The fourth of Indian Navy's stealth, Scorpene class submarine under Project 75, was launched at the Kanhoji Angre Wet Basin of Mazagaon Docks Ltd. (MDL), here on Monday, an official said.Like the previous Scorpene class submarines - Kalvary, Khanderi and Karanj - the new submarine 'Vela' has been built by the MDL with collaboration from Messrs Naval Group, France.Defence Secretary (Production) Ajay Kumar was the chief guest at the launch event and his wife Veena Kumar performed the launch ceremony at MDL here.'Vela', for which steel cutting commenced in July 2009, shall be powered using indigenously-developed batteries by Exide India and will now commence extensive sea trials.It is expected to be commissioned into the Indian Navy in around two years after the sea trials and would mark four attack submarines from P75 joining the Navy's lethal submarine fleet.With the launch of 'Vela', two more submarines in the same class - 'Vagir' and 'Vagsheer', which are under construction, will follow, said official sources.Each of these underwater attackers are 67.50 metres long, 12.30 metres in height, 6.20 metres beam, with a submerged speed of around 37 kmph (20 knots) and 20 kmph on surface (11 knots).They can carry a crew complement of 35 sailors plus eight officers and remain at sea for up to 50 days.