August 17, 2016

Why fewer SLBMs in each of the US and UK SSBN Replacements?

What I'm researching now, for publication in Submarine Matters tomorrow, is Why are fewer SLBMs being planned in each of the US and UK SSBN Replacements?

US 24 SLBMs down to 16 per sub.

UK 16 SLBMs down to 12 or 8 per sub.

So far variables I've taken as relevant are:

1. improvements in CEP?

2.  improvements in SLBM reliability?

3.  increases in numbers of penetration aids (eg. decoys)?

4.  that the number of SLBM slots in the US Ohios and UK Vanguard SSBNs were always/usually excessive and/or under-used - so the reduced SLBM numbers are a rationalisation downwards.

5.  are there only so many targets you need to hit to acheive an optimal deterrence?.

6.  are arms limitation treaties relevant? Something I don't keep across of - as I would assume that its not only the US and Russia needing to agree these days. I also assume agreement (a political issue) would be a function of technical advantage or disadvantage.

7.  are the planned reductions initial low-ball estimates, for domestic financial reasons or to keep opponents guessing?

8. A combination of variables. There will be increases in the number of MIRVs and penetrations aids per SLBM and connected with that lighter and more accurate (CEP wise) warheads/reentry vehicles.



Anonymous said...

Hi Pete

I think that the reduction in numbers of SLBM is based on the New START (Strategic Arms Reduction Treaty) (Russian: СНВ-III, SNV-III), nuclear arms reduction treaty between the United States of America and the Russian Federation [1]. A specialist in Nuclear Weapons Policy explains the New START in detail [2].

[2] “The New START Treaty: Central Limits and Key Provisions” by Amy F. Woolf, Specialist in Nuclear Weapons Policy, April 13/2016. See page 7, “SLBM Launchers”.


Josh said...

For the US at least there is ongoing arms reduction going on and the 24 tubes are overkill for the number of deployed weapons it is allowed. Its generally believed that the average number of warheads per missile is well below the full eight Trident is capable of.


Ztev Konrad said...

I have heard that the UK is still buying a standard SLBM module or CMC but is only using 8 tubes

"The Ministry of Defence has struck a £37 million deal with the US Navy to build twelve new missile tubes for the first of the Successor submarines – despite announcing in 2010 that, as a disarmament measure, it would be reducing the number of missiles carried on board each Trident submarine from 12 on the submarines which are currently in service to eight on the replacement boats."

The site has a lot of sourced background information on the UK nuclear industry and strategic program- but from a different viewpoint !

MHalblaub said...

German Wiki says there is a new Trident version: UGM-133 Trident II. The English Wiki hides it a little bit.

Far more power with nearly twice as much weight to lift far bigger MIRV into the right trajectory.
War head went from 100 kt TNT to 475 kt TNT equivalent.

Therefore improvement in CEP is there and reliability also.

With a bigger missile more heavy decoys could be launched. The had to be as heavy as a real MIRV to fly the same trajectory in the upper atmosphere.

It is not possible to just replace a 33 t missile with a 59 t missile without changing the submarine. May I remember the S-80 class (or Isaac Peral class) submarine fiasco.

The number of targets reduced itself. E.g. Warsaw and Kiev are no longer on such a list.

New Start reduces the amount of SLBMs.

Russia has to maintain less weapons so less money to spent for the greatest land on earth with an economy. Russia's GDP is less than Japan or Germany and not much more than the UK or France.

China does just need a few missiles for deterrence reason to keep an enemy at par while winning a conventional war.


Peter Coates said...

Hi S, Josh, Ztev and MHalblaub

Thanks for your comments. I'll reply to them properly tomorrow.

I'll also fill out more details (partly drawing on your findings) in the "...fewer SLBMs" article.

As you would have seen I've been much engaged in commenting on Taiwan today.



Peter Coates said...

Hi S

Thanks, I particularly looked at that you provided. It says:

"Under terms of the treaty, the number of strategic nuclear missile launchers will be reduced by half... It does not limit the number of operationally inactive stockpiled nuclear warheads that remain in the high thousands in both the Russian and American inventories" and then

"It will also limit the number of deployed and non-deployed inter-continental ballistic missile (ICBM) launchers, submarine-launched ballistic missile (SLBM) launchers, and heavy bombers equipped for nuclear armaments to 800. The number of deployed ICBMs, SLBMs, and heavy bombers equipped for nuclear armaments is limited to 700"

So the New START (Strategic Arms Reduction Treaty) would definitly influence the reduction in SLBM numbers in the US and likely the British replacement SSBNs. This could occur through fewer SLBMs on Each repalacement SSBN and/or, as is happening with the US, a reduction in the numbers of SSBNs (from current 14 Ohio SSBNs down to 12 replacements).



Peter Coates said...

Thanks Josh that you provided reinforces the importance of New START in reducing the numbers of SLBM and actively fielded MIRVs/warheads on each Trident II SLBM. Maybe 4 MIRVs per Trident?

So states:
"Beginning in 2015, launch tubes in Ohio-class vessels will be reduced to 20 each, in accordance with New START requirements.

"...Once all of the Ohio-class submarines have had their launch tubes capped at 20 each -- a project that is to take place in the 2015-to-2016 time frame -- the United States will be able to deploy no more than 240 submarine-launched ballistic missiles at any time..."

"The submarine set to replace aging Ohio-class vessels -- dubbed "SSBN(X)" -- is expected to have only 16 missile tubes, which will reduce further the number of sea-launched ballistic missiles that the United States can deploy. The replacement fleet is also envisioned to be smaller -- only 12 submarines instead of the current 14."



Peter Coates said...

Hi Ztev

Yes the US and UK decision to use multiples of 4 SLBMs in each SLBM module more commonly called "Common Missile Compartment (CMC)" or "quad-packs". I've also seen just 8 SLBMs planned for the UK's replacement SSBNs. does discuss 8 vs 12 well.

The site is indeed useful on the joint and UK angle.



Peter Coates said...

Hi MHalblaub

Indeed the Trident I "UGM-96" also called "Trident C4" was operational 1979, finally phased out 2005.

And then Trident II "UGM-133" also called "Trident II D5" became operational 1990, still in use. Much bigger, more bang.

I think improvement in CEP owes much to faster computer power allowing more adjustment per second in the MIRV/warhead before it hits.

The should be delivered in a couple of years. Its new style AIP (if working) will be of particular interest.

Very true US, UK, France have fewer "Russian" targets that need hitting, with Warsaw, Kiev, Budapest Prague and East German targets off the list. So fewer Western MIRVs/warheads needed.

New START is indeed a major importance.

New Russia with less money for nuclear forces is also a good point. Putin's patriotic policies can only justify so many Bucks for the Bang.