India's 5th S-4 Class SSBN, Armed With K-5 SLBM Missiles, Completes 50% Construction

In a significant boost to India's naval capabilities, the construction of the fifth S-4 class nuclear ballistic missile submarine (SSBN) is reportedly progressing steadily at the Ship Building Center (SBC) in Visakhapatnam. This new addition will elevate the Indian Navy's fleet of nuclear ballistic missile submarines to a total of five units, further solidifying the country's strategic deterrence.

The existing SSBNs, INS Arihant and INS Arighat, are sister ships with a submerged displacement of around 6,000 tons. While they share the same basic design, INS Arighat boasts significant internal upgrades, making it more advanced than its predecessor.

The S4 and S4* (Star), successors to the Arihant class, feature a stretched design and a submerged displacement of approximately 7,000 tons. Satellite images have captured these submarines at the outdoor fitment area at the SBC, offering glimpses into their development. Although this is the first official confirmation of a fifth submarine under construction, it is highly probable that its development is well underway.

Considering the S4's rollout from dry docks in 2022, it is estimated that the fifth submarine might already be over 50% complete. Nevertheless, it could still take a couple of years before it transitions from dry docks to the outdoor fitment area for further construction and sea trials.

The S4, S4*, and the unnamed fifth SSBN will mark a crucial milestone as the first Indian nuclear submarines equipped with the K-5 submarine-launched ballistic missiles (SLBMs). These missiles possess a range of 5000 kilometers, substantially bolstering India's nuclear deterrence capabilities.

In addition to these developments, the Indian Navy is also planning to develop the S5 Class of SSBNs, featuring a submerged displacement of around 13,000 tons. The S5 Class program is expected to gain momentum in the coming years, with the first submarine slated for induction in the mid-2030s. These submarines will reportedly be armed with K-6 SLBMs with a range exceeding 6000 kilometers and the highly classified K-8 missiles.

 

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Three ships planned in the S5-class, atleast based on available information.

Also, I am not entirely sure if S4, S4*, and this unconfirmed fifth Arihant-class boat will carry the K5. By all indications based on available parameters, the K5 would be a larger (as in, wider and/or longer) missile than the K4, and therefore, unless the latter Arihant-class boats have a larger hull or larger missile tubes, I have a feeling the K5 wouldn't fit.

That said, whole larger tubes are definitely possible, bringing those in (leading to a larger hull) as well as doubling the number of missile tube would be expected to lead to a displacement increase that would be more than the 1,000 tons that we are seeing. Moreover, based on what I have been able to analyse from satellite footage of Visakhapatnam (footage that is somewhat old now), S4 doesn't seem to have larger missile tubes.

Regardless, I would be very happy if the Arihant-class can, in fact, carry the K5. It would be a much-needed boost to our nuclear deterrence and second strike capabilities, especially of China or Bhikaristan try something nonsensical.

The S4 and S4* are supposed to be 1000 tons more and 10 meters longer. So, I believe, what you are supposing about bigger and longer tubes, would be possible with these enhancements.