Project 75 India Diesel-electric Submarine Programs (SSK) : Updates and Discussions

Who will win the P75I program?

  • L&T and Navantia

    Votes: 12 44.4%
  • MDL and TKMS

    Votes: 5 18.5%
  • It will get canceled eventually

    Votes: 10 37.0%

  • Total voters


Senior member
Dec 3, 2017
New Delhi
An Alternative Plan For P-75I, India’s Submarine Construction Program

In recent times, an interesting proposal related to design selection for Project 75I (P-75I), which is the Indian Navy’s (IN’s) latest programme to acquire six diesel-electric submarines (SSKs) of imported design via license manufacture at a domestic shipyard under the Indian Ministry of Defence’s (MoD’s) new ‘Strategic Partnership’ (SP) policy, has arisen in Indian naval circles. Being a ‘successor’ programme to the Project 75 (P-75) Kalvari Class (Scorpene) build project which is currently underway at the Mazagon Dock Shipbuilders Limited (MDL), the IN has apparently long sought a design for P-75I that is different from the Scorpene-2000 on which the Kalvari Class is based. However, owing to recurrent delays in getting P-75I off the ground, it is now being proposed by some quarters that an enhanced and further indigenized ‘Kalvari Class design’ itself should serve as a template for the project.

Proponents of this view also believe that this would make it easier to execute the anticipated Project 76 (P-76), which is supposed to be an IN program to acquire at least 12 SSKs of indigenous design by leveraging the capabilities built up via the P-75 & P-75I license build programs. It would therefore be worthwhile to examine the merits of the alternative proposal, especially by taking a look at what a similar path has yielded for South Korea.

Logistics Logistics

When envisaging a future IN SSK pool of around two dozen submarines (i.e 6 P-75, 6 P-75I and 12 P-76) essentially based on three different designs, the elephant in the room would of course be the logistical headache that is likely to be an outcome of such a mix. For instance, the weapon fit for these three classes of boats could be different, the naval facilities used for operating & maintaining these boats may also have to be different, and there would always be the issue of not being able to readily transfer trained submariners from one SSK class to another. All of this will naturally increase complexity and entail significant costs. Obviously, all this could be avoided to a great extent if P-75, P-75I and P-76 were more ‘related’ to each other, as it were.

In fact, the license build program for a P-75I that is altogether different from P-75 in any case would lead to additional monetary and time costs as a result of having to prepare the domestic supply chain for a new SSK design. And given that the SP policy seeks to primarily execute P-75I via a private domestic shipyard with no prior experience in SSK construction, a protracted time frame to get the first boat into the water cannot be ruled out either.

So, with all these issues in place, is it worth pursuing P-75I as it is currently envisaged or is the alternative being proposed i.e to continue building Kalvari Class derivatives, a better idea? I believe the alternative proposal holds water and for this we could take a closer look at Seoul’s Korean Attack Submarine program (KSS).

A Korean path for India?

Like in India, KSS also seeks to acquire technology from abroad and then create an indigenous SSK fleet in a step-wise manner that includes three phases. The first phase of KSS (KSS-I) kicked off with the induction of the first Chang Bogo Class submarine in 1993, which was basically a Type-209 built by Germany’s Howaldtswerke-Deutsche Werft (HDW), now a part of Thyssen Krupp Marine Systems (TKMS). ROKS Chang Bogo was followed by another eight units of its class, all built in South Korea. Of course, for the second and third Chang Bogo Class boats, most of the materiel was supplied directly from Germany. KSS-I was therefore extremely similar to India’s own acquisition of the Type-209 based Shishumar Class submarines whose first unit, also built in Germany, was inducted in 1986. The last two Shishumar Class boats were of course built by MDL under license from HDW, but as we know the project got truncated due to the political scandal that engulfed it. Ideally, India should have been able to continue this programme like the South Koreans would do by progressively increasing indigenous content.

In 2007, South Korea would commission the first Son Won-yil Class boat marking the culmination of Phase two of KSS (KSS-II), which involved the acquisition of nine units of an improved version of the Type 209 offered by TKMS called the Type 214. All nine were licence built by Hyundai Heavy Industries (HHI) with the addition of air-independent propulsion (AIP) systems. Thus, if one were to take P-75 as equivalent to KSS-I in import, a KSS-II equivalent design for the IN should naturally be a ‘Super Kalvari’ to be manufactured under P-75I. Such a design should have an increased percentage of indigenous components and sub-systems. For instance the SUBTICS combat management system (CMS) on the Kalvari Class could be replaced with an indigenous CMS derived from the indigenous CMS used by the IN’s Arihant Class nuclear submarines. This Super Kalvari could also be redesigned to incorporate an indigenous vertical launch system (VLS) for Brahmos missiles as is required of the P-75I design by the IN, in a manner akin to how an indigenous VLS is being incorporated into the Type 214 by the South Koreans. Moreover, given that an AIP system developed by the Defence Research & Development Organization (DRDO) is in any case meant to be retrofitted onto the Kalvari Class boats, addition of the same to the Super Kalvari will not be a problem.

