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A Test for Exotic Propulsion?

Can we calculate the gravitational field of a mass moving close to the speed of light? Franklin Felber (Starmark Inc) believes he can, with implications for propulsion. Back in 2006 we looked briefly at Felber’s work, describing what the physicist believes to be a repulsive gravitational field that emerges from his results. Felber discussed the matter at the Space Technology and Applications International meeting that year, where he presented his calculations of the ‘relativistically exact motion of a payload in the gravitational field of a source moving with constant velocity.’

Above a certain critical velocity, Felber believes, any mass will gravitationally repel other masses, an effect that is twice as strong in the forward direction of motion, but also works in the backward direction. An object lying in the narrow beam thus produced could be accelerated quickly and with little stress. He described the effect in a paper he submitted in 2005 to the arXiv site:

At radial approach or recession speeds faster than 3-1/2 times the speed of light, even a small mass gravitationally repels a payload. At relativistic speeds, a suitable mass can quickly propel a heavy payload from rest nearly to the speed of light with negligible stresses on the payload.

In other words, a mass moving faster than roughly 57.7 percent of the speed of light will repel other masses that are placed within what we could call an ‘antigravity beam’ in front or in back of it. If true, the effect would provide the energy source needed to produce accelerations otherwise impossible. In Felber’s studies, the supposed ‘antigravity’ effect becomes stronger as the mass approaches the speed of light more and more closely.

The advantages are listed in Felber’s recent 2009 paper:

This new means of ‘antigravity’ propulsion addresses the major engineering challenges for near-light-speed space travel of providing enormous propulsion energy quickly without undue stresses on a spacecraft. By conventional propulsion, acceleration of a 1-ton payload to 0.9c requires imparting a kinetic energy equivalent to about 30 billion tons of TNT. In the ‘antigravity beam’ of a speeding star or compact object, however, a payload would draw its energy for propulsion from the repulsive force of the much more massive driver. Moreover, since it would be moving along a geodesic, a payload would ‘float weightlessly’ in the ‘antigravity beam’ even as it was accelerated close to the speed of light.

The effect would take place within a narrow cone, but would be extraordinarily useful, in Felber’s view, if we could find a way to tap it, for the energy needs to reach these high velocities would be available naturally, and the stresses of acceleration would be manageable tidal forces in free-fall motion along a geodesic. The result is what Felber calls ‘hypervelocity propulsion.’

To say this is problematic is to state the obvious. How to tap into these energies? Here’s Felber’s thought on that, from the 2006 paper:

Whether the payload is accelerated by a strong or a weak field, the payload travels along a geodesic. The only stresses on the payload, therefore, are the result of tidal forces in the accelerated frame of the payload. These stresses can be arranged by choice of the trajectory to be kept within acceptable limits. Greater practical problems for gravitational propulsion are finding a suitable and accessible driver mass at relativistic velocities, and maneuvering the payload in and out of the driver trajectory.

The italics are mine, highlighting a key issue — if Felber’s work (which draws on a 1924 David Hilbert paper that discussed the repulsion of relativistic particles by a static Schwarzschild field) is correct, then we still have the problem of arranging our payload in relation to the driver mass. In other words, taking advantage of these effects would itself require breakthroughs in space propulsion that would render the advantage of using the effect minimal. It would assume a highly advanced space infrastructure, one capable of ranging freely through deep space, and apparently a lot of luck.

But let’s put aside practicality and look at the effect itself. Theories abound and what we need are workable ways of testing them, which is why so many people are dissatisfied with the various string theory formulations — how do we confirm what seem to be purely mathematical constructs? Felber’s new paper argues that the Large Hadron Collider will be capable of testing his ideas by measuring the forces on a test mass. The physicist believes such a test could be performed without interfering with normal LHC operations, assuming we get the LHC to ‘normal’ operations any time soon.

