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This topic is offered for comments, suggestions and constructive criticism of Calliban's initiative
Thanks for Calliban for opening this (to me ** very ** ) important topic!
(th)
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Here is the target of subject of interest to discuss
As posted by Tom Hanson
The premise is that Nuclear is not only Safe (when handled properly) but it is Essential (a) and (b) a person can live comfortably away from Earth with it as the energy supply for a habitat. However, the set of topics I am proposing are ** NOT ** limited to heat, light and electricity, which you can already supply. I'm inviting you (and your guest authors) to build up a topic that shows that food, water suitable for drinking, and all other supplies can be made on site using nuclear power. This is not done on Earth at the moment, so it will be a stretch to work out how to do it in Space.
However, my argument is now (and has been for a number of years) that all human needs can be supplied for a space traveler if sufficient energy is brought to bear on the problem.
________________________________The idea behind this topic is simple, but has enormous implications. Human beings have basic needs: food, fresh water, oxygen at the right pressure; and a suitable temperature range. If the energy inputs for these functions can be provided adequately by a nuclear fission or fusion power source, then human civilisation can be freed not just from the confines of the Earth, but the sun as well. Human colonies can be built throughout the solar system on icy moons or even within icy Kuiper belt or Oort cloud objects. Ultimately, human life can spread to the stars by slow migration, eventually colonising rogue planets as well as throughout the Milky Way, as well as Oort clouds of the 100 billion or so stars within our galaxy.
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relative topic nuclear is safe
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This Reactor May Have Finally Solved Nuclear Fusion's Biggest Problem
it has a heat exhaust system which is one of the issues for melt down....
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Length article with lots of images....
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For Calliban ... While you have reported your intention to take some time to think through the details of how fission/fusion hybrid systems might work, I would like to keep this topic close to the top of the active list in the forum.
To review for new readers, (and with the caveat that this is my interpretation of Calliban's intentions), I ** think ** that Calliban is hoping to find a way to achieve useful (and massive) space propulsion in the near future, by combining already known nuclear fission science and engineering, with still-developing knowledge of nuclear fusion.
To over simplify to the point of causing anguish among knowledgeable persons:
To the best of my knowledge (which is certainly limited)
1) Nuclear fusion bombs work as well as they do because they are ignited by nuclear fission devices.
2) The famous Orion deep space vessel was imagined as driven by small nuclear devices (see notes below)
3) Calliban is proposing to find the smallest possible combination of nuclear fission ignition to go with the smallest possible fusion package
Reference for #2 above:
Nuclear pulse propulsion is a theoretical method of spacecraft propulsion that uses nuclear explosions for thrust. It was first developed as Project Orion by the Defense Advanced Research Projects Agency (DARPA), an agency of the U.S. Department of Defense, after a suggestion by Stanislaw Ulam in 1947.Mar 27, 2013
Nuclear Pulse Propulsion: Gateway to the Stars
https://www.ans.org › news › article-1294 › nuclear-pulse...
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FeedbackProject Orion (nuclear propulsion) - Wikipedia
https://en.wikipedia.org › wiki › Project_Orion_(nuclea...
Project Orion was a study conducted between the 1950s and 1960s by the United States Air Force, DARPA, and NASA for the purpose of identifying the efficacy ...
Basic principles · Theoretical applications · Vehicle architecture · Potential problemsNuclear pulse propulsion - Wikipedia
https://en.wikipedia.org › wiki › Nuclear_pulse_propuls...Project Orion — The propellant then goes on to impact the pusher plate at the bottom of the Orion spacecraft, imparting a pulse of 'pushing' energy. Project ...
A vision of what Calliban may find is a BB pellet sized Gatling Gun mechanism to deliver hybrid fission/fusion explosions in the propulsion unit behind a space craft. While the thrust produced by a given packet may be small, once the technology is working, the propulsion units can be stacked in parallel, to provide whatever thrust is needed to accelerate a given mass.
The end point for this development would be a means of propulsion of RobertDyck's Large (passenger) Ship such that the vessel could leave Earth orbit rapidly and safely, travel to Mars on an optimum trajectory, and match orbits with Mars efficiently and effectively without placing the passengers and crew at risk.
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By making the size of the bomb explosions smaller the pusher plate gets less massive for the accumulating effect more like ion acceleration
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For SpaceNut re #7
Thanks for picking up on the potential capability of a hybrid fission/fusion propulsion system!
There may be (subject to Calliban's research, of course) a possibility that the "pusher" plate could be all magnetic.
