900 ft.?
Go on.
Maybe in the Mississippi Delta.
And what would happen if one was to cause a nuclear detonation by a sudden assembly of a nonspherical (shaped charge, like Pac-Man) supercritical mass? If it were possible to focus, say, 10-15% of explosion energy along the beam, one would get a bunker buster.
ROFL - By the time this thing makes it into production, we'll be able to bomb China from underneath...
This can work. Steam pressure must be extremely high. Propulsion by rocket engine. Pressure is high enough to make soil and rock flow as if it were a liquid. About 200,000 psi, maybe.