SB

It depends adversary.From 3000 km you can hit most usefull targets in almost all countries.

However it facilitate task of SSN hunters as area of firing is restricted and also ABM defense.

So why not with a top silent sub? But if you assume that a 2000 km margin away form the coast is a minimum, you will target objectives 1000 km only in land.Don't forgot major powers have sea floor acoustic barriers and a ASW aviation.

An other factors is that the closest to the coast , the more vulnerable your sub is to ballistic missiles.

To fire 16 missiles , you need 8 minutes.If a SSN is 200 km away with a SUBROC like missile (with an extended range) with a nuclear warhead and the ennemy has DSP satellites and BMD radars with a good reaction time, your SSBN could be destroyed before having fired all its missiles.

I would look to a 4500 km range as a minimum requirement which is achievable with a 2 stage missile (like Poseidon).

 

That's pretty interesting. How far at maximum is it feasible to extend these seafloor-based acoustic sensors you speak of? Also, I must say that I did not consider the fact that the submarine could be destroyed by a retaliatory attack before it managed to launch all its missiles. The solution to this, however, could be to increase the rate of firing from 1 SLBM per 30 seconds (2 per minute) to a faster rate. In principle, I see no reason why the rate of fire could not be doubled to 4 per minute (1 per 15 seconds). Even so, I guess, the submarine, having launched all its missiles, would optimally want to survive the counterstrike and thus would want to be far enough to escape the launch area before the arrival of retaliatory warheads. It would probably also help if the submarine would be able to launch its missiles while moving at a considerable speed and depth, which is probably impossible, but greater range of missiles would most likely be a more viable solution to the problem.