One thing that video left me wondering is what happens to the vaporized rock; how are we collecting or transporting it so it doesen't immediately re-solidify, stringify and block the hole?
That's a valid question. As the vaporized rock cools it needs to be directed to the annular walls of the borehole being drilled. If it flutters chaotically up the along the drillstring and sticks itself to the drillstring then you are effectively blocking the borehole as you drill. Even if you rotate the drillstring the cumulative effect is that the drillstring becomes a long length of sandpaper or a vertical grinder, grinding the fused rock from the annulus above where you are currently drilling.
You can see in that very video that it's not even an unsolved problem, it's an unaddressed problem. They currently handwave it away as "vent the molten rock" as if that is a solved problem.
At 6:34 in the video, they very briefly show a running test drill, and then cut immediately to the ceiling of the test chamber with a large specimen of rock wool.
That rock wool will completely clog any mechanism they could come up with. How do you reliably transport rock wool from 20 miles underground to the surface?
This project/company is a dead end unless they could magic away that problem.
It's true that it's not entirely clear but it seems there's a nitrogen gas that pushes the gasses back up ?
It's also not clear how much of the rock mass actually resolididy instead going away as gas but for the part that does, it seems to be do so in a fashion that resembles mineral wool.
