February 10, 2006: The U.S. has successfully tested an AIM9X Sidewinder air-to-air missile finding and hitting a target after being launched straight up from the ground. The 9X version of the Sidewinder has a much more sensitive heat seeker, as well as a wider arc the seeker can sense, making it capable of operating like this. The purpose of the test is to supply American submarines with an ability to take down aircraft, particularly helicopters, that are hunting them. U.S. nuclear attack subs have sensors that can detect a helicopter up there, but lack a weapon to respond with. Anti-submarine helicopters carry sensors (usually sonobuoys) that can get a more precise fix on a sub, and torpedoes, with which to destroy the sub below. The sub cannot outrun the helicopter. Actually, attempting to do that would just make more noise for the sonobuoys to pick up. Diving deeper won't work against the more modern torpedoes carried by helicopters. Thus the need for a weapon that can bring down the helicopter, before the sub takes a fatal torpedo hit. The anti-aircraft weapon would probably be in the form of a capsule released from a torpedo tube that, as it reached the surface, would release the Sidewinder missile.