[Merad]

There probably isn't much structural damage to the plane aside from the scraping/grinding on the bottom. Don't misunderstand, that's going to be bad damage - we aren't just talking about scratched paint. But it looks like the pilot set it down soft as a feather, they're definitely a pro.

Planes are so expensive that it's worth putting a lot of money into saving them. A replacement airframe comparable to the B-57 would probably cost $10 million, then you'd probably spend that much again to customize it for NASA mission. Even if they need to spend a couple million dollars fixing the WB-57 it beats the alternative.

Edit: It occurs to me that rather than use a different plane they'd probably reactivate another B-57 from the boneyard - but B-57's have been retired for > 50 years to restoring one would still be a significant project.