How could combat involving Alcubierre-drive starships occur?

Question

In a setting with Alcubierre-drive starships (as per my answer here), it is inevitable that once the technology becomes common enough and enough different polities and organizations have such ships, that conflicts will arise that may have no mutually satisfactory outcome, such that people will consider combat with such ships to be an acceptable risk.

However, how could combat occur between two or more Alcubierre-drive ships? How could a planet/star system defend itself against attackers with Alcubierre-drive ships? How could an Alcubierre-drive ship attack a body in normal-space? How could an Alcubierre-drive ship in flight even be detected?

In short, is combat or warfare involving Alcubierre-drive starships possible, and if so, how?

Answer 1

Create an interference pattern in the space time wavefront.

If I've understood correctly, an Alcubierre drive works by creating a negative wavefront in spacetime in front of the ship and a positive one behind. This moves spacetime around an insulated bubble of space, within which the ship can ride.

Because spacetime moves around the ship it's not possible to hit the ship directly. Any bomb or bullet will simply be warped around the back.

Perturbing the wavefront should differentially affect the speed at which spacetime flows around the bubble, distorting it's shape.

Distorting the leading wavefront in the middle might split the bubble in two. Creating an interference pattern should fragment the bubble and it's contents into many rapidly decelerating parts.

An Alcubierre drive missile.

The weapon would generate its own space time wavefront or series of wavefronts which, upon striking the gradient generated by the warping ship, would interfere with said gradient, just as a two ocean waves cancel or build upon each other.

A single strike might distort the bubble. Two simultaneous strikes might create chaotic interference patterns. This would fragment the spacetime bubble as the flow was redirected into the bubble, causing different regions of the bubble to move at different speeds.

It would be an elegant but messy way to die. The spacetime in which you stand literally torn to pieces.

It would also have the advantage of being fast enough to strike a ship in flight, provided you could solve the targeting issues, perhaps by firing along the direction of travel.

A weaponised Alcubierre drive

Of course such a weapon would be extremely dangerous. Because nothing can approach the drive itself you could fire it right through a planet for example.

Answer 2

Anything is possible. This post assumes an Earth-like technology with basically just space-enabled technology. So space-missiles, space-ships, space-mines, etc.

---

Possible the most effective way to attack an Alcubierre drive ship is to attack it's end point. The Wikipedia article taking about the Alcubierre drive talks about how to travel at very fast speeds using it, you need to begin the process of that travel as many years before as the destination is lightyears away.

Allen Everett and Thomas Roman comment that Krasnikov's finding "does not mean that Alcubierre bubbles, if it were possible to create them, could not be used as a means of superluminal travel. It only means that the actions required to change the metric and create the bubble must be taken beforehand by some observer whose forward light cone contains the entire trajectory of the bubble." For example, if one wanted to travel to Deneb (2,600 light years away) and arrive less than 2,600 years in the future according to external clocks, it would be required that someone had already begun work on warping the space from Earth to Deneb at least 2,600 years ago, in which case "A spaceship appropriately located with respect to the bubble trajectory could then choose to enter the bubble, rather like a passenger catching a passing trolley car, and thus make the superluminal journey."

So if one knew where the ship would end up, one could set-up an attack on the destination.

One could also send a projectile into "the bubble." The missile will then either hit the ship during travel or immediately after it arrives. This would not prevent a ship from arriving, necessarily, but it would likely prevent it from doing anything.

---

This rest of this post assumes that the "bubble" of space-time created by the Alcubierre-drive does not push all space away from it, so that only the space "native" (i.e. in the bubble when it was created) ever actually enters the bubble. If this is the case, sabotage would be required to attack an Alcubierre-drive ship in-flight.

The most effective way to attack/defend a moving Alcubierre-drive ship would be a mine that attached to the ship. An Alcubierre-drive still requires the ship to pass over all the space it travels through, it just does so at a very fast rate.

Another way is to send a projectile into path of "the bubble" (see quote above) that the ship will be traveling through. It would have to travel along the same route of the ship, but in the opposite direction, because estimation of an Alcubierre ship's position would be difficult to impossible.

Wikipedia says that the above to methods could work, because

A paper by José Natário published in 2002 argues that crew members could not control, steer or stop the ship because the ship could not send signals to the front of the bubble.

So even if they knew the mine was in their path while in the bubble, they could do nothing to prevent the inevitable explosion. This might result in the sending out of "dummy ships" to blow up mines and missiles before the main, expensive ship comes.

Answer 3

tl;dr: Disable their drive

Something that wasn't mentioned in other answers is the possibility of limiting the use or disabling the drive.

For example, in Star Wars the Interdictor Class Star Destroyer has gravity generators to stop jumps to hyperspace.

Considering that an alcubierre drive inherently requires warping space time, and gravity is the essentially the slope of space time, if the drive is possible, gravity generators are possible as well. Otherwise, something along the lines of Ion or EMP weapons could feasibly disable the drive. I would also expect a device as complex as an Alcubierre drive could be put out of commission by simply ramming the other vessel and knocking something out of alignment, either with the drive or the geometry of the ship.

Combat at warp with an Alcubierre Drive wouldn't involve dogfighting and bombardment.

I would presume that the warp speed depends on some kind of power to weight ratio similar to how the top speed of a plane depends on the power to weight ratio. The Star trek universe implies that more power means a higher maximum warp. Easy solution: a missile simply has a relatively bigger warp drive. And to borrow from Star Trek, the warp core of the missile can double as the payload.

... when the USS Equinox powered its warp drive with energy derived from the corpses of nucleogenic lifeforms, an increase of 0.03% was added to the warp factor ...

It would be difficult (by current standards) to aim of course, but the warping ship would be moving in a straight, and therefore predictable, line. If a missile can go faster than the ship it can intercept it. An Alcubierre-drive ship could feasibly shoot at a ship in normal space as well, it would just require extremely tight timing.

One issue with warp drives is they often can't be used in close proximity to a gravity well. I'd expect the ships to have a minimum safe distance. A planetary defense system would defend against warp capable ships as it would against any other. Missiles at warp could be an exception, and especially dangerous. Technically they're not moving, the space around them is so there may not actually be any air resistance to burn them up in the atmosphere, and they would impact the planet with an incredible force. They wouldn't be a precision weapon at all, and really only used for genocide.

As far as detecting a ship in flight, there is currently a prototype detector called the White–Juday warp-field interferometer. A perimeter of sensors around the solar system may work, it takes at least 2.5 hours for an object at the speed of light to get from neptune's orbit to the earth's orbit, so that may be enough time to fire missiles at it, or prepare for its arrival.

Answer 4

Ignoring the fact mentioned by DonyorM that the travel must be prepared well in advance, and supposing that ADSS (Alcubierre Drive SpaceShips) behave more in the style of Star Trek where the Captain is able to order changes when in FTL, or enter or leave FTL at will, combat involving ADSS would be a bit weird.

On one hand, it is almost impossible that two ADSS would ever get a combat between them. They are faster than any signal, so it is impossible to detect them from the front. You can only see them from behind or by side, and in these cases they are so fast that would be a waste just to try to follow them to engage, even having an ADSS on your own. Just a fraction of a second while you think after a sudden maneuver of the other ship, and they are millions of kilometers away from where you though they are.

On the other hand, they are very useful as weapons against slower than light targets like starbases and planets. They arrive almost undetected in order to bomb, deploy troops, or whatever other action you can imagine for airborne troops/parachute troops or the air force.