Small Fission reactor radiator waste heat as a buoyancy source for a very large balloon probe
Small fission reactor radiator heats balloon probe atmosphere with the radiator waste heat and provides electricity to probe science mission.This augments day/night solar incident energy that informs the balloon probe daily gain and loss of attitude.
May work well in very cold and dense atmosphere of Titan and the outer planets where the temperature difference of the gondola heated by the small fission reactor radiator provides greater lift (?)useful on Venus nigh time.
Balloon surface area could be insulated to retain fission reactor heat?
electrical power not used by science instruments could augment waste heat in balloon buoyancy which is important as this is a very high mass system!
very large balloon probe delivered by the Dragon docked to a uncrewed Soyuz or Progress capsule