Hacker News Reader

Comment by marvin | Hacker News Reader

Do you know anything about development work that's been made regarding manufacturing mirrors in space? I'm not thinking assembling them from pieces, I'm thinking more about melting some raw material and using some physical process to create in space something larger.

View on HN

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.

You also need a minimum thickness and stability if you ever want to turn the mirror to point elsewhere.

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.

edit: book -> novel

The manufacturing tolerances for large mirrors are very small, and it seems unlikely that we would be able to do this - note that barely any manufacturing has been done in space.

Assembling from pieces on the other hand, is more doable.

A potentially more interesting solution is liquid metal mirrors, either mercury-based or some sort of ferro-silver suspension managed electromagnetically.

A hollow toroid could be spun to provide force and the liquid would naturally form a parabola.

There've been a few experiments on earth and it could have huge cost saving potential in space. Instead of having to launch a 8m+ solid mirror machined to perfection, you could launch a lightweight toroidal substructure with a vat of reflective liquid at a fraction of the cost.

I wonder if something akin to glassblowing would work in zero-G.

Reply on news.ycombinator.com