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A Universe Optimized for Starships?

When you consider that conventional chemical rockets extract a mere 10-8 of the energy locked up in their fuel, the attraction of antimatter becomes undeniable. Could we build an engine that extracts 100 percent of the energy created by matter-antimatter annihilation? Louis Crane (Kansas State University) is dubious, pointing to problems of storage and the difficulty of making enough antimatter to get the job done.

Black Holes as a Propulsion Option

Working with colleague Shawn Westmoreland, Crane has been exploring a different and far more speculative option for upping the energy extraction levels. What about using black holes for propulsion? Specifically, Crane and Westmoreland ask whether Hawking radiation from black holes can power a starship, calculating that a black hole of about a million tons would be just the right size, small enough to generate the needed Hawking radiation, while large enough to survive for the duration of a century-long star crossing. Adam Crowl has written fascinatingly about this in Crowlspace.


Crane and Westmoreland’s paper on using Hawking radiation for this purpose has been kicking around on the Net for a bit, never quite making it to the top of the queue here, but Marcus Chown gives it a good look in the latest New Scientist, so let’s pause to examine it now. Rather than finding a nearby black hole, the two suggest using a gamma ray laser powered by solar energy to create one. The energy needed would be enormous, calling for solar panels 250 kilometers across in close solar orbit, a Robert Forward-esque engineering challenge.

Image: An artist’s impression of a black hole. Credit: Jörn Wilms (Tübingen) et al/ESA.

But if you could create such solar panels and let them soak up the needed sunlight to power up your black hole production facility, you’d wind up with something tiny that offered tremendous power. Says Chown:

The resulting million-tonne black hole would be about the size of an atomic nucleus. The next step would be to manoeuvre it into the focal range of a parabolic mirror attached to the back of the crew quarters of a starship. Hawking radiation consists of all sorts of species of subatomic particles, but the most common will be gamma ray photons. Collimated into a parallel beam by the parabolic mirror, these would be the starship’s exhaust and would push it forward.

Darwinian Selection Among Universes

Crane and Westmoreland think a starship powered this way could accelerate to close to the speed of light in a few decades, fast enough that relativistic time dilation would occur and vast distances could be crossed by human crews. Interestingly, a black hole starship like this should create gravitational waves that might be detectable here on Earth, assuming some nearby extraterrestrial civilization were using the technology. If coalescing black holes and neutron stars ought to be producing low-frequency gravitational waves, a black hole starship should leave a gravitational signature at ultra-high frequencies.

Chown does a good job with this material, and I recommend you check out his New Scientist article. He points to Lee Smolin’s idea that at the singularity of a black hole, new universes could be created and bud off from their parent. It stands to reason, then, that universes that are optimized for black holes are those likely to give rise to more and more such universes. And if we could make our own black holes, then life would play a role in making infant universes proliferate.

[Crane] believes we are seeing Darwinian selection operating on the largest possible scale: only universes that contain life can make black holes and then go on to give birth to other universes, while the lifeless universes are an evolutionary dead end.

His latest calculations made him realise how uncanny it was that there could be a black hole at just the right size for powering a starship. “Why is there such a sweet spot?” he asks. The only reason for an intelligent civilisation to make a black hole, he sees, is so it can travel the universe.

“If this hypothesis is right,” he says, “we live in a universe that is optimised for building starships!”

I don’t have time this morning to get into Chown’s discussion of Jia Liu (New York University), who has concocted a spacecraft powered by dark matter, but in any case the Jia Liu paper was in queue for next week, so we’ll talk about it then. Talk about living on the speculative edge — we don’t even know what dark matter is at this point! But as fun as these ideas are to kick around, they also let us roam through broad questions of cosmology and physics in ways that can provoke discussion and help us illuminate our current propulsion constraints.

Marcus Chown’s article is “Dark Power: Grand Designs for Interstellar Power,” New Scientist 25 November, 2009 (available online, but get it fast before it disappears behind the magazine’s firewall). The black hole propulsion paper is Crane and Westmoreland, “Are Black Hole Starships Possible,” available online.


Comments on this entry are closed.

  • timkendall November 27, 2009, 11:32

    Ha yes, Dark Power. I’d found this already. Who’s namedropped? Yes, Clarke. Imperial Earth. How funky would it be if this became as interesting as geostationary satellites once were, and space elevators may still be.

  • Paul Titze November 27, 2009, 12:44

    Is the Universe optimised for building starships? The answer must be yes. Since the Universe allows us to chart and navigate it then for nature to be consistent it must allow a practical solution to interstellar flight right? ;-)

    Cheers, Paul.

  • Administrator November 27, 2009, 14:25

    Paul Titze says:

    Since the Universe allows us to chart and navigate it then for nature to be consistent it must allow a practical solution to interstellar flight right? ;-)

    I like the way this mariner thinks!

