Japan tests rotating detonation engine for the first time in space

inceptivemind.com ^ | AUGUST 21, 2021 | ASHWINI SAKHARKAR

[Flick Lives]

[Nailbiter]

flr

[BiteYourSelf]

God was a knocking and he wanted in real bad.😏

[Openurmind]

So basically it is a pulse jet with organized timing and spin to it?

I wonder if that internal spin applies any torque to the whole assembly? Probably very minimal in any?

[ConservativeMind]

Jerry Pournelle and Larry Niven had a book in which small nuclear bombs were exploded beneath the rocket to get to space.

[hoagy62]

Yeah, the book was called “Footfall”.

[TChad]

Jerry Pournelle and Larry Niven had a book in which small nuclear bombs were exploded beneath the rocket to get to space.

Footfall

But this sounds more complex.

[LesbianThespianGymnasticMidget]

Kinda like a continuous spiral detonation (pulse) jet where the detonation wave(s) remain(s) in a plane. As if sitting on those torches wasn’t enough now they are going to be a constant explosion as propulsion.

[Jewbacca]

It’s a real concept:

https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion)

[backwoods-engineer]

No.

[Jewbacca]

I think that was Footfall.

There were some of the “old” ships in the reboot of Battle Star galactica that had this as a sunlight propulsion. They didn’t say anything but some of the craft had a huge cluster of nozzles in the back with timed explosions instead of a continuous stream.

I love when shows at least make an effort toward hard science.

[Jewbacca]

Sub light.

Stupid phone

[TChad]

The math required to do this work must be otherworldly.

[grey_whiskers]

Beat me to it!
...a Wankel rocket?

[grey_whiskers]

I remember those ads!

[BiteYourSelf]

Yup.

[Jewbacca]

No. The only thing similar is the name.

Briefly an explosion is a much more efficient release of energy than a continuous stream of fire going out the back of a rocket motor.

The problem is the release of energy is all at once.

So you need to either make it small and balance it with a bunch of little explosions or have some sort of shock absorber. Or both.

Think of a giant spaceship with 100 nozzles in the back in a big round cluster.

They’re all off. The captain says “go” and one single nozzle lights up for just a second. The another lights up for a second on the opposite side.

Boom. Boom.boom. You can see each one. On off. On off. Slow.

Then the pattern starts speeding up and eventually it looks like all the nozzles are lit up at the same time. They’re not. It’s just the pattern of explosions is going fast enough that it looks like they are all on.

It’s probably how we will go between stars.

[Openurmind]

Wonder how long it will burn before melting into slag. Got to admit though, the controlled wave spin is a cool effect.

[LesbianThespianGymnasticMidget]

More work extracted from the same propellant implies it will run cooler. Energy can neither be created not destroyed in the Newtonian realm. More work extracted means less waste heat.

In practice, I don’t know, but the physics predict this.

[Jewbacca]

You are correct that the thrust-to-waste-heat ratio is higher.

But the engine runs hotter because more is actually burned.