I can recommend Classic
Traveller from my own experience with it, and
Traveller+ (a freely available points-based character creation and combat system) which is
adapted for online play and made to complement Classic
Traveller. (It has certainly worked well enough for me...)
Classic
Traveller is still considered a commercial product, so I can't speak much more than to tell you that {your favorite search engine} is your friend.
Traveller+ is freely available - see
Traveller System Resources in
Heaven - Gaming Resources. for the link to the Crucible Highport (in Stuff).
Traveller is a classless system, but its normal character creation rules have characters descending from one branch of service or another (Navy, Marines, Army, Scouts, Merchants, Other)
Traveller+ greatly streamlines the character creation process, taking what was a "roll dice for stats and skills" system and converting it to a build points system which goes much faster and allows much greater flexibility (in my own humble opinion).
There are literally tonnes of online resources (including star maps of entire vast areas of space in the
Traveller Universe) available for free out there in cyberspace.
No matter what version of
Traveller you wind up using, the basic mechanic is to roll 2d6 against a Difficulty to accomplish a Task. Base difficulty is 8+ (meaning that 8 or better succeeds) for most average Tasks. Skills modify Task rolls, and environmental and other external factors modify the Difficulty rating. It's pretty much dead simple, mechanics-wise.
It sounds from the description of your game concept so far as if you may find
Traveller tech levels to be a bit low to meet your needs, but that may just be my take on it.
What subsequent versions of
Traveller treat on to some advantage is clarifying the Task system (
MegaTraveller started this trend), and giving much more detail to the Referee (
Traveller-speak for the GM) about the "Official"
Traveller Universe.
This is just my two Credits worth, and I'm admittedly an enthusiastic
Traveller fan-boi, so factor that in and keep a small Siberian Salt Mine
TM in your hip pocket.
EDIT:
QUESTION: What sort of ship technologies are you considering as standard in your game?
Traveller uses a "Jump Drive" for FTL transits that has a well-specified mechanic. This may not fit in with your vision. What I have done for games that don't fit that profile is whip up my own mechanics for alternate technologies, but that may not be something you'd want to do.
POSSIBLE ANSWERS TO YOUR BONUS QUESTION:
Another system that may work better? Look at Cortex or Cortex Plus (both commercial products), or even Tri-Stat dX (a free system). You'll probably wind up doing a lot of legwork no matter which system you use.
If space combat is a large part of your game, you may wish to look at
Full Thrust (a starship combat system which uses miniatures) as a jumping off point for some good ideas.
Good Hunting, and may the dice always treat you kindly.
This message was last edited by the user at 04:14, Thu 16 Mar 2017.