional jet engines run at RPMs in excess of 20000rpm. To get this same speeds for the same mass flown rates of say a J79 (F4-Phantom) you'd be looking at some massive electric motors. Conventional jet engines would be using electric motors if they were light enough already. There is a reason Rolls-Royce UltraFan uses a speed reducing gearbox for it's fan blades and not an electric motor. More to the point above, at hypersonic speeds, using a conventional compressor is sort or useless unless you can keep your air cool.
pfdietz 3y ago
An air breathing engine is used early in a launch. That means it's in competition with a rocket propelled first stage. But first stages are the least sensitive part of a rocket to Isp. They are more sensitive to thrust/weight ratio of the engines, and on that metric air breathing engines are grossly inferior to rockets.
- sigmoid10 3y ago
  I think this is not meant to directly replace the first stage engines for a conventional rocket. Instead you'd use an approach like SpaceShipOne where you launch like a normal plane using jet engines and then only fire rocket engines once you run out of air. It would be cool to have this approach in a single vehicle. Thrust to weight is less of a consideration there. Although it will still be expensive to carry two radically different types of engines. I'd love to see an engine like this that can seamlessly switch to burning oxidizer that was brought along for the ride. Maybe even combined with an aerospike to get every last bit of efficiency out of higher altitudes. Then we might get true scifi SSTO spacecraft. Think of a 737 but it can go to space.
  - schnitzelstoat 3y ago
    But instead of using the aeroplane you could just use a conventional first stage rocket? I don't think I understand what advantage the aeroplane gives.
    - defrost 3y ago
      Lift from wings means overall less fuel usage, launch from an aircraft increases the choice of "launch rockets from here" locations. ie. Can presumeably get closer to the equator and choose the desired "west to east" ascent line (and fall to earth line for debris in case of rocket failure).
      - Timshel 3y ago
        Video on the subject from EverydayAstronaut https://m.youtube.com/watch?v=AAt9WDQEMoA https://m.youtube.com/watch?v=AAt9WDQEMoA Those gains appear more marginal than expected.
wenyuanyu 3y ago
Not sure if I understood correctly, but does this mean that instead of going up vertically, with this engine, the "rocket" should fly near horizontally and stay in the atmosphere at the right altitude until it reached the highest possible speed given the air resistance, and then lift up by the 2nd stage rocket engines?
- lmm 3y ago
  Rockets already mostly do this - they start pitching over at a fairly low altitude (10-30km), or sometimes immediately on launch, and thrust near horizontally. But yeah, theoretically an air-breathing rocket would fly lower for longer, or for some designs even dive down for part of the trajectory.
  - dredmorbius 3y ago
    That's actually pretty backwards. Rockets take off vertically, then pitch over not for aerodynamics but because reaching orbital velocity requires going sideways VERY fast. They don't pitch over at very low altitudes (with rare exceptions) because the air resistance from high-speed movement is simply too great. Among the exceptions was the Nike Hercules missile interceptor. As its target was ballistic missiles on a hypersonic ballistic trajectory, the Nike Sprint had to go very fast, in the lower atmosphere, going from 0 to Mach 10 in 15 seconds, sustaining 100 Gs and reaching a skin temperature of over 6,000°F, glowing white, within seconds of launch: <https://yewtu.be/watch?v=kpHE9O8ckno&t=168 https://yewtu.be/watch?v=kpHE9O8ckno&t=168> Sounding rockets, used in early rocketry and atmospheric / astronomic research would in fact launch near vertically. Their goal wasn't to go orbital, but merely to get above (most) of the Earth's atmosphere. Early US sounding rockets were the WAC Corporal (max altitude ~235,000 ft / 72 km) and Aerobee (260 mi / 418 km), each with about 60 kg payload capacity. Neither was an orbit-capable launcher. <https://en.wikipedia.org/wiki/WAC_Corporal https://en.wikipedia.org/wiki/WAC_Corporal> <https://en.wikipedia.org/wiki/Aerobee https://en.wikipedia.org/wiki/Aerobee>
    - cm2187 3y ago
      I was wondering how a missile interceptor was even possible in the 50s given the insane precision required to hit a bullet with a bullet at those speeds, but it actually uses a nuclear warhead.
mike_d 3y ago
We already have the technology for cheap orbital launches. SpaceRyde was developing a balloon that would take payloads to the edge of space then use a small rocket to get it the last little bit and do orbit positioning. Unfortunately they got shut down by NIMBYs. https://spacenews.com/noise-complaints-help-bring-down-launch-startup-spaceryde/ https://spacenews.com/noise-complaints-help-bring-down-launc...
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- littlestymaar 3y ago
