Here is an evolving alternate system for spaceship combat in Traveller.
For combat out in space with really big ships I’d revert to the normal rules from the Class Traveller Book 2. These rules are intended to small ship combat — dogfights and close-quarters combat. For example, fighting while flying around in caverns inside and asteroid. The idea is to great a system that is more cinematic, recreating the fun of ship battles in Star Wars and similar films and TV shows.
I assume a very abstract time frame. We go by turns, all action happening simultaneously as is the Traveller norm. But no defined time increments. No defined speed either. Ships move in increments defined by their maneuver drives. Just imagine the Millennium Falcon fighting inside the Deathstar II. Things happen fast. How fast? Well, just fast. That’s all you need to know.
Each ship can move as many units (squares or hexes) as its maneuver drive number. Any difficult maneuvers require a pilot skill roll. A hit by lasers inflicts 1d6 damage points. When a ship takes 6 damage points, it has to roll on the normal damage tables in the books. So it is possible for a single hit to require a by-the-book damage roll. It’s also possible to take less damage in a single hit, but the damage accumulates. Will decide soon on different modifiers for different weapons – beam vs. pulse lasers, missiles, etc. Some very small craft, like mining pods might have only 6 possible damage points they can take, so 6 points destroys them. A fighter might have 12, but be very maneuverable and fast.
By thinking of the whole thing in more cinematic terms and using this very fast moving system the players can all be involved in the fight and use their relevant skills. Example from Into the Void, Game 7. While Roger was skimming the walls of the mine cavern walls, Barney was working to boost the slow Free Trader’s maneuver drive power to better deal with the very fast mining pods. Meanwhile, Flint and Lucky were manning the two laser turrets and blowing up the pods.
Keep in mind we are trying to have a fun ship fight using this system, not a tactical wargame. The goal is to make ship combat something that in integrated into the rest of the RPG, not like tacking a wargame on to the RPG.