Free from the author via KDP Select @
Amazon: (linkage for the lot)
The Big Ship and the Wise Old Owl by Sarah A. Hoyt (
ISFDB,
Wikipedia), a science fiction novelette originally published in Baen's Going Interstellar anthology in 2012.
Her fantasy short from yesterday is still free, as is her usual Baen Free Library book.
In a generation ship, everyone knows one generation will eventually arrive at the new planet. Everyone knows it, but no one knows how long or how many generations they've been in the ship.
Nia, a ship board engineer finds out in the confines of the ship, society has become too conformist and the leaders too powerful. It is not in their best interests that the ship should arrive or that their charges should ever leave.
Which is why it's a good thing that Nia and her friends can read the clues left in children's rhymes about an old secret deep within the ship.