Felber’s experiment would measure “… the repulsive gravitational impulses of proton bunches delivered in their forward direction to resonant detectors just outside the beam pipe. This test could provide accurate measurements of post-Newtonian parameters and the first observation of ‘antigravity’, as well as validating the potential utility of relativistic gravity for spacecraft propulsion in the distant future.” He believes such a test could be performed for less than one percent of the cost of NASA’s Gravity Probe B, whose total tariff may well have reached $1 billion. Lab tests can be cheaper than space tests, but will Felber’s ideas attact the needed funding even at these levels?

The 2009 paper is Felber, “Test of relativistic gravity for propulsion at the Large Hadron Collider” (abstract), while the 2006 paper is “Exact Relativistic ‘Antigravity’ Propulsion” (abstract). Technology Review looks at Felber here.

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Comments on this entry are closed.

  • george scaglione October 12, 2009, 12:58

    wow if i have read the above correctly then i congatulate mr felber ten times over! he has hit upon a favorite surmise of mine – the gravity drive.no kidding my friends to be able to use gravity for propulsion would indeed be a great thing.after all we have enough of it!!! also,i went back to the top of this article which has been so thoughtfully provided here by paul and reread it again!!! better than the first time! it is hugely exciting that of all things the LHC will be able to help out in this area! hope i will soon be knee deep in interesting comments to read from the majority of our members here! an exotic propulsion indeed. thank you one and all very respectfully your friend george

  • Tim Kendall October 12, 2009, 16:17

    Yes, ArXiv does say 3^-1/2. Mercifully.

  • Administrator October 12, 2009, 16:24

    Thanks for catching that, Tim. Now fixed.

  • Tom October 12, 2009, 19:59

    It all sounds a bit hard to believe really. I mean, the idea that you can accelerate a payload based on having a much more massive payload at really high speed is just a non-starter. It is just replacing the problem with a bigger (heavier) one. Add to this the fact that when the antigravity acts, the payload would accelerate away, so the accelerating effect would only work for a short time.
    Also, I don’t see how you can measure antigravity effects on particles that are so tiny (inside the LHC) that their (positive or negative) gravity against one another is miniscule.
    Lastly, the maths seems dubious.. isn’t a premise of relativity that the physics works the same regardless of the velocity of the observer.

  • Ron S October 12, 2009, 23:46

    I skimmed the paper last week, but I decided to look at it a little more closely today when I saw this post. On second reading I am even more disappointed with it than I was at first. There may be something here in regard to testing frame dragging more simply than with Gravity Probe B, but as to propulsion: I say, forget it.

    To begin, frame dragging is a prediction of general relativity. If it’s true, there is an real effect that could provide propulsion. However, the limitations of the technique look pretty ugly. Now I’m no physicist, but I have enough understanding to find the author’s claims a bit exaggerated.

    If we go back to special relatively, there is an interesting effect when two bodies pass each other at high speed. Each will see the near surface of the other body rotating in the direction as its motion, through a modest arc (I forget the actual calculation, which is velocity dependent). It’s a real effect in that what would otherwise be a hidden (visible) portion of the body becomes visible (hidden).

    Extend this to general relativity and I suppose you can have frame dragging due to this rotation (the paper instead refers to gravitomagnetic effects). In the weak field for a non-rotating body (or ‘driver’, as the author calls it), the effect is very small, even for a grazing pass, but there would be propulsion in the direction of the driver.

    Now we get into a surprising omission in the paper: quantification. The author admits this, but that isn’t good enough. Getting into the numbers will show where the technique is lacking.

    First, because the effect is small, the mass of the driver needs to be very large and it would have to pass very close. It isn’t enough that the driver have a mass much higher than the craft (or particle) to be appreciably accelerated. In fact, to get a useful effect the mass would have to be extremely high, enough (as the author states) to get within 3x the Schwarzchild radius. With physics as we know it, there is only one type of object that qualifies: a black hole. The effect, as I understand it for this case, is equivalent to entering the ergosphere of a rotating black hole (Kerr solution). The dragging effect in the ergosphere around a black hole is so strong that even a large mass traveling at near c velocity can have its velocity reversed and accelerated back to near c, and very quickly. This is what the author calls ‘hyperdrive’. Except — with no black hole, there’s no ergosphere, and we’re back to weak field solutions.

