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Space Transportation Science

Warp Drive Might Be Less Impossible Than Previously Thought 867

Posted by Unknown Lamer
from the warp-seven-engage dept.
runner_one writes "Harold 'Sonny' White of NASA's Johnson Space Center said Friday (Sept. 14) at the 100 Year Starship Symposium that warp drive might be easier to achieve than earlier thought. The first concept for a real-life warp drive was suggested in 1994 by Mexican physicist Miguel Alcubierre, however subsequent calculations found that such a device would require prohibitive amounts of energy, studies estimated the warp drive would require a minimum amount of energy about equal to the mass-energy of the planet Jupiter. But recent calculations showed that if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut, as opposed to a flat ring the warp drive could be powered by the energy of a mass as small as 500 kg. Furthermore, if the intensity of the space warps can be oscillated over time, the energy required is reduced even more."
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Warp Drive Might Be Less Impossible Than Previously Thought

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  • by hawguy (1600213) on Monday September 17, 2012 @07:16PM (#41368991)

    Does this theory at all reduce the chance that when the Warp Drive ship arrives at its destination that it will emit a huge gamma ray burst [universetoday.com]? This planet destroying side effect would sure put a damper on any kind of arrival party for the warp drive ship.

  • by wierd_w (1375923) on Monday September 17, 2012 @07:22PM (#41369071)

    Agreed.

    Other important caveats not listed are things like, duration of field perturbation, and effective field size.

    If it takes 500kg of raw mass energy equiv, to send something the size of a football on an ftl hop for 1 sec, it is still very very impractical.

    If we are talking something the size of manhattan island being shot at FTL for over a year for 500kg mass energy, things are difficult, but interesting.

    This still doesn't sole several other noteworthy problems with the alcubiere metric though. Things like hawking radiation snowplowing on the event shock of the warp field, nuking the ship and everything around it when the field drops as the ship leaves FTL.

    (Basically, the spacetime bubble the ship occupies behaves the same as the event horizon of a black hole, as far as virtual particle interactions are concerned. The pocket tearing past at ftl speed forces the particle pairs to become real, robbing energy from the warp field, and plastering radioative exotics all over the shock front. When the bubble collapses, that radiation gets released.)

    If they can pull it off, alcubierre's metric would only be useful for short jumps, not continual cruising, making it impractical for visiting very distant objects. It would also be an energy hungy monster.

  • by Chris Burke (6130) on Monday September 17, 2012 @07:36PM (#41369243) Homepage

    As far as I understand it warp drive doesnt break the speed of light locally, so I recon no weird time reversal stuff can happen.

    In Relativity, traveling faster than light relative to any reference frame, via any method, presents problems with causality. And the whole point of a Warp Drive is that someone will agree that you went faster than light, and thus went backward in time.

    When I last read about the Alcubierre drive, one relevant point that was mentioned was that the inside of the warp field is causally separated from the outside, which solves the problems of causality while in transit, but raises the question of how one starts or ends the journey.

    The ridiculous amount of energy required was another problem, more of a practical "how would you do that?" issue rather than a "how is it even possibly in theory?" question.

    But the thing is -- it may actually be possible to do this in our universe. And the assumptions of constant c and General Principle of Relativity may also be correct. Which may mean that the assumption of causality isn't. What a universe that would be.

  • by Space cowboy (13680) on Monday September 17, 2012 @07:38PM (#41369255) Journal

    No.

    In the real world, today, the phase velocity of light can easily exceed the speed of light in a vacuum. There is no time travel. There's no information transfer, either, due to the conditions of travel at that speed, but there's no time travel.

    From
    "On the other hand, what some physicists refer to as "apparent" or "effective" FTL[1][2][3][4] depends on the hypothesis that unusually distorted regions of spacetime might permit matter to reach distant locations in less time than light could in normal or undistorted spacetime. Although according to current theories matter is still required to travel subluminally with respect to the locally distorted spacetime region, *apparent* FTL is *not* excluded by general relativity."

