Errr you seem to have ignored/misunderstood my whole point there. The drones I'm talking about never attack an enemy major combatant/ship, nor do they want to, or even get close to them: they want to make the space between major combatants a more difficult place for the real weapons (missiles of some sort/terminal guidance projectiles) to exist in, either by wasting their fuel with evasive actions or preemptively locating and shooting them down. They don't need lots of dV to do that: just enough to loiter and keep up with the main ship maneuvers. With lasers being so short ranged (in space combat terms) and potential missile warheads like bomb pulsed xray lasers having quite a long range itself while not needing to worry about heat issues (as its 1 use/exploding), having active interdiction drones seems like a good idea! Not to mention all the other uses I pointed out.
This has the same problem that fighters do though. It "keeping up with the ships maneuvers" isn't actually minimal dV. (indeed its at minimum the same as your main ship, which is going to be maximizing dV). Any energy you're wasting deploying "not weapons" is dV you're taking away from your main ship because its fuel that it cannot consume. Or dV you're taking away from your weapons because its fuel they cannot consume.
That doesn't mean you may not attempt to intercept missiles with your own. But its all just missiles then.
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Point 1 has a serious problem: heat. The practicality of cooling a ship goes down sharply as its size increases, especially if that ship is doing things that are hot like firing weapons and riding giant plumes of fire.
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I don't think this is actually an issue. Your cooling apparatus does not need to be constrained to the form factor of your ship. You can heat water up really high and then vent the steam as an example. This doesn't make you stealthy, but you aren't stealthy anyway. While your actual form factor is functionally limited by square/cube law your venting apparatus can actually be linear in mass to surface area because the relevant value is the amount of space between radiators. Which is linear to the volume of the ship which is linear to the mass of the ship.
In terms of defense, surface area/volume ratio only matters if armor matters, which is highly dependent on how future technology develops, but it honestly isn't looking good for armor. Heavy armor is already obsolete in modern warfare when it comes to naval engagements; whether the analogy holds in space warfare is an open question depending on tech. I suspect yes: it is far easier to scale up a missile to penetrate a given amount of armor than it is to scale up armor, to the point where without some revolution in materials science I don't see how armor can compete. There might be some balance of light armor vs "shotgun" style weapons I'll admit.
This is neither true today nor would it ever be functionally true. The main reason for this is that armor always forces a response. Yes anti-tank weapons are good at cracking tanks. But tanks are still very valuable on the battlefield. Because bullets are not good against tanks. Being immune to certain classes of weapons is exceedingly valuable. Forcing your enemy to have a certain size of warhead in order to penetrate your armor is valuable. (bigger warheads means they need larger missiles to hit you which means they have fewer attacks)
And its going to be exceptionally valuable if bomb pumped lasers are a thing because they cannot have specific penetrating conditions. So any amount of armor reduces the final damage that the weapon does to its target.
Plus, in space there is no such thing as a "non shotgun weapon". Any weapon you want to fire at an enemy must account for the fact of where it can be by the time that weapon arrives. Even a weapon that tracks functionally has this problem (as its effective range is reduced every time it has to course correct to deal with any change in vector of its target)
Cross sectional area matters somewhat and in that case a larger ship has an advantage in terms of amount of equipment brought to bear vs exposed size. However, that in turn depends a lot on the guidance/accuracy of weapons. For unguided projectiles its critical; for missiles and terminal guidance projectiles? A lot less critical, depending on the ratio of weapon maneuverability vs ship maneuverability (which is heavily in favor of the weapon). I think that active countermeasures and ECM/spoofing are going to matter a lot more than putting the nose to the enemy.
Cross sectional area also matters in drive efficiency. Radial acceleration also applies to anything off axis when the main drive fires. You can reduce this by adding arches. But only so much.
And cross sectional area also means that you can angle armor. Which will be extremely valuable against all sorts of weapons. There is, additionally, very little loss in this. You lose nothing by minimizing your cross sectional area. And even if you DO want to have a broadside alignment a tube minimizes your cross-sectional area to as many attack vectors as possible while still maintaining at least a semi-optimal armor alignment.
This matters even more as weapons become guided because a low cross sectional area is necessary to produce armor angling against guided weapons. A high cross sectional area is trivially bad.
Point 2 is accurate! But at the same time, the most efficient and strongest shape for rotating quickly would be a sphere.
In terms of mass optimization yes. But not by a lot. And it comes with a lot of other disadvantages. The inability to angle armor(anything that hits center mass hits armor in an efficient penetrating and damaging fashion). Inefficient allocation of armored area (the larger your cross sectional area that you're pointing towards the enemy the more armor you need to take/the less armor that you can effectively use). Structural difficulties under acceleration. Pointless space allocations. (like, you can maybe argue for the convex forward facing area but why not make the back half concave? Or straight? You would save mass, have a more protected section that saves armor, you don't gain any cross sectional area. You could actually use that space for things like venting
[/quote]weapon maneuverability vs ship maneuverability (which is heavily in favor of the weapon)[/quote]
I am not sure that this is terribly true either. It may be in the immediate term but not necessarily over the life of the weapon. The reason its true in the short term is because the maneuvering limits for ships relate to their ability to rotate and their inability to accelerate at G's that would pulp their passengers. But not necessarily the overall net dV. If your missile has a day of travel time it doesn't matter as much that the ship accelerates slower than it in the immediate term if the missile can only burn for 2 hours of that day and the ship can burn for 24