Here is my argument that a few wheels of cheese (ie pretty much anything) can reflect and direct the plasma of a nuclear blast.The key is that they don't reflect the momentum of the blast. Rather, the momentum of the plasma gets transferred to the reaction mass... a bit like a Newtons Cradle.A key assumption is that the ionised fissile particles do not have much penetration. They quickly begin compressing the reaction mass and transferring kinetic energy. Also, despite the vast momentum of the plasma, in the reference frame of the plasma, the wall of cheese has the same mindboggling momentum, but more mass.The 1-d case of (a)-(c) can then be generalised to the 2d case depicted in (d) where a parabolic reflector directs the fissile plasma in a single direction while the now superheated reaction mass flies in all directions.
I don't think this works. Here is my view of it: The exploding material is a plasma. It's a ball, and not a plate, or front, of uniformly hot plasma. In the ball all the particles are moving randomly in an expanding sphere of uniform pressure. The individual particles that first hit the outer wall of cheese will angle off, but almost immediately bounce off another particle in the plasma, and take off at a random direction. So the net result will not be a jet, but an expanding sphere of (more or less) equal pressure plasma, mixing bits of melted cheese and nuclear material in an expanding ball.If the mixture of cheese and nuclear material hits an indestructible nozzle, then it will be redirected into a jet, but a jet of everything together. The better the mix, the better the jet.I think that for the nuclear material to behave as described in your image, you would need to have indestructible cheese.
No, it's a direct comparison to the state of the art of lowest viable fissile masses demonstrated. If you think the USSR (or anyone else) has demonstrated a sub-gram (or even sub-kilogram) fission-fusion freestanding device, then cite your sources. And for reference, that means actual citations, not just a link to your own forum post making unsourced claims again.
Quote from: edzieba on 05/20/2024 04:27 pmNo, it's a direct comparison to the state of the art of lowest viable fissile masses demonstrated. If you think the USSR (or anyone else) has demonstrated a sub-gram (or even sub-kilogram) fission-fusion freestanding device, then cite your sources. And for reference, that means actual citations, not just a link to your own forum post making unsourced claims again.I do, but it's a bit suspicious. In 1982 Orbis in the UK published a book called "Weapons of Tomorrow" by Brian Beckett. Page 21 has an illustration of a "Bi-conical Mini-nuke" which is claimed to deliver compression ratios of 5-7 (AIUI most implosion designs deliver about 2) which it is claimed would reduce critical mass below 100g. The cite is for an "S.Kalinsky Journal of Technical Physics, Warsaw, Vol 19, 4 1968"Which is described as "Journal of Technical Physics (formerly Proceedings of Vibration Problems) is a refereed international journal founded in 1959. The journal is devoted to the application of the phenomenological and continuum physics idea in: mechanics, thermodynamics, electrodynamics, coupled mechanical, electromagnetic and thermal fields, plasma physics, superconductivity and many others."Founder listed as "S. KALISKi" Copyright by "Institute of Fundamental Technological Research,Polish Academy of Sciences, Warsaw, Poland"The publication seems to have a fairly broad remit, so mini-nuke design could be within scope for them. I'll caution "Might be possible," is a long way from actually tested, and that degree of compression is a big jump from what seems to be in common use. I think the idea of a fairly obscure Polish physics journal which seemed to be published in English made me a bit suspicious.
Interesting, thanks! I guest that if they could get better compression, the weapon designers would? Or perhaps nuclear weapons are a case of 'good enough' with little point in going smaller.
Nuclear propulsion really suffers when you bring the notions of cost and reusability into the equation. At least Winterberg's proposal offers the possibility of relatively low fuel costs. And perhaps even low nozzle costs, if a physical nozzle can survive the really short exposure to the plasma. Although the boost times are quite long for large vehicles, and that might mean that the temperature in the nozzle structure goes up to the point significant cooling is required?
Can an equivalence be drawn between the plasma at re-entry as seen in Starship flight 4 and the plasma in a physical nozzle for a nuclear pulsed engine? I expect the plasma at re-entry is significantly hotter than the ship surface, so there is significant resistivity there? Or is the plasma from the explosion so hot that no analogy holds? could the Orion 'trick' of adding/spraying an ablative layer between each explosion be used?
Another completely random and unrelated idea :Instead of messing with superconducting magnet tech, perhaps we could combine* https://en.wikipedia.org/wiki/Pulsed_plasma_thruster* https://en.wikipedia.org/wiki/Explosively_pumped_flux_compression_generator.. to use the flash of a nuclear explosion to directly generate the intense magnetic field that directs its fission fragments away from a very large slightly ablative nozzle that has a merely moderate current running around its inner surface at that instant.If this worked, it could also be useful for increasing the effectiveness for some inertial-containment fusion concepts.
