A while ago this question on medieval travel was asked. I looked at it again today and it got me thinking about situations that would mandate travel in other settings, in particular what would force individuals to travel across interstellar distances. Obviously the people furnishing the option to travel those distances must themselves be involved so ships' crews are on the list of those who must travel. Also if there is interstellar colonisation then obviously colonists have to travel between the stars to get to new worlds.
So the question becomes; in a society spread across interstellar space what, if any, professions and/or situations, apart from crewing an interstellar vessel or colonising a new world, would absolutely require individuals to travel between worlds?
Good answers will include, and justify, only professions which can't possibly be practiced in a single solar system and situations that can't be resolved without leaving them lightyears behind.
Context notes, the setting has:
- completely safe, but quirky, non-instantaneous FTL Travel (average speed is 4 times the speed of light).
- no independent FTL Communication, the fastest way to get a message anywhere is usually by jumpship. Mailman is a secondary role of all legitimate ships' communication officers.
- travel for individuals is not free but it is, safe, cheap, and almost unrestricted (getting on or off a planet/habitat/station that has warrants out for your arrest is tricky but otherwise travel is normally easy, interstellar warrants are exceedingly rare; they're too awkward to enforce).
- humans are spread across hundreds of lightyears but have only densely colonised the star systems with 15-20 lightyears of Sol.
- large scale [interstellar] conflict is almost unheard of.
- individual star systems tend toward self-sufficiency but there is an overarching military-industrial command economy that ties all the heavily populated worlds together.
- trade in raw materials and fully integrated technological artifacts (like spaceships and orbital habitats and factories made to standard patterns) is reasonably common; this is the main reason that travel for individuals is so cheap and available, moving people is easy when you usually ship things the size of O'Neil cylinders.
- there is still material scarcity, some chemical elements are just too rare to create over supply in the current political-economic climate.
- while leisure time is generally more available most people still work for a living most places, just not as constantly or intensively as in the modern western world in most cases.
Important notes on Jumpships:
space travel is instantaneous for the ships and those aboard them but time still passes in the universe outside so jumping four lightyears is less than the blink of an eye for the ship but takes an average of a year to the rest of the universe. As far as anyone travelling is concerned they are in one place and then instantly at their destination. Single direct jumps are only possible between the closest of star systems but travelling tens of lightyears takes only days for those travelling while decades can go by in the outside universe.
the energy for making jumps is effectively free. It's not actually free, the equipment is expensive to build, and the energy does have to come from somewhere; a bill will be presented in due course. The point is established jumpships don't have to pay for fuel etc... just system maintenance.
jumpships are huge and because any given jump is relatively cheap they often travel below loading capacity, this leaves a lot of space that can be used for modular passenger accommodation at need.