A Workable Fusion Starship?

by Paul Gilster on January 23, 2009

by Adam Crowl

In the market for a mammoth starship? Recently released work by Friedwardt Winterberg, discussed here by Adam Crowl, points to fast interplanetary travel and implies possibilities in the interstellar realm that are innovative and ingenious. Adam notes in an e-mail that Winterberg’s drive has certain similarities to MagOrion, a system that in its earliest iteration combined a magnetic sail with small yield nuclear fission devices. Dana Andrews and Robert Zubrin first published that concept in 1997 and it has been evolving in the years since, but Winterberg’s work takes the idea into the realm of what may be a truly workable fusion design. Read on as we follow up our earlier story on Winterberg with a much deeper look.

Friedhardt Winterberg has worked on inertial confinement fusion since 1954 and was extensively involved in developing new fusion devices during the Cold War alongside bomb-makers like Edward Teller. Much of his non-fission triggering work was classified, but his declassified suggestions in 1970 for setting off fusion reactions via electron beams were adopted by the British Interplanetary Society’s “Daedalus” starprobe study, with all that implies for the interstellar community.

winterberg

However, Winterberg says in his new papers, electron beams just won’t work when triggering deuterium reactions. This is an important point. Bombs have typically used deuterium-tritium (D-T) reactions, but these release 80% of their energy as neutrons – useless for rockets and problematic for power generation. Pure deuterium (D-D) reactions are a better option and have been successfully triggered in bombs – the 15 megaton “Mike” test is one example – but they require a more intense burst of energy to cause a sufficiently rapid and energetic collapse to produce fusion in the target material. Something like a gigajoule of energy must be concentrated on the deuterium target within less than a tenth of a micro-second to produce fusion and not merely blow the target apart in a puff of hot gas.

Image: Friedwardt Winterberg, whose innovative propulsion concept now weds magnetic mirror technologies with fusion. Credit: Wikimedia Commons.

How to do so with present day technology and apply it successfully to rockets requires overcoming some serious problems. An intense proton-beam sufficiently rapidly acting to cause the fusion-making implosion has a beam-power of an unprecedented 10 petawatts (10,000 trillion Watts.) For it to rise to full power sufficiently rapidly – in less than a 1/10th of a microsecond – a voltage of a billion Volts is needed, which in a terrestrial laboratory would cover the machinery in gigantic sparks due to insulation breakdown of the surrounding air. How to avoid such wasteful artificial lightning?

In a vacuum the issue is less serious. Large voltages can be maintained by firing off charge as electron beams or small charged pellets. Winterberg imagines a spaceship wrapped in a set of superconducting coils to maintain the gigantic charge needed and create a magnetic mirror. Then a laser beam blasts a plug of solid hydrogen in the fuel target producing a jet of protons as a bridge between the ship and the target. This allows the massive charge of the ship to discharge as the desired high-energy proton-beam with sufficient power to collapse the deuterium fuel. The resulting fusion explosion produces a huge plasma wave that the ship’s magnetic mirror now deflects, transferring momentum from the plasma to the ship. Winterberg also discusses a means of triggering the same reaction in an atmosphere – via ultraviolet argon lasers.

winterberg

Winterberg is very critical of current efforts to compress fusion fuel via lasers because to be sufficiently energetic the lasers would be destroyed in the process. Winterberg turns this problem into a virtue by using an explosion-pumped laser-beam – a shaped cylinder of hexogen explosive detonates at 8 km/s and compresses a rod of solid argon, thus pumping its atoms into a UV laser-emitting state. This intense UV laser-beam then compresses a deuterium-tritium fuel target that in turn causes a bigger D-D fusion explosion. All this now rapidly expanding plasma, plus air sucked into the reaction chamber, now explodes out the rocket nozzle as a high-speed exhaust.

Image
: Superconducting “atomic” spaceship, positively charged to GeV potential, with azimuthal currents and magnetic mirror M by magnetic field B. F fusion minibomb in position to be ignited by intense ion beam I, SB storage space for the bombs, BS bioshield for the payload PL, C coils pulsed by current drawn from induction ring IR. e electron flow neutralizing space charge of the fusion explosion plasma. Credit: Friedwardt Winterberg.

So what sort of performance is expected? Winterberg’s interplanetary vehicle has an exhaust velocity of 100 km/s, while the launcher vehicle gets 10 km/s. Sufficient to industrialise the Solar System, Winterberg’s stated goal, but what of interstellar travel? Small fusion bombs in the right casing can trigger bigger explosions, thus potentially we have the makings of (large) starship fusion-triggering system.

Imagine an Orion or even Daedalus style vehicle, large enough to magnetically contain the fusion explosions more efficiently than the external fusion system Winterberg describes. To get the high performance fusion plasma need for starflight most of the propellant plasma has to be products of the reaction, not incidentals like the disintegrated argon laser or the fusion target chamber that contains the deuterium. The more diluted the mix, the slower the exhaust. Very large bombs are less diluted, but need larger vehicles to contain their blast. Thus Winterberg style starship-building potentially necessitates the gargantuan.

The Winterberg paper is “Deuterium microbomb rocket propulsion,” available online. The original MagOrion paper is Andrews and Zubrin, “Nuclear Device-Pushed Magnetic Sails (MagOrion),” American Institute of Aeronautics and Astronautics Paper 97-3072, 33rd AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, Seattle, Washington, 1997.

James M. Essig January 23, 2009 at 19:34

Hi Paul and Adam;

Adam, this is a most excellent article.

One way that nuclear bombs might be utilized to drive a fusion star ship simmilar to that proposed by Winterberg is to use antimatter caltlyzed or ignited pure fusion bombs. In this scenario, small quantities of antiprotons would be trapped in molecular cages by the repulsive charge between the cage atoms’ electron clouds and the negatively charged anti-protons. The sytem would be perturbed or otherwise induced to have the cages release the anti-protons thereby generation heat and ionizing radiation perhaps with great enough energy density to initiate a fusion wave throughout the entire mass of the pure fusion bomb.

