[dmurray]

It makes it all sound like a problem of engineering, not of physics.

It's really hard to vapourize all that rock and suck it out to the surface with a vacuum. But it's really hard in the sense that the vaporised rock might recondense and stick to the sides of the hole, not in the sense that vaporising the rock costs more energy than you get out of the hole in its 30-year lifetime.

[euroderf]

Would it be possible to blow chilled air down the hole that would quickly condense the rock vapor into particulates that don't stick and instead get vacuumed out ?