India needs 12 SSNs.

Gessler argues India has pressing needs for 12 SSNs for good reasons.

Below “"India's 75I Aim to Get Submarine AIP remains in Limbo." of February 17, 2022 Gessler wrote on Feb 17 .

Personally, I'd feel better if we just scrapped India's Project-75I program.  

I feel that at its core, the P75I is seeking to address a requirement that is no longer entirely relevant. The original requirement (defined in the late-1990s) called for procurement of 24 SSKs (including AIP & non-AIP ones). 12 of which were to be of a foreign design but constructed in India, and the remaining 12 of an indigenous design to be delivered after the first 12 were completed. 

The P75 & P75I tenders were meant to deliver 6 boats each toward the first 12. The P75 (Kalvari-class/Scorpene) is mostly done, the 5th boat has just set out for sea trials earlier this month and the 6th & last one is under construction.  

However we continue to wrestle with P75I, with no selection to be seen around the corner. 

But the thing is, the 24 SSK plan has already been modified - the Indian Navy had informed the Government that it seeks to ditch 6 of the 12 planned indigenous diesel subs, and replace them with 6 nuclear-powered boats instead (that's where the SSN program comes in, known as Project-75 Alpha but also referred to by some as Project 76).

https://www.hindustantimes.com/india-news/navy-seeks-amendment-to-30-year-submarine-plan-wants-six-nuclear-boats-101621307478586.html

Here's how I would rather have the submarine plan develop: 

1) Scrap P75I, abandon plans for procurement of AIP+LIB submarines - they no longer can provide the Indian Navy with a decisive edge against regional adversaries, let alone Chinese expeditionary patrols in the Indian Ocean Region. 

2) Make a follow-on order of 3-6 more SSKs of the Scorpene/Kalvari variety - with or without the indigenous DRDO-developed PAFC AIP (which is as yet unproven). This involves the existing production line in Mumbai & clearly defined local industrial partners. They have already built 5 Kalvari-class subs. 3-6 additional Kalvaris will mean significant reduction in time & money required to get additional hulls in the water. This should be in time to replace the 8 Sindhughosh-class older vesion Kilos (877EKM) and 4 Shishumar-class Type-209s currently in service. Even though the Kilos and 209s have received significant upgrades, they remain old hulls, especially the 209s. 

3) Make a bigger push to go nuclear. Back in the 1990s when the 24-sub plan was devised, the construction of nuclear-powered submarines in India was but a risky pipedream. India  had no idea if the ATV program would succeed or not. There were uncertainties as to what level of localization & design flexibility could be enabled down the line. Uncertainties included as to whether Indian yards & engineering companies' had the ability to absorb the fundamentals of N-sub design & construction. 

Today, there are 3 Arihant-class SSBNs in the water. The first, INS Arihant S-2, has already performed its first deterrence patrols (2018-19). The second is INS Arighat. The third is the extended (codename) "S-4" launched on Novemberr 23, 2021. This shows a significant level of design flexibility having been absorbed. India is now in a position to approach N-sub construction (and the investment in them) with a greater degree of confidence. 

I would prefer it if the plan for the second "indigenous" batch of 12 SSKs subs (which is now reduced to 6) were to be abandoned in its entirety and replaced with an additional 6 SSNs (for a total of 12 SSNs). 

The way I see it, 6 SSNs are simply not enough for the needs andmerging requirements of the Indian Navy. 

If we think with the assumption that the SSNs will have the exact same reactors with the same level of Uranium fuel enrichment (around 40% average) as the existing Arihant-class (which may or may not be the case but for sake of argument let's say it is)...it would imply a similar refuel time period [meaning 2 or 3 SSNs refueling in deep maintenance at any one time].

This means that in order to provide each of the 4 planned SSBNs (S2, S3, S4 & S4* ) with an SSN for protection & escort, 4 corresponding SSN hulls will be necessary, if the Indian Navy does not go toward a Bastion concept of deterrence posture. These 4 'escort' SSNs will become necessary if India SSBNs use the vast underwater trenches of the Indian Ocean. This will become a requirement as soon as Indian SLBMsfrom remote Indian Ocean launch areas have sufficient range to hit distant targetsl**).  

On top of that, the Indian Navy [will need around 2 to 3 SSNs] if India wants to possess 3 Carrier Strike Groups (first, centred on the Russian-built INS Vikramaditya is operational while the second, centred on the indigenously-built INS Vikrant/IAC-1 is in sea trials and the third, IAC-2 aka INS Vishal, is being conceptualized), so that at least 1 carrier group is available for operational tasking at any given time. 

With the current plan, the 3 carrier groups will have to rotate the 2 remaining SSNs between them as their main underwater escort. 

This leaves no extra Indian SSNs which can be tasked at any given time to carry out independent Hunter-Killer/Intelligence-gathering patrols across the Indian Ocean Region & into the South China Sea. Any such mission tasking is likely to require months if not years of advance planning. 

As you can see, the 6 SSNs planned under Project-75 Alpha are barely enough for the purely defensive needs necessitated by the wide frontage of roles performed by the Indian Navy (carrier groups + strategic deterrence posture). This is in stark contrast to the RAN where every single SSN can theoretically be available for such 'offensive' taskings due to lack of aforementioned defensive needs (no carrier groups, sharing of US nuclear defence umbrella). 

At a time when China did not have any Carriers (which wasn't that long ago), they actually had a lot more flexibility with regard to SSN deployments, plus their adoption of a Bastion concept for SSBN operations...but with PLAN expanding its frontage with Carrier groups, we'll have to see how their deployments change. I still tend to think PLAN's carriers are more for show & propaganda purposes and do not serve much of a role in the Chinese war doctrine...as opposed to the Indian Navy where the Carrier Group is central to the naval warfighting posture.

** You will note that India went to great lengths to never portray the Agni-5 as an ICBM, officially capping its 'known' range at 5,000-km, just 500-km short of officially being an ICBM. But when it comes to SLBMs, they were more open to marketing it with a 
K-5 SLBM 6,000-km range. Please refer to the slide below [perhaps of a K-5  SLBM] shown at Indian Institute of Technology (IIT) Bombay that I (Gessler) posted on Submarine Matters on April 18, 2021. See 3rd paragraph here). 

In my opinion, the extra press (and possible pressure) received when testing what the wider world officially considers an ICBM was deemed to be worth it. This is as long as it shows beyond a shadow of doubt that the major cities of the Chinese Mainland are within reach from the deeper locations of the Indian Ocean Basin (say, Chagos Trench [aka “Chagos Ridge”?]).

You will note that a [S4 or S4* mounted K-5 SLBM of 6,000-km ICBM range is only required if such a distant Indian Ocean] posture is to be adopted. Otherwise even a 3500-4000-km IRBM (like the existing K-4) would be sufficient if employed from within the Bay of Bengal.