@nyrath I'm working on a story that includes a sleeper torchship. Back of the napkin thrust at 1G puts 35 days of accelerating, 300 years of drifting, and 35 days of accelerating as a reasonable way to not need to pack a large moon's worth of argon as reaction mass in order to travel 20 ly. I'm thinking of a hull number of NRV-95-NEP as the story's main ship's designation... A Shelley class ship, with the class named after NRV-1, The Mary Shelley, with the class's hull numbers shifting to NRV-xx-NEV due to buerocracy (and the recent real-world NASA announcement/fantasy of a trans-martian ship using an ion drive that is electrically powered by a fission reactor (and all the power efficiencies be damned)). In universe, the laying of the hull NRV-07-NEV, named the A C Clarke... (and just before the launch of The M Shelley) would be given the "Nuclear Electric Vessel" (NEV) sub-designation due to the fact that, up to that point in Earth's future history, ships with nuclear reactors have the "NEV" designation, and bureaucrats don't want to create a new designation system without a legislative body approving it. So the fact that reaction mass passed through a reactor's core would become ionized means it's an "electric" system... The sub-designation of the Shelley class ships would change from Nuclear Electric Vessel sometime after the laying of the hull NRV-22-NEV, The P Anderson, to NRV-23-NEP, the colony torchship R A Wilson, a ship with the sub-designation of Nuclear Electric Propulsion. And thanks to this change, and the fact that these will be chartered (rich people's) colony ships, the yard workers in medium orbit would call future Shelley class NRV-xx-NEP ships "nepo ships."