Using an Alcubierre warp drive strictly for sub light travel

In a setting I've been working with, I sought a method of sublight travel that wasn't crazy engines or magic. I've already got FTL using a different method than the Alcubierre drive, so it wouldn't be used for this purpose. Furthermore, I postulate that the power requirements for such usage aren't attainable.

What, if anything, changes when the Alcubierre is only used at around 10% the speed of light? Does this change at other percentages?

I envisitioned the Alcubierre drive in this manner acting as a "Cruise mode" for travel within star systems. Plot your course, hit the drive and let autopilot take care of the rest.

Your sensors can detect other objects in the system and you can broadcast your path so collisions can be avoided. Furthermore, emergency safeties will drop the drive before any collision would occur.

Furthermore I assume that when you cease using the drive, the craft that was using it is no has a forward velocity. Clarification on this, if any would be helpful.

• What changes compared to what? An observer at rest? An 'FTL' hyperdrive? Aug 28, 2015 at 2:32
• if the user initiate the warp field and moved 100AU at 0.1c locally before turning off the field, the user would have covered a substantial distance let's say 100000AU inferring that the hat-shaped bubble of space carrying the spacecraft is moving at astonishing 100c (of course I'm exaggerating [now blushing...]) or do you actually mean the ship's velocity is 0.0001c so you'll get 0.1c when the field is on... which is which? Aug 28, 2015 at 7:18
• The behavior of the spaceship stopping when exiting warp like in Star Trek has been firmly ingrained in our brains, but the reality is that stopping that quickly would require just as much energy as it took to arrive at top speed in the first place, and in such a short interval, you'd need an "anti-inertia" drive onboard so you don't kill all its crew, which is perhaps even more science fiction than moving at 10% the speed of light.
– Neil
Aug 28, 2015 at 9:11
• Dropping the field abruptly while your ship is traveling at any constant speed including 0.0001c you will definitely experience reverse spaghettification as the space quickly return to normal and in your case congrats you had experienced Heat Death first hand [blushing again]ðŸ˜³ Aug 28, 2015 at 10:34
• @Neil That's what the inertial dampeners are for! I seem to recall reading somewhere (might have been on Memory Alpha) that if the inertial dampeners were to fail in a StarTrek-universe vessel, it would essentially be stuck at its current speed because any non-trivial change of velocity (or, we can probably assume, any significant course/vector change) would turn the crew into wet blobs on a wall.
– user
Aug 28, 2015 at 10:57

What changes occur at less than the speed of light?

To the best of my knowledge: not much.

In fact, NASA's Alcubierre plans explicitly involve cruising about at less than the speed of light before the main act. It's a case of not running before you can walk.

Also, forward velocity is required. My understanding was that you'd need some forward velocity when using the Alcubierre. If you didn't, you'd need to move the space you are in the entire distance of your travel with you. Conservation of momentum will require you to keep that velocity when exiting warp.

The drive itself should not have any differences between speeds but still might not be practical near planets and space stations.

The alcubierre drive warps spacetime so that the ship never moves relative to the 'bubble' it creates. So when the drive is switched off your velocity can be zero! This is not all good though, if you stop near a planet (which you probably are most of the time) the ship will fall toward the planet as you don't have the velocity to be able to orbit it. You would need a normal (Usual called sublight in books) drive to get your velocity high enough to be in a stable orbit around the planet. As you mentioned this would probably be automated.

To dock to a space station you would want maneuvering thrusters to allow you to make the small changes needed to align with the docking port. (Also the Alcubierre drive would destory the space station if it was turned on when you approached it.)

The big difference is you don't violate causality.

However, you still manipulate enough energy to destroy the star several times over (where does it come from?), and dragging the space warp around the solar system will destabilize all the orbits.