Sci Fi - Generation ship - not Orphans in the Sky - what's the title?

Question:

Sci Fi - Generation ship - not Orphans in the Sky - what's the title?

Maybe 30 years ago I read a book (could have been a short story or novella) similar to Heinlein's Universe and Common Sense (Orphans in the Sky) but NOT that book. Can't remember the author or title. . . . Passengers in a hollowed-out asteroid don't remember that they're on an interstellar voyage. Outer level is technicians who man the engines and produce manufactured goods. A young man decides to escape via the conveyor belts that take the manufactured goods out of that level to see what else there is ... He finds a level of farmers who call themselves Noahs. Climbs a mountain and finds a trap door into next level. There, people called Rovers produce entertainments meant to enhance "empathy". Finally, at inner level, he discovers the control room and the truth about the voyage. So what is this? Could it be an earlier version of Heinlein's novella? I think not, but I haven't been able to track this novel/story/novella down anywhere!!

Best Answer - Chosen by Asker: It might be "Captive Universe" by Harry Harrison. I've never read it, but I know it's about a generation ship and dates to around that time frame.

"Non-Stop" by Brian Aldiss and "Phoenix Without Ashes" by Edward Bryant (based on the original pilot by Harlan Ellison for "The Starlost") also date to that time, but your description doesn't match my memories of either book.

Hope that helps.