Space Combat - Framework

Generally speaking New Diasporia is about the background, not about the game system. But for aspects of the game which are either central to the concept or describe technology unique to the game universe it is very difficult to present the background in a way which will allow use of the material without adding game mechanics to the mix. If your preferred game system already has rules or a way in which to incorporate these concepts by all means use them. Game mechanics included here are for those who wish to have a set of rules ready made for the background.
The native game rule set of New Diasporia is GURPS 3rd Edition. Any rules present here are based upon or are variants of that rule set.
The area in which New Diasporia has the largest set of applicable rules is in space combat. Space combat rules are always almost entirely driven by the technology of the game universe. Often that in game technology is driven by the feel of the space combat experience desired by the creator. So for example, Traveller most closely resembles the age of battleships, while a game like Full Thrust or Star Wars D6 fulling incorporates fighter combat, like modern naval warfare.
As for GURPS, over the years GURPS has incorporated a number of different space combat rule sets. GURPS Compendium II introduced the Space Opera Combat System and the Abstract Space Combat System. GURPS Space has its own, slightly more detailed abstract space combat system. GURPS Traveller used a hex grid based combat system, optimized for the Traveller universe. GURPS Space has a sidebar conversion to allow the use of the GT hex system with GURPS Space. All of these systems are predicated on very low spacecraft acceleration, 6 Gs or less for GURPS Traveller.
I find the GURPS Traveller Rules the most useful after modifications. Each hex is 10,000 miles across. Time scale for each round is reduced from 20 minutes to 1 minute. Vessels traveling at >50 Gs acceleration tend to pass outside of effective combat range very quickly. Capital ship energy weapons have ranges in the 40,000 to 80,000 mile range. Missiles tend to have longer ranges, in the 1,000,000 mile range for a single stage missile and many times that for a multiple stage missile.
Classes of combat ships follow.