    Second, the interaction time (due to the velocity) is brief, so you either need a lot of black holes passing at a ‘safe’ distance or fewer passing very, very close.

    Third, there ain’t no free lunch — just as with conventional gravity assists, this interaction is merely a momentum transfer from the driver to the craft (momentum is a conserved quantity in relativity). The driver momentum has to come from somewhere, and that somewhere is the stream of driver objects. That’s a serious quantity of momentum that someone has to generate. Further, the amount of momentum transferred is very low except for those grazing black holes…

    Fourth, while it is true that the craft is ‘falling’ in the gravitational field of the driver and therefore there is no apparent acceleration felt by the craft or its occupants, the tidal effects mentioned in the article deserve scrutiny. If we keep the driver mass low, the resulting black holes are tiny. This matters since the tidal effects increase as the driver mass decreases, for a constant minimum distance (apsis) to the driver’s surface. To keep tidal effects manageable and also contain the craft entirely within the driver’s ergosphere so that all portions of the craft receive near-equal acceleration, the black hole mass must be large. As in, a substantial fraction of a planetary mass.

    So there we have it: you are sitting out in space inside your tin can while someone from millions of kilometers away is firing asteroid-mass black holes at you, that each pass within a few meters. As they do, you and the craft deal with uncomfortable and dangerous tensile forces, and difficult-to-control craft gyrations. These black holes then continue on toward your destination (they’re traveling in the same direction as you) to wreak havoc there and beyond. Don’t expect to find ET warmly welcoming you when you arrive, even if you can figure out some way to decelerate enough that you don’t suffer the same fate as those driver masses.

  • keith October 13, 2009, 7:54

    I think the key use of this would be clearing the path of a relativistic ship. Or would a ship not be massive enough?

  • Administrator October 13, 2009, 8:19

    Ron S writes:

    So there we have it: you are sitting out in space inside your tin can while someone from millions of kilometers away is firing asteroid-mass black holes at you, that each pass within a few meters. As they do, you and the craft deal with uncomfortable and dangerous tensile forces, and difficult-to-control craft gyrations. These black holes then continue on toward your destination (they’re traveling in the same direction as you) to wreak havoc there and beyond. Don’t expect to find ET warmly welcoming you when you arrive, even if you can figure out some way to decelerate enough that you don’t suffer the same fate as those driver masses.

    Exactly so. And thanks, Ron, for giving this idea such a thorough look. The deceleration issue you touch on briefly here is certainly significant, but so is the fact that any space voyaging accomplished with these methods already supposes a kind of mastery of space travel that would make using the technique pointless. So I’m in agreement with you that the propulsion angle is weak, but am still curious about the physics involved.

    keith writes:

    I think the key use of this would be clearing the path of a relativistic ship. Or would a ship not be massive enough?

    Interesting notion, given the problem of even the tiniest bit of debris in the path of a vehicle moving at these speeds. My assumption is that the ship would have to be far more massive than would make this practical, but I’ll let someone better at the math work that one out. Ron S notes above the tiny nature of the effect, and the huge masses necessary.

    Tom writes:

    I don’t see how you can measure antigravity effects on particles that are so tiny (inside the LHC) that their (positive or negative) gravity against one another is miniscule.

    Felber’s paper is interesting on that score — give it a look. I’d have to leave it to those more conversant with particle physics than I am, but I wouldn’t rule out this being a testable effect.

  • ljk October 13, 2009, 10:22

    Sounds like it might make one heck of a tactical interstellar weapon. Those
    black holes could be used to mop up any obstacles that get in its way.

