Oolite Bulletins

I'm trying to make a ship that will only be available to the player, and not spawn in the Ooniverse. How do I ensure that won't happen?

Don't give the ship any roles in shipdata.plist other than 'player'. Without any other roles defined, Oolite should ignore the ship completely. If you also don't want it to show up in shipyards, then set the chance at zero in shipyard.plist. You can still give yourself the ship via saved-game editing or a new custom startup in Oolite.