Author Topic: Chemonuclear Rocket  (Read 7206 times)

Offline sanman

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Chemonuclear Rocket
« on: 02/25/2015 03:29 pm »
If it were possible to trigger a nuclear fusion reaction from a chemical trigger - ie. without requiring any fission reaction - then what would the most optimally useful design be to base a rocket upon?

http://nextbigfuture.com/2015/02/confirmation-of-ultra-high-energy.html

Based upon the physics described in the link above, would an Orion-style nuclear fusion rocket be possible/practical? Or would there be some better design configuration to try instead?

Offline R7

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Re: Chemonuclear Rocket
« Reply #1 on: 02/26/2015 11:10 am »
Same problems as with metallic hydrogen. Takes giganormous pressure to make the stuff and then the question remains how stable is metastable at SATP? A physicist might rejoice something as metastable if it stays together for a millisecond but that has little practical value as rocket fuel or h-bomb fuse. Couldn't find half-life or something similar quoted for this matter.
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Offline SICA Design

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Re: Chemonuclear Rocket
« Reply #2 on: 02/26/2015 01:02 pm »
Same problems as with metallic hydrogen. Takes giganormous pressure to make the stuff and then the question remains how stable is metastable at SATP? A physicist might rejoice something as metastable if it stays together for a millisecond but that has little practical value as rocket fuel or h-bomb fuse. Couldn't find half-life or something similar quoted for this matter.
It's worth reading the article.

The last paragraph:
"For the ignition of a thermonuclear reaction one may consider the following scenario illustrated in Fig. A4. A convergent shock wave launched at the radius R = R0 into a spherical shell of outer and inner radius R0 , R1 , reaches near the radius R = R1 at a pressure of 100 Mb. After the inward moving convergent shock wave has reached the radius R = R1, an outward moving rarefaction wave is launched from the same radius R = R1 , from which an intense burst of X-rays is emitted. One can then place a thermonuclear DT target inside the cavity of the radius R = R1 , with the target bombarded, imploded, and ignited by the X-ray pulse. The ignited DT can there serve as a “hot spot” for the ignition of deuterium."

My understanding from that (could not find "Fig. A4") is that the chemical "superexplosive" is the momentary result of a conventional explosive shockwave. It would then instantly decomposes with a localised x-ray burst to trigger first DT and then DD fusion.

So no manufacture, storage, or handling required...

Offline sanman

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Re: Chemonuclear Rocket
« Reply #3 on: 02/26/2015 10:03 pm »
Yes - just for clarification, "metastable" here does not refer to something that lives long enough for you to touch it or gather it up. In this case, the "metastable" molecule survives for only a brief fraction of a second, but that's long enough for it to convert the chemical explosive kinetic energy into X-ray energy that can perform inertial confinement fusion triggering.

So this thing provides a mechanism to convert the chemical explosion into nuclear fusion triggering, without having to go through any fission intermediary step along the way to get to the fusion. That means no fallout. Since fallout was a concern for Orion, then maybe this mechanism could provide the means to do Orion mini-nuke explosions without the fallout problem.

What if you could have an Orion without fallout? Would that make the idea legitimately feasible - or would the idea still be non-workable due to other reasons?

Furthermore, would the Orion approach be the best way to make use of this chemonuclear physics for rocket propulsion purposes? Or would there be some other design that could work better?

Offline Asteroza

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Re: Chemonuclear Rocket
« Reply #4 on: 02/26/2015 10:28 pm »
Speaking of Orion...

That micro Voitenko compressor could be built as a cylindrical cartridge, complete with internal cup and double ended vacuum shock tube (mica caps over the shock tube, held in place by external pressure and a bit of glue?). Which would allow a pulsed x-ray source mechanism via something akin to a revolver cannon or gatling gun mechanism. If you had a sphere (or hemisphere?) surrounded by Voitenko compressor cartridge guns, it would be sorta similar to the that piston pulse fusion concept, firing x-rays on a center target area.

Offline ChrisWilson68

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Re: Chemonuclear Rocket
« Reply #5 on: 02/26/2015 10:40 pm »
Yes - just for clarification, "metastable" here does not refer to something that lives long enough for you to touch it or gather it up. In this case, the "metastable" molecule survives for only a brief fraction of a second, but that's long enough for it to convert the chemical explosive kinetic energy into X-ray energy that can perform inertial confinement fusion triggering.

So this thing provides a mechanism to convert the chemical explosion into nuclear fusion triggering, without having to go through any fission intermediary step along the way to get to the fusion. That means no fallout. Since fallout was a concern for Orion, then maybe this mechanism could provide the means to do Orion mini-nuke explosions without the fallout problem.

What if you could have an Orion without fallout? Would that make the idea legitimately feasible - or would the idea still be non-workable due to other reasons?

Furthermore, would the Orion approach be the best way to make use of this chemonuclear physics for rocket propulsion purposes? Or would there be some other design that could work better?

Even without any fission chain reaction going on to trigger the fusion, you still have fusion producing a large number of very energetic neutrons.  They're going to cause secondary fusion and fission in whatever they end up hitting, right?  So I'd think you'd still get various radioactive elements being created.  I don't know how to quantify it, though, compared to the fallout from a conventional thermonuclear explosion.