Perhaps some form of dense Deuterium, similar to the proposed metalic hydrogen state could be used to confine the fusing deuteron materials that might result in proton antiproton reactions in such a way the the heat generated from the reaction could set off the entire bomb.

The best fusion fuels have a yield of about 170 kilotons/kg whereas the state of the art nuclear warheads such as the W-88 stationed aboard Ohio Class Ballistic Missle Submarines have a yield of about 475 kt but have a mass of about 300 kilograms. A pure fusion bomb would therefor have a mass specific yield about two orders of magnitude greater perhaps enabling interstellar manned flight.

Thanks;

Jim

Adam January 24, 2009 at 20:08

Hi Jim

Winterberg’s ideas have proven fruitful for the interstellar community in the past and I’m hoping this new system proves inspiring for those better equipped to analyse the physics than myself. The idea of using the ship as a gigantic capacitor is intuitively appealling and combining that and the magnetic mirror for directing plasma kills two birds with one stone. Will be interesting to see what more informed playing with the basic idea results in.

Enzo January 24, 2009 at 22:05

Slightly off-topic, but still strongly related to interstellar travel. The other day I asked myself the question : ” what is the mass of an object traveling at 0.1 c whose energy is the same of 1000 kg traveling at 100 km/h ?”
In other words, I wanted to know how small an impactor could be to do the same damage to a starship traveling at 0.1 c as a 1 T car at 100 Km/h.
To calculate the answer I used classic mechanics, but using relativity would make things worse.
The energy of an object traveling at speed v is m*v^2/2. so
100 Km/h is ~27.78 m/s. 0.1 c is 3E+7 m/s, 1000 kg = 1E+6 g
I wrote the following equation :
1E+6*(27.78)^2=m*(3E+7)^2 => m= ~0.86 micro grams

So, for a starship traveling at 0.1 c impacting a particle of less than a micro gram, the impact energy is the same as 1 T at 100 Km/h.
Is this correct ?
How likely is a starship to encounter a particle of this size during the many years of traveling ? Anything that can be done to limit /eliminate damage ?

Adam January 25, 2009 at 20:08

Hi Enzo

You’ve raised one of the more vexing issues of high-speed interstellar travel and, to be honest, there aren’t too many clear answers. One option is to go slower and reduce the impact energies.

What isn’t clear is just what happens to the incoming particle and how its energy is absorbed in the structure of a vehicle. It’s thought that the impact will be akin to that of a cosmic ray collision – producing secondary radiation, like x-rays and short-lived particles, to be released. What seems doubtful is a “Daedalus” style erosion shield – a thin plate of beryllium – will alone absorb most of the energy. A high-speed particle won’t stop until it has exchanged its momentum with enough particles to thermalise. Instead it will create a cascade of ionization that travels through the vehicle’s structure in a cone. This would cause all sorts of problems and quite thick mass shielding might be needed to absorb it and protect the vehicle’s vitals. Alternatively self-healing electronics might be feasible allowing continual repair of the damage.

“Daedalus” also used a cloud of dust to disperse impacts at 200 km distance from itself – if this could cause all the impactors to be reduced to plasma and a spray of particles, then some kind of magnetic shield might be deployed, channelling the ionic debris away from the payload. High powered UV lasers might also be used to ionise a channel through the interstellar dust, thus allowing magnetic redirection of the flow before it struck the shield, which would reserved for larger particles. Very large particles might be destroyed via firing larger impactors at them, propelled by lasers.

As for how much is out there the size spectrum of dust can be deduced from how light is affected by passage through the interstellar medium and most of the dust mass seems to be in very, very fine dust mere nanometres across – “clumps” a few atoms across. There’s about 3 Jupiter masses of gas and dust for every cubic light-year – roughly 5 atoms of hydrogen per cubic centimetre. Or about a dust particle per cubic metre. Some parts of space are thinner, some thicker. A microgram dust particle is a giant and would occur every 10 km or so. If the vehicle is 50 metres across then it would travel about 50,000 km before it hit a microgram particle – if they exist. Larger particles normally occur inside star systems and are a major hazard of high-speed flyby missions.

Space is vast. For example, the trillion cometoids of the Oort Cloud are spread out, on average, about one every 1000 cubic AU. The odds of hitting one of those, for example, is less than 1 in 1 trillion. That’s better odds than fatal injuries received while flying in a plane or driving a car.

Ron S January 25, 2009 at 22:19

Enzo,

Looks about right. However there are complications. Foremost, while a low-speed collision is all about kinetic energy, it is not so at high-speed.

Imagine that same car at 100 km/h equipped with a needle-pointed lance. It would certainly penetrate just about anything. A microgram particle would somewhat similarly penetrate an insufficiently-armored vessel. When this happens it could very well transfer little of its kinetic energy to the vessel. It would leave a series of pinpoint holes as it passed through material before continuing on its way at lower speed and an altered direction. Of course the composition of the particle bears on exactly what happens.

If it does get stopped, its momentum is transferred to the vessel in part, while other parts go elsewhere. Some in chemical bonds and more in material ejected in other directions.

Let’s assume as a thought experiment that the vessel is impregnable and that the particle comes to a dead stop at the hull. There is still of lot of energy being conserved. All that momentum goes somewhere, and that somewhere is the vessel. Look for significant changes in direction of travel and angular momentum that would all prove problematic.

Even with some sort of energy field to deflect the particle before it reaches the vessel, there will still be a net momentum transfer to the vessel, dependent upon how much deflection occurs.