  This makes no sense. Getting up in altitude is the cheapest part of getting in orbit: the goal of the rocket is to bring you to orbital speed, which is what's hard. So the small rocket would still need to be almost as big (a bit smaller due to lower air friction at high altitude and the higher potential energy at launch, but only marginally so)
  - mike_d 3y ago
    > Getting up in altitude is the cheapest part of getting in orbit Think about it this way: The 30th second of a rocket flight consumes less fuel than the first second because you are carrying 30 seconds less of fuel. https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
- maxhille 3y ago
  Getting into orbit is more about horizontal speed than altitude.
  - sjducb 3y ago
    Rocket engines are much more efficient at lower atmospheric pressure. The bigger the nozzle the faster the exhaust gas. Efficiency is proportional to the square of the speed of the exhaust gas. The bigger the nozzle the lower the pressure of the exhaust gas. If the nozzle is too big then the atmospheric gas goes into the nozzle. That’s the limit on nozzle size for sea level launches. Starting high is better because you can have a MUCH more efficient engine.
marze 3y ago
Andrew Cote gives the missing details here: https://twitter.com/Andercot/status/1763063321857757210 https://twitter.com/Andercot/status/1763063321857757210
- JumpCrisscross 3y ago
  If it can truly "act as the first stage of a rocket," that's impressive--the most powerful jet engine ever built. If, instead, it will power a plane that will carry a rocket, that's a well-trodden path whose engineering problem is not particularly related to the carrier's efficiency. [1] https://en.wikipedia.org/wiki/Geared_turbofan https://en.wikipedia.org/wiki/Geared_turbofan
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  - carabiner 3y ago
    GTF is exactly what it is. The fact that Andrew Cote missed this is a testament to his lack of familiarity with anything in aerospace.
    - modeless 3y ago
      Don't geared turbofans typically have a fixed gear ratio? This is more like a continuously variable transmission for a turbofan. Seems novel at least.
      - JumpCrisscross 3y ago
        > Don't geared turbofans typically have a fixed gear ratio? This is more like a continuously variable transmission for a turbofan Yes and no. An electric compressor doesn't mean the turbine doesn't drive the fan. (It might make pre-cooling easier.)
        modeless 3y ago
JumpCrisscross 3y ago
I'm sceptical but optimistic. The problem with turbofans (the most efficient jet engine at high subsonic speeds) is the fan, compressor and turbine have different optimal speeds. (The fan wants to spin slow to promote a high bypass ratio without tearing the blades apart while the compressor and turbine want to run at full power.) The conventional solution is additional compressor and turbine stages. The novel one is the geared turbofan. Both, to my knowledge, are tuned for a specific airspeed and altitude. What these guys seem to be getting at is driving the compressor separately. That doesn't decouple the turbine from the fan, but if they're racing to Mach 3 and then dumping off, they don't need a fan. Altogether, there is an efficiency threshold past which a turbojet first-stage (probably rocket-supplemented) makes sense. Where I'm sceptical is in choosing launch as the beachhead. If you have a better turbojet--particularly one pitching efficiency over thrust--you should be building drones. Probably missiles. You'll get more build opportunities at a smaller scale, lengthening your runway and speeding up your learning curve. You have more customers and a cleaner path to export. You get to segregate the subsonic and supersonic markets in engineering time and capital deployment. The only reason to go for space first are passion over practicality, a need for vaporware-insensitive investors or an additional design advantage not yet disclosed.
- mvkel 3y ago
  Great points. So not only is the tech iffy, but the application is misguided.
  - JumpCrisscross 3y ago
    > not only is the tech iffy I make no comment on the quality of the tech–we don't know much about it. Only that based on how they describe it, the product-market fit seems forced for orbital launch.
- sjducb 3y ago
  Space is better for marketing and gaining traction. I strongly suspect they’re quietly talking to missile manufacturers.
- mechhacker 3y ago
inamberclad 3y ago
Why would you use an aerospace for this when conventional turbojets use an articulating nozzle? In fact, they'd be better off trying to develop and sell an articulating nozzle for a conventional rocket than a whole engine such as this
dredmorbius 3y ago
As Nitter is broken and Twitter has ... numerous issues, is there a non-Twitter source for this?
- treme 3y ago
  x is perfectly easy to use or to customize and allows instant sharing of short bits of information in whatever format.
  - klyrs 3y ago
    It's not really an alternative to twitter, though.
  - kataklasm 3y ago
    On mobile it barely loads the tweet for me, doesnt load any of the responses and if I go to the author's profile I get blocked by a login-wall. So no, "x" is not perfectly easy to use, it's utter garbage.
    - treme 3y ago
      make an account. that 2 min effort will allow you the freedom of all the content on x.
- TrickyRick 3y ago
