
UCF researchers develop new rocket-propulsion system - Arunprasath
https://www.spacedaily.com/reports/UCF_researchers_develop_groundbreaking_new_rocket_propulsion_system_999.html
======
tectonic
We covered the rotating detonation engine on Orbital Index a few months back.
The main conclusion was that, while more fuel efficient, the RDE is currently
way too unpredictable for real use. Here's a cool video of the circular
detonations though:
[https://www.youtube.com/watch?v=gEYFy3qRNdo](https://www.youtube.com/watch?v=gEYFy3qRNdo)

And the actual paper:
[https://journals.aps.org/pre/abstract/10.1103/PhysRevE.101.0...](https://journals.aps.org/pre/abstract/10.1103/PhysRevE.101.013106)

(If you're into this kind of nerdery, you might enjoy subscribing to our
weekly newsletter. [https://orbitalindex.com](https://orbitalindex.com))

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sitkack
I was thinking that a solid state hydrogen/oxygen gas generator might be a
safe way to store propellant, as it could exist in the inert, uncompressed
form.

[https://spectrum.ieee.org/energywise/transportation/alternat...](https://spectrum.ieee.org/energywise/transportation/alternative-
transportation/hydrogen-on-tap-device-trucks-fuel-efficient-vehicles)

I think using this for vehicles is the least creative application of this
tech.

~~~
p1mrx
It looks like AlGalCo makes an aluminum-gallium alloy that produces hydrogen +
aluminum oxide when mixed with water. This seems like it would be useless in
space, because the oxygen is locked away until you run the waste through an
aluminum smelter.

~~~
sitkack
Hmm, I wasn't thinking of re-usability for the aluminum. Just that it would
keep the propellants in a safe state. water+alloy might be better than nasty
toxic fluid + pressurized oxidizer. I am also not a rocket scientist.

~~~
Armisael16
It isn’t a question of reusable type - you need to have fuel and oxidizer to
burn things. A truck can use atmospheric oxygen for the oxidizer; a rocket
can’t.

I also imagine that the extra weight of the aluminum pucks would tank your Isp
(though I suppose you might be able to make back some tank weight).

~~~
sitkack
I willfully? missed that the O in the water binds to the Al so is unavailable
for combustion (it has to, otherwise what gets consumed?).

Oh, another take, it is a molecular pump that removes oxygen from the
environment and turns it into water, via burning.

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jessriedel
What is the maximum increase in fuel efficiency (e.g., ISP) with such a
design? I was under the impression that modern chemical rocket engines
operated near their thermodynamic limits. If that's the wrong question, what's
the right one?

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_Microft
I'm not sure what's the news here are (H_2 + O_2 instead of H_2 + air?) but if
you want to see experimental _continuous detonation thrusters_ in action, just
search for videos on Youtube.

[https://www.youtube.com/results?search_query=continuous+deto...](https://www.youtube.com/results?search_query=continuous+detonation+thruster)

I posted this elsewhere in the comments already but to save your time looking
for it, here it is again: a video of ignition and transition to continuous,
circular moving detonation in such a thruster:
[https://youtu.be/ERTei7D8LJs?t=28](https://youtu.be/ERTei7D8LJs?t=28)

~~~
nomel
This presentation really helped me understand what was going on:

[https://www.youtube.com/watch?v=Ws4kbgfpKCw](https://www.youtube.com/watch?v=Ws4kbgfpKCw)

~~~
jcims
Paul Rudd's smart brother.

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karagenit
One thought: this was done in a laboratory setting where they were able to
statically fine-tune the flow rates. In an actual rocket, it seems plausible
that external forces such as the acceleration of the rocket, changing force
from gravity, etc. could significantly affect the propagation of the
detonation waves, so the flow rates would need to be dynamically adjusted in
real-time (a non-trivial problem). Still, this is definitely progress!

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projektfu
Interesting. As I understand it, deflagration is usually used in rocket
engines because detonation is hard to control, but they’ve managed to control
it using very precise engineering.

~~~
loeg
I guess one question is, can they maintain that precise control over a long
enough period of time, without the explosions degrading the injection
apertures, to really use the technology.

