Another issue is the question of how visible submarines might be by 2050; it's possible in the next decade or two they may become very visible to relatively inexpensive sensors.
Seems unlikely. The laws of physics haven't changed so far as I know. Finding several thousand tons of quiet, slow moving, deep-dived submarine in a medium as radio/light opaque as sea water in the vastness of the world's oceans is always going to be a real problem.
A large proportion of ASW still relies on some sort of initial contact - following it out of its home port, fotuitous spotting of a carelessly raised periscope on a radar, a comms intercept, a chance magnetic anomoly detection, an array of hydrophones listening to it as it travels, or by scouring the oceans with active pinging. With the trend towards quieter boats, passive sonar / hydrophone nets will inevitably struggle to keep up - it's hard to detect sounds that aren't really there in the first place. And if a properly designed well cared for submarine is skillfully driven about the only thing that is not really under its captain's control is the use of active sonar by an adversary. And even then it can be devilishly difficult for the adversary.
Mutally Assured Destruction may be a crazy idea, but a submarine is still best for that job. In an increasingly nuclear-armed world you may as well have the ultimate otherwise you may as well not bother. Half measures can be rendered useless overnight by another country's political whimsy, yet one cannot upgrade a deterrent overnight.
@PeterGee,
Can the OP provide a link to this select committee report. Actual replacement costs for the boats are around £11 billion as I understand it, with other costs making the programme circa £25B. The SNP driven number includes 30 year operating costs, disposal costs for the current fleet and the new fleet. Assuming the same measurements I struggle to see how this becomes £250B plus.
Quite. It is indeed not going to be no where near that much. However, remember that Gordon Brown spent several hundred billion in a single afternoon saving the banks in 2008...
It seems reasonable to assume that the total program cost of the replacements is not going to be so very different to the total spend so far + planned disposal costs of the existing fleet of four. Magically pulling a number of £167billion out of the air when there's an objective real world representative example currently in service costing no where near that much suggests that the commitee's numbers lack credibility...