  https://nitter.poast.org/k2pilot/status/1763007610993991722 https://nitter.poast.org/k2pilot/status/1763007610993991722 Seems to be the last one online https://github.com/zedeus/nitter/wiki/Instances https://github.com/zedeus/nitter/wiki/Instances
p1mrx 3y ago
> The key insight is to use electric motors to drive a compressor Tech Ingredients made a "hybrid jet engine" based on this concept in 2018: https://www.youtube.com/watch?v=_ax0pI4Jp18&t=775s https://www.youtube.com/watch?v=_ax0pI4Jp18&t=775s
jvm___ 3y ago
Someone made the positive version of "Unsafe at any speed"
japanuspus 3y ago
Everyday Astronaut has a recent video on "why don't we launch rockets from jets"[0]. The video obviously does not include reference to the engine mentioned here -- but I think most of the points still stand. In particular - orbit is mainly about going fast, not so much about getting up high - your second stage will pay a structural price for allowing air-launch loads, and this structure needs to be carried to orbit - rockets are *big* [0]: https://www.youtube.com/watch?v=AAt9WDQEMoA https://www.youtube.com/watch?v=AAt9WDQEMoA
- audunw 3y ago
  I think what’s missing from Everyday Astronauts discussion is: what if we could make the plane/rocket go much faster. The cruise speed of a jet plane of 800-1000km/h may not be a high enough fraction of orbital velocity to be worth it. But what if you could fly even higher and faster, say 3000km/h, before you do stage separation? Now you’ve actually achieved a significant fraction of orbital velocity. Obviously that would require new technology. And in particular the main challenge is making an engine that can operate efficiently at a wide range of speeds. So this engine could change the equation. But I suspect it’d only make sense for smaller vehicles delivering personnel/cargo to arbitrary orbits on short notice. I also wonder how they can get enough electrical power without a big weight penalty. Keep in mind that Electron is already using electric motors for their pumps. So the question is kind of whether you could also use a motor to capture and compress air to exploit the oxygen in the air rather than having to carry it as payload.
  - fiftyfifty 3y ago
    Minimal orbital speed is somewhere around 25,000-28,000 kph. The fastest air breathing plane every built (SR-71) had a top speed of about 3,500 kph. So for the added weight and complexity of adding an air breathing first stage (wings, air breathing engines, landing gear etc) you are only getting about 14% of the way to the minimal orbital velocity needed, and that would be if your air breathing first stage could match the performance of the fastest plane ever built, keep in mind the SR-71 carried almost no payload. It is far more likely that any realistic air breathing first stage is going to get to less than 10% of orbital velocity, and that would likely be for launching a fairly small rocket. On the other hand the Falcon 9 first stage usually doesn't separate until 6,000-9,000 kph which is closer to 25-35% of orbital velocity, and that's while carrying almost 23,000 kg of payload plus the fully fueled second stage.
kulor 3y ago
An interview (1) with the founder Ian Brooke was illuminating on this jet and the wider opportunity it presents. He sheds a lot of light on the problem space (no pun intended) and how it can be tackled whilst being commercially viable. I particularly enjoyed geeking out the pros and cons of turbo-fan, RAM and SCRAM jets, rockets and the limits of physics. He's oozing Elon vibes in ambition, first-principle thinking, deep domain knowledge and commercial intelligence. One to watch. 1. https://twitter.com/1stPrinciplesFM/status/1762945809572925492/photo/1 https://twitter.com/1stPrinciplesFM/status/17629458095729254...
JoeAltmaier 3y ago
Expect to see every kind of innovation from here on out, as the launch ecosystem fills in every 'ecological niche'. Sure this isn't a direct competitor to {whatever pundits argue}. But if it works for even one kind of mission, then in this modern space age, it has a place. Like road vehicles, there are sedans, commuters, offroad, and heavy haulers, heck even trains. One vehicle will never do it all.
thoughtpeddler 3y ago
Can anyone speculate as to what kind of advancements in precision machining might enable this sort of new jet engine design? I feel, as a layperson when it comes to aerospace, that so much of the innovation is bounded by advancements (or lack thereof) in machining.
supportengineer 3y ago
What happened to the Reaction Engines / Skylon / SABRE? https://news.ycombinator.com/item?id=6062972 https://news.ycombinator.com/item?id=6062972
- Tuna-Fish 3y ago
  Still being worked on. It is a potentially higher-performing system than this one, but also dramatically more complex and expensive. This hybrid engine is interesting in how fundamentally simple and easy to build it is.
EricE 3y ago
Sounds about as practical as an electric supercharger. I would love to be wrong; I guess time will tell.
rich_sasha 3y ago
If the first stage is a SpaceX-style reusable stage, is there any benefit to a jet engine? I suppose perhaps it is more reusable, AFAIR the SoaceX stages have short-ish lifespans.