    People tend to think that a dangerous starship might carry all kinds of advanced
    weaponry, when in fact a ship itself could be used as a weapon. Something moving
    at relativistic speeds hitting an Earthlike planet will kill every living thing on its
    surface just from the kinetic energy alone.

    So if we see something moving at a decent fraction of light speed coming
    towards our Sol system and it is not slowing down, I suggest we at least try to
    have some planetoids ready as a potential defense, just in case.

    I highly recommend that everyone read this Web page carefully:

    http://www.projectrho.com/rocket/rocket3aa.html

    Very thought-provoking. Yes, it does come from a fellow who designs space war
    games, but the ideas still apply.

  • Ron S October 13, 2009, 13:10

    Tom: ” I don’t see how you can measure antigravity effects on particles that are so tiny (inside the LHC) that their (positive or negative) gravity against one another is miniscule.”

    Paul: “Felber’s paper is interesting on that score — give it a look. I’d have to leave it to those more conversant with particle physics than I am, but I wouldn’t rule out this being a testable effect.”

    An assumption the author makes is that the proton beam can be treated as a single mass, and therefore the sum is much greater than a test particle. I found this hard to accept, but then I’m no expert. My thought is that since the protons in the beam are far enough apart to not repulse significantly (while under the force of the accelerator’s magnets), the beam cannot be treated as a single object for the author’s experimental purpose. I think that to be treated as a single object, the protons must be bound by the strong force — i.e. heavy nuclei. But I could be wrong.

  • Tim Kendall October 14, 2009, 10:49

    The comments after the Technology Review article on Felber seems telling to a real scientist. The whole paper has a whiff of wacko all over it, I thought!

  • ljk October 15, 2009, 0:32

    Speaking of the LHC, here’s an unusual story:

    http://www.nytimes.com/2009/10/13/science/space/13lhc.html?_r=1

    And some smelling salts:

    http://www.math.columbia.edu/~woit/wordpress/?p=2373

    I also recommend the SF novel Einstein’s Bridge by John Cramer:

    http://faculty.washington.edu/jcramer/E_Bridge.html

  • Adam October 15, 2009, 7:15

    Odd results from GR’s equations aren’t all that unusual surely? Wormholes, CTCs, black-holes, frame-dragging… why should repulsion be seen as any weirder? I think Felber’s idea deserves more than narrow-minded ridicule.

  • george scaglione October 15, 2009, 9:19

    hello all it was very interesting to read all of your comments.strangely enough something seemed to be wrong with the site yesterday and i never got on.so today i was happy to see the site was once again available so i went on and reviewed all the comments again,lol,to include my own.needless to say i was a bit disappointed to see that my enthusiasm for gravity drive is not generally shared. i wonder if that might not change as more research is done,after all,isn’t that pretty much what tau zero is all about? and speaking of that – i sure hope that the LHC comes back on line soon! i,we,waited eagerly for that and then when it happened it seemed that it lasted for about 15 minutes before we had another loooong wait on our hands. gravity drive or not i have no doubt that by “just” (lol) advancing science there is no doubt that the LHC will be able to help out with propulsion concepts too.thank you one and all,respectfully your friend george

  • Ron S October 15, 2009, 10:55

    Adam, please read his paper. Criticism is not ridicule, although ridicule is not out of place for this paper in my opinion. There is no “repulsion”, just frame dragging: being dragged along when a heavy mass passes by due to the (relative) spin. Frame dragging is nothing new, and that’s what Gravity Probe B is measuring (weak field) around the spinning Earth.

  • ljk October 16, 2009, 11:50

    I thought this blog response to the recent Higgs Boson LHC issue was both
    interesting and informative even beyond the main story:

    http://backreaction.blogspot.com/2009/10/science-writers-and-public-bizarre-love.html

  • MrTolliver October 16, 2009, 23:55

    Am I the only one who thinks if this works, then it would be a rather nifty shield for all relativistic spacecraft against micrometeoroids and interstellar. Or am I reading this incorrectly?

