I'm afraid I'm going to be in the minority on this one.
I like Ken Liu's stories. But this just seemed, well, contrived. Specifically, contrived to tell a story about tragic Japanese self-sacrifice over American can-do optimism.
That's not my issue with the story. It's that it falls apart on basic science grounds. And when someone without a even a BS can see that, you've got a problem.
First, not only is the idea of a hat-trick killer asteroid beyond improbable, it strikes me as unlikely that a society that could build reasonably viable interstellar spacecraft couldn't deflect that rock. Because, really, *that's* easier. We have things now - rockets, nuclear weapons (No, not to blow it up, just nudge it), etc - that could do the job.
Second, I have trouble buying a tear in a solar sail small enough to be barely noticed and still be repairable, and yet still being able to affect the navigation of the ship. You can't really have both.
Third, - really, NO ONE else could navigate the struts? Because I know what I'd start training on Day 2 of the journey - repair crews. Because you're going to need them.
Lastly, because it was a Ken Liu story, I knew the second there was a tear in the sail where this was headed. Of course he'd have to sacrifice his fuel and hence his life - handy, that fuel - in saving the ship. Because he left the ship without a belaying line (frankly, I'd have less trouble believing he'd run out of air than have to use the fuel to recharge the torch).
Sorry.