[HN Gopher] Japan tests explosion-powered rocket for the first t...
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Japan tests explosion-powered rocket for the first time in space
(2021)
Author : zeristor
Score : 73 points
Date : 2022-10-01 14:50 UTC (8 hours ago)
(HTM) web link (www.autoevolution.com)
(TXT) w3m dump (www.autoevolution.com)
| tofof wrote:
| Here's a video that presents the science behind rotating
| detonation engines; the article was pretty light on detail. This
| video is at the other end of the spectrum, clearly intended for
| other researchers in this domain. Or, if it's over your head (it
| was for me, at least while trying to wake up), you can still
| enjoy the pretty damn cool high speed imaging of the detonation
| waves in this type of engine.
|
| https://youtu.be/Ws4kbgfpKCw?t=310
| jvkoch wrote:
| That's me - that video summarized my dissertation work. I did
| some follow-on modeling work using neural ODEs that's pretty
| neat, too: https://aip.scitation.org/doi/10.1063/5.0063624
| earthscienceman wrote:
| Wait. So. I do research in the polar regions and am
| interested in potential novel power sources for extremely
| remote environments. Is there any future where this kind of
| engine could be used for power generation? Say by storage in
| some capacity? Flywheel. Batteries. Etc. It seems to me it
| should be possible to detonate\fire when you need to top off
| your storage but that the design need not be limited to
| propulsion. Am I crazy? This is so far from my field of work,
| although I was originally a physicist.
|
| Energy density, ease of transport, robustness, and all sorts
| of other considerations dominate in an environment that is
| very hostile. Aside from nuclear power (which we will never
| get) the future is pretty bleak for us still when compared to
| the diverse technology available in more "normalcy climates.
| zeristor wrote:
| Deja YouTube, when you click on a link and find you had watched
| the first 5 minutes of it two years ago.
| sgt wrote:
| No, the link jumps to that point.
| ragebol wrote:
| Woah, exactly same here! Video starts 5 minutes in, so I
| watched and left off there some time. Wonder what the reason
| is there.
| arthurcolle wrote:
| The &t=${Timestamp} query parameter links directly to a
| point in the video
| ksaj wrote:
| the ?t=____ part of the URL sends you to a particular place
| in the video.
| zackmorris wrote:
| That's funny, I was just watching a hobbyist video about rotating
| detonation engines (RDEs):
|
| https://www.youtube.com/watch?v=fRMMSyCcTDI
|
| I live vicariously through channels like Integza and Tom Stanton.
| I've wanted to do some of this stuff for over 20 years,
| specifically electrohydrodynamic (EHD) engines, but spent nearly
| the entirety of the last 2 decades merely surviving. It's a
| strange feeling to watch the world make basically no progress
| over many years, then suddenly go through an inflection point
| where suddenly everything is solved and there's no way to catch
| up. Like with flying cars, reusable rockets, AI..
|
| I dunno, I just feel really inspired, but am also mourning the
| passing of my own life and all that wasted potential. These are
| all great inventions, super simple, easy to build, but why the
| heck were we forced to do everything the hard way for so long and
| still not make rent? These individual projects are really cool,
| but I worry that we aren't solving the fundamental problem of
| underemployment that forces fish to ride bicycles instead of
| swimming freely. Still just a rat in a cage and all that.
| dr_dshiv wrote:
| Yo, I hear you.
|
| Tell me more about the potential of electrohydrodynamic
| engines. What excites you there?
|
| I want to know whether it would be possible to efficiently
| ionize air and push it with electromagnetic pulses. It just
| seems so futuristic, you know?
| TaylorAlexander wrote:
| Works for fixed wing planes!
|
| https://youtu.be/IorDYGI1uqc
| zeristor wrote:
| Yes, that and a world of lonely people, if they could talk to
| each other they wouldn't be so lonely, if only it were that
| simple.
| badrabbit wrote:
| They might mostly just be lonely together then.
|
| Time waits for no one, from dust we came and to dust we shall
| go back.
