Gravity is an issue for mirror production. But it is far less of an issue than tension and deformation during the months- to years-long cooling of the substrate. The temperature and environment control to do that is challenging on earth, fairly impossible in space. Except with maybe a really really huge spacestation as a thermal sink, which we won't get for the next few hundred years I'd guess...
Aren't the terrestrial mirrors so thick due to the need to survive all the tilting under the strong terrestrial gravity ?
I would assume a micro gravity only mirror could be much thinner & thus easier to cool down. Or possible alternative techniques could be used to get the needed reflective surface geometry if it does not need to take gravity and atmosphere into account.
Yes, but stability against vibration and thermally induced warping is also important. So you could make the mirror thinner than on the ground, but not really thin.
I've read a novel from Daniel Suarez titled Delta-v. Chapter 31, Alchemist beginning on page 175 and ending on 177 changed my assumptions about that. With not that much suspension of disbelief. It's about chemical vapor deposition at large scale, the chapter, not the whole book. That is about near term asteroid mining.
