A short story about a gaffer - this guys job is to maintain/repair the star system that is used to fake out the residents on rocket ships. Cool job.
As he looks in the windows of the various ships, he sees 'civilization' at different phases. One has regressed to the bronze age, another is somewhere in the industrial revolution, one is modern and into science, etc.
The ships were built to seed other planets, Earth was doomed or something so these planet sized things were the way out. but they never launched.
A fake star system was built that looks real to the inhabitants over their heads, but they aren't actually going anywhere.
I have no idea how it ends - was the science ship close to figuring out the secret?
I read this in a collection of short stories in the mid 90's, late 80's. It was in one of those best of/hugo/nebula compilation books so it should be a known story but I can't find any trace of it. (It could be much older than 90's though as I believe the same book had the A.C. Clarke story; The Nine Billion Names of God)