  • Tulse November 27, 2009, 16:51

    Even after reading the paper I’m still not clear on how one actually keeps the black hole traveling with the ship, rather than just sitting stationary radiating energy and pushing the ship away. It’s not like one can bolt it down in the engine room.

    And I would think that one serious downside of such an engine is that it is always “on” — there isn’t a way to “throttle” the Hawking radiation of a black hole, and so it will constantly be pouring out this energy, even when you want to be parked. I have to imagine that would be a serious challenge to deal with — it would be like having an Orion drive that had to keep blowing up fusion bombs even when it was stopped.

  • David November 27, 2009, 17:28

    Great article. I must be misunderstanding something though. Assuming you created the black hole using any of these methods how would you maintain it’s distance to the craft. In a sense wouldn’t the energy needed to propel the black hole be somewhat equivalent to the energy released by it?

    If you are taking advantage of the emittance of EM radiation to alter your total output to keep the black hole with the ship.

    Back of the napkin calculations suggest that the gravitational pull would be fairly small between the ship and it’s black hole. Perhaps the paper itself deals with this. How does one propel the ship and the black hole at the same rate?

    In an attempt to not just poke a hole I’ll suggest a fairly uninformed possibility. Perhaps some sort of superconducting magnet arranged in a polar fashion could keep the hole with the ship. By injecting matter around an equatorial line the plasma generated at the surface could act as the attractor to the magnets so one is not trying to overcome the hawking radiation just to keep the black hole in range.

    And thanks for the link. Really enjoy the notion of Darwinian universe selection and any further reading on it would be welcomed.

  • David November 27, 2009, 17:36

    Looks like Tulsr beat me to it. In regards to stopping, assuming we had a method for keeping the black hole with the ship, one could rotate the parabolic mirror until the craft is turned around. The turn and stop would probably take up a huge part of the mission as the deceleration would have disastrous effects on the crew and craft. However you might just choose to enter a very tight orbit on a supermassive object so you wouldn’t fully stop.

    Also this doesn’t address an issue that has been brought up in previous articles. A grain of dust met by a craft traveling at .3c will have the kinetic energy of a semi truck. This makes Bussard ramjets seem enticing as the bulk of the forward facing part of the craft is fuel intake.

  • James M. Essig November 27, 2009, 20:29

    Hi Folks;

    Since a black hole’s radiative power by Hawking Radiation is equal to P = [h[C EXP 6]]/{(7680)[G EXP 2][M EXP 2]}, a 10 EXP 12 kilogram blackhole will radiate at [6.626 x 10 EXP – 34][[3 x 10 EXP 8] EXP 6]/{(7,680)[[6.673 x 10 EXP – 11] EXP 2][[10 EXP 12] EXP 2]} = 1.412 x 10 EXP 10 watts ship’s frame.

    The evaporation time of a blackhole is given by ev time = (2,560)[G EXP 2][M EXP 3]/{h [C EXP 4]} and thus for a 10 EXP 12 kilogram blackhole, t ev = (2,560)[[6.673 x 10 EXP – 11] EXP 2][[10 EXP 12] EXP 3]/{[6.626 x 10 EXP – 34] [ [3 x 10 EXP 8] EXP 4]} = 6.118 x (10 EXP 19) seconds ship’s time = 2 x 10 EXP 12 years ship time.

    Now imagine that a 1,000 metric ton rest mass ship could be coupled to the black hole via electrically charging the blackhole or otherwise setting up a coupling field between the ship and the black hole, assuming that the black hole ship would obey the relativistic rocket equation of Delta V = C tanh[(Isp/C) ln (M0/M1)] and assuming an Isp = 1 C expressed in units of C, Delta V = C tanh[(1) ln (10 EXP 6)] = 0.999999999998 C which yields a relativistic gamma factor of 1/{[1 – [(v/C) EXP 2]] EXP (1/2)} = 1 /{[1 – [(.999999999998/1) EXP 2]] EXP (1/2)] = 5 x 10 EXP 5 = 500,000.

    These numbers are a little bit harsh but if we can some how augment human life expectancy to a few trillion years, or perhaps develope cryogenic life suspension for periods of a few trillion years, then the possibility of sending human crewed vessels out to truely cosmic distances in space and time from the Milky Way becomes possible. Alternatively such space craft could do some sort of circulinear motion and come back to the Milky Way many quadrillions of years into the future. We could send time travelers from our era many quadrillions of years into the future to visit future human descendent civilizations or ETI civilizations. They might freak to notice a space craft show up with a NASA, ESA, or UN emblem on it.

    Some sort of black hole ramjet technology could be useful if collected interstellar hydrogen and helium could be funnelled into a blackhole and then reradiated as Hawking Radiation in a gainfull manner. Such a system could make an interstellar ramjet like craft or interstellar blackhole ramjet craft possible, perhaps even with a 10 EXP 12 kilogram rest mass black hole. The ship could maintain the rest mass of the black hole at equilibrium and accelerate essentially forever or as long as there is enough interstellar gas available to gainfully collect. A 10 EXP 9 kilogram rest mass blackhole might work better since the radiative power output of such a blackhole is on the order of 10 EXP 17 Watts which is a good driving power for a 1 million metric ton rest mass class black hole ship.

  • David November 28, 2009, 0:03

    >Even after reading the paper I’m still not clear on how one actually keeps the black hole traveling with the ship, rather than just sitting stationary radiating energy and pushing the ship away. It’s not like one can bolt it down in the engine room.

    Black holes can be electrically charged, right? If so they could, with sufficient engineering work, be dragged along with the spaceship by interacting with the black hole’s electric field.

  • andy November 28, 2009, 5:58

    Charlie Stross is always a good antidote for such suggestions that starships are workable concepts…

    It’s also worth checking out his essay about colonising the solar system. The comments thread is very amusing… see what happens if you throw cold water at the fantasies of the space cadets :-)

  • T_U_T November 28, 2009, 10:52

    Charlie Stross is always a good antidote for such suggestions that starships are workable concepts…

    The entire argument sums up like ” it would require far more energy than I am used to think about, therefore it is not possible”. That is not an argument at all. Example. If one were to ask you about feasibility of a flying machine that uses almost 3 and half times the power consumption of entire great britain ( 55 GW ), what would you say ? Naah, can not exist ? Ok . Saturn V. first stage. 190 GW power for more than four minutes. Naah ! can not exist. Or can it ?

    and now, more of the the same about interstellar propulsion. http://en.wikipedia.org/wiki/Fission-fragment_rocket

  • Ronald November 28, 2009, 11:40


    very off-topic (just feel free to remove this), but are you already aware of the potentially very significant news concerning new evidence for fossil bacterial life in the famous Mars meteorite ALH84001?


  • Administrator November 28, 2009, 15:21

    Off topic perhaps, Ronald, but too interesting not to mention!

  • Adam November 28, 2009, 15:43

    On the fact that black-holes are always on – true, but as Crane & Westmoreland discuss, not a show-stopper. Evaporating black-holes would then be useful for oneway interstellar propulsion – oneway until a new hole was made at the destination that is.

    But to effectively protect and propel a starship on such a ‘hot’ – hot doesn’t seem adequate a descriptor – source requires an effective gamma-ray mirror. Such a mirror can be used as a reflective enclosure to return the Hawking radiation back to the black-hole, thus maintaining it indefinitely.

    One fly in the ointment is the issue of quantum effects – will they allow total decay of a black hole’s mass? There are reasons for thinking maybe not, as recently discussed by Tony Rothman & colleague – quantum back-reaction may cause a new field to be created around a decaying black-hole which effectively screens it from further decay. I’ve asked Louis Crane for his thoughts on the issue and he’s on vacation currently, but interested enough to have a look at the relevant papers. So perhaps more to say on the matter before too long.

  • Administrator November 28, 2009, 16:41

    Adam, quantum back-reaction screening the black hole from further decay? Would love to learn more about this; be sure to tell us what Dr. Crane says.

  • Tulse November 28, 2009, 17:54

    a mirror can be used as a reflective enclosure to return the Hawking radiation back to the black-hole

    Wouldn’t that impart significant momentum to the hole opposite the direction of travel? In other words, wouldn’t that tend to force the hole away from the ship? Indeed, if one perfectly reflected all the radiation opposite the direction of travel into the black hole, wouldn’t that in essence cancel out the thrust it produces from the opposite side, causing the hole to remain stationary? Isn’t this the equivalent of putting a fan on a sailing ship to blow wind at the sails?

    I understand that we really don’t want to have to carry reaction mass, as that is grossly inefficient, but I just don’t see how one can use a black hole in its “naked” form to generate thrust that one can direct and still carry the hole with the vehicle. I can understand essentially using it as heat source for reaction mass, but as the source of thrust directly, I’m still confused as to how this is supposed to work.

    As far as I can see, a radiating black hole is essentially a rocket engine that is continually firing in all directions. So dealing with the thrust it produces in the desired direction of travel is a problem, one that isn’t solved by reflecting that thrust back into the hole, as that then just pushes the hole apart from the ship.

    A related point is that, although the Hawking radiation produced may be immense, only a small portion of it is ejected directly opposite the desired direction of travel. Most of the thrust is at an angle to the desired travel direction, and over all exactly half of the thrust produced is opposite the direction of travel (again, it’s a rocket that fires simultaneously in all directions). I don’t see how this can be used as anything other than a source of heat for reaction mass.

    (Perhaps it’s been too long since my undergrad physics days…)

  • Michael Pelletier November 28, 2009, 19:48

    They might freak to notice a space craft show up with a NASA, ESA, or UN emblem on it.

    Yeah, considering how inept government organizations have proven themselves to be time and time again, the notion that such a craft labeled in that way could make a quadrillion-year journey would be quite freaky indeed.

  • justcorbly November 28, 2009, 20:54

    The Romulans use artificial black holes to power their starships. No crystal weirdness for them!

  • David W November 28, 2009, 22:07

    Thank-you T-U-T
    3-5% light under current technolgy Lets move !
    Sounds like a good Model for Project Icarus to me!

    Back to off topic Mars . We had a grad seminar on Mars a few years ago and could not come to a firm conclusion at that time either
    I am still worried about contamination,so I would be pleased if we do the flybys of Mars and Venus and the asteroid and Phobos landing .Perhaps a sample return from and unmaned lander to the manned orbitor?

  • Benjamin November 28, 2009, 22:39

    David and Tulse have touched on important points: how do you trap this black hole and carry it? The authors already consider the mass of the ship and black hole to be on the same order of magnitude as the black hole’s mass, so the problem does not lie in accelerating the hole as well as yourself. Rather, the problem is that I simply can’t see how you’d contain this black hole.

    If we consider the obvious solution – give it electric charge – this has a flaw: the black hole emits charged-particle radiation, some of which you are attracting toward the ship. Even excluding the dangers of this radiation for the structure of the gamma-ray reflector as an engineering concern, you are going to reduce the electric charge of your ship until the black hole and the ship are at the same potential.

    I am uncertain as to whether any other forces could possibly be high enough to counteract the enormous force the BH must be applying to accelerate the ship so close to the speed of light in such a short time.

  • Benjamin November 28, 2009, 23:01

    I might also point out that this theme is treated in a wonderful science fiction novel…

    [major spoilers ahead]

    Learning the World, by Ken Macleod, where they use “cosmogonic drives” which involve creating microscopic black holes (for unspecified purpose, as part of the engine mechanism). This then entails the creation of many universes which are all better and better adapted for life: not because those universes with black holes proliferate, but assuming the “baby” universes are on average somewhat similar to their parents, by ensuring that universes which are amenable to life end up with large numbers of such black holes.

    In this respect I think Ken Macleod’s vision is more speculative than Crane’s, but overcomes the objections that already exist to Smolin’s argument about the existence of black holes being the only criterion.

  • John November 28, 2009, 23:22

    “The only reason for an intelligent civilisation to make a black hole, he sees, is so it can travel the universe.”

    Humans at their current state of development pretending that they can imagine all the possible uses of a black hole is a bit like Neanderthal man discussing the possible uses of a computer…and determining that it could only be used for holding his rock collection.

  • PIF November 29, 2009, 0:16

    Sounds like it is bulky, complicated, and cumbersome to make, deploy and use.

    Oriion ships were to be designed usingvery small fission bomd – like .5 kt, not fusion, since they would impart too much explosive force.

    Perhaps theUniverse is optimized for travel between stars, but we have either not discovered the tech, or more likely ignored the implications of tech already discovered – ie using field equasions (quaternions) as proposed by J. C. Maxwell, instead of Heavyside and Gibb’s vector equasions to describe the physical universe.

  • Chris November 29, 2009, 2:21

    Ok, lets assume that black hole propulsion works. Let’s also assume that .9999998% of c is reached by this method. How does one test the effects of near light speed on the human body, or any other material? How would we communicate with the brave space travelers before they reach their destination? Depending on the length of the trip, how can one ensure that there will be a home in which to return? Furthermore, unless we are speaking of the closest few stars to Earth, we need to travel many times faster than light speed to get to the stars in a human lifetime.

  • Adam November 29, 2009, 2:47

    In order to accelerate the hole and a ship, the hole is contained in a huge parabolic mirror. The reaction force of the impinging forward directed radiation moves the ship, while the hole is potentially propelled by its own emissions. The main problem is how to take the spherically symmetrical emissions of the hole and cause an acceleration making asymmetry. Radiation reflected back at the hole will impart momentum to it if absorbed, so perhaps the enclosure won’t be a parabolic mirror, but a spherical one with a hole to let propulsive light out.

    But consider – due to conservation laws a black-hole’s black-body emission is charge neutral. Thus it won’t lose charge to its Hawking radiation if already charged.

    Also to ‘suspend’ mass-loss the energy has to be returned to the hole – enclose it totally in a mirror and return all its energies back to it.

  • T_U_T November 29, 2009, 9:56

    David W. The acrid tone of your post leaves no doubt that what you really want to say is : “I’ve made up my mind, so don’t confuse me with facts. Humans don’t belong to space and nobody is going to change my mind about that.” Further communication is thus futile.

  • T_U_T November 29, 2009, 10:56

    Adam, there are no conservation laws that prevent radiation of charged particles from a black hole. If a black hole is charged, then one of the particle-antiparticle pair is more attracted to the black hole than the other, so one is more likely to leave and the other to fall back in. The net result is that the hawking radiation is enriched by particles of the same charge that the black hole has.

