by Adam Crowl
Adam Crowl has been following Friedwardt Winterberg’s fusion concepts for some time, and now weighs in with a look at Winterberg’s latest thinking on the use of deuterium reactions in advanced propulsion designs. If fusion is our best bet for interstellar missions, we need to get past the limitations of deuterium/tritium, which produces a neutron flux of such proportion that a manned mission would pay a huge penalty in shielding. Winterberg’s ideas on thermonuclear deuterium reactions offer a technique with high exhaust velocities, one with interesting echoes of Project Orion.
Back in the 1960s Robert Enzmann imagined immense fusion-propelled starships which saved tankage mass by storing frozen fusion fuel – chiefly deuterium – as a huge frozen ball. Enzmann and his co-workers eventually found that deuterium isn’t a very strong solid and a tank of some sort would be needed for mechanical support under acceleration. Even so attaching a starship to a great big mass of frozen deuterium seems a good idea, in light of Dr. Friedwardt Winterberg’s updated e-print from June, entitled “Advanced Deuterium Fusion Rocket Propulsion for Manned Deep Space Missions.”
Of course the trick is igniting the deuterium-deuterium reaction and getting a high fusion-burnup fraction out of the fuel-target. Winterberg is an unapologetic skeptic of SF style interstellar ‘short-cuts’, rightly pointing out the non-evidence for anything like wormholes or warp-drives. Interstellar travel can only be seriously contemplated on the grand scale via fusion rockets.
Image: The Enzmann starship, as envisioned by artist Rick Sternbach in a 1973 issue of Analog.
Igniting Deuterium (and the Benefits)
The two fusion reactions presently within our technological reach require relatively abundant deuterium, namely deuterium-tritium and deuterium-deuterium reactions. The D-T reaction has two liabilities – most of its energy goes into uncharged neutrons and the tritium has to be continually made via breeding it in a lithium jacket subjected to that same neutron bombardment.
The D-D reaction is not so easily done as the D-T, but Winterberg’s work makes the prospects look good with sufficient effort. In this most recent paper he suggests a way of reducing the wasteful loss of kinetic energy to electrons and neutrons. Firstly the electrons are allowed to escape the fusion target after the initiation of the fusion compression process – this merely requires the target to have a sufficiently small width. Secondly the neutron/ion kinetic energy fraction can be altered by causing an auto-catalytic fusion detonation wave to form in the burning front of the fusion reaction. This causes x-rays produced by the reaction to focus on the unburnt fuel, preparing it for the fusion reaction itself.
The estimated exhaust velocity is fairly high, an estimated 19,000 km/s (0.063 c) which means a 120,000 ton starship attached to 12,000,000 tons of deuterium can do a delta-vee of ~0.29 c. With an efficient magnetic sail that means the journey speed approaches ~0.29 c, albeit with the mass-penalty of the sail.
The Shadow of Orion
Winterberg’s discussion gives some interesting insights into the “Orion” atomic rocket effort. Freeman Dyson wasn’t alone in being disturbed by the fallout issues with the fission pulse units and triggers and it was this concern which inspired Winterberg to develop non-fission triggers for pulsed nuclear fusion. Thus all the fusion starships inspired by Winterberg’s early work on electron beam ignition, like “Daedalus”, were in turn inspired by “Orion” and the fallout fears of its developers.
Non-fission triggers are a laudable goal of fusion propulsion research, but they pose a conundrum for slowing proliferation of thermonuclear weapons. Winterberg prefers a very high-powered proton beam ignition system for in-space flight, which would require a mile-long Super-Marx Generator to store up enough power for the beam here on Earth. Not a proliferation risk in either manifestation. However his preferred fusion launcher system does have military implications, using high-explosive driven argon UV lasers to trigger a two-stage DT/DD fusion pulse. Such a device could be used as a low radioactivity nuclear weapon – tritium dispersal poses its chief radiological hazard.
Image: Pure deuterium fusion explosion ignited with an intense ion beam. D deuterium rod, h hohlraum, I ion beam, B magnetic field, R miniature target rocket chamber, H2 solid hydrogen, L laser beam to heat hydrogen in miniature rocket chamber. Credit: F. Winterberg.
Fission and the Space Imperative
Winterberg’s final discussion of keV energy chemical super-explosives is the more disturbing prospect in some ways. Lines of research indicate that some elements can be forced into metastable bonds between their inner electron shells, thus storing up keV energies in chemical form. Regular outer shell chemistry produces mere electron volts of energy per reaction, released as visible light and UV light photons, but keV energies mean x-ray photons, the sine qua non of fusion triggering.