The key factor is the strength of the explosion. If the pellets are BB sized (ie, smaller than a pea) then it seems possible (pending study results) that a strong magnetic field could withstand impact by ions heading East, and bounce them West, which would be out the stern of the rocket.
The magnetic field needs to (somehow) absorb enough energy from each pellet to be able to sustain the reaction.
Again pendingt Calliban's research, we may learn that existing laser designs (adapted for this situation) may be able to create favorable conditions for fission material to reach critical mass, and thus to create the conditions needed for ignition/compression of the deuterium.
Here is a citation for a (large) pdf from ARPA on the 2017 state of Pinch fusion research.
A Compact Fusion Device based on the Sheared
Flow Stabilized Z-Pinch*
Uri Shumlak for the FuZE Team
U. Shumlak1, H.S. McLean2, B.A. Nelson1, A. Schmidt2
,
E.L. Claveau1, E.G. Forbes1, R.P. Golingo1, D.P. Higginson2
,
A.D. Stepanov1, K.T. Tummel2, T.R. Weber1, Y. Zhang1
1University of Washington, Seattle
2Lawrence Livermore National Laboratory
with Zap Energy Inc.
ALPHA Annual Review Meeting
29-31 August 2017
San Francisco, California
*This work
I am looking for a report I saw yesterday, about progress in the Z pinch concept. The article (which I have yet to find) reported that instability of the Z Pinch plasma can be addressed by sending a sheath of faster ions outside the ions to be pinched.
As I remember the article, the researchers involved reported making progress in achieving stability of their plasma.
The long term potential of this method includes (according to the article) the possibility of leaving one end of the machine open to vacuum, so that the products of the pinch operation are expelled to the rear of the vessel, and the magnetic reflector at the front of the engine would recoil against the pressure of the ions sent in it's direction. That recoil would eventually find it's way into the mass of the ship itself.
That would happen (I assume) through force exerted upon the coils of the magnets, which would themselves be mounted firmly on the main girders of the vessel.
(th)
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The concept that I am attempting to develop is slightly different to the way in which a hydrogen bomb or boosted fission bomb works. In these cases, the fissile charge is wrapped around the secondary fusion stage and ignition of fusion is provided by a combination of x-ray heating of the secondary charge and inertial confinement, as the heavy fissile material is heated to plasma and expands compressing the secondary to literally millions of atmospheres. As the secondary ignites is releases fast neutrons, increasing the fission in the primary, heating it even more. So a classic hydrogen bomb does rely on coupling between the two stages.
The fission fusion micro pellet explosions that I am attempting to develop, rely on lasers, ion beams or z-pinch to compress a pellet of fusion fuel, much as conventional inertial confinement fusion experiments do. In ordinary IC fusion, the goal is to compress the pellet to very high density and then use a laser to create a hot spot. The conditions within the hot spot greatly exceed the lawson criterion and it propagates like a detonation wave through the pellet. There are lots of problems with this fast ignition approach. To reduce ignition energy to levels where net energy is produced, very high density must be achieved in the imploding pellet. This is problematic because very powerful lasers are needed to produce the required compression and even using of a hohlraum, plasma instabilities tend to disrupt the pellet before sufficient compression is reached. The laser facility is also huge, it could never realistically fit into a space vehicle. So what I propose is to use tiny amounts of fissile material at the centre of an imploding fuel pellet to generate the hot spot needed to trigger fusion.
This approach offers a number of advantages. Fission products are highly charged fragment atoms that carry away most of the energy of a fission event. They have a very short range in solid matter - about one hundredth of a mm. In compressed matter, even less. The critical mass of a fissile material is proportional to the inverse square of its density. So compressing the material to 1000 times its normal density at the centre of a pellet, reduces critical mass from tens of kg to tens of milligrams. The compressed fusion fuel of an imploding fuel pellet also provides an excellent neutron reflector around the fissile core. The key to the concept is the coupling that occurs between the fissile core and the surrounding fusion material. The fissile core is so small, that most of the fission products escape it and deposit their energy in a thin shell of fusible material around the fissile core. As they do so, they heat the surrounding deuterium to plasma, with temperatures of hundreds of millions Kelvin. A substantial fraction of these plasma ions undergo fusion, releasing neutrons which enter the fissile core generating more fission events. As compression proceeds a hot spot forms at the centre of the pellet and when a critical density is reached, the ions streaming from the central region become a detonation wave that rapidly fuses all of the ions in the pellet.