  • Tulse November 29, 2009, 11:13

    Radiation reflected back at the hole will impart momentum to it if absorbed, so perhaps the enclosure won’t be a parabolic mirror, but a spherical one with a hole to let propulsive light out.

    That scheme, however, would waste a huge portion of the energy produced by the hole — only the small bit radiated opposite the direction of travel would be used, and the rest would be pumped back into the hole. This approach is hugely inefficient (although I suppose efficiency may not be a concern with such an enormous power source). The other major problem is that the black hole itself is mere attometers across, so the “exhaust port” would have to be similarly tiny and impervious to erosion from the radiation, a rather impressive engineering feat.

  • James M. Essig November 29, 2009, 12:25

    Hi Folks;

    A really cool form of technology would be one that essentially alters the zero point field electromagnetic structure in a region of space just outside the black hole so that the effective “rate” of zero point field virtual photon pair production goes way up thus leading to a great increase in Hawking Radiation Production and energy emmissions from a black hole.

    Assumming that a one solar mass (~ 10 EXP 27 metric tons) black hole could some how be created artificially and be used to power a one trillion metric ton rest mass space craft, and an assumed Isp value equal to 1 C expressed in units of C, the relativistic rocket equation of Delta V = C tanh[(Isp/C) ln (M0/M1)] would yield Delta V = C tanh[(1) ln (10 EXP 15)] = 0.999999999999999999999999999998 C which yields a relativistic gamma factor of 1/{[1 – [(v/C) EXP 2]] EXP (1/2)}
    = 1 /{[1 – [(.999999999999999999999999999998/1) EXP 2]] EXP (1/2)] = 5 x 10 EXP 5 = 500,000,000,000,000.

    We can lexocographically describe higher gamma factor scenarios but we very soon enter into the realm of the absurd even for civilizations that are capable of stellar scale construction projects. Given any ability to do future galactic mass scale construction projects, who knows what the gamma factor limits would be.

    Some really big caveats to such large scale black hole powered craft are not only the ability to tailor the rate of Hawking Radiation emmissions, but also the ability to harness the Hawking Radiation for driving force without ablissimating the space craft being propelled, the ability to hold the space craft in front of the blackole, the ability of the space craft not to be sucked into the black hole by its close proximity to the black hole, among several others.

    If one is willing to have miniscule positive translational accelerations, then the power flux handling capabilities of the space craft would not need to be so tremendously rigorous.

    I do not expect such extreme space craft black hole systems to be constructed any time soon, but given one trillion to 100 trillion years of Human and/or ETI technological evolution, it is hard so say what will ultimately prove possible.

  • george scaglione November 29, 2009, 13:21

    everybody,have gone through the above a couple of times and have to admit that i do not quite understand the concept of the use of black holes for propulsion.admittedly at this juncture i happen to have alot of things going on that are occupying 90% of my mind in my private life.but if anyone here can clarify at all i’d really appreciate afew words on this which seems to me to be a facinating subject.respectfully to one and all your friend george

  • David W November 29, 2009, 15:59

    I dont know what I said to tut but I am a big fan of human space travel

  • James M. Essig November 29, 2009, 20:30

    Hi George;

    Thanks for asking.

    The concept essentially involves the notion of using black hole Hawking Radiation emissions from a black hole coupled to a space craft perhaps via the black hole’s gravitational field; or in the case where the blackhole is suitably relectrical charged, by the blackholes electric field.

    The smaller the blackhole the greater the rate of Hawking Radiation power release from the black hole. We do not notice stellar scale black holes and supermassive black holes emit radiation because the degree of radiated power is miniscule. A stellar massed blackhole will live about 10 EXP 66 years and a supermassive blackhole such as the ones that power quazars will last about 10 EXP 100 years.

    However, as the size of a black hole approaches say one million metric tons, the rate of power release goes way up. As the black hole’s mass descreases to about 1,000 metric tons, it is essentially exploding because of its Hawking Radiation release.

    The idea of this thread is to utilize a small blackhole of about 1 million metric tons coupled to a space craft wherein the gamma rays emmitted as Hawking Radiation would be reflected and focused by some sort of exotic gamma ray reflector type of rocket cone such as a parabolic reflector. Thus, an effectively gamma ray black hole based type of photon rocket is contemplated.

    Hawking radiation is the theoretical result of mass-energy loss of a black hole that occurs as a result of the gravitational field of the blackhole occasionally pulling in one of the zero point virtual particles of a pair of such particles for virtual pairs that form just outside of the blackholes Event Horizon as a result of zpf vaccuum fluctuations. Since one such particle on occasion falls into the blackhole, it becomes spatial-temporally seperated from its external counterpart and the external particle flies away.