In all likelihood such super-explosives will require dynamic compression to create, probably requiring the apparatus to be too heavy for bombs – but what if such materials could be ‘quenched’ to STP conditions? Then we’d have a real proliferation risk. Ted Taylor, the late co-worker of Dyson on “Orion”, once dreamt a solution to non-fission triggering of fusion reactions, but never told anyone for fear of the implications.
As Arthur C. Clarke once said nuclear power not only makes spaceflight possible, but imperative…
Hi Paul/Adam,
Interesting paper by Winterberg particulary section 9 where he talks about getting large amounts of hardware into orbit using lasers etc, so far all the designs I’ve seen (whether fission, fusion, anti-matter, Bussard ramjets etc) all are BIG spacecrafts and unless the main hardware is built somewhere already in space, getting the components into orbit could be a very big challenge…
We want to go to distance places beyond our solar system but ironically as Winterberg says:
“To lift large payloads into earth orbit remains the most difficult task.”
The Earth’s gravity problem is back with us again…
Cheers, Paul.
The energy per mass unit of D+D->T + proton is much less than D+T. It’s true in the latter reaction that most of the energy ends up with the neutron, but that’s shielded by LIGHT elements. In fact the best use is to use lithium, which then makes more tritium.
Hi Keith
In the reactions computed by Winterberg the D+D primary reaction proceeds to completion, so the T and He3 products of D+D also fuse into He4. Thus the high exhaust velocity.
Lithium fusion is certainly an attractive concept, but much, much harder to initiate.
I recently e-mailed Freeman Dyson concerning winterbergs works. He basicly said the main problem is costs. We need REAL investment into space exploration before any large scale missions are even possible. We spend more on payloads than on launch/propulsion. NASA is only getting .05% of the GDP and that money is spread so thin that they can only dream of thinking big. Winterberg is thinking big and I am glad. I hope thinking big becomes the priority again because we need to inspire the young with dreams of reality opposed to dreams of fiction. Though dreams of fiction will always have their place in shaping our possible futures, Id just rather get started making our future NOW. Think Big, Make Dreams!
We want to go to distance places beyond our solar system but ironically as Winterberg says:
“To lift large payloads into earth orbit remains the most difficult task.”
We will go to the stars some time after we have large scale solar system wide economic development and settlement.
Hi Adam;
Thanks for the above article on nuclear fusion.
I often ask my friends and some relatives the rhetorical question, “What might we do with Nuclear Fusion ?”, when the subject of manned interstellar travel comes up as to whether or not it will ever occur.
I usually answer the question upon receiving blank stares with an answer in the form of the recitation of the following roster set or simmilar set: {Fusion rockets, Fusion powered ion drives, Fusion powered electron drives, Fusion powered photon drives, Fusion powered neutrino drives, Fusion powered magneto-hydrodynamic-plasma drives, Fusion powered electro-hydrodynamic-plasma drives, Fusion powered electro-magneto-hydrodynamic-plasma drives, Improved interstellar ramjets, Fusion pellet runway drives, Fusion powered magnetic field effect propulsion systems which react against interstellar magnetic fields (this obviously would require extremely strong ship basesd magnetic fields), Remotely beamed fusion fuel powered systems, and the like.
For those who like the idea of the acceleration of a space craft somehow in one huge feld swoop, I have discussed the concept of the assembly of huge nuclear fire crackers, such as devices that would have the form of nuclear shaped charges which might focus the explosive energy fluz density to several orders of magnitude greater than that achievable by an ordinary spherically detonating, or approximately so, nuclear device: perhaps even an additional several orders of magnitude for each additional staging of the shaped charge effects- the caveat being the ability to somehow accelerate such a space craft by this means without destroying it by either the acceleration or the blast energy.
I can imagine some sort of nuclear explosion based magnetic field flux compression that might be used to propell an appropriately oriented dipole space craft, and if some loop holes in classical electrodynamics would permit, an effectively monopolar magnetic field emmitting space craft. Such a magnetic flux compression would most likely work best with a nuclear reaction sequence that minimizes energetic neutron production, the reason being that the high velocity electrically charged fusion products produced would more readliy react with a standing magnetic field in order to so compress it.