    Also worth reading the 'difficulties' of the 'worm bubble' effect, and how those difficulties might be addressed by this new research.

    I'm not saying it's possible, but it's too soon to rule it out, either.

    [section: not entirely serious, but...]
    My personal take is that Gene Roddenberry was an alien whose goal was to nudge us in the generally correct direction without apparently doing so. To do this, he (it?) created a TV series called 'Star Trek' in which all advances we'd need were demonstrated to agile minds. Once it has been conceptualized, if it is possible, someone somewhere will eventually do it...
    [/section]

  • by Chris Burke (6130) on Monday September 17, 2012 @07:47PM (#41369345) Homepage

    But that's the point of how warp drive works - you bend space so that you don't travel faster than light.

    You locally don't. The warp ship doesn't actually accelerate at all. This is how you get around the relativistic energy equation.

    However, someone will observe you traveling faster than light, going from point A to point B faster than light would travel the same distance. If nobody sees you traveling faster than light, then how can you say you did so at all?

    And the whole point of relativity is that the laws of physics have to hold everywhere. That observer, depending on their own velocity in space-time, potentially see you arrive at your destination before you left, violating causality according to them.

    Given a few such warp ships, you could even arrange it so that that person would receive a message they had written and sent with you before they had actually written it. And then causality is broken for everyone.

    But hey, maybe it's not a causal universe! I await their experiments.

  • by wierd_w (1375923) on Monday September 17, 2012 @07:53PM (#41369415)

    If going 99.9999% C, it would take you an outrageous amount of (outside) time to flick the switch. The universe could end before then!

    Still, assuming you did indeed flick the switch, it would be the same as with sound propogation. An ambulance travelling at 99% speed of sound with sirens blaring will emit a higher frequency sound, until after it passes, and then the tone will be dialated the other way.

    The light won't move faster. Instead, the frequency will be insanely high. Your infrared emitting tungsten filament bulb will be emitting gamma ray photons.

    If you are going 100% speed of light, you will *never* succeed in toggling the switch.

    Here is where the whole FTL thing becomes unnecessary:

    If you are taveling 50% of C, the degree of seperation between internal and external clocks will be sufficient that even though it takes you 400 years to reach that star 200 light years away, a considerably shorter time will be recorded by the ship's onboard clock.

    The closer to C you travel, the less "time" you experience. So, FTL is not necessary. The crew will be alive and well, and feel only a few months have passed on their 400 year journey. Everyone they left back home will be dead and buried, but for them, only a few months will have passed.

    If all you care about is *your* lifetime, FTL is not needed to explore the universe.

  • by Ralph Spoilsport (673134) on Monday September 17, 2012 @07:54PM (#41369421) Journal
    There's about 1 hydrogen atom / proton per cubic meter. Even at sub-c speeds, they create seriously radioactive friction. And running into a grain of sand at some % of c would have the effect of a large bomb. So, you not only have to warp space, you have to move the matter IN the space, and do it at >c velocity. Since matter can't move >c, you can't get the protons and occasional neutrons and sand grains and other interstellar detritus out of the way. A grain of sand hitting anything at 10c would be catastrophic, and within a few hours of colliding with the interplanetary and interstellar medium would turn the ship into a glowing radioactive dead thing.
  • by Anonymous Coward on Monday September 17, 2012 @07:55PM (#41369425)

    The negative mass (energy) required is not expressly forbidden. We've just never seen anything with such a property and the existence of it would raise some interesting questions. But you could say that about a lot of things that have come out of particle physics....

  • by sortius_nod (1080919) on Monday September 17, 2012 @07:57PM (#41369441) Homepage

    It's amusing, because the shape they have come to is essentially the same shape as the warp field on the Enterprise.

  • by wierd_w (1375923) on Monday September 17, 2012 @08:09PM (#41369537)

    I believe that is exactly what I said, when I mentioned that it was a caveat not addressed by the article. "Football sized" had no bearing on the verbiage of the article, and was instead meant to be taken as-is. Eg, an effective warp bubble big enough to barely hold a football is not practical in any sense at the energy cost listed.