    Since inorder to balance the energy books wherein a zero point particle that flies away from the black hole is said to have positive energy, the particle that falls into the blackhole must be said to have negative energy or negative mattergy with the result that the black holes total mass-energy is reduced by a miniscule amount each time this process happens.

    If the black hole did not lose mass-energy by such a process, the effect would be essentially the creation of net mass energy from an already existing structure where such mass energy did not previously exist. This would violate the mass energy conservation principle of thermodynamics, thus the reason for assuming that all black hole radiate some Hawking Radiation.

    The rate of energy release is inversely proportional to the square of the black holes mass and so blackholes radiate energy away faster and faster at a non-linear rate. As blackholes become small, they will essentially explode because the rate of energy release becomes so extreme.


    Your Friend Jim’

  • Aidan B November 29, 2009, 22:15

    I hope that I am not being really stupid when I say this, but what is stopping the ship from just falling into the black hole? Why would we even begin to think about a black hole powered ship when we have no way to stop the ship from becoming the black hole’s next meal?

  • Benjamin November 30, 2009, 2:28


    The black hole would be something around a million tonnes. That sounds like rather a lot, but its gravity is negligible. There’s barely any gravitational pull on the ship from the black hole, and the problem is rather in making sure there IS some pull to keep the ship and its power source in the same configuration throughout the flight! You can’t grab a black hole, so you need to be using some non-contact force to incorporate it into your ship.

    In fact, in general, it’s awfully hard to fall into even massive black holes: the hardest place to get to in the Solar System, for instance, is the Sun, because you need to lose so much angular momentum, which would otherwise mean that you’d pick up speed as you came in, miss the Sun, and go flying back out again. Orbits at reasonable distances from a black hole aren’t qualitatively different: you no more get sucked into a black hole than you get sucked into the sun.

  • MaDeR November 30, 2009, 4:25

    @Aidan B: Black hole is not magic vacuum cleaner. BH with mass of milion tons will exert gravitational pull of, guess what, milion ton. A few skyscrappers.

    @James M. Essig: You still did not explain how you want to take BH with starship.
    “coupled to a space craft perhaps via the black hole’s gravitational field;”
    You are joking, right?

    “or in the case where the blackhole is suitably relectrical charged, by the blackholes electric field.”
    Someone else mentioned problem with it.

  • Adam November 30, 2009, 8:12

    Hi Aidan B

    The black hole is really, really tiny so it poses no danger in that respect. It’s also pushing out a lot of energy as radiation so that anything merely falling in will be pushed away.

  • Adam November 30, 2009, 8:15

    I should add… pushed away as a mass of ions, since the output is incredibly “hot”, in more ways than one. A gamma-ray reflector of some kind is utterly essential IMO though Louis Crane thinks some kind of thermalisation system might be possible. Hopefully the LHC will make some charged, stable supersymmetric particle that we can use as a gamma-reflector…

  • george scaglione November 30, 2009, 17:13

    jim and the several people who spoke after him thank you very much i now have a much more clear idea of how all of this might work.although getting energy from the small black hole seems quite reasonable as stated above i none the less fear that this is just one of those concepts that will wait quite awhile before we might be able to realize it. maybe QUITE awhile.but i certainly hope as mentioned above that the LHC will be a big plus in this form of research maybe even yielding some good ideas that could be utilized in this and other regards as they involve space craft propulsion ideas and concepts.look forward to hearing more.thank you one and all ! your friend george

  • James M. Essig November 30, 2009, 17:20

    Hi MaDeR;

    Actually I am not joking. A future human civilization that can produce macroscopic massed blackholes might possibly be able to produce neutron dense or quark matter dense rods or appendages which could protrude out from the center of the gamma ray reflector and/or energy absorber. The million ton rest mass blackhole could be located very close to an attraction mass at the end of the rod or protrusion. If the black hole was close enough to the attraction mass, then it could be pulled in toward the attraction mass while the blackhole’s radiation would push on the reflector.

    The reason for using some very dense types of materials for the protrusion and attraction mass might be the radiation resistance of the materials due to the nuclear binding force between its composing nuclear particles. A weakly interacting cold dark matter protrusion and attraction mass might be better since such a mechanism would likely react very weakly or not al all with gamma rays.

    If a non-rotating positively blackhole is attracted to a negatively charged member, then the case for holding charged blackholes reduces to simple classical electrodynamics in principle.

    Larger blackholes might be easier to manage since their rate of Hawking Radiation release is much less as the rest mass increases on a per order of magnitude basis. Thus the stronger gravitational field coupled with the reduced radiative power might come in handy for space craft powered by say 10 million to one billion metric ton rest mass black holes

  • Eniac November 30, 2009, 19:21

    A gamma ray mirror IS necessary, any thermalization would very unfavorably impact the Isp. There is no known physics for such a reflector, so the black hole is every bit as speculative as the dark matter, I think.

