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The danger of FTL?

  1. Jul 14, 2009 #1
    For kicks, I have been reading the following AIAA/NASA paper on hypothetical space drives:

    http://www.grc.nasa.gov/WWW/bpp/1997-J_AIAA_SpaceDr.pdf

    Now, I have to admit that I only have a cursory understanding of general relativity & differential geometry.

    But assume for a moment the unlikely possibility that one or more of these concepts is feasible and engineer-able. Imagine that such a drive was activated within our solar system, with an extra-solar destination. Given the sharp instantaneous S-T curvature implied by these designs and the instability of the N-Body (N>2) problem, wouldn't such a technology pose a serious threat to an inhabited system?

    Specifically, wouldn't the artificial curvature induce changes in the Christoffel symbols in S-T; ultimately propagating outward as a gravitational wavefront as S-T returned to it's original shape? If so, would it seem likely that these field gradients might stabilize a gravitational system?

    Thanks in advance for everyone's time/help/explanations/corrections!
     
  2. jcsd
  3. Jul 14, 2009 #2

    DaveC426913

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    Unless I'm mistaken, you're asking if a hypothetical FTL drive would create gravity waves. And would they be big enough to affect planetary orbits.

    Of course, this is all fantasy, but...

    Just because they create waves that ripple across the solar sytem, doesn't mean it will destabilize anything.

    To resort to the waves-on-a-pond analogy, you're imagining the drive creating a whirlpool funnel in the lake big enough to alter the courses of vessels, I'm imagining it would merely make ripples on the surface.
     
  4. Jul 14, 2009 #3
    Yep; that's what I was asking. I imagine that you may be right; but given the magnitude of the disturbance needed to warp space in the needed way, it just seems intuitive that the ancillary effects of a warp field would be non-negligible.

    The analogy that I guess put this in my mind was propagation of waves from shocks in fluid dynamics. Of course, I don't imagine that S-T is completely analogous to a fluid continuum, but I can't help but think that gravitational waves would emanate from a shock in an exponentially decreasing manner with respect to distance (although im not sure if that's the conventional model). In this way, gravitational waves would carry very large amounts of momentum close to the warp bubble, but would be minuscule over stellar distances (and thus hard to detect). As I understand it, this is similar to how interaction between black holes are conceptually modeled.

    I wonder if anyone has tried to numerically model the theoretical local effects of an alcubierre warp event (with all hypothetical hand-waving assumptions of practicality and energy requirements allowed) on the gravitational dynamics of, say, a 2 or 3 body problem.

    Anyways, I appreciate the input, given how contrived the question really is to begin with! :)
     
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