I suppose you could hope for lots of impacts (if you’re equipped to withstand them) since, like in Brownian motion, the sum total of the momentum changes should sum to zero in the limit. ;-)

James M. Essig January 26, 2009 at 6:14

Hi Adam;

I am also very encouraged that nuclear fusion is once again starting to seem promising for manned interstellar travel.

I remember the days when the interstellar ramjet was often touted as the best potentially high gamma factor to very high gamma factor vehicle for manned interstellar travel. Then further analysis with regard to drag induced by the interstellar medium and the density of the interstellar hydrogen and/or helium gas/plasma turned out to reduce the performance capabilities of the ISR in theory. I still have some hope that the ISR in some future yet to be thought of versions can be ressurected as a high gamma factor capable craft, the higher the gamma factors, the happier myself and a great deal many of us space heads will be.

But we need to start some where, and since we understand very well the fusion reaction sequences, even though our understanding of the electrodynamic-hydrodynamic behavior of 10 million K to 1 billion K plasma could definately stand some improvement , I have high hopes that the problem of fusion rocket thrust can be cracked. Having almost all of the fusion massive products exit in the form of charged particles as opposed to, say the 80 percent of the massive products existing in the form of neutrons for Deuterium Tritium fusion, bodes well for practical manned interstellar fusion rockets.

Once again, thanks for contributing the above article. It is most inspiring.

Regards;

Jim

Adam January 27, 2009 at 20:21

Hi James

Thanks for the nice comment. As for ISR I think it’d only achieve high gamma-factors via mass-annihilation (reverse baryogenesis) and we’re not really sure of all the parameters involved in that process yet. I’ve noted before that Frank Tipler thinks macroscopic sphalerons will be produced in the near-future, to enable colonisation of the Universe, but that’s just his out-on-a-limb opinion. If his neutrino rockets powered by mass annihilation become feasible, then ISRs will only be limited by the heat management required to handle an extremely blue-shifted CMB. Gamma-factors of 1000 might be the maximum feasible – a large carbon heat absorber/radiator glowing white-hot would be needed until the CMB temperature declines as the Universe expands.

James M. Essig January 27, 2009 at 23:43

Hi Adam;

Thanks for the above comments and additional details about ISRs. A neutrino rocket powered by mass annihation would be interesting. I will have to checkout Frank Tipler’s work. I will definately go for a gamma factor of 1,000. If we could learn to extend the human life span to say a few thousand years, a gamma factor of 1,000 will permit us to hop from galaxy to galaxy atleast within our local group.

I have read that perhaps one gram to 100 gram masses of say U-235 could be made to fission if the initial flux density of antimatter induced fission fragments would effectively produce a self sustaining supercritical mass.

An interesting application would be one where very large fission masses would be set off by antimatter induced fission involving perhaps U-238. Some of the cold war Superbomb 20 megaton range designs accordlingly included a hydrogen bomb surrounded by a U-238 jacket which could undergo efficient fission when stimulated by the burst of hydrogen bomb produced neutrons. Fission of either U-235 or U-238 has a yeild of about 25 megatons/metric ton instead of the often quoted maximum theoretical limit of about 2 megatons/metric ton mass for modern thermonuclear devices.

Either way, I seem to have become enamoured by the concept of nuclear rockets over the past few days, perhaps because they might be brought to practical fruition in only a couple to few decades.

Regards;

Jim

Enzo January 28, 2009 at 6:52

Adam, Ron,

Thanks for your replies. I would have followed up earlier but I was away for a couple of days.
It is clear that what would happen depends on how the energy of the particle is dissipated. Assuming it being ice, I quickly calculated a diameter of around 50-60 micrometers for 0.1 microgram. If it went just through the ship almost undisturbed, I doubt it would cause too much damage. I doubt that even a person would be severely damaged by a hole of 50-60 micrometer of diameter through their body (with some exceptions like maybe the optic nerve and similar).
The problem is that the particle will loose some of its energy as it traverses the ship. The total energy (calculated as m*v^2/2) is only about enough to raise the temperature of 92 kg of water by 1 degree. However, when localized, even a small fraction of that energy can be quite destructive and Adam’s estimate of 1 microgram particle every 10 Km looks quite scary.

James M. Essig January 28, 2009 at 11:45

Hi Enzo;

The deposition of kinetic energy in one feld swoop can indeed have devistating effects om targets.

I read where a new 50 calibre handgun that was fairly recently brought to market has a muzzle energy of about 4,000 foot-pounds or about 5500 Joules. This out does the 44 Magnum of the Dirty Harry movie in which Clint Eastwood starred by a factor of about 2. Yet 0.01 micrograms or 10 nanograms traveling at 0.1 C would have a KE of KE = (1/2)(10 EXP -11){([3 x (10 EXP 7)] EXP 2} joules = 5,000 Joules.

In the field of ballistics, at ordinary fire arm muzzle velocities, the rate at which the energy is deposited or the power of the impact ,dE/dt, for 1,000 to 10,000 joule projectiles is extremely distructive. So some sort of good shield would be required to protect a craft from the gradual degrading effect of even only 0.01 microgram particles at 0.1 C. My thinking is that a thick layer of water might help, perhaps a layer several meters to 10s of meters if not a hundred meters thick. Perhaps just inside such a layer of water would exist a vacancy in which a strong magnetic field would be set up to divert or diffuse any charged matter punching through the water. The beauty of the water layer is that it would refill the gap immeadiately after the 0.01 microgram particle went through or should I say, the ball of plasma as it went through.

I think the problem of 0.1 C nanogram to microgram particle impacts can be addressed with current technology and enough shielding materials. Any 0.1 C precursor manned interstellar starships will probably be very large to begin with.

