There have been more than a few questions covering Alcubiere warp drives, many about what happens with one at FTL and a few about using them at sub-light speeds.

I'm curious about what happens at more pedestrian speeds (tens to hundreds of kilometer per hour as opposed to percent light speed)

If someone fired up their warp drive underwater what would happen? More specifically, what happens to the water outside and at the boundary of the warp bubble (I'm guessing that the water inside the bubble gets moved around much the same as the ship)

Please ignore the practicality and the general absurdity of creating what amounts to a warp-powered submarine.

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    $\begingroup$ It might be better to consider using it in an atmosphere first, then extend that to the incompressibility of water. $\endgroup$
    – Separatrix
    Commented Jul 7, 2017 at 7:41
  • $\begingroup$ Is your drive strictly what people generally characterize as an Alcubiere drive? Something closer to a Star Trek implementation with a "bubble" or "envelope" would have differing effects. $\endgroup$
    – Dan
    Commented Jul 7, 2017 at 15:06
  • $\begingroup$ Even in Star Trek, they didn't use Warp speeds in Star Systems (this wasn't a catostrophic failure when they broke this rule... and knowing they did... it was just considered a very risky manuver. That said, kicking it into warp drive in atmosphere was never done). $\endgroup$
    – hszmv
    Commented Jul 7, 2017 at 18:54

1 Answer 1


Lots of explosions. Activating an Alcubierre warp-drive isn't recommended for habitable planets, their oceans or possibly even persons of the Alcubierre warp-drive spaceship, er sorry, warp-drive submarine.

Matter, what was formerly water, caught in the compaction volume of the Alcubierre warp bubble could be crushed down to the point where the nuclei of the atoms themselves will disintegrate to radiation. Even if the compaction doesn't go that far, when it uncompacts that densified water will blast outwards. Which looks like an explosion. With or without the massive pulse of radiation if the compaction goes too far.

In the expansion phase of warp-bubble, matter, once again the seawater, will be rapidly expanding outwards. This also looks like an explosion. When the expansion collapses back to normally dimensioned spacetime this could look like an implosion.

In summary, don't try this at home. Don't try this on your home-planet. Not in anyone's ocean, unless you want to do their real estate a lot of harm. This is not taking into account the high probability of destroying your warp-powered submarine. The take-home message is stick to driving your warp-drives in space.

  • $\begingroup$ Sorry, I didn't understand very well, Would water molecules make nuclear fusion between each other? That would be very catastrophic. $\endgroup$
    – Ender Look
    Commented Jul 7, 2017 at 17:27
  • $\begingroup$ Would this still be the case even at normal submarine speeds? $\endgroup$
    – Samwise
    Commented Jul 7, 2017 at 22:25
  • $\begingroup$ @Samwise. This depends on the volume changes needed for those speeds, but the "gravitational" forces involved could be catatstrophic. Energetically submarine technology is astronomically cheaper and easier to implement. Alcubierre need power levels equivalent to the mass-energy of the planet Jupiter. Much easier to attach a propeller to a spaceship and make the other changes for it to be a submarine. $\endgroup$
    – a4android
    Commented Jul 8, 2017 at 2:49
  • $\begingroup$ @EnderLook The nuclei of atoms could be crushed by the forces involved in compacting space. There would be much chance for fusion to take place. Although it might be possible, the helium nuclei themselves would be compacted even smaller. There could be some interesting reactions at the level of quarks. $\endgroup$
    – a4android
    Commented Jul 8, 2017 at 2:51

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