(edit) deleted my previous reply that was too wordy.. it just pointed out we need to balance not just momentum but also kinetic energy, listed a bunch of examples showing fast incoming matter hitting heaver matter often result in a fraction bouncing back: a ball bearing hitting a tank, a laser hitting some hull plating. but really just underlined I dont know the precise inelacity to choose, thus this post which might point to the answer.-----------------------------------I wonder if revisiting the https://en.wikipedia.org/wiki/Carnot_cycle would answer this..I have a vague memory that it put an absolute upper limit on the amount of useful work that could be extracted from an expanding gas.This might answer how inelastic the collision is, ie when the massively hot cheese expands, how much push it can give and how much energy is wasted and does no useful work. The fundamental physics is probably the same as steam pushing a piston.(It has been a looong time since I looked at that though)I will leave this here until I think I can produce something that isnt just handwaving.
There's an upcoming NASA workshop on August 20th-22nd to 'advance Space Nuclear Propulsion (SNP) technologies'; might get a pulsed plasma update.
Interesting, but my guess is that at 40 kWe, this is not for large payloads? Or perhaps not for very great speeds. We've been discussing systems in the GW range, mostly. Eventually, of course, the Watts add up.
Wednesday, September 11, 1:50 PM PST2024 Phase II (5) Brianna Clements, Howe Industries, Pulsed Plasma Rocket (PPR): Shielded, Fast Transits for Humans to Mars
Quote from: lamontagne on 06/06/2024 03:53 pmWinterberg's proposal offers the possibility of relatively low fuel costs. And perhaps even low nozzle costs, if a physical nozzle can survive the really short exposure to the plasma. Although the boost times are quite long for large vehicles, and that might mean that the temperature in the nozzle structure goes up to the point significant cooling is required?The cost/benefit trades change quite a bit in space with nuclear. A large-ish nozzle that gets very hot could radiate that heat quickly in space. It would then all depend on how frequently it was cycled and the thermal stresses placed on the material during that cycling.
Winterberg's proposal offers the possibility of relatively low fuel costs. And perhaps even low nozzle costs, if a physical nozzle can survive the really short exposure to the plasma. Although the boost times are quite long for large vehicles, and that might mean that the temperature in the nozzle structure goes up to the point significant cooling is required?
Marathon Fusion is making progress on streamlined, commercialized tritium recovery. Here plasma filters through a metal membrane, to extract tritium quickly via "superpermeation".Commercial tritium recovery should improve pulsed D-T drive economics, by closing the necessary breeding cycle efficiently.
Marathon Fusion, a startup developing fuel processing technology for the fusion industry, has won an award from the Department of Energy's (DOE's) Innovation Network for Fusion Energy (INFUSE) program to advance its metal foil pump technology for fusion energy.With the award, Marathon Fusion aims to advance the development of commercially viable fuel processing solutions on a timeline consistent with the decadal vision for the first pilot plants on the grid.The award will be used to fund work with Professor Colin Wolden at the Colorado School of Mines on engineered membranes used to recycle deuterium and tritium fuel from vessel exhaust. Professor Wolden was previously funded by the Advanced Research Projects Agency-Energy (ARPA-E) for research into efficient tritium processing with membranes "engineered for high performance, stability, and environmental compatibility"...
The Department of Energy has awarded four companies spots on a potential 10-year, $2.7 billion contract to procure uranium enrichment services to help establish a domestic supply chain of high-assay low-enriched uranium, or HALEU, used for deploying advanced nuclear reactors.According to award notices published Wednesday, the HALEU Enrichment contract awardees are American Centrifuge Operating, General Matter, Louisiana Energy Services and Orano Federal Services.HALEU Enrichment RFPIn January, DOE issued a solicitation for the HALEU Enrichment indefinite-delivery/indefinite-quantity contract, which covers the production, storage and transportation of enriched uranium hexafluoride to deconversion facilities.Enrichment and storage activities must be performed in the continental U.S. in compliance with the National Environmental Policy Act.The department noted that establishing a domestic HALEU supply chain supports President Joe Biden’s Investing in America agenda by helping meet net-zero emissions goal by 2050, creating jobs, strengthening U.S. competitiveness and improving energy security.
Not specifically space related, DOE Selects 4 Vendors for $2.7B Uranium Enrichment Contract [Oct 18]QuoteThe Department of Energy has awarded four companies spots on a potential 10-year, $2.7 billion contract to procure uranium enrichment services to help establish a domestic supply chain of high-assay low-enriched uranium, or HALEU, used for deploying advanced nuclear reactors.According to award notices published Wednesday, the HALEU Enrichment contract awardees are American Centrifuge Operating, General Matter, Louisiana Energy Services and Orano Federal Services.HALEU Enrichment RFPIn January, DOE issued a solicitation for the HALEU Enrichment indefinite-delivery/indefinite-quantity contract, which covers the production, storage and transportation of enriched uranium hexafluoride to deconversion facilities.Enrichment and storage activities must be performed in the continental U.S. in compliance with the National Environmental Policy Act.The department noted that establishing a domestic HALEU supply chain supports President Joe Biden’s Investing in America agenda by helping meet net-zero emissions goal by 2050, creating jobs, strengthening U.S. competitiveness and improving energy security.