Regards;

Jim

Adam January 28, 2009 at 20:20

Hi Guys

I think any more insights on this issue will need a better understanding of nuclear collisions and the kinds of fragments and ionizing radiation that results in the 10-100 MeV energy range. Intuitively I think the best defense is a dense precursor shield that causes the incoming debris to be scattered – the resulting plasma we can redirect with magnetic fields and x-rays from bremmstrahlung can be shielded against. I think micron-width channels of ionization bored through humans and computers will be unhealthy at the very least. All our usual expectations are wrong when it comes to these high speeds because shockwaves and the like are so much slower than the “impacting” objects themselves – think lightning rather than meteorite impacts.

Enzo January 28, 2009 at 23:20

One more thing about this that I can’t get out of my head.
I have no idea what the fragment could be made of, but it could be possibly made of some ice of light atoms (mostly hydrogen and it’s isotopes).
Now, at 0.1 c, each proton in each nucleus in the fragment will have an energy of 1.67e-27*(0.1*c)^2/2 = 7.515e-13 joule. 1 joule = 6.24e+18 electronvolt (ev). The fragment is effectively a bundle of particles each with at least 7.515e-13*6.24e+18 = ~4.5 Mev .
This is not like a normal hot plasma with a range of particle velocities : ALL of them point in SAME direction at 4.6 Mev for each proton.
Now, imagine the fragment impacting : I can’t say what would happen for sure, but it looks to me that a large number of them would end up colliding with each other at more 100 Kev.
Wikipedia, in the page about nuclear fusion puts the fusion barrier for D-T at only 10 Kev. It sounds like some of the impactor could undergo nuclear fusion rather easily regardless of its composition.
If that is the case, things get a LOT worse for the starship. Quick calculations with only 10% of the material undergoing fusion add a few orders of magnitude in energy to the impact.
Is this a show stopper for “fast” (0.1c) interstellar travel ?

george scaglione January 29, 2009 at 10:30

hello all,first thank you for sharing your ideas! next,i would like to have my say so batten down the hatches because here it comes : i have read that it is not possible to exceed the speed of light in ordinary einsteinian space because of the exceedingly small particles (maybe even from the zero point field) that you would be constantly ramming your ship into.well in my opinion and yes it calls for a heck of alot of engineering and physics to be developed the answer could be this,equip your ship with a field projector that would constantly make a rip in space time right in front of you that you would constantly fly into! no particles because you would in effect be making your own space rather like the way warp drive tinkers with space itself.the point being that as i have suggested in the past the actual motive force for such a thing could be derived from either fusion drive as is being discussed or warp drive itself. ideas or comments always welcome.thank you very much your friend george

James M. Essig January 29, 2009 at 17:01

Hi George;

The idea of the field projector is absolutely brilliant. Also, if it can be made to work in Einsteinian 4-D spacetime, perhaps it can be made to work in hyperspace or higher dimensional space. In short, your idea is an awesome idea. You could in effect fine tailor the nature of the space time ahead of the ship including the curvature and zero point properties of such a projected space.

Adam, regarding the ISR neutrino rocket concept, I can imagine other weakly interacting hot dark matter particle might work also. Perhaps selectrons, squarks, and/or sneutrinos rockets could be supersymmetric bosonic analogues to the photon, graviton, or neutrino rockets assumming that these supersymmetric bosons travel at C. As I think about the possibilities of exotic rockets, rocket science in the literal sense is seeming to become much more enjoyable to me.

If the laws of special relativity breakdown for large bodies traveling at extremely high gamma factors, assuming we can find an appropriate shielding material to permit such, perhaps a craft could some how jump past light speed or tunnel past light speed and become superlumimal. If the craft developed a velocity of C + e where e is very small compared to C, the craft might travel back in time, perhaps a Planck unit of time, for every kilometer to lightyear distance it traveled in space thus perhaps leading to effectively instantaneous travel with respect to Earth time without the paradox or dangers of backward time travel since time travel backward “within” one Planck time unit might not be fully defined in its effect on the universe.

Either way, the study of high gamma factor rocket kinematics is important and will I feel remains so. Fusion rockets are I feel just a beginning of a fantastic and fascinating endeavor.

Thanks;

Jim

Adam January 29, 2009 at 19:36

Hi Enzo

Fusion occurs when the relative velocity of the particles is ~10 KeV and so it won’t really happen amongst the particles of the incoming debris. Protons striking nucleii at MeV energies might cause some to transmute to other elements, or bust other protons out of the nucleii (spallation), but fusion reactions release particles in the MeV range which is roughly the same energy as the incoming particles we’re discussing, so not much energy enhancement is likely. There will be gamma-rays released by such collisional fusions and those will be a problem – incidentally lightning also produces gamma-rays, potentially at lethal intensities (that’s still being determined.)

Thus why I think active shielding that deflects the particle storm will be needed. I suspect that to reflect effectively the x-rays produced by a precursor shield a starship will need a needle-nose of good x-ray reflecting metals. Who’d've thought interstellar vehicles would need streamlining???

Enzo January 29, 2009 at 20:29

Hi Adam,

I’m not really familiar with fusion, just reading on Wikipedia. Are you saying that if energies are too high (like Mev compared to 10 Kev), fusion won’t happen ?

Enzo January 29, 2009 at 20:49

Sorry, I think you are saying that fusion also produces particles in the Mev range and that therefore there would not be much energy enhancement.
However, as the particle impacts, a lot of momentum will be transferred to the impacting surface. At some point you should have a much bigger blob but with less energies per nuclei (like 10 Kev). Wouldn’t then fusion take place ?

James M. Essig January 30, 2009 at 0:46

Hi Adam;

I rather like the idea of streamlining for interstellar vehicles. Given the potential drag on star ships at very high gamma factors, if and when such is achieved, the idea of drag coefficients and “aerodynamics” or should I say “astrodynamics” will be a big engineering R&D field.

