I thought that the possibilities of this topic deserved it's own thread so here it is.
Quoted form Arenamontanus :
Thinking a bit about naval strategy:
What kind of weapons are being fielded, can they be defended against, and what kind of missions will the ship be sent on? If the weapons are hard to defend against the ship has to be stealthy and hard to hit. Looking at the core book description of the destroyer having railguns, nuclear and HE missiles, point defense lasers and fighters, tells us a few things:
Railgun projectiles currently move with velocities a few kilometres per second. This is comparable to normal inter-spacecraft velocity differences: just putting a pebble in the way of your enemy will do plenty of damage on its own. It also means that it will be hard to hit an enemy that is manoeuvring since by the time the projectile reaches where it was, it will have had plenty of time to go somewhere else. Even spamming space with a cloud will be hard since the volume where the ship could go is very large. If the distance to the enemy is d, it moves with velocity v like the projectiles and can accelerate up to a km/s^2, then the total volume where it could go is .5*pi*a^3*d^6/(3*v^6) - for d=1000 km, v=10 km/s and a=5 G I get a volume of 62 million km^3. [I assume the projectile traverses the distance in time d/v, during which the enemy has accelerated up to .5*a*(d/v)^2 away from the extrapolated path.]
If railgun projectiles go much faster, then things cheer up for the attacker. A 100 km/s projectile gives the enemy ship just 62 km^3 to hide in, and a 1000 km/s projectile just 62,000 m^3 (and they are going to intersect the volume too, not just sample a single point). Increased acceleration tolerance of the enemy of course equalizes things a bit, but the deciding thing is the relative distance between the ships - you can't hit anybody beyond a certain radius - and the speed of the railgun projectiles.
Note that habitats are sitting ducks here, possible to hit almost from anywhere with a high-accuracy shot.
The probability of hitting a ship with cross-section area A will be ~4*v^4*A/(pi*d^4*a^2). [I assume the projectile will hit somewhere in a circular cross section of area pi*(.5*a*(d/v)^2)^2, and if it hits within a particular area A it hits. ] Assuming A=0.1x0.1 km for an impressive Destroyer, with the above 10 km/s projectile the chance to hit is just 10^-8. For 100 km/s it is 0.0005, and for 1000 km/s you are pretty certain to hit. If the ship is just 10x10 meters, then even the superfast projectile is back at 5% chance again. This makes fighters sensible - they can likely keep a small cross section and high acceleration. Also note that if the distance is just 100 km the hit chance goes up a lot - you want to shoot close to the enemy, but not be close to him.
The kinetic energy from a 10 km/s 1 kg impact is 50 MJ. At this point the kinetic energy starts to become bigger than any (chemically) explosive force you can put in the projectile. 100 km/s is 5 GJ (about one ton of TNT) and 1000 km/s is 500 GJ (100 tons of TNT). They will penetrate to a distance about equal to the projectile length times the ratio of projectile to armour density (Newton's penetration law). This is actually an interesting problem: you want to deposit all this energy inside the ship, so you want to tune the projectile length to its armour. Too heavy projectiles and they go straight through the ship - sometimes having no armour at all the smart strategy (just hope they do not hit your antimatter). Too light projectiles and all energy gets deposited outside the armour.
Since the lasers are point defences rather than main armaments (with v=300,000 km/s, you would be able to hit anybody visible within at least a lightsecond), I think we can deduce that it is hard to project a sufficiently high energy beam far enough, but that it can become tough on short distance. I expect railgun projectiles are hard to hit, but missiles are the likely main targets.
Missiles can presumably accelerate at least a few 100 G. They can also adjust their course to get close to ship targets and then launch something nasty. However, they likely need to get reasonably close to do this given the above discussion. They likely lack the energy to launch railgun projectiles, but instead launch a bunch of warheads or fire a one-short laser. So they will always be vulnerable to point defences, which will successfully defend the ship if they disable the missile before it detonates. Conversely, if it detonates then it can deliver far more oomph to the enemy than a railgun projectile. There is essentially no way a ship can handle running into a point-blank nuclear fireball or piece of antimatter.
Together, this seems to imply that
1. Missiles are the real ship killers, and much effort will go into detecting, avoiding and disabling enemy missiles.
2. railguns are useful against certain targets, but either require enormous velocity or rather short distance fighting.
3. Fighters make sense since you want to bring sensors, railguns and missiles close to the enemy while staying far away yourself.
4. Armour might mainly be against railgun impacts (and other debris) rather than missiles, and it might be better to have a ship that is resilient to a few impacts than have a heavy armour that brings down your acceleration.
5. Railguns make sense against fighters, since they can not accelerate as much as missiles but will be close to you.
6. Maintaining distance is a good way of avoiding to be hit. Hence, you want to be faster than your enemy (and stealthy). Second best is having a big acceleration, tied with a small area.
If I were a naval planner for the Titanian Commonwealth or the Planetary Consortium, I would likely start by deciding that the major naval ships would not have any space for biomorphs onboard, and quite likely not much of synthmorphs either. The sheer amount of space and mass that has to be spent on keeping a biomorph alive is large, and they have to be protected from accelerations, temperature, radiation, you name it. An infomorph crew and tiny repair synthmorphs/nanoswarms would work much better. This way the ship could be made as stealthy as possible (by keeping a low temperature), as small as possible, and able to handle extreme accelerations. My idea for a major high-tech naval ship would probably be something like a tiny Borg cube, dropping off fighters and modules in a large cloud while staying hidden. Armour would be sacrificed for redundancy.
The Jovian Junta, having to have biomorphs onboard, cannot do as heavy accelerations and will be forced to have bigger ships. So they can add lots of armour to withstand railgun fire, and lots of point defences plus sensors to catch any incoming missiles. To have a chance at hurting the enemy they need plenty of fighters, again pretty heavily armoured/defended since they cannot be too nimble (expendable pilots cannot fix the lack of acceleration tolerance: a pulped kamikaze pilot is useless). To my mind, that suggests that they would really want to get their long-distance weapons better: either very fast railguns, or *powerful* lasers.
[doff's my admiral's hat folded from newspaper]