    Given the mirror, the parabolic form would work just exactly like Orion, no fan-powered sail problem here. Putting it in a spherical mirror would also work, as long as the mirror is perfect (It might as well be, since it is made from unobtainium). Leave an opening on one side , you get thrust, leave no opening , the engine “idles”, with no thrust. The energy is not lost, it is recycled back into the hole, efficiency is 100% (thank you, unobtainium).

    If carefully crafted to have a magnetic field of reasonable strength, the black hole should be quite easy to “bolt” to the ship using a couple of coils and an electronic feedback circuit. All coils, circuits and crew quarters, of course, better be on the OTHER side of the unobtainium shield.

    The lifetime of a black hole can be extended indefinitely and its size/power regulated by feeding it matter, so I think the bit about the “universe made for space flight”, does not hold up very well.

  • Eniac November 30, 2009, 19:58

    And that dust grain with the truck impact, that was based on an off-the-cuff assumed mass for a dust grain that was at least three orders of magnitude larger than actual interstellar dust grains. The impact energy of those real dust grains is more in the range of a well-pitched baseball. Not bad, but a truck it is not.

  • Duncan Ivry November 30, 2009, 21:39

    After having read the article “A Universe Optimized for Starships?” and the … well … “pertinent” comments, my first thought was: “Hey, I have an education in mathematics and physics; I earn my money this way; I will stop wasting my time reading the Centauri Dreams forum”.

    But then I remembered myself, that I like science fiction very much, including the freaky one. And now I say “Thank you” to Paul Gilster, to the commenters, and to the … well … scientists — or should I say “science fiction authors” — like Crane and Westmoreland. I let you entertain me. You are better than Robbie Williams.

  • Eniac December 1, 2009, 0:47

    Maybe there is hope, without unobtainium.

    It might be possible that a black hole with a magnetic field captures the charged particles of its Hawking radiation along the field lines, forming a plasma shell similar to the van Allen belts of the Earth. It might be possible that this plasma is dense enough to absorb most gamma rays. It might be possible that the charged particles in the plasma, following the field lines, converge back on the back hole at its poles, like a much more intense version of the northern lights. It might be possible that the only particles able to escape this arrangement will do so at the poles, where they do not have to cross field lines, and form two extremely focussed relativistic jets in opposite directions. It might be possible that the magnetic field of such a hole is neither too strong nor too weak to allow magnetic confinement with a magnetic coil of reasonable field strength. It might be possible that the plasma shell is small enough to fit inside such a coil. It might even be possible that a reasonable external magnetic field along the axis of the hole unbalances the particle trajectories enough that one of the jets disappears or at least becomes much weaker than the other.

    Then, we could build a doughnut-shaped star ship that has a black hole at its center, a magnetic coil around it to contain both hole and plasma, and machinery plus crew quarters arranged around the periphery, with some shielding.

    A lot of “might be possible’s”, and I am not plasma physicist enough to judge if any of them are or not. But, since we were speculating, anyway, I think it is an intriguing thought. Better than unobtainium or dark matter, anyway. We know relativistic jets like this do exist at actual black holes on a much larger scale, so at least that part is not pure fiction.

  • Ronald December 1, 2009, 9:22

    Again off-topic, Paul:

    About the superiority of super-earths:


  • Ronald December 1, 2009, 12:31

    Duncan Ivry: very acrid. Apparently you haven’t been reading much here.

  • James M. Essig December 1, 2009, 13:20

    Hi Folks;

    I think it is far to soon to throw in the towel regarding the possibilities of at some point, producing macroscopic quantites of Cold Dark Matter or even electrically charged super symmetric matter.

    Remember the early days of nuclear physics and radioactivity during the late 19th/ early 20th centuries when Madaam Curie was experimenting with radio-activity. The total supply of industrial produced samples of radioactive materials (which were not initially understood) was very small.

    One of the early researchers of radioactivity reasoned that the energy available from such materials was as much as 100 million times that available from the best known chemical reactions. He reportedly muzed that the energy available from this radioactive substance could blow the entire Earth up. Although perhaps a great exageration, he saw the tremendous energy available from the radioactive material he was studying.

    Leo Szilard rationally anticipated the development of the atomic bomb well before the beginning of the Manhattan Project had begun.

    The point is we simply can not rule out the development of bulk artificially produced cold dark matter or super symmetric electrically charged matter.

    But what if we cannot develop miniature blackholes for many thousands of years to follow?

    Perhaps we can develope the next best thing in the form of quark nuggets that would emit an analogue to Hawking Radiation albiet on a much more limited scale. Since the quark nugget(s) would not be spatial temporally decoupled from the adjacent spatial-temporal volume, perhaps any reification and seperation of zero point photons could in effect produce net energy out of the pure vacuum of space time in a manner that would seemingly violate the energy conservation. The photons that fell into the quark nugget would increase its mass and the photons that traveled away from the quark nugget could be used for space craft propulsion systems.

