tanksoldier said:
Captains using these weapons probably have to fill out an "environmental impact statement" or some such bureacratic nonsense.
...but how do you secure them so they don't end up dropped on colonies?
I think this is probably one of the reasons why the navies in 2300AD are relatively tiny. You simply don't want to have huge numbers of nuke-armed ships flitting about. Maybe it's also a provision the Melbourne Accords (something similar to the 1920's Washington Treaty on battleships).
Even today's nuclear weapons have some fairly elaborate safeguards on them to prevent unauthorized use. I'd imagine that even with the setting's conservative technology assumptions the safeguards are even more elaborate in the 24th century. The weapons are also probably boobytrapped so that if anyone tampers with them they set of some of the conventional explosives, disabling the device and probably killing the ones messing with it.
I would suspect that ship captains have rules of engagement that don't permit them to use detonation warheads except in very specific circumstances, and it may be that your average Frigate or destroyer captain can't even use them even if they wanted to until they get the code-key from the task force commander. I'd also bet that standard post-battle protocol is to round up any loose missiles or submunitions whenever possible.
Even if your terrorists get a nuke and manage to get it to work without killing themselves, they've got several problems.
First and foremost, everyone's going to be on high alert for the missing weapon, at least in the system or arm where it disappeared. They're not going to stop until they find it.
Secondly, how are you going to get your weapon on target? If it's a missile, you're going to need military-grade fire control to engage anything but a stopped vessel or a space station. If it's a submunition and you want to "drop it on a colony" you're still going to need a delivery system. Missiles are a no-go: their stutterwarp drives won't work in low orbit, let alone in atmosphere. Ditto for a submunition unless you put it in an aeroshell and even then you're going to need some sort of aiming system if you're going to do more than just provide a light show.
Third, at some point in this escapade you're going to need a starship to either transport your warhead to the target system, or use it as an orbital platform to drop your nuke-armed aeroshell onto the colony. Remember in 2300ad starships don't grow on trees: they're generally owned by a government, transnational foundation or coporation, or (in the latest edition) a libertine merchant family. None of them is likely to want to be come #1 on everyone's "to kill" list for any amount of money.
Really, the only way this works is if a whole military crew goes rogue and immediately drops something on the world below, or blasts their station to bits. I just don't see it as being that likely.
Besides, terrorists don't need nukes to kill large numbers of people or spread fear. For a really current example, just look at the Boston Marathon attacks: so much terror and disruption caused by readily-available consumer products.
Your average colony has all sorts of stuff that can be used to commit mayhem just laying around: hydrogen stockpiles, nuclear fusion plants, massive magnetic linear accelerators (i.e., catapults), fertilizers, or you could simply sabotage the station's life support systems. Many colonies have cargo routinely dropped by aeroshells. You could simply do a lot of damage just sterring one of those deliveries off course, or sabotaging the shell so that vital cargo doesn't arrive.
Of course, chasing a stolen nuke (or being a ship captain that finds one in his cargo hold) would make an awesome adventure seed.