# Opal Mining Town in Australia #

I have used a 1 meter Fresnel lens to melt rock into lava, so sunlight can indeed be used for process heat. Whether you'd be able to vary the focal length in order to create a tunnel is a different question. I have read a short story (perhaps by Mike Combs?) in which a tunnel was dug to the center of an asteroid, and ice placed in the center, then the whole rock heated with concentrated sunlight until it became molten and the ice flashed into steam, making a huge pressure vessel from the ex-asteroid; similar processes might be used to tunnel through rock on the moon or Mars. Ed

Received: Thursday, November 13, 2008, 10:33 AM

I wonder if the availability of 1350 watts/m^2 in space is sufficient for a parabolic reflector to melt its way thru rock, providing both a tunnel and sealing the surface of the tunnel rock for pressure containment? Such mirrors would be a great deal lighter than rock boring, mechanical equipment but at the same time, it would be limited to line of sight,ie, you could only melt the tunnel in a straight line. Still, that might be sufficient for a basic Lunar site.

Gary 7