    In order to determine how far the ship could travel at 10xC with 500kg raw mass energy, we need to know how long (dialated ship time) that energy takes to be released, and how long (external observer time) the bubble will remain stable.

    That information was not provided.

  • by Anonymous Coward on Monday September 17, 2012 @08:10PM (#41369539)

    We have seen this effect, just not in regular solid matter; we can see it in certain configurations of regular matter, such as the Casimir effect. So it's not *real* exotic matter, but it does show that negative energy is technically an observable thing. How exactly we can make use of that to do the necessary space-folding is still unknown. It's an incredibly hard, potentially impossible engineering problem, but impossible engineering problems have a tendency to become trivial given enough time and motivation.

  • by nine-times (778537) <nine.times@gmail.com> on Monday September 17, 2012 @08:24PM (#41369673) Homepage

    In fairness, the claim that it "might be less impossible than previously thought" may be accurate. It could be less impossible and still be pretty much impossible. And I don't think anyone believed that a warp drive could be built without violating some of our current laws of physics.

  • by erice (13380) on Monday September 17, 2012 @08:33PM (#41369735) Homepage

    Exotic matter, by definition, requires violations of the known laws of physics.

    That's a very peculiar definition of exotic mater you have there. Elsewhere, "exotic matter" generally refers to matter of a type neither observed nor predicted by current theory. No violation of known physics is implied. It is just that we haven't seen any and there is no particular reason to believe that it exists.

    The particular flavor of exotic matter needed for the warp drive is "negative" matter. Negative matter has negative energy. Unlike antimatter where antimatter + matter = lots of energy, negative matter + matter = nothing.

    'Last I heard, running the usual math through with negative matter results in some situations that don't make a lot of sense. They aren't necessarily wrong or forbidden, we just don't know what they mean. Math is like that sometimes.

  • by nedlohs (1335013) on Monday September 17, 2012 @08:44PM (#41369829)

    Maybe you should try some different physics classes. It's just special relativity. If you have a faster than light travel/signalling then there will be an interial frame of referance in which that travel/signal went back in time. Since the first postulate or relativity says that the laws of physics are the same in all inertial reference frames that means backwards in time travel/signalling is possible in all inertial frames of reference and we have killed causality. Or alternatively the postulates of special relativity (and hence the theory) are wrong.

    http://www.theculture.org/rich/sharpblue/archives/000089.html [theculture.org] has some reasonable spacetime diagrams for an example.

  • Re:Make it so. (Score:2, Interesting)

    by Anonymous Coward on Monday September 17, 2012 @08:48PM (#41369865)

    I would think that the warping of space would be the big issue, not the kinetic energy. How much warping would it take to throw off the atmosphere or a chunk of the crust? What would happen if a chunk of the planet was temporarily missing and gravity forced the planet to round out--and then the piece comes back? No extra energy would be needed, just the gravitational potential energy stored in the planet.

  • by mark-t (151149) <[markt] [at] [lynx.bc.ca]> on Monday September 17, 2012 @09:26PM (#41370111) Journal

    It is more correct to say that "exotic matter" refers to some substance that has never been observed to exist and possesses one or more properties that are so radically distinct from properties you would find more conventionally that it might as well be magic.

    Examples: A frictionless pulley; a shield against gravity; an invulnerable metal.

  • by rubycodez (864176) on Monday September 17, 2012 @09:32PM (#41370157)

    indeed, the recent (nearly confirmed) discovery of dark matter is one example of exotic matter outside of known physics until the last two decades.

  • by wierd_w (1375923) on Monday September 17, 2012 @09:43PM (#41370217)

    That's what a tachyon is! (Well.. more or less...)

    A tachyon is a "particle", forced to always travel at FTL velocity, because it has "imaginary" mass.

    The alcubierre metric makes use of "negative mass energy" to negate 100% of the vehicle's effective mass, and a little more, causing the "vehicle + engine" composite to become essentially an enormous tachyon. (More or less...)

