India Silently Launched its third Arihant-class Nuke Submarine in Visakhapatnam: Here's what you need to know about S4 SSBN

Nuclear powered submarine in India: India has silently launched its third Arihant-class submarine at the Ship Building Centre (SCB) in Visakhapatnam. It is a nuke submarine, the launch of which was reported by UK-based Janes Defence Weekly based on satellite imagery sources.

What did the UK-based magazine report? 

Janes Defence Weekly in its December 29 report stated the following:

1- The submersible ballistic nuclear submarine (SSBN), also known as S4, was launched by India on 23 November 2021. 

2- It was later relocated to near the fitting-out dock that was presently occupied by INS Arighat, India's second nuke submarine. 

3- The satellite imagery cited by the magazine confirms that at 7,000-tonnes, the S4 SSBN is slightly larger, with a load waterline measurement of 125.4m as compared with 111.6m of the 6,000-tonne INS Arihant, the lead boat in this class. 
4- The S4 – and successive boats – were given the ‘Arihant-stretch’ variants tag.

5- The newly launched boats' additional length accommodates expansion of the submarine’s vertical launch system which has doubled to support eight (missile) launch tubes, enabling the SSBN to carry eight K-4 SLBM which is currently under development. 

Who developed India's third nuclear submarine?

The third Arihant class submarine has been jointly developed by the Defence Research and Development Organisation (DRDO), the Department of Atomic Energy (DAE), select Indian Navy (IN) personnel and Russian scientists and technicians. 

Significance of nuclear-powered submarines

India has planned to build four nuclear-powered submarines. Of these, one is already commissioned into the Indian Navy while the other will be commissioned in 2022. 

The nuclear-powered submarines will help India to add maritime strike capability to its existing land and aerial-based capacity in delivering strategic weapons.

Background

The first SSBN INS Arihant was launched in 2009 and was commissioned into the Indian Navy in 2016. The second SSBN INS Arighat was launched in 2017 and is expected to be commissioned into the Indian Navy in the third quarter of 2022. Its commissioning has been possibly delayed due to the ongoing COVID-19 pandemic. The S4 SSBN is expected to be commissioned into the Indian Navy in 2024 as it is currently under the fitting-out dock. 

Also Read | India committed to 'no-first-use' of nukes and 'non-use against non-nuclear-weapon states': All you need to know

What is the Nuclear Doctrine of India?