As we begin the second round of our debate on sea-based nuclear weapons in the Indo-Pacific, here is the first clear image of the INS Arihant, India's first indigenous nuclear-powered submarine, to be armed with either a dozen 750km-range nuclear tipped ballistic missiles or four larger missiles with 3500km range. The image above is a still from a news report by India's NDTV, which broke the story yesterday.

An earlier image gave very little away, whereas in this shot we can clearly see the distinctive 'hump' aft of the sail, where the ballistic missiles will be housed. I'm no naval architect, but the sail looks to be of a rather dated design, reminiscent of the Soviet-era Kilo-class submarines the Indian Navy already operates. That's not too surprising, since Arihant has been in development since 1998. On the other hand, the designers seem to have done a much better job of integrating the missile hump with the hull than has China with its Type 094.

As our debate on sea-based nuclear weapons has already shown, the performance of the submarine is critical for strategic stability in the region. If the ship is noisy and easy to track, it will not give India the guaranteed second-strike capability it wants in order to dissuade an adversary from mounting a surprise attack. And of the ship is armed only with relatively short-range weapons such as the 750km K-15 missile, it would need to operate dangerously close to an adversary's home waters, thus making the ship vulnerable and destabilising. The longer-range K-4 missile has been tested from an undersea platform but is years from being operationally deployed on Arihant and her eventual sister-ships.

The Lowy Institute gratefully acknowledges support from the John D and Catherine T MacArthur Foundation for this Interpreter debate, which is part of a broader research, dialogue and outreach project on strategic stability in Indo-Pacific Asia.