Arun Prakash, a former Chief of the Indian Navy has written an excellent article in the Indian Express, November 7, 2018, concerning the significance of Indian Prime Minister Modi's celebrated “first Arihant deterrent patrol” .
This is an abridged version, with the full version at: https://indianexpress.com/article/opinion/columns/the-significance-of-ins-arihant-nuclear-submarine-navy-5436432/
"The significance of Arihant
[This “third leg of the nuclear triad”, has major problems] for three reasons.
First, there is the issue of missile ranges. From a submarine patrol area in mid-Bay of Bengal, Islamabad is 2,500 km, while Beijing and Shanghai are over 4,000 km. Even from the northern-most edge of the Bay of Bengal, Kunming is 1,600 km and Chengdu 2,000 km. Therefore, to target cities and nuclear forces deep inside China or Pakistan, from a “safe haven”, India needs a submarine-launched ballistic missile (SLBM) of 6,000-8,000-km range. The missile, reportedly, carried by the Arihant is the K-15, whose range falls below 1,000 km. SLBMs of longer range are, possibly the way, but they will equip Arihant’s successors.
Second, India has, so far, followed an unorthodox system, in which the National Command Authority (NCA) managesthe nuclear deterrent through a “troika”consisting of the Strategic Forces Command (SFC), the Department of Atomic Energy and DRDO. While scientists are the custodians of nuclear warheads and help mate them with the SFC’s missiles and IAF fighter-bombers, the MoD and [Defence Minister (in Hindi “Raksha Mantri”] remain out of the loop.
Which brings us to the third area of concern — an effective command and control structure to cater for this new capability.
The Chairman Chiefs of Staff Committee (COSC) is, notionally, a key functionary in the nuclear command chain,...Under existing rules, the appointment of chairman is tenable by the senior-most service chief who may (depending on his retirement date) serve for durations, varying from 30 days to 18 months....
The nuclear-reactors of our SSBNs will need re-fuelling (with fresh Uranium rods) every few years. The process being a rather lengthy one, India would require an inventory of at least 3-4 SSBNs to maintain one on deterrent patrol off each seaboard. A small force of nuclear attack submarines (SSN) would be required for protection of SSBNs and other roles. Thus, in a 50-60 year perspective, India should be looking at a nuclear submarine force of 8-12 SSBNs and SSNs.
While Indian scientists, engineers and designers have learnt a lot about the complex technologies involved in nuclear submarine construction to ensure that Arihant’s successors are substantially, made in India, there are key areas of R&D which call for urgent focus and where we may need assistance. These include propellant technology for SLBMs of inter-continental range; the design of a SSBN which will accommodate a battery of 16-24 such SLBMs; and the indigenous development of a powerful nuclear-reactor to drive a 10,000-12,000 ton SSBN...”
Admiral Arun Prakash when he was Chief of the Indian Navy.