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Bobandis458 t1_j6i5sr4 wrote

I've heard about this RDRE, it's a cool concept but I've seen very few details on performance. Does anyone have a number for its specific impulse? Has it been tested in vacuum yet?

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danielravennest t1_j6ilyom wrote

Nope. This test was a proof of concept engine. The next version will be a fully functional engine that they can measure specific impulse, thrust, and engine life for.

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snowmunkey t1_j6ipgcr wrote

Early calculations for solid core engines could be as high as 800-1000 seconds using hydrogen as the propellant.

Edit: nevermind, I didn't realize this article was about rotating detonation engines, I thought it was about nuclear-thermal engines

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BackflipFromOrbit t1_j6ky8nv wrote

Japan launched a small scale RDE into space on a sounding rocket. Iirc they ran it for a few seconds in a vacuum.

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RenuisanceMan t1_j6m1gzx wrote

It's not a great as the article seems to think, it's around 500 secs from hydrolox according to Scott Manley. A few pictures I've seen make it look like an aerospike which makes sense with an annular combustion chamber, so may well be good for a first stage or an SSTO. Another concept I've seen recently is a sort of nuclear thermal/ion hybrid with an ISP of a few thousand whilst generating serious thrust, this makes more sense for deep space.

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Dragongeek t1_j6jr8yv wrote

iirc hydrogen-fueled air-breathing RDEs are theorized working up to Mach 5 at 8000-9000 isp and hydrocarbon fueled ones about half or a third that isp.

It's all theory though, but very attractive

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cjameshuff t1_j6k5pl3 wrote

Air-breathing engines aren't comparable to rocket engines. They have big specific impulse numbers because the specific impulse is no longer the impulse available from the propellant, but what's available from just the fuel after that fuel's been combined with the air. And since it's wildly variable with airspeed, it only makes sense for craft that cruise in a given range of airspeeds...in this case, Mach 5 and less.

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a10t2 t1_j6jw269 wrote

I haven't seen numbers anywhere near that. For a hydrolox RDRE they're hoping to hit maybe 550 s.

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