Rotating Detonation Engine of some kind? I've had a bit of a thrust-crush on that configuration since I heard they were working on the fluid dynamics to make them work. Pulse Detonation Engines are cool and all, but no one wants a kilometer of tailpipe hanging off the ass end of their vehicle. That fluid problem really is the Achille's heel of RDE, because it requires such a clean airflow in the thing, in order to synchronize the blast waves. The longest burns to date, so far as I know, have been with LOX.

ethbr1 3y ago
They look otherworldly too. Recent NASA test: https://m.youtube.com/watch?v=UShD03eG9IU https://m.youtube.com/watch?v=UShD03eG9IU
- nielsbot 3y ago
  Was this a destructive test? Thing looks like it destroyed itself. (What's with the foil just flying all over the place?)
  - ridgeguy 3y ago
    Some of the instrumentation wire harnesses were wrapped in foil, which got ripped off by air currents driven by the exhaust plume. Foil wraps shield against heating by IR radiation from the plume. It's cheap but effective.
  - MilStdJunkie 3y ago
    The sound from these things can literally tear other nearby assemblies apart. Aside from the "clean flow" problem, this is another gigantic engineering hurdle to scaling these things up to a larger size. There's such a thing as too powerful.
nielsbot 3y ago
> no one wants a kilometer of tailpipe hanging off the ass end of their vehicle speak for yourself
JumpCrisscross 3y ago
> Rotating Detonation Engine of some kind? No, if only by the sound. By the way, what happened to SABRE [1]. Slowly plugging along, or a victim of Brexit? [1] https://en.wikipedia.org/wiki/SABRE_(rocket_engine)#History https://en.wikipedia.org/wiki/SABRE_(rocket_engine)#History
- mattashii 3y ago
  Most "news articles" on the company website over the past year were joint projects from spinoff technologies and corporate rewards, with the most exciting things being them raising 40 million last year. In the meantime, I've noticed that another company "Hermeus" is building on similar concept engines to be used on their hypersonic planes, though currently they seem to be targeting modified versions of existing jet engines (changing the compressor while keeping combustion chamber intact), not a whole new model of jet engine.