    If we can learn to live forever, the following scenarios might be possible.

    For the condition wherein a 1,000 metric ton rest mass space craft would obtain just one electron volt per 10 EXP 1,000 years background reference frame time, the craft should obtain a kinetic energy in 10 EXP 10,000 years background reference frame time of (10 EXP 10,000)/(10 EXP 1,000) eV = 10 EXP 9,000 eV ~ 10 EXP 8,981 Joules which would yield a relativistic gamma factor of 10 EXP 8,958. That is one followed by 8,958 zeros. Even if the sequestration rate of zero point field energy is positive but miniscule, we can as long as we have positive acceleration no matter how small but finite, achieve arbitrarily high relativistic gamma factors. We might achieve such gamma factors provided we could find a way to completely cloak a space craft from astro-dynamic drag and radiation.

    Now for constant acceleration, proper time is given as follows:

    To = (c/g) ln { {[[ (C EXP 2) + (Vo EXP 2)] EXP (1/2)] – [Vo/[[1 – [(Vo/C) EXP 2]] EXP (1/2)]]}

    { [[C EXP 2] + [[(g)(t) + [Vo /[1 – [(Vo/C) EXP 2]] EXP (1/2)] EXP 2]] EXP (1/2)] + [(g)(t)]

    + [Vo/[[1 – [(Vo/C) EXP 2]] EXP (1/2)]] } / [C EXP 2] }}

    For V0 = zero, we obtain the following simplification

    To = (c/g) ln C { {[[C EXP 2] + [[(g)(t)] EXP 2] EXP (1/2)] + [(g)(t)]}

    /[C EXP 2] }

    Now assume that g = (10 EXP – 100) m/(sec EXP 2) and t = 10 EXP 1,000 years; we obtain T0 = 10 EXP 103.5 years.

    Note that (10 EXP 1,000 years)/(10 EXP 103.5 years) = 10 EXP 896.5. The effective integrated time dilation factor or gamma factor is thus 10 EXP 896.5.

    Now assume that g = (10 EXP – 1,000) m/(second EXP 2) and t = 10 EXP 10,000 years. To = 10 EXP 1,005.5 years.
    Note that (10 EXP 10,000)/(10 EXP 1,005.5) = 10 EXP 8,994.5 = the effective total integrated relativistic gamma factor of the space craft.

    The point is regardless of our religious or philosophical orientation, we all somehow at some level dream of and are inspired by a vision that the human race will last forever and that our existence is not futile. Working toward that dream and an era of peace will enable all things to be possible. Let us not put arbitrary limits on our civilization by statements that we will never be able to accomplish black hole drives or we will never be able to produce gamma ray parabolic or spherical reflectors.

  • Duncan Ivry December 1, 2009, 16:50

    James M. Essig: “Let us not put arbitrary limits on our civilization by statements that we will never be able to accomplish black hole drives or we will never be able to produce gamma ray parabolic or spherical reflectors.”

    Well, James, on one side: saying, that we will not be able to build certain exotic devices; on the other side: putting limits to our civilization. You can overdo things. Above that, just in physics and technology there are good reasons opposed to what you call “arbitrary”.

  • Eniac December 1, 2009, 17:09


    10 EXP 1,000 years, or even 10 EXP 103.5, is an awfully long time to be waiting to go to the stars, even if you lived forever. Likely, there wouldn’t be any stars around by then. Similarly, I would rather not have to wait until the advent of devices using macroscopic quantites of Cold Dark Matter, electrically charged super symmetric matter, fuel extracted from higher dimensions, or free zero point energy. That could take nearly as long.

    Far from throwing in the towel, I am instead looking elsewhere for solutions with the potential for somewhat shorter term gratification. 2*10 EXP 1 years, perhaps, or at most 10 EXP 2 years. That magnetic black hole would be a cool way to do it, if it wasn’t for the absence of the most important ingredient, the black hole. That one I haven’t figured out, yet… :-)

  • David December 1, 2009, 17:51

    Eniac, thanks what is a reasonable mass for an interstellar dust particle?

  • James M. Essig December 1, 2009, 18:09

    Hi Duncan;

    I stand by the spirit of my above comments. The history of science and technology over the previous 200 years speaks for itself. For those who hope that current scientific paradymns in physics will not be shattered by developments in high energy physics such as the research objective’s at the LHC, the proposed TeV range Linac, and the now openly discussed muon collider, my gut feeling is that all such folks are going to undergo future shock.

    As for visionary science fiction writers, history points out that Joules Verne could not have been more right on concerning the nuclear powered nuclear armed submarine, and the Apollo Moon Missions. I see as impossible proofs that science and technology will not take additional leaps and bounds. Now, we will just have to wait and see what they discover at the LHC.