In article ,
Rand Simberg wrote:
What are the limits? Could a 100m diameter optical telescope be built?

Possibly, but there'd be little point, since you can get equivalent
resolution with multiple-mirror systems.

Actually, there are groups working on concepts for a 100m ground-based
telescope, notably the European OWL project. The main mirror *is*
segmented, but apparently there are practical advantages in having a
single filled aperture rather than a wide scattering of smaller mirrors.

There's no reason why you couldn't build an OWL in space, although it
would be an expensive project if it used current infrastructure.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |