Curious Idea. Using a projectile made of ice at high velocity to make precision welds. I don't know how they intend to accelerate the Ice Bullet. Sure would make installing the floor pans nice.

http://www.newscientisttech.com/article/dn11003-invention-

I've actuall been to the facilities at OSU. Sounds like a development from the Edison Welding institute.

Sounds like this is a variation on "stir welding"

Check this link

Stir Welding

I think this is how valves are welded to the valve shank. One piece is turns very fast (using a flywheel) and pressed hard against the other part. Friction heats up both parts and they weld themselves together. Dissimiliar metals can be welded this way.