Given that the vast magority of baryonic matter within our universe exists in the form of fusion fuel which has yet to be tapped by nature in stellar furnaces, it seems as though we as a civilization should be seriously looking into to this potential energy source to power our space craft: a truly cosmic energy source.
Perhaps we can state from a philosophical perspective that the relativistic gamma factor of future human space craft is limited only by the ability of humanity to aggregate natural fusion fuel, in either a continuous or batch mode. Thus to the extent that humanity can engineer arbitrarilly large linear distributions of fusion fuel, either in continuous or batch mode, commensurately arbitrarilly high gamma factors should be obtainable. What sorts of kinematic arrangments of fusion fuel (including perhaps fusion fuel batches that somehow extent into higher dimensional space, or perhaps such that are somehow parallel-ly extended into our very current 4-D space time but which are co-located in such space time) would enable essentially unlimited gamma factors, we can not yet know, but the efforts of folks like Adam Crowl to further the cause of fusion powered starships will not go un-noticed as humanity eventually realizes the dream of star flight.
I am for any and all forms of research utilizing nuclear fusion to power space craft
Winterberg deserves a lot of credit for making the pure fusion concept a reasonable prospect in this context, but such work has a dark pedigree with its origins in the H-bomb research programs of the 1950s-60s. We should always be mindful of what fear has lead some to contemplate, plan and prepare to do – to launch thermonuclear destruction upon their rivals at first signs of them doing the same. Opening up the space frontier with those same nuclear weapons would go a long way towards mitigating and allaying those fears by giving us room to move and a better perspective on resource availability. Our ingenuity can allow us to adapt the worlds we’ve found Out There to our needs, and even adapt us in turn to those worlds.
Perhaps that’s why multi-thousand ton launch vehicles are better to contemplate than smaller efforts, because we yearn to launch forth en masse for those New Worlds.
To “arbitrarily high gamma factors”: While I think that something close to light speed is feasible, there are a number of pesky problems. First of all, the rocket equation with its nasty exponential sets a fairly low limit for fusion, even if you could assemble all the fuel in the universe in a single ship. Besides that, there are some other factors that will prohibit arbitrarily high gamma factors, among them interstellar gas and the cosmic microwave background.
RE: The Shadow of Orion
This is inescapable. The concept is know as “Jon’s Law for SF authors”: “Any interesting space drive is a weapon of mass destruction. It only matters how long you want to wait for maximum damage.”
http://www.projectrho.com/rocket/rocket3a.html#johnslaw
The point is that energy is energy. Starships require huge amounts of energy. There is no way to prevent the energy stored in the starship from being used destructively instead of for propulsion. The same applies to the technology used in the engines.
Hi Eniac;
Concepts such as the fusion pellet runway do not require that the space craft carry its fuel on board from the start. Likewise, neither do improved versions of interstellar ramjets. Both of these systems can in theory operate without carrying nuclear fusion fuel on board, thus the relativistic rocket equation would not apply in its simple form of Delta V = C tanh{[Isp/C] ln (mo/m1)} where Isp is expressed in units of C less than or equal to one.
Regarding ways to deal with interstellar drag, perhaps some sort of negative electromagnetic refractive index meta-materials could be used to ironically pull the craft forward by impinging CMBR and star light. Matter wave materials that would operate on matter waves are theoretically possible, and might be used to cloak the space craft from impinging dust. molecules, and atoms provided the dust particles are small. Such a matter wave negative refractive index material mechanism might operate simillarly to EM negative index materials and be pulled forward by the impinging matter waves.
A good source for current research on negative EM index materials is the research being done at Duke University. The classical electromagnetic effects of such materials in terms of ramifications that go beyond Maxwell’s equations are not fully understood yet, although negative EM index refractive meta-materials have definately been developed within the lab and so their existence is now incontrovertical.
One might also use some sort of efficient drag energy absorber to collect the impinging kinetic or electromagnetic energy and recycle the energy into propulsive thrust so as to greatly reduce the net drag energy.
The sequestration of any hydrogen that might exist in hyperspace might permit unlimited hyper volume fuel access as the number if such hyperspatial dimensions approaches infinity or as the higher dimensions approach a perfect continuum. The number of 3-D one meter cubes containing on average 3 hydrogen atoms per cube would translate into infinite fuel supplies for a 4-D space 1 meter cube since a 4-D space cube as such contains an infinite number of stacked 3-D 1 meter cubes for the case that the 4th spatial dimension is perfectly continuous. Likewise, a 5-D one meter cube would contain an infinite number of 4-D one meter cubes, and so on.
