Darths & Droids

Launching things at ludicrous speed is a classic way of damaging targets. So much so that people have even come up with ways to do it in Dungeons & Dragons 5th Edition, using nothing more than the rules as written and a bit of a sideways squint that ignores actual physics: the peasant railgun.

To summarise briefly for those who don't care to click:

Hire 2280 peasants and get them to stand in a line. D&D rules say each peasant occupies a space 5 feet square, so the line stretches for 2 miles. (Good lord, give me the metric system, please.)
Hand the first peasant an object. Have all the other peasants take a Ready action, which triggers on them receiving the object and specifies that in response they will pass it to the next peasant in line.
Peasant 1 hands the object to Peasant 2. Peasant 2's Ready action triggers, and they hand it to Peasant 3.
And so on...
Because of the way Ready actions work in the rules, all of the peasants' Ready actions trigger and complete before the end of the 6-second combat round.
The object therefore gets passed from Peasant 1 to Peasant 2280 in under 6 seconds.
This means the object travelled 2 miles in 6 seconds, or an average speed of 1200 miles per hour. (This is kind of where most analyses end, but if you figure that the object accelerated uniformly from rest, then its final speed will be twice as much. Not that it makes much difference.)
Peasant 2280 lets the object go and it flies towards whatever you've aimed your peasants at.
In the canonical peasant railgun, the object is a 10-foot wooden pole weighing 7 pounds. If you calculate the damage it causes using the falling objects velocity rule, it does 300d6 damage (at 1200 miles per hour).
Next round you can give Peasant 1 another object and all the other peasants can retake their Ready actions. So you can reload and fire the railgun every 12 seconds.

Not to be satisfied with merely breaking the sound barrier, if you get just over a million peasants you can totally fling that object faster than the speed of light.

If you're a player and try to implement this in your game, arguing that the rules as written allow it, then your DM is totally justified in slapping you down with a 10-foot pole.

Commentary by memnarch (who has not seen the movie)

Wait, why can't someone fly a star cruiser remotely? Aesthetics of space piloting aside, computers basically do all the calculations for hyperjumps along with running most of the rest of the ship, right? Sure, people might make all of the decisions when something happens, but in this case it's like saying someone needs to always be in the driver's seat of a car. For fancy flying and racing, sure, people are needed. For flying straight ahead and ramming into something? Just put the equivalent of a stick through the steering wheel and a brick on the accelerator. Something like wiring up the hyperjump switch to a couple of cables attached to an escape pod or shuttle. Escape pod flies out, switch gets closed, and the ship hyperjumps into the target. You've then got the problem of being in a much smaller space ship which may or may not be able to evade the rest of the fleet, but the gigaton (probably more?) explosion from the collision might be enough to damage the rest of the fleet, or at least blind them.

Anyway, if Poe really wants to launch an asteroid that fast? Just throw an asteroid at one end of Snoke's ship before the hyperjump. The ship is big enough to act as a large stick, and even if the ship isn't rigid enough to resist bending, the resulting explosion should be enough to launch the asteroid super fast.

Transcript

Poe: To win more, you gotta bet more. And rig stuff.
Finn: We kind of outstayed our welcome on Canto Bight. What’s going on there?
Poe: Well, we’re going to use the hyperdrive modulator to fly the Radish straight at Snoke’s ship at lightspeed.
Rose: That sounds awesome!
Poe: And use it to power a trebuchet—
Rose: Poe! You don’t need a trebuchet! The Raddus itself will be a hypervelocity kinetic weapon! Snoke’s ship won’t stand a chance.
Poe: Right. I knew that.
Finn: There’s just one problem.
Poe: Yeah. No asteroid flung at 0.999c.
Finn: You can’t fly a star cruiser remotely. Someone needs to be on board to operate the hyperdrive.
Poe: Hmmm.
Finn: Who’s going to do it? It can’t be you.
Poe: Hmmmm...