Enzo;

That is a good question. Since the plasma produced by the incoming particle will consist of atoms or should I say primarilly nuclei in terms of the overall mass of the particles that were initially, the composition of the incomming particle, the relative velocity of the particles that once composed the incomming particle will all be roughly the same. There may be some distribution in the spread of particle energies of the particles that once composed the incomming particle, but I can imagine that most of the resulting plasma particles in the form of nuclei will have an relative energy distribution of perhaps only a few to atmost 10 eV within the average of the incoming particles’ energies.

Since 0.1 C hydrogen nuclei have a kinetic energy of about 10 MeV each with respect to the ship and its shield, a given incomming particle, even if all of its energy was deposited in a reaction involving another hydrogen or deuterium nuclei within a water shield would at most probably result in one fusion, perhaps at most a few, considering that the energy released from a typical low atomic number fusion event is around 10 MeV which is not to far removed from the typical energy barrier required to be overcome inorder for the incoming protons or alpha particles to have a high probability of fusing with a hydrogen nuclei or deuteron on a single encounter.

Note that fusion events can take place within a mass of hydrogen or deuterium wherein the relative kinetic energy of these particles is on the order of about 10 KeV, however the chance of a fusion event happening in a given collision event is very small at 10 KeV relative energies. However, if you have a huge “vat” of hydrogen nuclei with an average relative kinetic energy of 10 KeV, you will see some fusion events and so fusion at 10 KeV is not impossible. Mostly what makes such fusions at these relatively low energies possible is the process of quantum mechanical tunneling in which a particle can tunnel through an energy barrier that is classically forbidden. A good example is a particle climbing or tunneling through an repulsive energy barrier of 10 eV in which its impinging energy is only 2 eV.

This tunneling behavior is common at the level of the atomic nucleus and the probability of a particle tunneling through a given energy barrier decreases very rapidly for increases in the particle’s rest mass and the spatial width of the barrier. This is why we do not observe tunneling of atomic or subatomic particles over macroscopic distances. You might have to wait much much longer than 10 EXP 1,000 years to observe the tunneling of a chocolate chip out of the bag enclosing it. Although if a way can be developed to somehow to cause the chocolate chips to tunnel from the grocery store shelve into my mouth, I would be a happier man.

Regards;

Jim

george scaglione January 30, 2009 at 10:11

hello jim and adam and enzo,lol – everybody!!!! thank you for the great comments! jim i am glad you like my idea of “tailoring” space so much.i have no doubt that that or something like it will be given serious consideration in perhaps the not to distant future.what with the fact that scientific progress seems to follow an exponential curve (if curve is the right word lol) – as i have mentioned to others as recently as yesterday – i would not be suprised if we where doing this stuff in say “only” 50 to 75 years!!! adam/enzo i also feel privilaged to be able to “look in on” your discussion of starflight,design of starships and propulsion one of my all time favorite subjects! hope i hear more from everybody soon. your friend george

Mut January 30, 2009 at 21:44

Hi Adam,

I’m a 12 year old boy who’s always wondered, why don’t we try to make rockets that run off of hydrogen atoms since it’s the most aboundent element in the universe, and fuse them into helium atoms like the sun. Will it work or not, if not why?

Null February 1, 2009 at 15:24

Mut, that is exactly what is being discussed here. Deuterium is an isotope of hydrogen.

David February 1, 2009 at 16:07

One thing I’ve been wondering for a while now: If all the energy output of the sun were deflected to go in one direction, how fast would it accelerate? Would this be fast enough to get to a nearby star in the next few billion years?

What I’m picturing is a ringworld-style contraption with a gigantic, balooning reflective sail stretched over the ring. The ring itself would be accelerated away from the sun by the solar wind and photon pressure from the sun on the large sail. This means that the ring’s center of mass would not be at the same place as the sun’s center of mass. If it could be designed so that the acceleration from the solar radiation could be balanced by the acceleration due to gravity of the ring’s center of mass “falling” to the center of the sun’s mass, then the entire system would have a net acceleration in a specific direction. The rotation and orientation of the ring could be steered and stabilized by deformations in the mirror sail. For example, it could be rotated in mid-trip to begin the deceleration phase.

I know that such a huge “spaceship” could never accelerate very fast, but it sure would be “traveling in style” to take our sun with us as we go! Ultimately, the idea is to park the sun into the orbit of another, younger star (making a binary star), transferring the ring from the one to the other, and continuing on before our sun turns to a red giant. Alternately, we could park in a very wide stable orbit around a binary star, build a new ring around each (perhaps with material that we skimmed off our sun and fused into carbon), and then gradually separate the two stars and split our civilization in two. A few hundred billion years of this might be enough to thoroughly populate the galaxy.

I know there are there would be huge engineering hurdles at every step of this project, and it’s just fantasy. But even such fantasizing would be silly if the energy of the output of the sun is just too small to accelerate the sun at any sort of useful rate.

Scooter February 1, 2009 at 17:15

Ah, James proposes storing antimatter inside molecular cages. In Schlock Mercenary they use fullerene cages. They also note that carrying this kind of dust in paper bags is not particularly friendly to the environment. Any environment.

Scooter February 1, 2009 at 17:20

Mut: Hydrogen fusion is exactly what is being talked about here. Deuterium is easier to manipulate than common hydrogen; look deuterium up on Wikipedia as I think there are links there to details of the advantages of deuterium and tritium. As mentioned above, the differences between the materials affect their uses and related engineering.

Alhazred February 1, 2009 at 18:48

100 meter diameter = 3×10^4 m2 frontal area.

.1C = 3×10^7 m/sec

Thus 9×10^11 m2/sec volume is swept out.

(1 m3 = 1.0×10^6 CC

5 H/CC = 5.0×10^6 H/m3) = 8.3×10^-18 g/m3

7.4×10^-6 g/sec

86,400 sec/day = .65 g/day

Assuming a mass of vessel of on the order of 4 billion KG (roughly 100m diameter with a density equal to H20) then
assuming 100% momentum transfer to the spacecraft the actual momentum loss due to the interstellar medium would be
fairly trivial, in fact essentially quite close to zero. So from that standpoint no streamlining would be required.