jacknews 3y ago

"The key insight is to use electric motors to drive a compressor." Is this for the air intake? There must be a speed limit to this surely, and then you have to close intake and switch to rocket mode or something? And then there's the weight of the batteries and motors - I guess you could re-purpose those as oxidizer pump or whatever maybe. And is that an aerospike? A nice idea, but problematic for thermals. I mean I assume they have something working, but I'm skeptical of the concept.

JumpCrisscross 3y ago
> must be a speed limit to this surely, Why? Scramjets combust supersonic flows [1]. > aerospike If this is a jet engine, as described, that's the back of the turbine. [1] https://en.wikipedia.org/wiki/Scramjet https://en.wikipedia.org/wiki/Scramjet
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- jacknews 3y ago
  I don't think scramjets have turbines?
  - JumpCrisscross 3y ago
    This isn’t a scramjet. We watched it cold start and it has a compressor.
    - jacknews 3y ago
      Exactly, so why are you posting a link to scramjets, in relation to supersonic combustion? I don't think a turbine engine can handle hypersonic speeds, and so this will only work in the first phase of flight, as a booster. Or if it's intended for SSO, the intake will have to close at higher speeds, or the very least the turbine stopped, and the engine switch to rocket mode, with oxidizer pumped in somehow. And then the 'back of the turbine' will likely have thermal issues.

PBnFlash 3y ago

This seems to not have consideration for hypersonic air flow. If this is just a lifting engine it can only provide a small fraction of delta v.

inamberclad 3y ago
I asked this of the Stratolaunch people several years ago. They said there's an advantage to simply lifting the vehicle that high, it's already starting with more potential energy than it would at sea level. However, it hasn't seem to have made them competitive...
- JumpCrisscross 3y ago
  > there's an advantage to simply lifting the vehicle that high, it's already starting with more potential energy than it would at sea level This implies dropping to presumably start a scramjet? Otherwise, all you're getting is a bit of altitude and softer max Q. The surprise advantage of air-launched vehicles is you can launch from any airfield. The surprise disadvantage is you need strength two directions; vertically, when it's thrusting, and horizontally, when it's hung underwing.
- powderpig 3y ago
  Virgin Orbit anyone?

akamaka 3y ago

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.

thot_experiment 3y ago

Press X to doubt. I'll believe it when I see it. "The key insight is to use electric motors to drive a compressor" Uhhhh what? This just does not seem like a good approach, admittedly most of my aerospace knowledge comes from KSP and Scott Manley videos, but the atmosphere thins out pretty damn quick and if they're saying that they can get a benefit on a first stage by getting their oxidizer from atmo in exchange for a bunch of hardware and batteries color me extremely skeptical. This is a field that has had it's problems attacked by a lot of very smart people and the even if this made sense (to my amateur eye it doesn't) the devil is in the details. Hope I'm wrong though!

SkyMarshal 3y ago
Are they really using batteries, or do they have constant electrical generation via a turbine or something? Seems batteries for this thing would add a lot of weight.
- JumpCrisscross 3y ago
  > batteries for this thing would add a lot of weight The only reason I can think they would choose launch over e.g. drones is that it's powerful but doesn't last long. That implies supercapacitors.
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- cobbal 3y ago
  The electron rocket used batteries to drive the fuel pumps for a liquid engine that could get into orbit. It used a lot of LiPo batteries, which it jettisoned as they were used up.
powderpig 3y ago
Conventional jet engines run at RPMs in excess of 20000rpm. To get this same speeds for the same mass flown rates of say a J79 (F4-Phantom) you'd be looking at some massive electric motors. Conventional jet engines would be using electric motors if they were light enough already. There is a reason Rolls-Royce UltraFan uses a speed reducing gearbox for it's fan blades and not an electric motor. More to the point above, at hypersonic speeds, using a conventional compressor is sort or useless unless you can keep your air cool.

pfdietz 3y ago

An air breathing engine is used early in a launch. That means it's in competition with a rocket propelled first stage. But first stages are the least sensitive part of a rocket to Isp. They are more sensitive to thrust/weight ratio of the engines, and on that metric air breathing engines are grossly inferior to rockets.

sigmoid10 3y ago
I think this is not meant to directly replace the first stage engines for a conventional rocket. Instead you'd use an approach like SpaceShipOne where you launch like a normal plane using jet engines and then only fire rocket engines once you run out of air. It would be cool to have this approach in a single vehicle. Thrust to weight is less of a consideration there. Although it will still be expensive to carry two radically different types of engines. I'd love to see an engine like this that can seamlessly switch to burning oxidizer that was brought along for the ride. Maybe even combined with an aerospike to get every last bit of efficiency out of higher altitudes. Then we might get true scifi SSTO spacecraft. Think of a 737 but it can go to space.
- schnitzelstoat 3y ago
  But instead of using the aeroplane you could just use a conventional first stage rocket? I don't think I understand what advantage the aeroplane gives.
  - defrost 3y ago
    Lift from wings means overall less fuel usage, launch from an aircraft increases the choice of "launch rockets from here" locations. ie. Can presumeably get closer to the equator and choose the desired "west to east" ascent line (and fall to earth line for debris in case of rocket failure).
    - Timshel 3y ago
      Video on the subject from EverydayAstronaut https://m.youtube.com/watch?v=AAt9WDQEMoA https://m.youtube.com/watch?v=AAt9WDQEMoA Those gains appear more marginal than expected.