~~~
sandworm101
At the fuel flows they are using, the explosions aren't that much of an issue.
These look like wisps of hydrogen and oxygen in a vacuum chamber, not a big
jet of fire steaming out of a nozzle. The detonation wave doesn't look like it
is contacting much of anything.

They have a sustained rotating ring, a detonation chasing itself around a
circle. That's great, its more efficient, but it is a long way from a working
engine. They need a properly shaped chamber, a nozzle, and a few other things
before they can test for the expected increase in ISP.

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deepsun
I think article could have more mentions of previous developments of rotation
detonation engines.

Navy experimented with it (for efficiency, not rockets) since 2012.

E.g here's overview with images:
[https://www.sciencedirect.com/science/article/pii/S100093611...](https://www.sciencedirect.com/science/article/pii/S1000936115002356)

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andyljones
SciHub mirror of the paper:

[https://sci-hub.tw/https://www.sciencedirect.com/science/art...](https://sci-
hub.tw/https://www.sciencedirect.com/science/article/abs/pii/S0010218019305838)

It's a 'brief communication' of three pages, so not many details. Most
interesting thing is the citations, one of which is to the _much_ more
enlightening 'Rotating Detonation Rocket Engine' tech readiness report from
the Air Force in 2018:

[https://www.researchgate.net/profile/William_Hargus/publicat...](https://www.researchgate.net/profile/William_Hargus/publication/326263199_Air_Force_Research_Laboratory_Rotating_Detonation_Rocket_Engine_Development/links/5d9e0f0c299bf13f40d0cbbb/Air-
Force-Research-Laboratory-Rotating-Detonation-Rocket-Engine-Development.pdf)

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ur-whale
Little did I know: there is a "Combustion and Flame journal".

Exciting.

But then ... instant sadness ... another compendium of taxpayer-funded
research walled off and milked by elsevier.

[https://www.journals.elsevier.com/combustion-and-
flame/](https://www.journals.elsevier.com/combustion-and-flame/)

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andrewljohnson
The question I have after reading this press release is, "Why was it
previously thought to be impossible?" as stated in the beginning of the
article.

Further down, the release seems to indicate lots of people thought it was
possible and have been studying it, "The technology has been studied since the
1960s but had not been successful due to the chemical propellants used or the
ways they were mixed."

So just an engineering problem, which are seldom impossible.

~~~
jonplackett
Would love someone clever’s opinion on this too.

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adrianmonk
> _rocket-propulsion system once thought to be impossible_

I can't be the only one who read those words and for a split second thought,
"They got the EmDrive working?!?!" But this is completely different.

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borkt
[https://youtu.be/WvBpuJ0fa98](https://youtu.be/WvBpuJ0fa98) Here is some low
res footage of one in action

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obituary_latte
Is there an ELI5 breakdown of this anywhere?

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andrewljohnson
IANA Rocket Scientist, but I'll try.

Rather than have one big continuous burn, the rocket engine rotates to create
many small burns, by mixing and igniting small amounts of two gases at just
the right frequency and amounts. This apparently leads to a more efficient
conversion of chemical to kinetic energy.

This sounds similar to how a car engine uses a fuel injector to inject then
burn small amounts of fuel to make the pistons go.

~~~
foobarian
What I understood from the article: it's not the engine that rotates.

Instead, the fuel mixture ignites in one spot, and the explosion spreads at
Mach 5 around the engine but once it reaches the end of the combustible fuel,
more is injected behind it so the explosion can just keep traveling around in
circles.

Judging by the article they managed to get that working, and also came up with
a better way to take videos of this happening (high speed camera, tracer
chemicals in the hydrogen, better signal strength).

~~~
beamatronic
There used to be one, does anyone remember Rotary Rocket? They had a small
vehicle they claimed could SSTO.