Because of the coupling and neutron reflection, ignition of the pellet should require far less compression than conventional IC fusion. No separate laser apparatus is needed to generate a hot spot. The more modest compression could be generated by ion beams which are electrostatically accelerated. This is a far more compact driver assembly, which should be small enough to fit in a space craft. The extremely high temperatures generated in the vicinity of the fissile core, should allow lawson criteria to be reached for pure deuterium, without need for expensive tritium. Alternatively, if the pellet were fitted with an appropriate tamper material, lithium deuteride could be used as fuel. This has the additional benefit of being a stable solid at room temperature. This makes it easy to store pellets.
The nuclear fission that occurs to trigger the fusion reaction will generate radioactive fission products. There is no way of avoiding this. But the hope it that the very small quantities of fissile materials needed will represent only a very small proportion of the final energy release, such that very little radioactivity is generated per MJ of energy released. One way of reducing the amounts of fissile material needed to trigger each microexplosion, is to use deuterons as the driving ions that ablaze the pellet surface material driving compression. As compression proceeds towards the final value, the driver assembly voltage can be made to spike towards 1 million volts. This will result in a sudden increase in deuteron energy arriving at the surface of the pellet. As the incoming deuterons interact with the fuel in the pellet, some of them will fuse, generating a shower of neutrons. This will provide the trigger needed for core criticality and allows it to coincide exactly with the achievement of critical pellet density.
What I hope to do in the first few months of this year, is model this system using a spreadsheet programme. This should allow some assessment to be made of feasibility. I don't think there is any hope of modelling such a closely coupled system computationally. At some point, it will need to be live tested in a purpose built facility. Because we are using fissile materials to trigger the process, testing will be extremely difficult from a regulatory viewpoint. It would be much easier (though still difficult) if the fissile materials used were in the form of low enriched Uranium (% fissile <10%).
A reminder of what success in this area could mean. Not only would we have a space drive with ISP >10,000 and T/W >1g; this technology could be used to construct extremely compact fusion reactors, without need for huge electromagnets or driver lasers. These would have power density comparable to fission reactors, without the problem of long lived radioactive waste. So fission triggered IC fusion really could be the holy grail energy source that solves many of our Earth based problems, as well as giving us the keys to the universe.
Last edited by Calliban (2022-01-02 14:03:36)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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For Calliban re #9
With the objective of (trying to) help forum members and readers to quickly find your post, I'll offer a couple of tags...
SearchTerm:deuterons used as ignition support for hybrid fission/fusion propulsion system
SearchTerm:Hybrid fission/fusion drive concept by Calliban
My interest in your post is enhanced by the suggestion that your design might be able to use Deuterium. I recognize that the lithium version may have advantages, but competition for lithium these days would tend to make the material more expensive than it might have been otherwise.
On the ** other ** hand. lithium may be found in abundance off-planet, so it would become an attractive material for consideration.
(th)
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A lump of lithium the size of a golf ball gives you the energy benefit of a tank of oil several metres aside. I can't see lithium cost or availability being a problem with this idea. The cost of the fuel materials will be a rounding error in the final cost of power.
A bigger problem with lithium is that neutron interaction is needed to convert it to tritium, which then reacts with deuterium. This increases the required plasma confinement time, as two reactions need to take place. Onnthe other hand, the resulting tritium deuterium fusion is a much better neutron source for inner core fission and makes it easier to use lower enriched Uranium or even Thorium, as a lot of fast fission will take place. Not a problem at the centre of a hydrogen bomb, because the scale of the system is greater and the fissile jacket acts as a very efficient tamper, both of which naturally increases confinement time. But the system we are discussing here is orders of magnitude smaller. It is the size of a full stop or a biro ball under full compression. So it isn't clear to me that lithium will remain confined for enough time to burn.
I am not the best person for this sort of work really. It has been several years since my original nuclear engineering degree. These sorts of questions need a plasma physicist. Dr Zubrin himself may be able to take this idea further than I can (he is a nuclear engineer with an additional mathematics degree). But I am going to do as much ground work as possible in the hope that a specialist can puck this up and develop it further.
Last edited by Calliban (2022-01-02 14:44:02)
"Plan and prepare for every possibility, and you will never act. It is nobler to have courage as we stumble into half the things we fear than to analyse every possible obstacle and begin nothing. Great things are achieved by embracing great dangers."
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Rolls-Royce Expects UK Approval For Small Nuclear Reactors By Mid-2024
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