wenyuanyu 3y ago

Not sure if I understood correctly, but does this mean that instead of going up vertically, with this engine, the "rocket" should fly near horizontally and stay in the atmosphere at the right altitude until it reached the highest possible speed given the air resistance, and then lift up by the 2nd stage rocket engines?

lmm 3y ago
Rockets already mostly do this - they start pitching over at a fairly low altitude (10-30km), or sometimes immediately on launch, and thrust near horizontally. But yeah, theoretically an air-breathing rocket would fly lower for longer, or for some designs even dive down for part of the trajectory.
- dredmorbius 3y ago
  That's actually pretty backwards. Rockets take off vertically, then pitch over not for aerodynamics but because reaching orbital velocity requires going sideways VERY fast. They don't pitch over at very low altitudes (with rare exceptions) because the air resistance from high-speed movement is simply too great. Among the exceptions was the Nike Hercules missile interceptor. As its target was ballistic missiles on a hypersonic ballistic trajectory, the Nike Sprint had to go very fast, in the lower atmosphere, going from 0 to Mach 10 in 15 seconds, sustaining 100 Gs and reaching a skin temperature of over 6,000°F, glowing white, within seconds of launch: <https://yewtu.be/watch?v=kpHE9O8ckno&t=168 https://yewtu.be/watch?v=kpHE9O8ckno&t=168> Sounding rockets, used in early rocketry and atmospheric / astronomic research would in fact launch near vertically. Their goal wasn't to go orbital, but merely to get above (most) of the Earth's atmosphere. Early US sounding rockets were the WAC Corporal (max altitude ~235,000 ft / 72 km) and Aerobee (260 mi / 418 km), each with about 60 kg payload capacity. Neither was an orbit-capable launcher. <https://en.wikipedia.org/wiki/WAC_Corporal https://en.wikipedia.org/wiki/WAC_Corporal> <https://en.wikipedia.org/wiki/Aerobee https://en.wikipedia.org/wiki/Aerobee>
  - cm2187 3y ago
    I was wondering how a missile interceptor was even possible in the 50s given the insane precision required to hit a bullet with a bullet at those speeds, but it actually uses a nuclear warhead.

mike_d 3y ago

We already have the technology for cheap orbital launches. SpaceRyde was developing a balloon that would take payloads to the edge of space then use a small rocket to get it the last little bit and do orbit positioning. Unfortunately they got shut down by NIMBYs. https://spacenews.com/noise-complaints-help-bring-down-launch-startup-spaceryde/ https://spacenews.com/noise-complaints-help-bring-down-launc...

deleted 3y ago
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littlestymaar 3y ago
This makes no sense. Getting up in altitude is the cheapest part of getting in orbit: the goal of the rocket is to bring you to orbital speed, which is what's hard. So the small rocket would still need to be almost as big (a bit smaller due to lower air friction at high altitude and the higher potential energy at launch, but only marginally so)
- mike_d 3y ago
  > Getting up in altitude is the cheapest part of getting in orbit Think about it this way: The 30th second of a rocket flight consumes less fuel than the first second because you are carrying 30 seconds less of fuel. https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
maxhille 3y ago
Getting into orbit is more about horizontal speed than altitude.
- sjducb 3y ago
  Rocket engines are much more efficient at lower atmospheric pressure. The bigger the nozzle the faster the exhaust gas. Efficiency is proportional to the square of the speed of the exhaust gas. The bigger the nozzle the lower the pressure of the exhaust gas. If the nozzle is too big then the atmospheric gas goes into the nozzle. That’s the limit on nozzle size for sea level launches. Starting high is better because you can have a MUCH more efficient engine.