If the 4th dimension of space is quantized at the level of the Planck Length, then a 4-D one meter cube might plausibly contain 10 EXP 35 one meter 3-D cubes and thus contain many metric tons of fuel. If the fifth dimension of space is quantized at the level of the Planck length, then the plausible quantity of fuel in a 5-D one meter cube would be about 10 EXP 36 metric tons. For each additional quantized higher dimension for a respective one meter hypercube in flat Euclidean space, the quantity of fuel would plausibly grow by a factor of 10 EXP 35.
0.29c is not a bad maximum velocity at all! That’s almost 3 years to the light year, though it is not really enough to take advantage of time dilation to make the trip seem shorter to those on board. How many interstellar colonists could a large 120, 000 ton starship carry? Also, what type of shielding would necessary to protect the ships crew and components at such mind-boggling velocity?
Good article.
As noted, any technology that can get anything to ~0.29 c has military implications. Even moderately advanced VASIMR scale tech and robotic electric solar sails would let fairly free roaming out to near earth asteroids and the asteroid belt. Big rocks could be diverted to pound fixed targets on earth.
Moving up the kinetic energy scale quickly outclasses any existing nuclear bombs.
Advanced space tech means super Kinetic weaponry. Does not matter how you do it but if you have freedom of cheap movement to orbit and around the inner solar system – you can kick the ass of anybody stuck on earth.
Mastering fusion for energy generation and your country has 10 to thousands of times the energy budget of non-fusion enabled countries. A country with virtually no upper bound on cheap, clean energy is insanely rich.
super energy rich means super wealthy =energy rich and money rich translate to military strength. See WW2 – US outproducing Japan and Germany
Brian: While your point is well taken, I think it is hard for kinetic weapons to outclass nuclear. The best you can reasonably do, I think, is park your weapons in Earth solar counter-orbit, where they would have a relative velocity of around 60 km/s, and could be delivered fairly quickly if there are enough of them. IIRC, even at that speed, you are still way below the energy density of fusion fuel. In fact, this would have to be true, otherwise there would be no hope to reach relativistic velocities using fusion.
Also, kinetic weapons are not as fail-safe as nuclear ones can be made. A tiny mistake and you could hit the wrong side of the planet…
Here is a 1982 art piece by Rich Sternbach of two Enzmann starships
visting an alien gas giant system:
http://www.ricksternbach.com/spaceart2.html
I found this Enzmann starship artwork on the cover of the 1986 Boskone
program by Bob Eggleton:
http://www.nesfa.org/boskone/images/b23-600.jpg
brian and winchell/nyrath echoing each other is a case of great minds thinking alike. Of course once belligerents are armed with fusion weapons a vehicle propelled to high enough speeds to match fusion bombs in its kinetic energy is a rather less steerable device than the equivalent explosive device fired off at reasonable speeds. If we could launch relativistic missiles then the game changes, but a perimeter of high-acceleration interceptors might make such missiles ineffective – they have even less time to deploy counter-measures than we do to deploy (already emplaced) defenses against them. If can develop Jordin Kare style micro-sails launched at mega-gee accelerations then we have the making of relativistic guns – for defence or offence.
This is all a bit off-topic, but then the binary nature of interstellar technologies is nowhere more stark than when we consider fusion propulsion, especially via “bombs”. I hope we’ll get all our eggs out of this one basket some time soon and Winterberg’s concepts might well help us do it too.
I do not see how a “pellet runway” overcomes the rocket equation. In the end, all fuel still needs to be accelerated to ship velocity before it can be burned. Plus, it has to be brought somehow out to where no-one has gone before, and then slowed down enough for the ship to catch up? It would seem that requires even more fuel than a simple rocket.
If you want to beat the rocket equation, you need to work “from behind”, with particle, light, microwave, or pellet beams which are supplied with the required energy locally, in the solar system, and then projected out towards the ship. Particle, light, and microwave beams are unsuitable, really, because they cannot be collimated enough. That leaves intelligent pellets, which can collimate themselves using limited corrective propulsion. Currently, I think the best approach is Kare’s microsails, which are accelerated using laser beams locally and then home in towards the ship to give it a push.
Hi Eniac;
The fusion pellets may be of a pure fusion type that emits as much energy as possible in the form a gamma rays.
The fusion pellets could be ignited within a ships energy extraction chamber as the ship passes by or they could be ignited behind a pusher plate or other energy absorbing mechanism as the craft passes by them.