| GordonS wrote:
| Anyone able to provide some info on why this type of engine might
| be "better"? Is it's use likely to become widespread? Can it be
| scaled up to propel larger craft?
| kortex wrote:
| RDEs are more efficient than regular rocket engines. Also, a
| big part of engineering rocket combustion chambers is balancing
| power with combustion instability, which can cause flame-out at
| best, and rapid unscheduled disassembly at worse. RDEs lean
| into that high energy stochiometric reaction to eke out more
| efficiency. Due to the tyranny of the rocket equation, even a
| modest increase in efficiency can greatly increase payload to
| orbit.
| xeonmc wrote:
| Pushing on solid wall is more effective than pushing on air.
| Shockwaves are effectively momentarily solid air that you could
| push on. RDE basically uses shockwaves as turbine blades.
|
| (technically I should say "incompressible vs compressible" but
| you get the imagery)
| dr_dshiv wrote:
| I _assume_ because you can use (mini)nuclear explosions in deep
| space?
| numpad0 wrote:
| Detonation engines has nothing to do with nukes, it's just a
| different way of burning fuel, in a _detonation_ mode
| /regimen/whatever. Which is I suppose more violent and rapid
| and efficient, but much more finicky compared to conventional
| _combustion_ method /type/phenomenon.
|
| Sort of like ramjet vs scramjet difference. "I guess that's
| better, if you think it can be done, I don't know though"
| thing.
| handol wrote:
| The detonation produces higher pressure and temperature,
| causing higher exhaust gas velocities. More energy in the
| exhaust means more push from the same amount of propellant.
| About 15% more. The other _yet to be realized in practice_
| advantage is that by eliminating the compressor stages on a
| rocket engine its construction is simplified, and despite
| needing a much stronger combustion chamber, it could actually
| be lighter.
|
| If it can live up to more efficient, cheaper, and lighter then
| it will certainly see widespread use.
|
| There are bound to be issues with new larger designs, but
| nothing show stopping is expected.
| badrabbit wrote:
| ELI5: why don't they use "tiny nukes", basically engineer a small
| (less than 10cm/1in) nuclear bombs that explode in a chamber at
| the back of the space ship?
| retrac wrote:
| The critical mass of a bare sphere of plutonium-239 (the
| isotope usually used to make bombs) is about 10 kg. Some
| percent can be shaved off this with a neutron reflector around
| the core and other design tricks. The American W54 warhead of
| the 1950s was 23 kg and the core was probably around one-third
| of the entire mass of the bomb. That is likely the practical
| limit for traditional designs.
|
| As for what might be feasible within the laws of physics,
| rather than current engineering, I'm not sure there's a clear
| answer. Increasing the density of the fissile matter reduces
| its critical mass, which is why they implode the core with
| conventional explosives in most designs. There are other ways
| of compressing matter to very high densities. For example,
| subjecting it to hot enough plasma, like in a magnetic
| confinement fusion reactor, might work. But stuff like that is
| science fiction and will be for a long time.
| oceanplexian wrote:
| W48 is the best we could do in 1963, that was 59 years ago.
| I'm sure if they did build a better one we wouldn't hear
| about it. For example Suitcase nukes are probably a real
| thing, or at least something like the soda machine from Sun
| of All Fears.
| uup wrote:
| https://en.wikipedia.org/wiki/Outer_Space_Treaty
| [deleted]
| MetalLord wrote:
| It was thought of
| https://en.m.wikipedia.org/wiki/Project_Orion_(nuclear_propu...
|
| Now I don't know how feasible is making a nuke as small as you
| suggest.
| badrabbit wrote:
| Thanks, now i remember hearing about this.
|
| > Project Daedalus later proposed fusion explosives
| (deuterium or tritium pellets) detonated by electron beam
| inertial confinement. This is the same principle behind
| inertial confinement fusion. Theoretically, it could be
| scaled down to far smaller explosions, and require small
| shock absorbers.
|
| That's an interesting tidbit about the size. Also reminds me
| of the Deadalus spaceship from the stargate universe.
