I can't remember the title or the author, but I remember reading a story based on a similar premise years ago - the first interstellar ship goes out from Earth to a nearby star, only to barely escape as it goes nova shortly after they arrive. They first think it's just a coincidence, but later suspect that their ship's drive might have been the cause. On their way back home they make up a desperate plan to drop out of FTL drive way out of the solar system to make sure Earth's sun would be safe. This would stretch their supplies, etc. because the flight will now take years instead of months. While traveling they realize that turning on the drive might have had the same effect as turning it off. They stop at the right distance from Earth to catch the light from the time of their departure and observe as the sun goes nova.

This was used in “Another Life” on Netflix.

Any mass moving faster than light and still able to interact with matter that isn't, will necessarily have enough kinetic energy that any warhead would be an afterthought. That also doesn't necessarily improve matters in the Earth impactor case, since shattering a single large impactor without changing its vector only creates many small impactors. Some models make that look a little worse than the status quo ante, while more optimistic ones just say it's exactly as bad, but either way, if the mission is to see that zero rocks hit Earth then it isn't really a win.

I'm more interested in the idea that, the longer your FTL leg, the less well you're able to see where you're going - not that that's likely often necessary for starships any more than for sailing vessels, but you can think of circumstances in which it might matter. Too, it might come to be considered unneighborly to take too direct a course anywhere, lest you inadvertently Kessler-spray your destination.

Insystem use of the drive would be most complicated by this in general, especially since there's rarely much point in visiting stars without lots of rocks around them. You might also not be able to make sharp maneuvers in FTL, hence needing to plan legs with care not only for safety, but to minimize time and reaction mass spent on slow thruster rendezvous maneuvers. This has implications for travel time, navigation in general, and thus implicitly for supply chain logistics, travel time, and thus what's feasible both economically and politically - especially should it coincide with the absence of any FTL comms cheaper and faster than "record a message and then have a packet boat take it where it needs to go".

What I said is about the limit of my knowledge unfortunately.

However here’s the paper from the University of Sidney that goes into much greater detail.

pdf warning https://arxiv.org/pdf/1202.5708v1.pdf

From the paper:

> These results suggest that any ship using an Alcu- bierre warp drive carrying people would need shielding to protect them from potential dangerously blueshifted particles during the journey, and any people at the des- tination would be gamma ray and high energy particle blasted into oblivion due to the extreme blueshifts for P+ region particles.

> We know what happens to matter at those speeds, it becomes infinitely "heavy" and would experience time in relative light-years (I mean time-to-travel at light speeds) no?

I don't think we do know what happens. Relativistic mass approaches infinity at exactly c. Beyond c we obviously have no data, but if we just apply the same equations the relativistic mass would drop back to a finite value. A finite complex value.