[HN Gopher] NASA validates revolutionary propulsion design for d...
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NASA validates revolutionary propulsion design for deep space
missions
Author : mpweiher
Score : 88 points
Date : 2023-04-01 18:35 UTC (4 hours ago)
(HTM) web link (www.nasa.gov)
(TXT) w3m dump (www.nasa.gov)
| cs702 wrote:
| It reads, sounds, and looks _really cool_.
|
| We live in interesting times.
| out_of_protocol wrote:
| Anybody know what Specific impulse we are talking about?
| According to wikipedia, current values for rockets are around
| 300s
| phkahler wrote:
| Not sure the relationship, but they say 600PSI chamber
| pressure, or about 20 bar. Spacex is push 200 to 300 bar
| pressures. I would think this means they're currently at a low
| ISP. The challenge with RDEs has been keeping them lit, I e.
| Keeping the detonation wave going indefinitely. Once that's
| done they can work of efficiency. Seems like they're at that
| point now.
| wolfram74 wrote:
| Pressure can tell you about thrust, but I don't think its as
| strongly linked to specific impulse. However looking at the
| wiki article on the RS25 which is pretty high up there being
| a hydrolox engine, I see it's also got a chamber pressure in
| the 200+ bar range.
| sounds wrote:
| This was a smaller prototype. Unless they release a theoretical
| Isp model for scaling up the engine (which, would we believe
| them if they did?) we can't know for certain yet.
| vanattab wrote:
| In the theoretical limit how much improvement in efficiency could
| such engines provide?
| mdorazio wrote:
| Up to 25% improvement compared to conventional rocket engines
| according to the Wikipedia page. I haven't found an actual ISP
| measurement for this NASA engine, though.
| kossTKR wrote:
| 25% sounds super disappointing from a laymans perspective and
| not very "revolutionary" in the grand scheme of time and
| space.
|
| Can't wait until AI will be able to iterate advanced
| engineering designs in simulation space at incredible speed.
| goawaythrwaway wrote:
| This is the most HN-circa-2023 comment of all time
| grogenaut wrote:
| From 10% to 35% is a 25% improvement, you're still at
| 35%... From 70 to 95% is a 25% improvement, but it's a lot
| more. Going from 98 to 99% is only 1% but also like really
| a 10x improvment.
|
| Rockets are operating at pretty decent efficiency, 25%
| improvment on an internal combusion engine would be mind
| blowing and make EVs way less interetsting.
|
| There are theoretical maximum efficencies for various types
| of engines due to thermodynamics. You always lose energy to
| heat. Entropy is a b**.
| Lichtso wrote:
| Technically, from 10% of something to 35% of something is
| a 350% improvement or a 25 percent _point_ improvement.
|
| https://en.wikipedia.org/wiki/Percentage_point
| grogenaut wrote:
| yes but people often conflate/confuse that... saying the
| delta in %'s... not % improvement. I agree with you, I'm
| attempting to point out how a small % increase is a huge
| actual improvement. This GP was saying that a 25%
| improvment in the efficiency of a rocket engine was not
| much to a layman.
| dotancohen wrote:
| Actually, from 10% of something to 35% of something is a
| 250% improvement. You already had the first 10%.
| dotnet00 wrote:
| Simulations aren't really the limiter on engine efficiency,
| SpaceX etc already lean heavily on simulations.
|
| The limiters on engine efficiency at this point are mostly
| materials and costs, and even the latter are coming down
| with better fuels (eg Methane, which is extremely popular
| with rockets debuting this decade) and different design
| philosophies (eg SpaceX's Raptor engine, which is
| supposedly under $1M per engine while being the most
| advanced flight tested rocket engine out there).
| Tommstein wrote:
| Agree that 25% doesn't sound very exciting or
| revolutionary, but computers have been used to design
| space-related stuff for a while, for example,
| https://www.jpl.nasa.gov/nmp/st5/TECHNOLOGY/antenna.html .
| I would be surprised if no one had tried it with propulsion
| systems yet.
| messe wrote:
| Is that a 25% improvement in ISP/exhaust velocity or another
| metric?
| drtgh wrote:
| It seems that 25% paragraph on wikipedia cites a non-
| technical article[1] from 2018:
| "Theoretical calculations have shown that detonation
| combustion is 25% more efficient than the isobaric
| combustion cycle, which corresponds to constant-pressure
| combustion, which is implemented in the chambers of of
| modern liquid propulsion engines."