  • James M. Essig October 17, 2009, 8:56

    Hi Folks;

    This new anti-gravity drive thread is interesting. I would have never imagined a repulsive gravitational field being emitted in a narrow beam in front of a very relativistic large mass.

    One can imaging a staging type effect wherein a first stage would entail a host body white dwarf with a mass of about 10 EXP 27 metric tons being accelerated to perhaps .9999 C whereupon the antigravity beam generated would accelerate a second stage that has a rest mass of perhaps 1 billion metric tons to a relativistic gamma factor of say 10 EXP 20 wherein the second stage would then accelerate a payload with a rest mass mass of say 1,000 metric tons to a gamma factor of perhaps 10 EXP 26.

    One can imagine that a white dwarf could be accelerated to a yet higher gamma factor, whereupon a fourth stage or even e fifth stage would be utilized.

    And what if the accelerating mass was composed of negative mass. Perhaps upon acceleration to relativistic velocities, we would discover that the forward effects would be attractive and would out pull the backward attractive effects or perhaps compound any backward repulsive effects.

    Either way, this is a very interesting concept.

  • Ronald October 19, 2009, 4:27

    See also:
    http://nextbigfuture.com/2009/10/60-tesla-superconducting-magnets-would.html
    It seems Häuser and Dröscher are at it again (or still). With such strong magnets it should be possible to (quote): “enable testing of gravitational field propulsion within the next two years”.

    We live in exciting times!

  • James M. Essig October 20, 2009, 22:11

    Hi keith;

    Regarding your above comments;

    “I think the key use of this would be clearing the path of a relativistic ship. Or would a ship not be massive enough?”

    We can imagine a repulsive gravity beam that would push materials out of the path of a space craft operating in conjunction with a magneto-hydrodynamic-plasma drive, an electro-hydrodynamic-plasma drive, or an electromagneto-hydrodynamic-plasma drive craft wherein at least a portion of the repelled interstellar materials would be pulled backward and around the space craft in conjunction with the proximate interstellar materials to the space craft that lie outside of the beam path. This thrusting mechanism would operate in a manner similar to traditional MHPD, EHPD, and EMHPD systems.

    The forwardly repelled material can make for an excellent rest mass specific potential energy dense electrodynamic reaction mass being that the materials as such might be thrusted ahead of the space craft with a relatively high gamma factor with respect to the space craft and then pulled back by the space craft’s electrodynamic-hydrodynamic-plasma drive mechanism.

    Since the forwardly directed kinetic energy and momentum of the interstellar materials accelerated by the gravity beam would be reversed in orientation by the electrodynamic-hydrodynamic-plasma drive, the electrodynamic propulsive fields would have a longer time to interact with a given differential rest mass element of interstellar materials thereby leading the craft to regain most if not all of the energy that the space craft would have otherwise lost thus resulting in at least a great reduction in potentially serious astrodynamic drag.

    The MHPD, EHPD, and/or EMHPD systems could operate in conjunction with fusion powered interstellar ramjet, a fusion rocket, or perhaps a matter antimatter rocket. Versions of such reactionary propulsion systems might include ion, electron, photon, and perhaps even neutrino rockets.

  • Greg October 23, 2009, 15:07

    I hate bursting anyone’s bubble, but wouldn’t this effect be noticed in collisions between two beams in any synchrotron? I would think beams of particles would push at each other as both of their areas or cones of “anti-gravity” would be pushing at the on-coming particle?
    I just don’t see how this effect could have been missed? If it exists at all.

  • ljk February 19, 2010, 0:24

    Gravity’s effect on time confirmed

    Atom interferometer makes ultra-precise measurement of gravitational redshift

    http://physicsworld.com/cws/m/1644/113295/article/news/41740