|
| But it sounds like politics is the only limit here, surely
| they can ammend the treaty to allow space-travel work under
| IAEA supervision.
| foobarian wrote:
| Welp, why make a small one then? Just make a big one :-)
| detaro wrote:
| - Can't make nukes that small (you literally can't fit critical
| mass in that size I think, afaik smallest developed ever are
| 155mm artillery shells)
|
| - massive mess if it goes wrong in any way
|
| - putting nukes in space is banned by treaty and would be an
| ugly precedent
|
| -Japan has committed to not making nukes and has for obvious
| historical reasons a difficult relationship with the topic.
|
| (If Japan wanted to become a nuclear power, they relatively
| easily could for a country that doesn't have any, but that
| would be a major thing and not a side thing of some science
| project)
| [deleted]
| badrabbit wrote:
| I hope they amend the treaty with IAEA being able to enforce
| things and all. I think we can leave japan out of this too, I
| don't see why one country is so important.
|
| Isn't 155mm 15cm? Close enough I would say if it was an
| actual fission explosion.
|
| As for safety, nukes in space are safe and you can launch
| them using conventional propulsion and use nukes only in
| space and also launch from point nemo or cook islands so you
| are at least 3000mi away from large populations.
|
| I get these challenges are real but if the advantage over ion
| propulsion is great then it sounds like they are worth
| overcoming.
| kbenson wrote:
| Maybe I have a biased view of world events, but it feels
| like there's less respect for joint agreement in the world
| and less respect for regulation, or allowing regulation the
| ability to function as designed, at least in the U.S. (and
| it _seems_ like the world is heading a similar direction).
|
| Lessening an absolutist stance on this in favor of a more
| nuanced regulatory policy that requires more in depth
| checking seems to me like something we'll regret later when
| we find the agency is toothless, either because it always
| was in regards to this or because it was slowly defanged
| without people noticing.
| lantry wrote:
| > you can launch them using conventional propulsion and use
| nukes only in space and also launch from point nemo or cook
| islands so you are at least 3000mi away from large
| populations.
|
| If something goes wrong during the launch and the rocket
| explodes, isn't that basically exploding a dirty bomb in
| the upper atmosphere? Is 3000 miles really enough of a
| buffer zone?
|
| https://en.m.wikipedia.org/wiki/Dirty_bomb
| [deleted]
| badrabbit wrote:
| From that article: > Since a dirty bomb is unlikely to
| cause many deaths by radiation exposure, many do not
| consider this to be a weapon of mass destruction.[2] Its
| purpose would presumably be to create psychological, not
| physical, harm through ignorance, mass panic, and terror.
| For this reason dirty bombs are sometimes called "weapons
| of mass disruption". Additionally, containment and
| decontamination of thousands of victims, as well as
| decontamination of the affected area might require
| considerable time and expense, rendering areas partly
| unusable and causing economic damage
|
| Since that paragraph is talking about detonation over a
| populated area, 3k miles away even in the atmosphere I
| would think wouldn't cause much of an actual harm.
|
| But a solution might be to enrich the radioactive
| material in a space station in orbit.
| MichaelCollins wrote:
| The 155mm W48 nukes were real nukes, but very inefficient.
| One 155mm nuclear shell weighed 54kg and had a yield of
| 0.072 kilotons of TNT. A 16" nuclear shell weighed about
| 20x as much but had a 200x greater yield (15-20 kilotons of
| tnt)
| [deleted]
| BenjiWiebe wrote:
| 155mm was the diameter. According to Wikipedia they were 34
| inches long. So quite a bit bigger than a 10cm sphere,
| which is what was implied in the question.
| badrabbit wrote:
| Makes sense, thanks.
| [deleted]
| tjpnz wrote:
| Sibling comment is a good summary of most of the issues. I
| would add that you would lose quite a bit in payload mass to
| the additional shielding you would need so as to not fry your
| electronics/kill your crew. This would be in addition to what
| you would already be carrying to protect against existing
| ionising radiation from solar flares and alike.