Now, lets see what you’d run into for total energy.

KE = 1/2mv^2

KE = 1/2 x 7.4×10^-9 x 9×10^14 = 3.33×10^6 joules/sec

This is enough energy to raise about 1 million grams of water 1 degree C in one second. That’s a substantial amount
of heat and would thus require a substantial amount of heat rejection. More to the point if we were to assume that the
shield was largely water and massed say 1×10^12 g (25% of the mass of our 4 billion KG ship) then in 1000 seconds it
would increase in temperature by 1 degree C. Not too bad, and it doesn’t seem like it would be a major problem.

So, overall I don’t see a fundamental problem. If a shield can be designed that just plows through the interstellar
medium at the front of the ship and absorbs whatever it hits, then at a basic level it seems like the ship would just
follow along behind and the shield would just slow down and heat up a rather small amount. Of course it would depend
on where the bulk of the energy was deposited. The leading edge of the shield could easily erode (just boil or spall)
away pretty quickly.

OneAhead February 1, 2009 at 19:07

Possibly the single the biggest problem with traveling outside the earth’s magnetosphere is cosmic radiation. You need massive shielding to diminish this radiation to levels that can be survived for extended periods of time. In that context, charging your spaceship to a GV electrostatic potential is not helpful. “Empty space” is filled with charged particles and neutral atoms. A GV electrostatic potential will not only suck all negatively charged particles towards it, but also ionize neutral atoms in the vicinity. Torrents of particles will strike your spaceship at GeV energies from all directions, generating deadly radiation levels. Traveling at relativistic speeds doesn’t make things better. The amounts of atoms and ions you will be zooming past will make your spaceship white hot with GeV impacts and at the same time discharge your ship more rapidly than you can ever charge it. In summary, this idea only works on paper in truly empty space (which you won’t find when traveling to nearby stars).

James M. Essig February 1, 2009 at 20:19

Hi David;

That is a very interesting concept.

If half of the Suns output could be transformed into stellar kinetic energy, I can imagine if one assumes that the sun will fuse 1/4 of its hydrogen, then the total energy contributed to solar KE would be about (0.007)(0.125)(Solar Mass) or roughly 0.1 percent of the precursor solar mattergy output. This would yield a velocity somewhere around 0.03 C to 0.04C which is considered mildly relativistic. In 5 billion years, the Sun would travel along with Earth a distance of about 0.03 (5 x 10 EXP 9) to 0.04 (5 x 10 EXP 9) light years or roughly 225 million Light years. My estimates for star light to KE conversion are somewhat optimistic but they are in the ball park of what might be accomplished

As we arrived at other stars systems and galaxies, we could move stars. Red Dwarf or low end M class stars can shine for upward of 100 trillion years and also convert almost all of their hydrogen so that about 0.7 percent of their mass is converted into starlight. Assumming half of this energy can be converted into ship based KE, 0.35 percent of the star’s mass would be converted into stellar KE. These bad boys could reach about 0.06 C and could travel a whopping 0.06(10 EXP 14) lightyears or 6 trillion light years from the Milky Way not assumming expansion of the universe. This is about 400 times the radius of the currently observable universe. Assumming expansion of the Universe, the distance traveled in 10 EXP 14 years would be several orders or magnitude greater, yet, and the recessional velocity from Earth would be several orders of magnitude greater than C.

Regards;

Jim

Yakov Lansky February 1, 2009 at 22:46

Addressing the impactor hazard, here is a way around it. It also solves the so called Einsteinian limit velocity ‘c’, one of the sillier ideas man has ever produced. Find the Higgs particle and then find a means to create them and its opposite number the anti-Higgs particle. Since these are postulated to cause matter to ‘have mass’, then the anti-Higgs might negate this. Also, the standard model may not be all that complete; and there may also be a kind of ‘WIMP’ particlethat gives volume to space alongside an opposite number that causes space to contract, or negates the spaceWIMP leading to a local space collapse. Put these two together and high velocity space transport is not necessary; better yet, transliminal displacement rates become quite easy as the ‘ship’ is not really moving, just the space in front of it is contracting and the space to the rear of it is expanding, both at extreme yet reciprocal rates. These deformations of spacetime would require some shielding of the ship and its interior spaces to prevent damage. Such may be provided by a kind of ‘contra-coup flow’ with a second and smaller set of generators in close proximity operation to the ship’s hull acting as a counter force to the drive forces and also channeling the spatial flow and its entrained matter to the sides of the ship. Higgs forces inside the ship interacting with magnetic forces could supple synthetic gravity so that the ship’s occupants experience no accelerating forces even while the effective transit rate may be thousands of times ‘c’. Such control only begins to become possible with the recent advent of computer abilities sufficient to the task. It may be a while before the quantum nature of space and its associated baryons and leptons are discovered be they WIMPs or whatever…or subunits of the baryons and leptons in a further fractalization of our ‘known quantum reality’. At that time the world that may laugh at the above may then secretly start to build it.
Shades of the space elevator whose cable just became possible thanks to recent work at Cambridge University:
http://www.physorg.com/news151938445.html
This work makes long elastic strong carbon nanotubes plentiful, possible, and cheap. Check it out!

george scaglione February 2, 2009 at 11:41

mut and david i have read your postings above and can only ad in this context – in my humble opinion the problem is this – we are dealing with problems that,so,largely exceed our ability to do things in so far as the technology that we currently have that alot of work remains ahead!and certainly not work of a trivial nature! but yakou…in that vien,you have opened my eyes,thank god for the work at cambridge.it is a perfect example of the kinds of strides we need and are apparently getting to do things that we could not before! jim,the velocities you mention above are also really impressive not exactly light speed or faster but as i have been saying above ,a step in the right direction! my best to every body your friend george ps and mut keep on questioning! let me leave you with a quote that i keep in my office by albert einstein,”the important thing is not to stop questioning”all the very best ,george

Hans Bausewein February 2, 2009 at 16:33

“Workable Fusion Starship Proposed” on Slashdot:

http://science.slashdot.org/article.pl?sid=09/02/01/142239

“As described at Centauri Dreams, the design has certain similarities to MagOrion, …..”