Also, if you're doing something like Orion, those neutrons will be flying out over the surface of the Earth, hitting people directly.  In addition to fallout, there's the direct effect of the primary radiation on those people.

Again, I don't know what the dose would be, so someone would need to do the calculations.

Offline sanman

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Re: Chemonuclear Rocket
« Reply #6 on: 02/26/2015 10:50 pm »
Even without any fission chain reaction going on to trigger the fusion, you still have fusion producing a large number of very energetic neutrons.  They're going to cause secondary fusion and fission in whatever they end up hitting, right?  So I'd think you'd still get various radioactive elements being created.  I don't know how to quantify it, though, compared to the fallout from a conventional thermonuclear explosion.

Also, if you're doing something like Orion, those neutrons will be flying out over the surface of the Earth, hitting people directly.  In addition to fallout, there's the direct effect of the primary radiation on those people.

Again, I don't know what the dose would be, so someone would need to do the calculations.

Well, if you could use materials composed of lighter elements to construct some of the housing and surrounding structures, then maybe that might reduce the secondary fission.
Also, if you're launching from some remote equatorial launch platform in the middle of the ocean, maybe that could reduce the risk of directly irradiating human beings.
Maybe this type of rocket could only be used to haul freight, and be completely unmanned.

Offline Damon Hill

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Re: Chemonuclear Rocket
« Reply #7 on: 02/26/2015 11:01 pm »
How weaponizable is it?

Offline RonM

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Re: Chemonuclear Rocket
« Reply #8 on: 02/26/2015 11:14 pm »
In the classic Teller-Ulam thermonuclear device, the secondary uses uranium or lead to encase the fusion fuel and has a core of plutonium or uranium to initiate fusion. So even with replacing the primary fission trigger, there is still is a lot of fissionable material involved in the process.

It will take more than just replacing the trigger to make a clean H-bomb. Even if you could, as Chris mentioned, you would still have the neutron radiation.

While it would make Orion type nuclear rockets slightly less dangerous, the military would love to get their hands on H-bombs without fallout. Perhaps this is a line of research that should not be followed, or at least remain a closely guarded secret. You wouldn't want just anyone to be able to build these things.

Offline sanman

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Re: Chemonuclear Rocket
« Reply #9 on: 02/26/2015 11:38 pm »
Well, a nuke is still a nuke, in terms of international treaty restrictions, etc. The fact that it's chemically triggered wouldn't change that. Sure, you wouldn't want terrorists, etc to get their hands on this technology to make a nuclear suicide vest, but it's not like anyone could test their device without setting off detection monitors.

However, now that I think about it, a fallout-free chemo-nuclear bomb might be useful for terraforming or even doing tunneling or mining on Mars or the Moon. Maybe you could melt the Martian icecaps with it.




Offline Jim

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Re: Chemonuclear Rocket
« Reply #10 on: 02/27/2015 12:01 am »

However, now that I think about it, a fallout-free chemo-nuclear bomb might be useful for terraforming or even doing tunneling or mining on Mars or the Moon. Maybe you could melt the Martian icecaps with it.

No such thing as fallout-free when detonating in or on soil.

Offline sanman

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Re: Chemonuclear Rocket
« Reply #11 on: 02/27/2015 12:41 am »
Yeah, I thought you'd say that - but what about icecaps? That's not soil, that's all light elements.

Offline ChrisWilson68

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Re: Chemonuclear Rocket
« Reply #12 on: 02/27/2015 03:51 am »
Yeah, I thought you'd say that - but what about icecaps? That's not soil, that's all light elements.

I thought the point of your suggestion was to dig big holes in the dirt.  I'm not sure what the point of vaporizing icecaps would be.

Actually, I think there's something to your original suggestion of using a nuke to move large amounts of dirt and rock.  As Jim pointed out, you'd get a lot of radioactive byproducts even if the bomb itself didn't have a fission trigger, but maybe that's OK.  Creating a very large underground space might be very useful for setting up a colony.  The worst of the radioactive elements decay quickly (which is what makes them the most deadly to begin with), so if you wait a while, the artificial cave will be safe to live in.  Living deep underground you get shielding from energetic nuclei from the sun and extra-solar sources, which is probably more dangerous than the residual radiation from the blast.  And you don't have to do much work to keep an atmosphere sealed inside.

Offline Damon Hill

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Re: Chemonuclear Rocket
« Reply #13 on: 02/27/2015 04:46 am »
Actually, wouldn't a fissionless bomb using just hydrogen (and maybe lithium) be relatively wimpy?  Might be more of an antipersonnel neutron bomb.

Could an unusually high yield chemical bomb compress a very sub-critical mass of a fissionable element to make an extremely small nuclear bomb, perhaps much more easily than getting a useful fusion yield?  Wonder what the minimum mass could be?