|
| From another article[2] of the same year:
| "Conservatively speaking, a rotating detonation combustor,
| or RDC, should reduce specific fuel consumption by about 5%
| compared to a conventional engine. This measure of fuel
| efficiency is calculated by dividing fuel consumption by
| power output. A rotating detonation engine generates more
| power, which drives down specific fuel consumption. A
| reduction on the order of 5 percent would be a
| breakthrough, given that designers of conventional engines
| "try to eke out fractions of a percent," says Scott
| Claflin, director of advanced concepts at the Rocket Shop,
| Aerojet Rocketdyne's innovation organization."
|
| [1] https://rg.ru/2018/01/18/levochkin-vozmozhnost-
| sozdaniia-det...
|
| [2]
| https://aerospaceamerica.aiaa.org/departments/increasing-
| eng...
| wolverine876 wrote:
| > that 25% paragraph on wikipedia cites a non-technical
| article[1] from 2018
|
| The article you footnoted is also in Cyrillic.
|
| After all this time, it's amazing to see people trust
| Wikipedia. It's like they don't care if it's true or not;
| it's entertainment, pretending to know, not knowledge.
|
| A perfect way to spin your wheels forever and go nowhere.
| messe wrote:
| > The article you footnoted is also in Cyrillic.
|
| And your comment is in Latin, going by your terminology.
| In the age of decent online translators, do you care to
| elaborate on why that's a problem?
| [deleted]
| [deleted]
| downvotetruth wrote:
| Real Engineering's video today likely causing resurfacing from
| Jan https://www.youtube.com/watch?v=RVxgyz_avQM
| boringuser2 wrote:
| What's up with all of these crazy technical developments after a
| period of relative stagnation?
|
| Aside from it being merely random or selection bias, it's
| plausible that there's some kind of AI assist beyond what we know
| happening behind the scenes.
| sxyuan wrote:
| These baseless speculations about ChatGPT are somewhat ironic
| given that the article itself alludes to what has unlocked this
| specific advance:
|
| "The RDRE achieved its primary test objective by demonstrating
| that its hardware - made from novel additive manufacturing, or
| 3D printing, designs and processes - could operate for long
| durations while withstanding the extreme heat and pressure
| environments generated by detonations."
|
| It's much easier to imagine that steady advances in
| manufacturing, computational modeling, and "mundane"
| technologies like that are contributing to progress like what's
| described in this article... Rather than some super secret AI
| assistant.
|
| Please, folks, don't give up on reading just because computers
| can do it too now. :)
| redeeman wrote:
| i dont think thats plausible? we do not have AI
| boringuser2 wrote:
| How do you know?
| twic wrote:
| People have been working on rotating detonation engines, and
| making steady progress, for years. The idea dates to the '60s,
| but i think work really picked up about a decade ago.
| PartiallyTyped wrote:
| I said a few days ago that it is very likely 3 letter agencies
| and other organisations have had GPT4 equivalent models for
| some time now. It doesn't seem that unlikely that some branches
| of the US gov would have much more advanced models.
| boringuser2 wrote:
| You're right, it kind of makes me think AGI won't come about
| from LLMs.
| valine wrote:
| Maybe ChatGPT is helping cut through bureaucratic tape. I know
| it's helped me become much more persuasive in my communication.
| If your goal is to convince the US government to spend money
| testing your rotational detonation engine, your odds of success
| go up if an LLM helps you write the email.
| getoffmycase wrote:
| This has to be an April Fool's day joke right?
| 7thaccount wrote:
| I hope haha.
| slowmovintarget wrote:
| Date on the article is 25 Jan 2023, so seemingly not.
| throwbadubadu wrote:
| OH MY.... Came here to say "Wow, this is so much more exciting
| than the 123th LLM/GPT and the 2746th "this is my experience /
| use case with AI" (sorry) "but sure, some one will come and
| claim that: GPT-8 would have designed that alone given the
| right prompt!!" ... and then need to read this. :(
| sacnoradhq wrote:
| At first, I thought it was an insanely scaled ion drive and then
| maybe a toroidal aerospike.
|
| Nope, no grids and there's water. Holy damn.
| dotnet00 wrote:
| Scott Manley did a video on Rotating Detonation Engines a few
| years ago https://m.youtube.com/watch?v=rG_Eh0J_4_s
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(page generated 2023-04-01 23:00 UTC)