That's Gonna Leave a Mark

Or, well, not.

I was thinking. The scene in Serenity when Whedon acts like an emotionally abusive yandere, by killing the second of the two beloved characters he kills in that picture, is silly. I said it before, it should've destroyed both ships, and also, why do they have a window?

But I decided to prove it. So I have done the math.

1. Any object moving at 3000 m/s will impact with the force of its own weight in TNT. Reentry velocity is Mach 25, or 8705.25 m/s.
   
   8705.25/3000=2.83575


2. Kinetic energy varies with the square of the velocity.
   
   2.83575²=8.04148


3. I don't know what the Serenity and the Reaver ship's masses are, but it's quite likely they're ludicrously high, just like Star Wars ships' masses. 8 times those ludicrous masses is probably well into the kiloton range.
   
   If that wasn't clear, I'll break it down. Hitting another ship at re-entry velocities is likely to have the same effect as a direct hit from a medium-yield nuclear bomb.

But tell us again how realistic it is, just because the ships don't make noise.

Late addendum: After a perusal of the Firefly wiki, it turns out the Firefly-class is only 158.76 Mg empty weight, which is quite reasonable for a spaceship. However, 8 times that is still 1270 Mg, so it is a low yield nuke (1.27 kT). And besides, we don't know how massive the (much bigger) Reaver ship is.

Also, kudos to whoever noticed spaceships are supposed to be light—the Firefly-class's dimensions are about what you'd expect for an aircraft of its mass, if not even lighter (26th-century materials?). Well done, gentlemen. Now if only the writers weren't hell-bent on wasting your hard work.