I have noticed that missile launchers do not fire as fast as they should. When you select a ship you can watch it’s guns fire by the status bar for each weapon. Energy weapons will continuously fire when they are in range, as can be seen by as soon as their bar hits full they fire. Missile weapons do not do this. They will fire, and the bar will fill up, and they won’t fire again for a while. I think they don’t fire until the previous shot has landed, or died out after missing. Either way, weapons like Megaton Launchers will fire, the missiles will be half way to the target and the bar is full, and the weapon sits there for several seconds not firing.
You’re correct, each launcher can only have one salvo in the air at once. I would assume this is intended to limit the damage that they do at extreme long range, and encourage a bit more of a “close encounter” of the gratuitous kind.
It’s a little irritating, as it vastly cuts down on the effectiveness of the launchers, especially of the slow missiles, and makes their actual performance very hard to judge without testing them in a battle.
Maybe two salvos at a time would help with that, but I’m not sure it wouldn’t just delay the problem…
it helps balance. if your missiles are always hitting/aiming at the right things, you get a higher rate of fire than if they’re wandering around having missed, or tracking fighters.
try using target painters / (?) tracking modules.
failing that - close the range 
It just seems like a very unrealistic/artificial way to balance missiles, and can’t see it as being intended. If it is intended there needs to be more explanation on how they work.
I think a better way to balance missiles would be to not have this restriction, and adjust their accuracy and/or other statistics.
Yeah, it’s the artificialness of it that gets to me…
I know that there are justifications you could use to support the current behaviour (heck, I extraoplated some elsewhere in another thread), I’m just not sure you SHOULD justify it, at present. I can also think of ways around the limitation if we’re talking entirely in-setting. For example, if you need the processors to concentrate on one missile to guide it in, that’s fine. Just fire the second set vaguely in the right direction and send them new guidance data once the old set expires or dies - that still only has one ACTIVE set of warheads per launcher, but would probably double the amount of warheads on target. It probably wouldn’t work closer in, as you’d lose the second set of warheads before they went active and deployed decoys, but hey, there are all sorts of this type of argument you could make.
Thing is, none of them matter, because it’s a game. I’m just saying the current method of balancing missiles at very long range is that they seem pretty artificially nerfed by the one-set-per-launcher restriction, and, for example, updating point-defenses to make a more natural counter to such things would probably be better in my opinion.