I just read Heinlein’s novella Universe, about an interstellar world-ship gone horribly wrong, and found it fascinating. It was collected in The Science Fiction Hall of Fame, Volume Two A, edited by Ben Bova. I’m wondering if RAH ever continued or expanded on this story, which ends in a rather dangling way that is artistically right but left me wanting more.

The sequel to Universe is Common Sense. Both are collected in Orphans of the Sky, available from Amazon.

There was a brief mention of the discovery of the descendants of Orphans of the Sky in Time Enough for Love

For me "Common Sense" is a letdown from "Universe," to the extent that I agree with Panshin's evaluation (Heinlein in Dimension, page 26): "Heinlein concludes with a catalog of the bits of luck that enable them to be successful. The catalog is three pages long. This is not excusable." Maybe if he'd written the sequel later in his career, it might have been better developed - but as it stands, "Universe" is much the stronger story.

A few other Science Fiction Hall of Fame novellas have what could be classified as sequels or prequels. I learned many years later that Eric Frank Russell's "...And Then There Were None" was the last in a sequence of "Great Explosion" stories later published together in one book, although it stands beautifully on its own. Also, in volume 2B, there's James Schmitz' "The Witches of Karres"; in that case I'd read the 1966 novel first, so I never had the chance to experience the novella on its own (it has a few minor differences from the novel, near the end). Also in volume 2A is Jack Williamson's "With Folded Hands," which I first came across in a Silverberg-edited anthology, Men and Machines, in the early '70s - it has a novel-length quasi-sequel with none of the same (human) characters, The Humanoids. (In both books, "With Folded Hands" appears at the end - as it must; how do you follow an ending like that?)