Gessler: Future Indian SSNs, SSGNs & SSBNs: Comment 2

Following India's 6 Future Alpha SSNs - SSBN Protectors of April 7, 2021 Gessler made some learned and extensive comments on April 9, 2021. Pete has added many links. Here is the second of 3 Gessler instalments:

Regarding the use of vertical launch systems (VLS) system to launch SLCMs from the Alphas - I don't think they will go down that way. Allow me to explain my point of view. 

In the 2030s, when the S-5 SSBNs start becoming available for carrying forward the role of what the Royal Navy calls Continuous At-Sea Deterrence or CASD... (I'm using that expression because the hydrodynamic testing model of S-5 has it's bow planes attached to the hull roughly at the same spot where the UK Vanguard-class SSBN has them, instead of on the conning tower like Arihant class...though the similarities are likely to end there).

As each new S-5 becomes available to take over the CASD role, a corresponding Arihant-class boat would in all likelihood be retired from performing any form of deterrence role, after which it would probably be subjected to a scheduled refit and  refueling of the reactor. So what will the Indian Navy do with these boats then? They would still have at least 10-15 more years of service life left. 

My guess: they will convert them into performing a role that is somewhat less demanding (on the part of keeping at least one boat operational at all times) - into an SSGN role. When the Arihants are subjected to refit and refueling, the nuclear armed K-4 IRBMs/SLBMs  ballistic missiles can be swapped out and replaced with up to 5 or 6 Nirbhay-type SLCMs per silo. The Arihant's silos were designed to accept either one K-4 or three smaller K-15s mini-SLBMs per tube so we know it is designed to support the multi-round ejection systems needed for such 'pack' VLS. 

The K-15 missile has a diameter of 0.74m compared to 0.52m for the Nirbhay, so it can potentially pack 5 or 6 (more?) Nirbhays in those tubes I'm guessing, for a total of 20-24 vertically-launched cruise missiles per boat (someone needs to do the math on that diameter, either way very similar to the 7-round Tomahawk [Virginia Payload Tubes (VPT)] on some Virginia-class boats). 

So, better to not encumber the Alphas with the additional weight and power requirements needed to fulfill an SSGN role - better to let them be as light and sleek as possible for reasons of speed, stealth as well as reactor efficiency, all critical for a hunter-killer SSN. 

Considering India does not have stockpiles of hundreds and hundreds of nuclear weapons, we might not even have the number it would be needed to simultaneously arm 3 or 4 S-5 class as well as 3 Arihant-class (discounting the S-4*). So it would have to be an inevitability to bring the Arihants off the line as deterrence platforms once the S-5s start coming in.