marze 3y ago

Andrew Cote gives the missing details here: https://twitter.com/Andercot/status/1763063321857757210 https://twitter.com/Andercot/status/1763063321857757210

JumpCrisscross 3y ago
If it can truly "act as the first stage of a rocket," that's impressive--the most powerful jet engine ever built. If, instead, it will power a plane that will carry a rocket, that's a well-trodden path whose engineering problem is not particularly related to the carrier's efficiency. [1] https://en.wikipedia.org/wiki/Geared_turbofan https://en.wikipedia.org/wiki/Geared_turbofan
- deleted 3y ago
  [deleted]
- carabiner 3y ago
  GTF is exactly what it is. The fact that Andrew Cote missed this is a testament to his lack of familiarity with anything in aerospace.
  - modeless 3y ago
    Don't geared turbofans typically have a fixed gear ratio? This is more like a continuously variable transmission for a turbofan. Seems novel at least.
    - JumpCrisscross 3y ago
      > Don't geared turbofans typically have a fixed gear ratio? This is more like a continuously variable transmission for a turbofan Yes and no. An electric compressor doesn't mean the turbine doesn't drive the fan. (It might make pre-cooling easier.)
      - modeless 3y ago

JumpCrisscross 3y ago

I'm sceptical but optimistic. The problem with turbofans (the most efficient jet engine at high subsonic speeds) is the fan, compressor and turbine have different optimal speeds. (The fan wants to spin slow to promote a high bypass ratio without tearing the blades apart while the compressor and turbine want to run at full power.) The conventional solution is additional compressor and turbine stages. The novel one is the geared turbofan. Both, to my knowledge, are tuned for a specific airspeed and altitude. What these guys seem to be getting at is driving the compressor separately. That doesn't decouple the turbine from the fan, but if they're racing to Mach 3 and then dumping off, they don't need a fan. Altogether, there is an efficiency threshold past which a turbojet first-stage (probably rocket-supplemented) makes sense. Where I'm sceptical is in choosing launch as the beachhead. If you have a better turbojet--particularly one pitching efficiency over thrust--you should be building drones. Probably missiles. You'll get more build opportunities at a smaller scale, lengthening your runway and speeding up your learning curve. You have more customers and a cleaner path to export. You get to segregate the subsonic and supersonic markets in engineering time and capital deployment. The only reason to go for space first are passion over practicality, a need for vaporware-insensitive investors or an additional design advantage not yet disclosed.

mvkel 3y ago
Great points. So not only is the tech iffy, but the application is misguided.
- JumpCrisscross 3y ago
  > not only is the tech iffy I make no comment on the quality of the tech–we don't know much about it. Only that based on how they describe it, the product-market fit seems forced for orbital launch.
sjducb 3y ago
Space is better for marketing and gaining traction. I strongly suspect they’re quietly talking to missile manufacturers.
mechhacker 3y ago

inamberclad 3y ago

Why would you use an aerospace for this when conventional turbojets use an articulating nozzle? In fact, they'd be better off trying to develop and sell an articulating nozzle for a conventional rocket than a whole engine such as this

dredmorbius 3y ago

As Nitter is broken and Twitter has ... numerous issues, is there a non-Twitter source for this?

treme 3y ago
x is perfectly easy to use or to customize and allows instant sharing of short bits of information in whatever format.
- klyrs 3y ago
  It's not really an alternative to twitter, though.
- kataklasm 3y ago
  On mobile it barely loads the tweet for me, doesnt load any of the responses and if I go to the author's profile I get blocked by a login-wall. So no, "x" is not perfectly easy to use, it's utter garbage.
  - treme 3y ago
    make an account. that 2 min effort will allow you the freedom of all the content on x.
TrickyRick 3y ago
https://nitter.poast.org/k2pilot/status/1763007610993991722 https://nitter.poast.org/k2pilot/status/1763007610993991722 Seems to be the last one online https://github.com/zedeus/nitter/wiki/Instances https://github.com/zedeus/nitter/wiki/Instances

p1mrx 3y ago

> The key insight is to use electric motors to drive a compressor Tech Ingredients made a "hybrid jet engine" based on this concept in 2018: https://www.youtube.com/watch?v=_ax0pI4Jp18&t=775s https://www.youtube.com/watch?v=_ax0pI4Jp18&t=775s

