Divergence

As originally stated though the background for New Diasporia can be applied to any game system, the game itself was developed using GURPS, primarily 3rd Edition, especially some of the Traveller rules, but also GURPS Space. Here and there other GURPS source book rules are used. Some rules come from GURPS 4th Edition, though modified for use with the 3rd Edition rules.
I have also stated that there are fundamentals of the GURPS Rule set, primarily in Tech Levels, Tech Level advancement and maintenance rules which have been modified, primarily to support the background but also because they don't work reasonably as originally constructed.
During the original playtest for GURPS Traveller it was noted that the rules for missiles and spinal mounts resulted in missiles dominating, a circumstance that did not well reflect the original Traveller material. Several rule modifications were introduced to mitigate this, but resulted in other problems vis a vis ship survivability against spinal mounts.
In New Diasporia this is not so much a problem. Traveller Meson weapons do not exist and particle weapons are primarily relegated to close support planetary use. While Laser and Grazer weapons are used, especially in the close support and anti-missile roles space combat is dominated by missiles.
That is real space combat is dominated by missiles. Subspace combat is another story. In subspace missile drives propel a missile not faster than other B/G powered vessels, making missiles ineffective. Subspace combat is heavily dominated by energy weapons which have very much reduced ranges, just as do sensors.
A variety of energy weapon sizes are available for use on spacecraft. Lasers and Grazers typically mounted in turrets (1500 cuft for turret space, 500 cuft for mounts and rotation space.) New Diasporia turrets typically do not contain crew spaces. Weapons may also be mounted in barbettes. Barbettes come in 2500 cutft and 5000 cuft versions which require 500 cuft and 1000 cuft of internal volume for mounts and rotation space respectively.
Smaller turrets can also be used for close support weapons (which in Traveller are called planetary weapons), but such weapons are typically only mounted on battleriders and small craft like pinnaces.
Weapons may also be fix mounted. Missile tubes may be fixed mounted individually or they may be mounted in missile bays. Missile bays typically come in 25,000 cuft and 50,000 cuft sizes. The difference in fixed mounted weapons and weapons mounted in a bay is that a weapon bay includes a targeting computer and laser communications links sufficient all of its launchers. Fixed mounted weapons must use an external computer with the proper software and a separate communication suite, which is probably mounted in a turret somewhere.
It is also possible to fix mount an energy weapon, but only the battleriders use spinal mounted energy weapons, typically heavily supplemented by missile tubes for use in the anti-missile role. A fixed mounted energy weapon cannot be used in the anti-missile role.