~~~
randallsquared
That was very different: conventional rockets for ground-to-orbit, but landing
with folding helicopter-like rotors. I think the original concept was to use
the helicopter rotors to get to high altitude before throttling up, which was
supposed to save a lot of fuel, but that was dropped pretty early.

~~~
m4rtink
I think they actually wanted to use some rotating set of engines and fuel
tanks early on with the rotation taking care of propelant flow.

IIRC they dropped that early on as well.

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DarmokJalad1701
What is the theoretical Isp for such a system? Or is that relevant only once
this is paired with a nozzle?

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baybal2
I read the paper, there are no data on actual performance. There may well be
no significant advantage

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korijn
The title is a nice pun.

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credit_guy
> 4,500 to 5,600 miles per hour

That's about 2-2.5 km/s. Compare this with the exhaust velocity of the main
engines of the Space Shuttle, 4.4 km/s. It's not clear why this is considered
to be groundbreaking.

~~~
SECProto
> the exhaust velocity of the main engines of the Space Shuttle, 4.4 km/s.
> It's not clear why this is considered to be groundbreaking.

And ion thrusters have an exhaust velocity in the 20-50 km/s range. Things can
be groundbreaking for different reasons.

But in the case of this article, I dont think the velocity mentioned is the
exhaust velocity. It says the "rotating detonations are continuous, Mach 5
explosions". This is likely the flame front speed inside the combustion
chamber (a traditional rocket engine has subsonic flame front, ie
conflagration not detonation). The exhaust velocity is a different
measurement, after the nozzle/bell (converts thermal to kinetic energy). Here
[1] for more details.

I'm interested to hear more about the possibilities this combustion chamber
design brings up.

[1]
[https://en.wikipedia.org/wiki/Rocket_engine_nozzle](https://en.wikipedia.org/wiki/Rocket_engine_nozzle)

~~~
credit_guy
> And ion thrusters have an exhaust velocity in the 20-50 km/s range

I compared with the Space Shuttle main engine because they are both hydrogen-
oxygen engines.

As for the speed they mention, it's not clear why they focus on that one. At
the end of the day, there are only 3 things that matter for a rocket engine:
exhaust velocity, how fast it can burn the fuel, and the mass of the engine.
You want the highest exhaust velocity, and the lowest mass of the engine. For
the upper stages, you don't need to be able to burn fuel that fast, but you
wouldn't mind that either.

All other things are implementation details. Now, the Space Shuttle main
engine achieved 86% of the maximum theoretical exhaust velocity [1]. If this
innovation here managed to increase this to 90% or more, that would be quite
interesting, but hardly groundbreaking if it adds substantial mass to the
engine.

> I'm interested to hear more about the possibilities this combustion chamber
> design brings up.

I would be interested too. This article was quite unilluminating
unfortunately.

[1] [https://space.stackexchange.com/questions/17129/is-there-
a-m...](https://space.stackexchange.com/questions/17129/is-there-a-maximum-
isp-for-exothermic-chemical-reaction-rockets)

~~~
SECProto
> At the end of the day, there are only 3 things that matter for a rocket
> engine: exhaust velocity, how fast it can burn the fuel, and the mass of the
> engine.

While those are primary factors, and a rocket won't go up if they aren't good
enough, they aren't the only ones (or else every rocket engine would be
hydrolox staged combustion, like the SSMEs). Other key factors are engine cost
(SSME does terrible here), fuel type (hydrolox needs way larger diameter
boosters, isn't worth it for first stage), combustion stability (allows
engines to throttle, key for max-Q and reducing max g as stage empties,
especially on upper stage), reusability (important for some systems),
controllability (how quickly it can throttle)... While their importance
gradually diminishes, there is a list hundreds long of different trade-offs
made in engine development. The reason I said I'd like to know more is indeed
because that article wasn't informative. I certainly am not writing it off
because it can't be plopped in a rocket right now

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LForLambda
The advertising on this page is particularly aggressive.

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dezmou
I want to hear the sound of this think

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canada_dry
Tangentially, RIP UCF's IDS.

I'd be curious to see some stats on this. I.e. what is the uptick of attacks
(esp from curious nation states) after something like this is announced.

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atum47
well, I was testing something on s a clone version of a game and end up
publishing that version to the app store. When I uploaded the game on my
phone, my progress ware gone, all my saves. the colone version created a new
database (thank God without deleting the old one). my game only had like 1k
installations, and I found out my mess quick enough. just published a new
update with the original database name and was lost.

~~~
atum47
well, I wrote my comment on the wrong thread. I don't know what happened. I
meant to comment that on a thread about failures. Sorry.