| badrabbit wrote:
| Your last point about having to do radiation shielding
| anyways is interesring. I wonder if there are now materials
| or designs that can address this since it was firsr
| researched in the 70s and 80s.
| credit_guy wrote:
| It's not clear to me why they avoid talking about specific
| impulse or exhaust velocity. When you are in space, this is what
| matters. If you don't increase them, it's meaningless to say the
| engine has "higher efficiency".
| api wrote:
| Higher iSP is usually what more efficient means for rockets at
| least in space.
| zeristor wrote:
| Scott Manley did a video 2 years ago on rotating detonation gun
| engines, them being 25% more efficient. More bang for your buck?
|
| https://www.youtube.com/watch?v=rG_Eh0J_4_s
|
| I almost did mechanical engineering, in my placement before
| starting a degree I didn't start I was working with detonation
| guns to fire tungsten carbide into machined parts to make them
| last far longer in nuclear power stations.
|
| That had finished, just work on jet engine blades.
| legrande wrote:
| I always wondered, did we put the nukes on the wrong end of the
| rockets? I mean a nuclear warhead can cause serious damage, but
| if you put it behind a rocket for controlled propulsion, we can
| explore deep space, which is better. Why go to war when we can
| become space faring instead? It's much more humane, civilized,
| and less embarrassing as a species.
| numpad0 wrote:
| Because space settlement could pose a threat to you guys, I
| mean the US, and also because of cosmic radiation. Habitats
| with thick enough shield are way too impractical to launch from
| down here, and must be _somehow_ constructed in space, which is
| hard.
| louhike wrote:
| As I understand , nuclear power wasn't used for space
| exploration mostly for political reasons. It's considered quite
| unpopular to put nuclear engines which fly above people heads.
| There are therefore a lot of regulations for the use of nuclear
| propulsion, which has discouraged its use for now.
| roywiggins wrote:
| Well, political reasons generally, and the Partial Test Ban
| treaty in particular. It turns out there's really good
| reasons to limit the number of bombs detonated in the
| atmosphere, and for that matter the number of bombs, period.
|
| https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls.
| ..
| nine_k wrote:
| > _detonation and compression waves at extremely high frequencies
| (1 to 100 kHz)_
|
| Finally spacecraft will be able to produce the characteristic
| "vvvzzzhzhzh" sound we know from movies like Star Wars. Heard
| only inside the ship, of course, but likely it will permeate the
| whole ship while the engine is on.
| mrtweetyhack wrote:
| kbr2000 wrote:
| The title lured me into thinking it would be another Project
| Orion
| [https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...]
| :)
| forgotusername6 wrote:
| I thought this too. Though there is a treaty (https://en.wikipe
| dia.org/wiki/Partial_Nuclear_Test_Ban_Treat...) which bans
| nuclear detonations in space.
| fuzzythinker wrote:
| Wouldn't the ban not make sense if we only use it in deep
| space instead of LEO?
| dhosek wrote:
| I remember reading an Isaac Asimov story where aliens learned
| that we did all our nuclear detonation on the planet's
| surface instead of on space and decide that humanity should
| be quarantined and not allowed into the interstellar society.
|
| Of course living through the decades since Asimov wrote that
| story, it seems the aliens have plenty of other reasons to
| keep our species quarantined.
| krapp wrote:
| It's a common trope in sci-fi, but also silly when you
| consider the scale of space and how radioactive it already
| is.
|
| And then consider that any civilization capable of
| interstellar travel would already need to be harnessing
| energies that make nukes look like firecrackers.
| ridgeguy wrote:
| Sort of in the same vein, here's a PNAS report [1] of a
| continuous combustion detonation engine. No circulating
| detonation wave, no pulses, just steady combustion in a
| propellant stream fast enough to stabilize the detonation region
| at a feature in the engine.
|
| Just speculation on my part, but I would think the Isp would be
| higher than the usual chemical combustion regimes due to higher
| temperature in the detonation volume. Pretty interesting stuff.
|
| [1] https://www.pnas.org/doi/full/10.1073/pnas.2102244118
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