[HN Gopher] UCF researchers develop new rocket-propulsion system
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UCF researchers develop new rocket-propulsion system
Author : Arunprasath
Score : 154 points
Date : 2020-05-02 13:34 UTC (9 hours ago)
(HTM) web link (www.spacedaily.com)
(TXT) w3m dump (www.spacedaily.com)
| canada_dry wrote:
| 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.
| tectonic wrote:
| 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
|
| And the actual paper:
| https://journals.aps.org/pre/abstract/10.1103/PhysRevE.101.0...
|
| (If you're into this kind of nerdery, you might enjoy subscribing
| to our weekly newsletter. https://orbitalindex.com)
| sitkack wrote:
| 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...
|
| I think using this for vehicles is the least creative
| application of this tech.
| aerospace_guy wrote:
| I'm a recent subscriber and i really enjoy your material. Have
| y'all through about something similar for the aero side of
| aerospace?
| tectonic wrote:
| Thanks! We sometimes talk about atmospheric vehicles, but are
| mostly focused on space.
| Symmetry wrote:
| Is this actually more fuel efficient than a hydrolox expander
| cycle like a RL-10? Any sense of how much?
| tectonic wrote:
| Honestly don't know.
| adrianmonk wrote:
| > _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.
| deepsun wrote:
| 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...
| borkt wrote:
| https://youtu.be/WvBpuJ0fa98 Here is some low res footage of one
| in action
| jessriedel wrote:
| 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?
| LForLambda wrote:
| The advertising on this page is particularly aggressive.
| atum47 wrote:
| 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.
| projektfu wrote:
| 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.
| seiferteric wrote:
| Sounds similar to the jet version, pulse detonation engines
| (PDE) https://en.wikipedia.org/wiki/Pulse_detonation_engine
| wtvanhest wrote:
| Yeah, I wasn't expecting much, but it sounds like a real
| potential breakthrough.
|
| I'd love to see someone with experience in the industry comment
| boredgamer2 wrote:
| There is a comment at the bottom of the article from an
| expert in the Air Force:
|
| > William Hargus, lead of the Air Force Research Laboratory's
| Rotating Detonation Rocket Engine Program, is a co-author of
| the study and began working with Ahmed on the project last
| summer.
|
| > "As an advanced propulsion spectroscopist, I recognized
| some of the unique challenges in the observation of hydrogen-
| detonation structures," Hargus said. "After consulting with
| Professor Ahmed, we were able to formulate a slightly
| modified experimental apparatus that significantly increased
| the relevant signal strength."
|
| > "These research results already are having repercussions
| across the international research community," Hargus said.
| "Several projects are now re-examining hydrogen detonation
| combustion within rotating detonation rocket engines because
| of these results. I am very proud to be associated with this
| high-quality research."
| loeg wrote:
| 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.
| credit_guy wrote:
| > 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.
| avmich wrote:
| Maybe the speed mentioned here - ~5000 mph - is the speed of
| detonation wave, not the speed of exhaust gases? Theoretically
| the latter should surpass the Shuttle's Isp.
| pengaru wrote:
| > This system improves rocket-engine efficiency so that more
| power is generated while using less fuel than traditional
| rocket energies, thus lightening the rocket's load and reducing
| its costs and emissions.
| CarVac wrote:
| With constant exhaust constituents, exhaust velocity _is_
| rocket-engine efficiency.
| karagenit wrote:
| Well, the article states the targeted use-case is in the upper
| stages of a rocket i.e. in cases where peak power is less of a
| concern than efficiency.
| SECProto wrote:
| > 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
| obituary_latte wrote:
| Is there an ELI5 breakdown of this anywhere?
| [deleted]
| andrewljohnson wrote:
| 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.
| perl4ever wrote:
| Thanks, but I feel there's more to the story. For instance,
| in car engines, there's a lot of attention paid to
| _preventing_ detonation. And the article doesn 't seem to
| provide any information about possible performance
| improvements involving numbers. This seems like a pattern
| with short articles about some supposed leap forward and I
| still find it annoying and frustrating although I expect it.
| I'd like to ask the author - why do _you_ think it 's
| groundbreaking?
| borkt wrote:
| Uncontrolled detonation or pre-ignition is a problem in ICE
| not because it creates less force, but rather because it
| creates more force and at the wrong time. If engines could
| be made strong enough to remain reliable while operating on
| detonation, and the pulses timed right, I imagine you would
| get more energy out of a given volume of fuel. This whole
| problem is avoided in a rocket combustion chamber without
| all the rotating parts
| foobarian wrote:
| 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 wrote:
| There used to be one, does anyone remember Rotary Rocket?
| They had a small vehicle they claimed could SSTO.
| randallsquared wrote:
| 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.
| boredgamer2 wrote:
| How does it eject this energy to propulse through space, if
| it's just spinning in circles inside the engine?
| andrewljohnson wrote:
| Thanks, I feel enlightened. You could write press releases
| :)
| _Microft wrote:
| Here is a video from the Technical University of Berlin
| where the transition from ignition to the continuous
| circular detonation was also filmed among other things.
|
| I'll link directly to the transition part:
|
| https://youtu.be/ERTei7D8LJs?t=28
| nico_h wrote:
| according to the article, it's the _explosion_ that rotates
| around the engine, not the engine
|
| << rotating detonation rocket engine>>
|
| << The rotating detonations are continuous, Mach 5 explosions
| that rotate around the inside of a rocket engine >>
|
| maybe like a wankel engine without the rotor?
| usrusr wrote:
| My layman's attempt at understanding and explaining: a
| conventional rocket burns where the two fuels meet, whereas
| this one creates an unignited mix and then an ignition wave
| travels through that mix, apparently that's something that
| happens at mach 5. They build a circular explosive gas cloud
| that they replenish before the ignition wave comes through
| again. The big engineering achievement in this is to master
| precise high speed injection to the point where they always
| have a fresh cloud of pre-mixed explosive gas in place right
| before the explosion wave comes through.
|
| I'm certainly no "Combustion and Flame" reader but if this new
| method is such a big deal and has been theorized since the
| 1960ies then I guess a burn of pre-mixed gas must be known to
| be even more violent than combustion at the mixing boundary.
| deepnotderp wrote:
| Rather than deflagration combustion, this engine uses
| detonation combustion (supersonic flame front). Theeoretically
| this is much more efficient, but is extremely difficult to
| control.
| ur-whale wrote:
| 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/
| [deleted]
| [deleted]
| andrewljohnson wrote:
| 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 wrote:
| Would love someone clever's opinion on this too.
| DarmokJalad1701 wrote:
| What is the theoretical Isp for such a system? Or is that
| relevant only once this is paired with a nozzle?
| baybal2 wrote:
| I read the paper, there are no data on actual performance. There
| may well be no significant advantage
| korijn wrote:
| The title is a nice pun.
| [deleted]
| andyljones wrote:
| SciHub mirror of the paper:
|
| https://sci-hub.tw/https://www.sciencedirect.com/science/art...
|
| 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...
| dezmou wrote:
| I want to hear the sound of this think
| karagenit wrote:
| 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!
| _Microft wrote:
| 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...
|
| 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
| nomel wrote:
| This presentation really helped me understand what was going
| on:
|
| https://www.youtube.com/watch?v=Ws4kbgfpKCw
| jessriedel wrote:
| That is a great talk.
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