Fusion pellet runways with 1 kiloton to 1,000 kiloton yield shots might be laid out over a long period of time, perhaps over 10 to 100 years, and have self steering and course correction mechanisms.
The only losses in using the fusion pellet runway that I see as being of significance are the relativistic dopplar red-shifting based ones for the emmited gamma rays for the case where the fusion pellets are detonated behind a pusher plate or other energy absorber.
Another way of doing the fusion pellet runway is to lay the pellets out in deep space orbit around the Sun wherein the entire length of the track can be constructed simultaneously or in multiple sections simultaneously. The craft could be suitably charged so that the Lorenz turning forces exerted by the Sun’s magnetic field would steer the craft in a circulinear orbit in order to access the pellet explosions. The electrical charge on the craft could be increased as needed to accomidate the higher centripital accelerations required as the gamma factor of the craft increased inorder for the craft to utilize the fusion pellets.
brian wang October 27, 2009 at 16:32:
“Mastering fusion for energy generation and your country has 10 to thousands of times the energy budget of non-fusion enabled countries. A country with virtually no upper bound on cheap, clean energy is insanely rich.
super energy rich means super wealthy =energy rich and money rich translate to military strength.”
Maybe, but the availability of abundant cheap and clean energy would at the same time also largely eliminate the need for most military show of force. I know, of course, that part of the reasons for conflict in this world is ideological, but ideology is often only the direct rationale or justification, true root cause for most conflict, or at least the violent expression of it, being very basic and biological: competition for scarce resources.
The perceived need of an advanced technological society, fully mastering nuclear fusion, for military confrontation with a less advanced society for resource competitive reasons (for instance for oil !), seems somewhat like the US seeking military confrontation with Amazon indians over their cassava crop.
The mastering of nuclear fusion will probably not add significantly to our past and present abilities of wholesale destruction, while opening up grand avenues of possibilities with regard to energy, other resources, and space exploration.
Call me irretrievably optimistic, but when it comes to nuclear fusion I can only see a very large black figure at the bottom line.
If you think about it, energy IS cheap and plentiful already (11 cents a kWh, where I live). We have mastered nuclear energy for 50 years, but except for the French no-one has made much of it, yet. You have to be quite an optimist to think that fusion will be completely different.
Eniac: “You have to be quite an optimist to think that fusion will be completely different.”
But as I said, I am. And only the optimists survive (or was it the realists?) ;-)
I think it was the pessimists…. ;-)
I agree with Ronald’s optimism, but I am dubious about “free energy” being a solution to the world’s ills. No doubt it’d be a good start, but there’s a lot to do. Perhaps the best thing about visible efforts to colonize space is the potential for giving people hope in human achievement, and thus the nerve to face their own problems. Turning our sights inwards will only depress us, I suspect from my own experience of depression.
Referring to a previous post, if a starship traveled at .3c and hit a piece of dust with a mass of 1 ?g it would have twice kinetic energy of a truck traveling at 55 mph. Did my own version using what I believed was a large truck of 9000kg.
9000 kg Truck at 55mph (25 m/s):
http://www.wolframalpha.com/input/?i=.5+*+9000+kg+*+%2825m%2Fs%29^2
1 ?g Dust at .3 c (89900 km/s):
http://www.wolframalpha.com/input/?i=.5*+.001+mg+*+%2889900+km%2Fs%29^2
Interested in proposed solutions to this sort of problem!
The commenting software didn’t handle the wolfram links properly:
Truck: http://bit.ly/38mTJL
Dust: http://bit.ly/3FQbFG
Fusion power of one form or the other will be necesary of course , but the real botleneck is in achieving a workable all-round plan for reaching the stars .
Some components seem to be unavoidasble if we want to do it before the planet runs out of rawmaterials :
1 It needs to be a generation ship , which mean BIG
2. Fusion powered propulsion system to lifesupport and to slow down at new starsystem
3. A moonbase capable of suplying most of the rawmaterials for starship , only a magnetic catapult can lift it cheaply to moon orbit
4. A beampowered acceleration system , perhabs utilizing existing powerstations , perhabs a laser powered magnetic sail .
5 The whole starship-buildig project ITSEF will have to be a “generation projekt” (like the PYRAMIDES !) , and this has historicly only been done by using religion as motivating force…
Here ofcourse is the REAL BOTTLENECK , selling the project to the taxpayers..
Another hard question is how to get large quantities of deuterium out of moonwater ?