On August 9th, four years after being publicly revealed, the first Indian nuclear sub, INS Arihant (Destroyer of Enemies), turned on its nuclear power plant for the first time. If all goes well (and that is a big “if” in the Indian armed forces) Arihant may be ready for sea trials within a year. An SSBN (nuclear powered ballistic missile carrying sub), Arihant will carry nuclear armed K15 ballistic missiles designed and manufactured in India.
It was in 2009 that India first launched Arihant. This came after over a decade of planning and construction. What was not revealed at the time was that the Arihant was launched without its nuclear reactor, which was not ready until 2010. The Arihant was launched when it was because work on the sub had been going on for more than a decade and it was becoming embarrassing to have nothing to show for all that effort. According to the original plan, the first of six Arihants were supposed to enter service in 2008. That has been delayed several times and after 2009, Arihant had to return to dry dock to have the power plant installed. Arihant has to be launched again and undergo sea trails, which will probably reveal things that have to be fixed. Based on past experience it may be several years before Arihant actually enters service.
The 6,000 ton Arihant has four vertical launch tubes, which can carry twelve (three per launch tune) smaller K15 missiles or four larger K-4 (based on the Agni 3) missiles. The K-4 has a longer range of 3,500 kilometers. The K-4 is still in development. Two more Arihants are under construction. The Arihant is based on the Russian Charlie II sub, which it resembles. The Charlie class had eight launch tubes, outside the pressure hull, for anti-ship missiles. Arihant has a crew of 90-100 and six 533mm (21 inch) torpedo tubes in addition to the four vertical missile launch tubes.
A recently arrived leased Russian Akula II nuclear sub will basically serve as a training boat for India's new nuclear submarine force and that program is already underway. Russia retired all its Charlie class subs in the early 1990s. India leased one from 1988-91, and gained a great deal of familiarity with nuclear sub operations. But all those sailors have since retired and the new Akula is needed to recapture all that nuclear sub experience.
Earlier this year the Indian K15 SLBM (Sea Launched Ballistic Missile) underwent its final development test and is now ready to be installed in the Arihant SSBN. This comes after five years of testing and tweaking. Back in 2008, India began a series of twelve test firings from a missile cell designed to fit into the Arihant. These test firings were not done from the Arihant but from the cell placed in the ground or underwater to simulate launch from the sub. Seven launches took place in 2008, and the rest since then. In 2007, India announced that it had perfected the technology for launching ballistic missiles from a submerged submarine. That meant the silo design had been perfected as well.
The seven ton K15 has a 700 kilometer range with a one ton warhead and 1,900 kilometers, with a 189 kg warhead. The latter weight is sufficient to handle a nuclear warhead if India has been successful in developing warhead technology to the same point the U.S. and Russia were over three decades ago. The first SLBM was the U.S. Polaris A1, which began development in the 1950s and entered service in 1961. Like the K15 it was a two stage solid fuel missile. The Polaris A1 weighed 13 tons, had a range of 2,200 kilometers, and a one ton warhead.