France Creates SAMs For Subs

France is now developing SAMs (surface to air missiles) systems for submerged diesel-electric submarines under attack by helicopters or fixed wing aircraft. One system uses a periscope-like device that pushes a missile launcher above the water where one or more Mistral (similar to the U.S. Stinger) missiles are fired at any nearby helicopters or low flying aircraft. A second system launches a larger Mica missile via a torpedo-like device. While Mistral has a max range of six kilometers, the Mica (normally carried by jet fighters) has a range of up t0 80 kilometers.  

The French are pretty confident these systems will work as similar weapons have been developed and built (but never actually used) before. For example, four years ago Germany successfully tested IDAS (Interactive Defense and Attack system for Submarines) by launching an anti-aircraft missile from a submerged submarine (U-33, a Type 212 equipped with Air Independent Propulsion). IDAS is still in development and not expected to enter service for at least two more years. 

The IDAS anti-aircraft missile is 2.45 meters (7.6 feet) long, 180mm in diameter and weighs 118 kg (260 pounds). It has a 13.2 kg (29 pound) warhead and a range of at least 15 kilometers. The main targets will be ASW (Anti-Submarine) helicopters and low flying ASW aircraft. Two IDAS missiles fit into a metal frame that in turn fits into a torpedo tube. The IDAS missiles take about a minute to reach the surface, ignite its rocket motor, spot any target within range and go after it. If the IDAS misses, the air bubble from the torpedo tube launch of the missile, will reach the surface, indicating where the sub is. At that point, the helicopter or aircraft can drop a torpedo. The sub has countermeasures for these torpedoes, but these devices are not guaranteed to work every time, or against every type of torpedo (some are better at detecting, and getting around, countermeasures.)

The sub commander would use IDAS if he calculated that a helicopter was likely to spot him with active sonar sonobouys or dipping sonar. IDAS can also be aimed at a surface ship (as in the bridge or a helicopter sitting on the platform at the rear of the ship. This is done using the fiber optic link, which can use used to designate a target. Otherwise, the missile uses its heat seeking sensor. 

Even when missiles systems like are available for use it's uncertain if any navy will buy them. The concept of anti-aircraft missiles for subs is several decades old and never actually used. But it's possible, so new models keep showing up.