I thought I'd just pop in and point out that Babylon 5, Second Edition has some pretty interesting things to note as hard SF:
=COMBAT
- Unified ground combat, aerial, and space combat rules.
- Enough info is given for ships to allow for minis play (using the B5 Call to Arms wargaming rules)
- Can be run gridless and still make sense.
- Works just as well for capital ships and fighters.
- Can be simplified further if you want to gloss over a battle.
=ROLE-PLAYING
- Influence and contacts mechanic allows for sophisticated politics.
- Core classes include soldier, agent, diplomat, officer, scientist. There are others but these are interesting from the OP perspective.
- Hit Points are scarce; most characters get one or two a level. Good for grittier play.
- Weapons are reasonably realistic and priced.
- Telepathy (psionics) is written in a way that allows it to be ignored.
= COMBAT OVERVIEW
Basically, each commander gets a certain number of orders per round (based on level+feats, NPC ships can just use crew quality).
When not using a grid, range is short, long, or sensor range. Orders like "close in" and "pull back" change your range and available weapons. Orders include things like "fire at will", "get those systems back on line", "launch fighters", and so forth; all of these get resolved by some appropriate skill check (such as pilot, operations(gunnery), and so forth).
The thing that works well here is that large fleets don't bog things down, and that all the players can be involved whether on the same capital ship or in individual fighters. This is something that I've never seen done smoothly before.
Having ship stats that work for wargaming mode is also very handy; it allows to shift back and forth as practicality and desire dictate - you can run an epic battle using the gridless mode and shift to the minis for the dramatic finale.