    This poses the problem of how to escape the bubble once created; theoretically speaking, doing so would not be possible! However, interaction with the hawking radiation might provide the solution. As the particles intersect the field, they steal energy from the field, by making the pair real. (One of the particles gets glued to the front, the other gets lost to space.) This loss of energy depletes the field, forcing its collapse. When that happens, the ship returns to being causally connected.

    (This however, makes the effect useless for anything but *really* distant objects, or with very very powerful fields.)

  • by nine-times (778537) <nine.times@gmail.com> on Monday September 17, 2012 @10:06PM (#41370363) Homepage

    Two ships travel at c in opposite directions for a period of time. When they decelerate and return to the same frame of reference that they started from, the distance between them will be equivalent to one ship having travelled at 2c for the same period. It doesn't matter what the people in each ship perceive from within their reference frames while they're moving.

    No, they won't.

    Let's say that three ships are stationary relative to each other, sitting right next to each other, and two of them accelerate very quickly to just under the speed of light in opposite directions. Each ship travels for what their clock says is one year, and the third stays where it is. After a year, they stop very quickly, and measure the distance that they are from each other. How far away from each other will they be?

    The correct answer is 1 light-year. Only 1, not 2.

    From each ship's point of view, when it took off going almost the speed of light, the other ship travelled very slowly in the opposite direction. The third ship that didn't move saw each ship travel away at almost the speed of light. However, from the third ship's point of view, only half a year passed, which explains why they're only 1 light-year apart. That's what we call "time dilation".

  • by Jane Q. Public (1010737) on Monday September 17, 2012 @10:55PM (#41370703)

    "No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics."

    Incorrect. There is nothing we know of that actually works to prevent the violation of causality. There are a number of ways it can theoretically be done.

    See Tipler, "Rotating Cylinders and the Possibility of Global Causality Violation".

    All rhetoric (like the post at that link) aside, all we really have about it is guesses. The fact that we have never observed anything, so far, that would violate causality says absolutely nothing about the possibility. Further, it is not necessarily true that limited instances of causality violation would render the entirety of physics invalid, any more than relativistic situations render Newton "invalid". They are "special cases". That is all.

  • Re:Make it so. (Score:5, Interesting)

    by RsG (809189) on Tuesday September 18, 2012 @01:36AM (#41371503)

    I'll assume, for the sake of argument, that conservation of energy still applies to the discussion. That is, you can't move a chunk of the crust into orbit without expending more energy than the gravitation potential energy thusly imparted into said chunk.

    Let's assume the energy to make the handwavium drive go is equal to the potential energy of a 500 kg mass, as it says in TFS. Presumably we've got matter-energy conversion or antimatter fuel to make this work, that's no more implausible than the handwavium required to make the FTL drive work in the first place.

    How much energy is liberated by converting 500 kg into energy, say in the form of 250 kg antimatter to 250 kg matter? About two hundred and fifteen times as much as was released by the largest nuclear weapon ever detonated. Make no mistake - that's a huge amount of energy, but nowhere near planet cracking levels. For another point of comparison, the impact that (probably) killed the non-avian dinosaurs was a couple million times as powerful.

    Further, if we've got some way of supplying that kind of power, in a package small enough to fit on a spacecraft, wouldn't the power plant itself be a more dangerous weapon than a handwavium suicide run? Dangerous in the sense of city busting, not planet cracking.

  • by hherb (229558) <horst AT dorrigomedical DOT com> on Tuesday September 18, 2012 @03:56AM (#41372057) Homepage

    Traveling faster than light does not necessarily violate causality.
    If I could travel instantly from place A to place B which is 1 light year away, I would arrive at B long before the light arrives. However, the "absolute" time at place B is exactly the same as at place A, the fact that an observer depending on optical information via photons lazily traveling at the speed of light from B to A would only be able to see me arriving there a year later has nothing to do with causality. If I instantly travel back to A, I am still not arriving any earlier than I departed, and hence have not moved in time, only in space - and once again I cannot violate causality.

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