jvm___ 3y ago

Someone made the positive version of "Unsafe at any speed"

japanuspus 3y ago

Everyday Astronaut has a recent video on "why don't we launch rockets from jets"[0]. The video obviously does not include reference to the engine mentioned here -- but I think most of the points still stand. In particular - orbit is mainly about going fast, not so much about getting up high - your second stage will pay a structural price for allowing air-launch loads, and this structure needs to be carried to orbit - rockets are *big* [0]: https://www.youtube.com/watch?v=AAt9WDQEMoA https://www.youtube.com/watch?v=AAt9WDQEMoA

audunw 3y ago
I think what’s missing from Everyday Astronauts discussion is: what if we could make the plane/rocket go much faster. The cruise speed of a jet plane of 800-1000km/h may not be a high enough fraction of orbital velocity to be worth it. But what if you could fly even higher and faster, say 3000km/h, before you do stage separation? Now you’ve actually achieved a significant fraction of orbital velocity. Obviously that would require new technology. And in particular the main challenge is making an engine that can operate efficiently at a wide range of speeds. So this engine could change the equation. But I suspect it’d only make sense for smaller vehicles delivering personnel/cargo to arbitrary orbits on short notice. I also wonder how they can get enough electrical power without a big weight penalty. Keep in mind that Electron is already using electric motors for their pumps. So the question is kind of whether you could also use a motor to capture and compress air to exploit the oxygen in the air rather than having to carry it as payload.
- fiftyfifty 3y ago
  Minimal orbital speed is somewhere around 25,000-28,000 kph. The fastest air breathing plane every built (SR-71) had a top speed of about 3,500 kph. So for the added weight and complexity of adding an air breathing first stage (wings, air breathing engines, landing gear etc) you are only getting about 14% of the way to the minimal orbital velocity needed, and that would be if your air breathing first stage could match the performance of the fastest plane ever built, keep in mind the SR-71 carried almost no payload. It is far more likely that any realistic air breathing first stage is going to get to less than 10% of orbital velocity, and that would likely be for launching a fairly small rocket. On the other hand the Falcon 9 first stage usually doesn't separate until 6,000-9,000 kph which is closer to 25-35% of orbital velocity, and that's while carrying almost 23,000 kg of payload plus the fully fueled second stage.

kulor 3y ago

An interview (1) with the founder Ian Brooke was illuminating on this jet and the wider opportunity it presents. He sheds a lot of light on the problem space (no pun intended) and how it can be tackled whilst being commercially viable. I particularly enjoyed geeking out the pros and cons of turbo-fan, RAM and SCRAM jets, rockets and the limits of physics. He's oozing Elon vibes in ambition, first-principle thinking, deep domain knowledge and commercial intelligence. One to watch. 1. https://twitter.com/1stPrinciplesFM/status/1762945809572925492/photo/1 https://twitter.com/1stPrinciplesFM/status/17629458095729254...

JoeAltmaier 3y ago

Expect to see every kind of innovation from here on out, as the launch ecosystem fills in every 'ecological niche'. Sure this isn't a direct competitor to {whatever pundits argue}. But if it works for even one kind of mission, then in this modern space age, it has a place. Like road vehicles, there are sedans, commuters, offroad, and heavy haulers, heck even trains. One vehicle will never do it all.

thoughtpeddler 3y ago

Can anyone speculate as to what kind of advancements in precision machining might enable this sort of new jet engine design? I feel, as a layperson when it comes to aerospace, that so much of the innovation is bounded by advancements (or lack thereof) in machining.

supportengineer 3y ago

What happened to the Reaction Engines / Skylon / SABRE? https://news.ycombinator.com/item?id=6062972 https://news.ycombinator.com/item?id=6062972

Tuna-Fish 3y ago
Still being worked on. It is a potentially higher-performing system than this one, but also dramatically more complex and expensive. This hybrid engine is interesting in how fundamentally simple and easy to build it is.

EricE 3y ago

Sounds about as practical as an electric supercharger. I would love to be wrong; I guess time will tell.

rich_sasha 3y ago

If the first stage is a SpaceX-style reusable stage, is there any benefit to a jet engine? I suppose perhaps it is more reusable, AFAIR the SoaceX stages have short-ish lifespans.