The scientist said several steps are involved after achieving criticality and the reactor must be fully tested before it is sent to the sea. Integrating the ballistic or cruise missiles will take time and a few more years are needed to prove the platform and its systems, first in harbour, then at sea and lastly, under water, at increasing depths.

'Therefore, announcement of India's entry into the nuclear submarine club with a half-baked product without the nuclear reactor -- let alone the weapons systems -- is perhaps premature,' the scientist said.

'After all the project had remained under wraps for over 20 years and another few years would not have made a difference.'

In contrast, although India was the fifth country to set up a nuclear reprocessing plant in 1964 even before Germany and China, the late Homi Bhabha, father of Indian atomic energy programme, announced the achievement only after it was commissioned and started to produce plutonium, he pointed out.

Nataraja Sarma, former BARC physicist and co-author of 'Nuclear Power in India: A Critical History', says it makes safety sense to first check out the seaworthiness of the basic submarine without the reactor core and then assemble the reactor.

'Once big components like reactor vessel, heat exchangers and the lead shielding (for protecting crew from radiation) are transferred to the submarine before closing its shell, the remaining smaller components including the fuel assembly can be introduced later to complete the construction,' he said.

Arihant is far from reaching operational status but the coconut breaking that released it from the Visakhapatnam dry dock was nevertheless an important day for India, the scientists say.

'What is significant about the launch is that now India has publicly acknowledged its quest to acquire a nuclear submarine and has shown it has the ability to design and build such a platform,' Uday Bhaskar, a former naval commander and now head of the National Maritime Foundation, is quoted as saying in the journal.

(K.S. Jayaraman can be contacted at killugudi@hotmail.com)