Duds and Armageddon

That wasn't because the British thought the majority of their warheads were duds. It was because they thought that several would be shot down by the ABM system as well as the prerequisite allowance for failures.

I also think that you've got to take into account the difference in intention of a nuclear deterrent; the UK arsenal is enough to be able to start a nuclear war – but not enough to fight one in any meaningful sense. As such, all it really does is act as a ‘diplomacy multiplier’ in that it makes the guys in the Kremlin pick up the phone when international tension is really bad. That, and (hopefully) remind people that any attack would be - to put it mildly - costly.
 
If I'm reading this right the primaries in Polaris warhead primaries wouldn't go off because of the boron wire would retract onto the spool, so no fission at all.

As for the others, as strange as it sounds 15kt isn't much for a large city with a lot of concrete buildings, the 5psi radius is 1.67km. Whereas if the W59 for example went to it's full 1mt the 5psi radius would be 7km.

Probably worse than that. As I understand it, smaller thermonuclear weapons like you would find in ICBMs and SLBMs (and generally all around in later nuclear arsenals) only had about 5kt or so in the primary.

Plutonium is expensive, Lithium-6 Deturide is cheap.
 
That wasn't because the British thought the majority of their warheads were duds. It was because they thought that several would be shot down by the ABM system as well as the prerequisite allowance for failures.
Equivalent to the 35% failure rate stage in the process :p
 
Equivalent to the 35% failure rate stage in the process :p

A failure rate of 35% includes warheads that will not explode, but some of those are likely to be included in the warheads that are knocked out by the ABM system around Moscow, so perhaps we can write off 5 rather than 6 missiles from an R class boat at the very start.

That will leave 33 warheads in 11 clusters before Chevaline and 22 warheads in 11 much bigger and decoy filled clusters after Chevaline to face the ABM system. Now if the British warheads are 95% reliable by themselves that means 31 and 21 will explode if they are not interfered with.

The question is how effective is the Soviet ABM system and can the Soviets devote multiple ABMs to each British cluster? If they fire 2 per cluster they use 22 of their 64 missiles, if they fire 3 per cluster they use more than half of their missiles. I'd suggest that when Chevaline was deployed with the decoys and warhead separation and intrinsic hardening and assuming the ABM was similarly only 65% reliable the Soviets would have had to use almost all 64 ABMs against the 11 British Polaris missiles because the Soviets would have to knock out the duds as well as the live warheads.
 
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