The third phase of KSS (KSS-III) seems quite similar to what P-76 seeks to achieve, in that it envisages the construction of an ‘all Korean’ SSK with the design IP residing in South Korea. KSS-III submarines will be completely built in South Korea, with a high percentage of Korean systems as replacements for all original German systems on the Son Won-yil class. Now, just as TKMS served as a design advisor for KSS-III, India could also initiate a joint design venture with Naval Group for P-76 in the future. In this manner, an indigenous SSK on par with the best submarines in the world can be developed. It would be able to incorporate a VLS extension, DRDO’s AIP, indigenous weapons and an indigenous CMS; all built exclusively to the IN’s requirements. Obviously, the carrot for Naval Group to help build an ‘indigenous Indian SSK’ would be participation in P-75I just as KSS-II was an incentive for TKMS to agree to KSS-III.

Super Kalvari

A Super Kalvari for P-75I would also take less time to build given that MDL already has the infrastructure and pedigree for this family of designs. Moreover, in partnership with MDL, a private shipyard could be developed to create a parallel line for SSK manufacture, something that will be utilized to the fullest extent when P-76 takes off. By having two shipyards build the same SSK design in parallel to each other, delays due to equipment sourcing and technology absorption can be mitigated to a great extent, thereby helping the IN reach its goal of acquiring a fleet of at least 24 highly advanced SSK units in a reasonable time frame and in an affordable manner.
The Super Kalvari would require a new contract which means negotiations with the French without a competing product available. That will be bad for the exchequer. That's why we are aiming for the Super Kalvari through a tender.
  • Agree
Reactions: Bali78
For now building at least 2-4 more of Kalvari class subs would be best short term solution for India as it will help us in keeping construction yard busy . Customizing Kalvari to suit our needs and indigenizing the components as much as we can to avoid costly imports would have been step our North eastern enemy would have done . Whene we can design a nuclear sub with little help in some critical areas we can very well build diesel subs in-house which is already being assembled for some time. Its more of a will issue than skill issue.
Super Kalvari???

One with AIP + VLS, other one without AIP but with VLS


The LOX tanks...pointing towards AIP, also note the 4 VLS>>>>


The French are offering an extension of this contract incorporating Indian AIP and pump jet propulsion tech. Basically a new scorpene. GoI should negotiate it as G2G contract. IN doesnt have time for AON, then RFI, then RFP and Trials, then selection and Financial discussion and approval from Def min and Finance. We are looking at a time frame of 5-6 years just for contract stge. If it atleast an follow on order for 3 is given for the same sub we can get the subs and keep the technology running.

NS have been a big letdown. She is using this ministry as a opportunity to do pleasure rides.
Lovely! Once we finish putting them inside scorpenes we will be able to build our own Diesel electrics instead of going abroad!
  • Agree
Reactions: ni8mare
@Pokemon I deleted that Post, as some articles States that it's SAIL which supplied it & others 'Heavy Engineering Corporation, Ranchi'.

I'll update this Post & share the Source(s).
  • Like
Reactions: Paro
Air Independent Propulsion (AIP) I Land-based prototype [LBP]


Endurance mode user trial of NMRLs Land-based Prototype (LBP) for Air Independent Propulsion (AIP) complete.

Endurance mode user trial of Land-based Prototype (LBP) for Air Independent Propulsion (AIP) System for submarines for a period of 14 days was successfully completed at Naval Materials Research Laboratory (NMRL), Ambernath, on 2 December 2017.

Primary performance parameters as per trial directives were met satisfactorily. The endurance trial was carried out in presence of Indian Navy and part of the plant was operated by Navy’s representatives. Easy operability and safe operation of the plant was appreciated by the user.

The AIP, developed by Naval Materials Research Laboratory (NMRL) is a 250 kW Phosphoric Acid Fuel Cell (PAFC) based system, that allows up to 14 days of underwater endurance for a submarine running solely on power supplied by this system.

NMRL’s AIP system incorporates a set of innovations that make it a rather contemporary system. For one, NMRL’s AIP package has an onboard hydrogen generation plant, which produces hydrogen ‘in situ’ that too without any combusion, unlike many other AIP configurations where hydrogen for a mission has to be carried on board in tanks.

PAFC has much longer service life than any other commercially viable FC type and has much better tolerance to impurities in the reactants used even when compared to polymer electrolyte fuel cells (PEMFC). But, PAFC operating temperatures are usually higher in comparison to PEMFC and overall power to weight ratio is lower.

The PAFC is designed such that series/parallel stacks can be used for power generation levels of up to 500 kw, this modularity of NMRL’s AIP solution enable it to be used in submarines other than the Scorpene as well. This also naturally increases the survivability of the system, since even if one of the modules fails, the control system for the PAFC stacks can reconfigure the remaining operational units to continue to supply power output, albeit at a reduced quantum.

The development of an indigenous AIP system by DRDO and its complete domestic industrialization is a significant milestone in the development of FC technology in India. Apart from the Scorpene programme, whatever diesel-electric submarine design is chosen for construction under Project-75I is also likely to be a recipient of NMRL’s AIP solution.
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