What is Khonshu Alpha?
Khonshu Alpha is a spacecraft. A vast, colossal starship the size of a small country.
It is a generation ship, designed to carry a whole civilization across the void between the stars. FTL doesn't exist in this universe, so Khonshu Alpha was equipped with everything it needed to maintain life and civilization for years, centuries, even millennia if need be. The population, crew and passengers, probably numbered in the millions.
The Major Malfunction
At some point in the Khonshu's journey, something went wrong. The ship's systems began to fail, and there were mass casualties, including most of the crew. The ship systems were functional enough to keep basic life support working, but most other services were spotty at best. Soon, the advanced technological society aboard the ship fell apart, and passengers began to band together to survive.
The ship continued on for centuries. Over the years, knowledge of technology and history was lost, and the survivors formed primitive, tribal societies. Most denizens of the ship don't even know they're aboard a starship.
They only know that they once lived in Paradise, but were punished with the Major Malfunction for their sins, and now have to eke out a living.
The players will be among the few brave (or foolhardy) enough to start exploring, discovering the nature of their world, and perhaps even starting to restore it.
Also, his other RPG: Gamma World – https://en.wikipedia.org/wiki/Gamma_World
There are also some fictional inspirations, including Brian Aldiss' Non-Stop, the absolutely terrible TV show The Starlost, and that one Star Trek episode – For the World is Hollow and I Have Touched the Sky. Lots of others as well.