Hans

spaceman February 3, 2009 at 3:04

I agree with S. Hawking in his suspiscion that it will be our advances in information technology and its interface with biology and chemistry that will enable us to conquer interstellar distances via suspended animation of more or less indefinite length. Right now, chemists estimate that humanity has explored maybe as much as 1% of chemical compounds allowed by the laws of nature. Furthermore, we aren’t even complete sure how all of the compounds that make up that 1% interact with each other. Computer power and the ability to see inside of cells and turn genes on or off are increasing pretty much yearly. Can anyone imagine what kinds of things we will be able to accomplish via the field of chemical biology, let’s say, fifty to a hundred years from now!?

george scaglione February 3, 2009 at 10:56

spaceman – i read what you said above and i see you kind of agree with me that we are dealing with concepts about which we need to know alot more.so hawking looks to suspended animation for starflight!? kind of makes me wonder how many people would want to go if they had to be in a sleeper ship for 200 or so years first? do you recall the origins of “khan” on star trek? anyhow ,glad to hear any ideas you’d care to forward. thank you your friend george ps i have always considered pretty much only faster and in my humble opinion better ways to get there faster sleeper ships i am not so sure about.

James M. Essig February 4, 2009 at 3:01

Hi George and Spaceman;

It would be simply awesome if we could prolong human life indefinately, I mean learn to medically intervene in the aging process so that we in a sense develope physical immortality even though our bodies might be corruptable and of the mechanically soft nature that they currently have.

Medical intervention or prevention of DNA/Chromosomal age related damage, and/or the nanotech repair of such, full replacement of damaged tissue in cases where the damage to the human body is not so extreme as to result in death or irreparability, and good accident avoidance measures would help in this regard.

Since the half life of protons is shown to be atleast about 10 EXP 35 years as a result of experiments looking for proton decay, perhaps the human body can be made to live in a working conscious state for as long as we can find baryons, life sustaining elements, or have the ability to produce such in the event that the supply within our bodies or habitats would eventually decay if left to its own devices.

Imagine the great extent to which our intellects, our emotions, our positive feelings, and the like psychodynamic aspects of our personalities coudl develope given 10 EXP 40 years of life. The ability for spiritual development would be awesome. Even if we were limited in kinenatic abilities to those which we currently possess in the soft tissues that make up our bodies and brains, the oportuinity for intellectual, moral, psychological, emotional, social, affective, and spiritual growth would still be enourmous. Perhaps it is simply our vulnerability to physical injury that will enable us to cooperate on a scale never before seen by man.

I like to remind myself that with peace, all things are possible.

In short, I definately see that biology will be critical to our journey ever further out into this cosmos. With indefinate life expectancies, travel of untold quadrillions of light years even at mildy relativistic velocities becomes possible.

Thanks;

Jim

george scaglione February 4, 2009 at 15:56

jim, you make some very good points above.there is no doubt that really advanced socieities could do alot and lol certainly more than we can now do! in time if we do not destroy ourselves we probably will be able to catch up with them.it is so great to be back on tau zero and therefore able to catch and comment on so many great concepts and ideas! why i had let myself drift is something i will never understand.thank you jim and everyone.please keep those fantastic ideas comming! :) your friend george

Rick S. February 5, 2009 at 10:59

Not to be negative, I think this could be a workable solution but; if you are using superconducting ring(s) to store the charge and provide the magnetic mirror then how do you compensate for the energy loss caused by charged particle interactions with the magnetic field? Another issue is the trapped charged particles from the exhaust, which would reduce the overall thrust of the engine.

This design could be used in conjuction with the Bussard Ramjet design as the other end of the magnetic mirror could be used to as a ‘net’ to capture interstellar gas and use it in the fusion reaction, this would provide more fuel to the engine or reduce the fuel storage requirement, or was this included in the design? Also, the magnetic mirror (as shown) would provide protection against cosmic radiation that would otherwise plague the travelers on such a vehicle.

Rick S. February 5, 2009 at 11:30

Enzo:

You are quite right to be concerned about even the smallest particles at the speeds the vehicle would eventually be traveling. However, if realizes that with the magnetic mirror and the fact that there are two ends of the vehicle one realizes that what we have is a magnetic solenoid. If there is a magnetic field at one end of the vehicle with sufficient field density to deflect a fusion reaction then there is one at the opposite end with a similar, if not the same, density. This would act as a shield against the incoming charged particles and could even be used in the same fashion as a Bussard Ramjet to funnel the interstellar gas to the reaction chamber and ultimately reduce the amount of fuel that needs to be carried on the voyage. The kinetic energy of the charged particles could be used in a generator to generate some of the electricity necessary for life support and other functions aboard the craft. What would have to be done is design the craft as a thick tube with the inhabited and engineering space in the wall of the tube. The tube walls would be lined both outside and inside with superconducting cables to generate the magnetic field for the mirror and shield. Non-superconducting coils on the inside wall of the tube would be required for the generator using the b-field of the particles to create electricity, which would serve to slow down the particles for use in the fusion reaction.

Larger particles would pose a problem but if one could target them with a laser of sufficient energy to charge the particle then the magnetic shield could deflect them. Intermediate particles, however would be an issue as they could not be targeted with the laser nor could they be deflected into the fusion chamber or away from the ship if they do not have a charge. Maybe a conical berylium shield would work for these particles.

