I don't know if I'm the only one (though I doubt it), but while looking at the Rogue Trader (and, later, Battlefleet Gothic) art of space battles and starships dramatically facing off in fleets or side by side and firing at each other like sea ships of old, I realized something...
Those never happen within the actual game. If you (as I) want these kinds of space battles to occur, you really, REALLY, need to nerf the scale of space combat. And while doing so, you may also fix a couple physics issues with the game, too.
The problem is, the Rogue Trader starship rules (which are actually based on Battlefleet Gothic rules and scale) state that 1 VU is equal to 10,000 km, and most weapons have ranges averaging 6 VUs (which means they fire up to 12, so thats 120,000 km) If that is so, space combat would almost never (probably 99% of the time) occur at the ranges shown in the art. Indeed, even at point blank range (1 VU away) your art should depict one ship only, and its opponent, even a 6km long ship, would only be a speck in the distance, even less visible than the stars in the background. Furthermore, the 1% of the time ship would actually fire at each other at those ranges would really be just a snapshot frame of the battle, and thats because of the ship's speed.
Have you noticed that if a ship has a speed of 10 (not even the fastest a ship can go), it goes at 200,000 kph (10 VU per 30 minutes). That's over 55 km PER SECOND, so unless the two ships have exactly the same speed and exactly the same course, even the slightest derivation would mean they would be out of sight in a matter of seconds, not to mention if they were going in opposite directions! The question of speed also brings a couple problems.
If your target is at range 6 (60,000 km away) and is going at speed 10 (200,000 kph), do you realise just how fast your macrobatteries ordnance need to be shot at in order to have even the slightest chance to hit your target? A bullet shot by a gun goes a couple thousand kph, but I know that's really not the same scale, and thats against atmosphere. But lets say the ordnance is shot at FIVE MILLION kph. By comparison, a moreton wave, essentially the shockwave on the surface of the sun resulting from solar flares, which are deflagrations that would easily vaporise the entire Earth, travels at around 3.6 million kph (so that's insanely fast, and probably unachievable by any sort of solid projectile battery, even in the 41st millenium, but lets say they can) At that speed, the ordnance travels at nearly 1,400 km per second. Our target is moving 55km per second, so the batteries would anticipate and fire ahead of course, but even at that ordnance speed, it would take more that 43 seconds for a shot to reach the target! So the thing is, if a ship is making any kind of evasive manoeuvres (by that, I mean adjusting either speed or heading by even 1% or 1 degree in any direction, and although I agree the ships aren't manoeuvrable at all, they still can go from 200,000 kph to a full stop or any speed in between within 30 minutes, and/or make at least one full 90 degrees turn within that timeframe, so it clearly is possible), they would evade the shots by several kilometers! Even if you shoot a lot, and with ships that aren't that manoeuvrable, with these kinds of scales, it really becomes nearly impossible for solid projectile batteries to hit.
Even worse though is the idea of ships ramming! At those speeds, that clearly becomes next to impossible, and if it should happen, the results would be cataclysmic! Lets take a small raider with a mass of 5 megatons (that's 5,000,000,000 kg) and moving at speed 10 (that's 200,000 kph) who rams a stationary ship (so its actually possible to hit it). The frigate would probably get slightly damaged by that action as well, seeing as the collision would generate kinetic energy of over 6 GIGATONS of TNT (so yeah, more than 300 20 megaton nukes all in one go), probably more than enough utterly destroy both ships in the process. Clearly, you can forget about the subsequent boarding actions...
Anyways, while I know starships have to be able to go at these kinds of speeds, and faster, to travel between planets in a solar system, it is clear that combat should occur at much slower speeds, and on a smaller scale, and I feel it will not only make more sense, but will also allow the kinds of battles you see in the art to take place. To accomplish this, here are some houserules I'd use (see, I didn't only come here to complain! )
1- Reduce VUs to 10 km, not 10,000. This will make probably reflect more accurately the ranges depicted in the space combat art.
2- Reduce combat round duration to 10 minutes. This still makes space combat last a lot longer than regular character firefights, and allows time for repairs and moving around the ship, and makes a ship going at speed 10 go at around 600 kph
3- Distinguish cruising speed from combat speed. Cruising speed would be equivalent to current rules speed and used mainly to get from plent to planet within a system, but require most of the ships power to accomplish. Combat speeds represents ships moving at minimal speeds and using mainly trusters to gain maximal mobility and use all weapons and systems to maximum efficiency, and to avoid probably fatal collisions with other ships or debris during battle.
4- Extend weapon ranges rules to use the same range systems as character combat (long and extreme ranges, allowing ships to fire at more than 3 times the stated range, instead of less than twice)
So, there you are. What do you think?