Offline KelvinZero

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Re: Chemonuclear Rocket
« Reply #14 on: 02/27/2015 05:23 am »
This may not provide a method to get off the planet, but it might provide an excellent motivation  ;)
« Last Edit: 02/27/2015 08:25 am by KelvinZero »

Offline Lampyridae

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Re: Chemonuclear Rocket
« Reply #15 on: 02/27/2015 05:57 am »
Yeah, I thought you'd say that - but what about icecaps? That's not soil, that's all light elements.

On Mars? They've got a lot of dirt mixed in, not to mention CO2 ice and probably dissolved salts. It would still be dirty as hell. Far easier to get the energy by slamming asteroids in.

Offline R7

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Re: Chemonuclear Rocket
« Reply #16 on: 02/27/2015 10:32 am »
My understanding from that (could not find "Fig. A4") is that the chemical "superexplosive" is the momentary result of a conventional explosive shockwave. It would then instantly decomposes with a localised x-ray burst to trigger first DT and then DD fusion.

So no manufacture, storage, or handling required...

Thanks for the correction, I got the false impression from the article that the super explosive was premade because the previous paragraphs discussing means to create the required 100Mbar which were cumbersome at best.

Various sources quote conventional implosion pressure using tamper-pusher system reaching "several megabars". To me several sounds a lot less than 100, even less than 10. This would require large sphere around the fusion device just to allow the shockwave to converge and even larger explosive lens system around it to get the shockwave going. Minutemen would be replaced with SLS...

The "an outward moving rarefaction wave is launched from the same radius R = R1 , from which an intense burst of X-rays is emitted" baffles me. If converging shockwave reflect just when it reaches 100Mbar then how would the reflected diverging wave sustain 100Mbar pressure? Or does that mean the X-rays are created only from thin region at R1?

Is there some sort of seemingly free lunch in the SIMS creation process so that you get more energy as X-rays than is contained as chemical energy in the conventional explosives? If not I remain dubious that the released radiation intensity is anywhere near the levels required in thermonuclear devices.
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Offline R7

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Re: Chemonuclear Rocket
« Reply #17 on: 02/27/2015 10:43 am »
Yeah, I thought you'd say that - but what about icecaps? That's not soil, that's all light elements.

Seriously suggesting that would soil a lot of pants in EPA.
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Offline RanulfC

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Re: Chemonuclear Rocket
« Reply #18 on: 03/03/2015 03:59 pm »
Yeah, I thought you'd say that - but what about icecaps? That's not soil, that's all light elements.

I thought the point of your suggestion was to dig big holes in the dirt.  I'm not sure what the point of vaporizing icecaps would be.

Actually, I think there's something to your original suggestion of using a nuke to move large amounts of dirt and rock.  As Jim pointed out, you'd get a lot of radioactive byproducts even if the bomb itself didn't have a fission trigger, but maybe that's OK.  Creating a very large underground space might be very useful for setting up a colony.  The worst of the radioactive elements decay quickly (which is what makes them the most deadly to begin with), so if you wait a while, the artificial cave will be safe to live in.  Living deep underground you get shielding from energetic nuclei from the sun and extra-solar sources, which is probably more dangerous than the residual radiation from the blast.  And you don't have to do much work to keep an atmosphere sealed inside.

Somewhere there's a study, (there always is even if its a 'secret' one :) ) that suggested just this with "regular" nuclear charges and used underground nuclear test results to show it could be done. I recall seeing photos of such detonation chambers with people inside taking readings and measurements just a few days after the detonation.
The point of the study was it works great, if you have the right type of soil. If not the chamber isn't stable without reinforcing and it would probably be cheaper and easier to build it that way from the start. The other issue is depth as a detonation chamber has to be pretty deep to avoid surface connected cracks and fissures and subsequent collapse from the same.

The idea of a "pure" fusion detonation is that it has a LOT less radioactive residue than one that requires a fission trigger but that doesn't mean radiation free :) It does mean that a fusion device becomes much smaller and easier to "hide" as it doesn't have the fission bits leaking radiation to give it away. Hence the reason the military is interested in such devices. (As well as others with less savory reasons since if you don't have to go to all the trouble to build fission devices so you can build fusion devices...) Fusion devices are also "tune able" in output both to yield and output radiations which gave rise to the whole concept behind the neutron bomb.

Fallout is directly related to what the bomb fireball picks up and circulates around with the fissile and other materials within the fireball. The higher off the ground the better 'blast' effects and the less fallout from a device, hence the reason you really don't want to launch an Orion by direct detonation from the ground if you can avoid it. (Though William Black has a basic design of and technical explanation of what a "good" Orion spaceport would look like on his Deviant Art pages which I can't access from this computer. His better idea is to use chemical thrusters to push you up to an altitude where you set off the first nuke. The main problem is with even a small "scout" vehicle your talking engines bigger and more powerful than the F1 to get it to work :) )

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Offline Stormbringer

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Re: Chemonuclear Rocket
« Reply #19 on: 03/04/2015 11:06 am »
welp... that Orion documentary video said something about lift off from a tungsten clad pad. It claimed that a relatively thin tungsten layer would withstand an Orion take off and virtually eliminate secondary induced radiation and fall out.
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