Recently, the Indian Navy’s fourth Scorpene-class submarine Vela, constructed by the Mazagon Dock Shipbuilders Ltd (MDL), was launched at the Kanhoji Angre Wet Basin of MDL.

About Scorpene Class Submarine:

  • These are diesel-electric attack submarines jointly developed by the French company - Naval Group (formerly Direction des Constructions Navales (DCNS)) and the Spanish company - Navantia.
  • They feature diesel propulsion and additional Air-Independent Propulsion (AIP).
  • AIP is a marine propulsion technology that allows a non-nuclear submarine to operate without access to atmospheric oxygen (by surfacing or using a snorkel).
  • The system of AIP fitted in this class of submarines is a modified version of nuclear propulsion system with heat being generated by ethanol and oxygen. 
  • And the combustion of the ethanol and stored oxygen, at a pressure of 60 atm, generates steam which powers a conventional turbine power plant.
  • These submarines can undertake multifarious tasks typically undertaken by any modern submarine which include anti-surface as well as anti-submarine warfare.

Project 75and 75I:

  • Project 75 was launched in 1997 by the Ministry of Defence to acquire 24 submarines.
  • After the Kargil War in 1999, Cabinet Committee on Security approved a 30-year submarine building plan that called for two parallel production lines, each constructing six submarines.
  • The older Project 75 was brought under the new plan, with the two production lines to be built under Project 75 and Project 75I using transfer of technology from different foreign manufacturers.
  • Under the new project 75I, the Indian Navy intends to acquire six diesel-electric submarines, which will also feature advanced air-independent propulsion systems to enable them to stay submerged for longer duration and substantially increase their operational range.



  1. It is the fourth Scorpene class submarine being built under the project 75I by Mazagon Dock Shipbuilders Ltd through transfer of technology.
  2. This involves appropriate technical support by the Naval Group to Mazagon Dock Shipbuilders Ltd in the field of construction, integration and tests of the submarines in India which is achieved through transfer of technical data package to MDL through information system as well as on job training to MDL’s personnel on critical technologies.
  3. Leveraging the experience and the transfer-of-technology of the Scorpene project, with enhanced and upgraded infrastructure, MDL, is ready for undertaking construction of the future submarines.
  4. The AIP fitted in these submarines enables them to operate for more than 21 days under water, depending on variables such as speed.
  5. The complete list of the submarines of this class are:
    • INS Kalvari - Active
    • INS Khanderi – Active
    • INS Karanj – Sea trials
    • INS Vela – Sea trials
    • INS Vagir – Under construction
    • INS Vagsheer – Under construction