September 20, 2005: After years of negotiations, India has signed a deal to buy six French Scorpene class diesel submarines. These are similar to the Agosta 90B subs (also French) that Pakistan has bought. The first of the Agosta's was built in France, but the other two were built in Pakistan. The third Pakistani Agosta is still being finished, it was delayed over a year because Islamic terrorists had killed some of the French engineers working on the project.

The two designs are similar, with the Scorpene being more recent (and the result of cooperation between a French and a Spanish firm.) The Agosta is a 1,500 ton (surface displacement) diesel-electric sub with a 36 man crew and four 21 inch torpedo tubes (with 20 torpedoes and/or anti-ship missiles carried.) The Scorpene is a little heavier (1700 tons), has a smaller crew (32) and is a little faster. It has six 21 inch torpedo tubes, and carries 18 torpedoes and/or missiles.

Both models can be equipped with an AIP (air independent propulsion) system. This enables the sub to stay under longer, thus making the sub harder to find. AIP allows the sub to travel under water for 4-5 days at low speed (5-10 kilometers an hour). The Pakistanis have an option to retrofit AIP in their current two Agostas.

With both nations having these modern subs, they have very lethal weapons against surface warships. With well trained crews, Agostas and Scorpenes can get close to just about any surface ship, no matter how good the defenders anti-submarine defenses are. But it's the AIP boats that are the real killers. Without AIP, subs spend most of their time just below surface, using their diesel engines (via a snorkel device that breaks the surface to take in air, and get rid of the engine exhaust.) Snorkels can be spotted by modern maritime patrol aircraft, and both nations are getting more of these.

India has not said if it is getting AIP for its Scorpenes. The price of the contract is quoted as $300 million for each boat. That could include AIP, because the boats are being built in Indian yards, which have much lower costs. European built AIP boats go for about half a billion dollars each. Typically, AIP adds about $100 million to the cost of a sub.