September 17, 2009: Once more, developers are working on weapons that enable submerged submarines to attack aircraft overhead. There was recent successful test of the U.S. Tomahawk Capsule Launching System (TCLS) releasing a AIM-9X Sidewinder air-to-air heat seeking missile. This is all part of an effort that began during the Cold War, particularly for non-nuclear subs. While most of this work halted when the Cold War ended in 1991, it has since been resumed.
Last year, for example, Germany successfully tested launching anti-aircraft missile from a submerged submarine (U-33, a Type 212 equipped with Air Independent Propulsion). The IDAS (Interactive Defense and Attack system for Submarines) missile used is 7.6 feet long, 180mm in diameter and weighs 260 pounds. It has a 29 pound warhead and a range of at least 15 kilometers. The main targets are 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, an 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.) So using something like IDAS, or TCLS, is a gamble.
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.
IDAS is a year or two away from availability, but it's uncertain if any navy will buy them. A similar system to IDAS (Triton), was developed in the 1990s, but never entered service. IDAS is a continuation of this. 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.