I've now played your game for some time, and here's what I think.
The game idea is great and the implementation is also very good. I didn't manage to break the gameplay in almost any way, so it seems to also be pretty bug free.
Also, your graphics are beautiful and in my opinion, the art style is perfect for a game like this. The game runs pretty smoothly despite the huge amount of actors used, so it's also coded-well. Only time when the framerate dropped more was when I was using the biggest radar diameter.
Is one supposed to be able to drill left or right when flying in a high vertical tunnel? Sometimes I was able to do that, but most times I wasn't. It should be fixed to work consistently, otherwise it'll look like a bug.
Another thing was that sometimes when I dug straight down, the machine turned red as if it took fall damage even though I only fell one block.
And by the way, just asking, is the hull supposed to take damage from every fall from too high, so that one would need to fix it every now and then? Or have I misunderstood the concept of the hull? I'm just curious, because I'm not quite sure of its function in the game.
Anyway, you've done great job and the game plays, looks and sounds very good already. Can't wait for the final release!
Keep up the good work!