Mut February 5, 2009 at 20:23

So, I’m confused will converting deuterium be converted into helium atoms and creat kenetic energy?

Adam February 6, 2009 at 8:33

Hi Mut

Exactly. Deuterium fused together makes helium. In the Sun the fusion actually has several steps – two protons fuse and make deuterium, add another proton and make helium-3, or smack two deuterium together and make helium, or a deuterium and helium-3 together makes a helium-4 and a proton. Most of the Sun’s energy comes from those processes.

A few percent comes from what’s called the C-N-O cycle – add 4 protons to carbon-12 and eventually it becomes an unstable oxygen-16 which then splits off a helium-4 and leaves behind a carbon-12, thus recycling the carbon. In stars hotter than the Sun the CNO cycle is dominant, and in much larger stars it happens very quickly, fusing all the hydrogen in just a few million years. Such stars are hot enough to fuse helium, then carbon, and then elements all the way to iron and nickel. Once that happens no more energy can be made from fusion and the star collapses, eventually exploding as a core-collapse supernova. During that explosion a lot of elements heavier than iron & nickel are made, including fission fuels like uranium and thorium.

Mut February 6, 2009 at 23:23

so my dream can be proven? and how hot would a star necessrarily have to be?

ljk April 1, 2009 at 12:19

Fusion Catches Fire

By Alan Boyle, March 31, 2009

All of a sudden, nuclear fusion is becoming an energy buzzword instead of an energy joke: One route to fusion is being hailed as having the potential to become a “holy cow game-changer,” another mainstream method is getting a multimillion-dollar boost, and a dark-horse candidate is stealthily moving forward as well. Heck, even cold fusion is back in the game.

So what’s behind the seemingly sudden interest?

Full article and video here:

http://cosmiclog.msnbc.msn.com/archive/2009/03/31/1872580.aspx

Adam April 10, 2009 at 20:08

Hi Mut

Sorry I didn’t answer sooner, and hopefully you’ve discovered the answers yourself, but in case anyone Googles for an answer I’ll reply. The temperature of a star can be quite “low” and still fuse deuterium. In fact large planets, 13 times heavier than Jupiter, probably fuse deuterium in a hot layer around their heavy element cores. It only takes a few hundred thousand degrees – BUT deuterium, found naturally, is in short-supply. Only about 0.05% of hydrogen is primordial deuterium, so when it is burnt it burns very, very quickly. A deuterium star runs out of fuel in just 50 million years – not even out of infancy for a star.

So where does it come from in Main Sequence stars if it provides most of their energy? Above about 3 million degrees in a star’s core the protons are going fast enough for a low proportion of them to quantum-tunnel through the Coulomb Barrier and fuse together to make deuterium. Below about 10 billion degrees this process is driven almost entirely by quantum mechanical effects – let me emphasise we owe our light and life to the slow fusing of protons via Quantum Mechanics. Once made the deuterium fuses quickly, as usual, and virtually none sticks around for very long. Its reactions provide most of the Sun’s energy.

In slightly hotter star cores a different reaction, the CNO Cycle, makes helium out of protons by sticking them in a sequence to a Carbon-12 nucleus, that acts like a catalyst. Proton-proton fusion still happens, but the CNO cycle is much more temperature sensitive and so it dominates the fusion cycles in stars above about 1.2 solar masses. Above about ~20 solar masses the stars are so hot in their cores that they very rapidly fuse both hydrogen and helium – and the helium reaction is even more temperature sensitive.

Friedwardt Winterberg April 19, 2009 at 17:31

The exhaust velocity for a fusion reaction is more like 1000km/sec. To explore the solar system an exhaust velocity of 100km/sec, reached by the addition of liquid hydrogen as a propellant to the fusion fireball is to be prefereed. Only for interstellar missions, still in the distant future, one must aim at the highest possible exhaust velocities.

ljk May 22, 2009 at 13:45

Man-made star to unlock cosmic secrets

By Jonathan Fildes

Science and technology reporter, BBC News

Page last updated at 01:17 GMT, Friday, 22 May 2009 02:17 UK

NIF can recreate the conditions inside an exploding star

When the world’s most powerful laser facility flicks the switch on its first full-scale experiments later this month, a tiny star will be born on Earth.

The National Ignition Facility (NIF) in California aims to demonstrate the feasibility of nuclear fusion, the reaction at the heart of the Sun and a potentially abundant, clean energy source for the planet.

But whilst many eyes at the facility will be locked on the goal of satisfying humanity’s energy demands, many scientists hope to answer other fundamental questions for mankind.

“In recreating the process of fusion it was always understood that we could pursue three areas of interest and value,” explained Dr Erik Storm of the Lawrence Livermore National Laboratory (LLNL), the home of NIF.

First and foremost, NIF has been built for national security purposes, to study the conditions that exist in nuclear explosions and the way that nuclear weapons perform.

“That gives you an ability to maintain a credible nuclear deterrent in the absence of underground nuclear testing,” said Dr Storm.

“Then, we can study the physics of fusion – can you make a fusion power plant here on our planet? And we can do basic physics and planetary science.”

Full article here:

http://news.bbc.co.uk/2/hi/science/nature/8044620.stm

Gustavo August 7, 2010 at 20:14

I think the issue of a suitable shield is the key element in this interstelear travel.
Just suppose you have your ship and your fusion engine in tip top condition.
As the speed builds up with a very bearable aceleration of 1 g ( it might take around a year to reach C) the damages on the ship will get worse day by day.

By the time the starship reaches C all the crew would be dead from microscopic impacts that had perforated human bodies like needles.

I bet if I could live 800 years that in the near future we could feel pretty happy just by mining jupiter or the other planets in our own solar system for minerals we need in our domestic lives.

Gustavo

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