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In the US, a rotating detonation rocket engine takes flight

arstechnica.com

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Re: In the US, a rotating detonation rocket engine takes flight

#71

Post by K0balt »

amy214 wrote: post #65
K0balt wrote: post #57

Earlier quoted context omitted.

Flying it the high limits of the atmosphere reduces sonic boom intensity due to both the extremely low density of the air and the distance from the ground. Ultimately, sonic boom is a sign of wasted energy, so if (big if) we can make aircraft that conform to the required aerodynamic ideals for efficient hypersonic flight, they will be relatively quiet. Just like with regular air travel, though, I would expect a few d…

what about noise is you're supersonic noise and sound is about a mile back

I think the concern is for the frothing masses of earthbound unfortunates, not the passengers hurtling gloriously towards destiny miles above the troublesome surface of the planet.

Re: In the US, a rotating detonation rocket engine takes flight

#72

Post by lupusreal »

deelowe wrote: post #39
verzali wrote: post #11

>Sassie Duggleby and her husband, Andrew Duggleby, founded Venus Aerospace nearly five years ago with the long-term goal of developing powerful rotating detonation engines and building a hypersonic aircraft that could carry perhaps a dozen passengers and travel at astonishingly fast speeds worldwide. As an engineering project it sounds really cool, but is the application really commercial travel? I would have thought…

It's a smokescreen for hypersonic missile development. It's a common tactic. I knew someone who worked on a novel satellite surveillance system. Their pitch was that it would allow them to engage in futures trading because the resolution of their satellites would allow unique insights into global trade for certain markets using realtime optical imaging. The guy was former Lockheed. One night at dinner I told him to c…

Tbh military surveillance satellites are used for economic espionage, not just military. The US used to, and still does I'm sure, keep track on agricultural yields and similar, because that information can inform strategic decisions and negotiations.

Re: In the US, a rotating detonation rocket engine takes flight

#73

Post by zck »

numpad0 wrote: post #66
ColinWright wrote: post #2

From the article: "In contrast to a traditional rocket engine, in which a highly pressurized propellant and an oxidizer are injected into a combustion chamber where they burn and produce an energetic exhaust plume, a rotating detonation engine is different in that a wave of detonation travels around a circular channel. This is sustained by the injection of fuel and oxidizer and produces a shockwave that travels outwa…

The most fundamental idea of a detonation engine is that, if you substitute fuel "burning" process with subsonic propagation used in every conventional engines with fuel "explosion" process with supersonic wavefront, the reactions will become more instantaneous and energetic and that improves efficiency. This is the detonation part of detonation engine concept. The rotating part is a solution to the problem that forc…

>...if you substitute fuel "burning" process with subsonic propagation used in every conventional engines with fuel "explosion" process with supersonic wavefront...

This fragment confused me, because it looks like there are three substitutions. There aren't; there's only one. Read it as:

If you substitute fuel burning (which has subsonic propagation, and is used in every conventional engine) with fuel explosion (which has a supersonic wavefront)...

The first and third "with" link a noun (the respective process) with a property (how fast it shoots gas out the back). The second "with" is the substitution.

English is hard! I'm a native speaker, and I had to take a look at a few webpages to understand just this part! And I'm still left with questions, like why subsonic is described as having "propagation", but supersonic is described as having a "wavefront". Is this a distinction with a difference? I don't know.

Re: In the US, a rotating detonation rocket engine takes flight

#74

Post by Akronymus »

twic wrote: post #60
xeonmc wrote: post #43

Earlier quoted context omitted.

Just think in terms of the P-V diagram, you want the pressure increase curve to be as vertical as possible to maximize the area enclosed by the cycle

This doesn't help at all. Diagrams are diagrams, what does it actually mean physically?

Explosions release more energy in a shorter time, which leads to a higher peak temperature and thus higher kinetic energy in the products. This directly results in more pressure/thrust.

Re: In the US, a rotating detonation rocket engine takes flight

#75

Post by lowestprimate »

twic wrote: post #60
xeonmc wrote: post #43

Earlier quoted context omitted.

Just think in terms of the P-V diagram, you want the pressure increase curve to be as vertical as possible to maximize the area enclosed by the cycle

This doesn't help at all. Diagrams are diagrams, what does it actually mean physically?

Think of it as similar to hi compression automobile engine (race car) being more efficient vs a low compression engine (tractor engine). Not exactly correct but a way of starting to think about it

Re: In the US, a rotating detonation rocket engine takes flight

#76

Post by numpad0 »

zck wrote: post #73
numpad0 wrote: post #66

Earlier quoted context omitted.

The most fundamental idea of a detonation engine is that, if you substitute fuel "burning" process with subsonic propagation used in every conventional engines with fuel "explosion" process with supersonic wavefront, the reactions will become more instantaneous and energetic and that improves efficiency. This is the detonation part of detonation engine concept. The rotating part is a solution to the problem that forc…

>...if you substitute fuel "burning" process with subsonic propagation used in every conventional engines with fuel "explosion" process with supersonic wavefront... This fragment confused me, because it looks like there are three substitutions. There aren't; there's only one. Read it as: If you substitute fuel burning (which has subsonic propagation, and is used in every conventional engine) with fuel explosion (whic…

I must admit that I'm in fact not a native English speaker and my sentence construction is still jarring at times... sorry for that.

That distinction was not intentional, but IIUC, chemical reactions propagating faster than the speed of sound(of surrounding material, not necessarily of air(which idk how is it even defined, ductile limit or something(of air!?))) has effect of consolidating what would normally be multiple consecutive waves of density changes following one another, into a single shockwave with higher peak pressure, and higher peak pressure in an engine is generally thought to lead to higher exhaust gas velocities and better efficiencies so long that the engine holds. I think this is what some comments mentioning P-V diagrams and Carnot efficiency is meaning to say, except mine is in uneducated terms.

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