The United States has developed the widest variety of these weapons. Since the introduction of the Mk 43 in the 1950s, the standard American air-launched torpedo is small (324mm/12.75 inches), and carries, at most, 100 pounds of high explosives. But the high explosives are not the same as they once were. The explosive back then was Torpex. Today, the explosive of choice is PBNX-103, which is roughly twice as powerful as TNT.
Today, the United States uses three major air-launched torpedoes: The Mk 46, the Mk 50, and the Mk 54. The Mk 46 was an improvement on the Mk 43/Mk 44 torpedoes, originally designed to destroy Soviet nuclear submarines. The versions in service today are the Mk 46 Mod 5 (dropped from helicopters, maritime patrol aircraft, and fired from surface ships), which came out in 1989, and the Mk 46 Mod 6 NEARTIP, which emerged in the 1990s (with more resistance to countermeasures). The Mk 50 Barracuda was to replace it, since the Mk 46s performance was iffy against submarines like the strongly built Alfa. The Mk 50 was faster (officially 74+ kilometers per hour, true speed is probably 111 kilometers per hour), and its warhead is a shaped charge, which puts all the force of an explosion in to a hot jet of metal that goes in one direction, and through the increasingly thick hulls on Soviet subs. The concept was first used to punch through the armor of tanks. However, with the end of the Cold War, the Barracuda wasnt needed as badly. The threat no longer was deep-diving nuclear attack submarines like the Alfa, Oscar, Akula, and Sierra classes. Now, the threat is smaller, and less robustly constructed diesel-electric and air-independent propulsion submarines.
Two new torpedoes have emerged. The first is the Mk 46 NEARTIP, which is a rebuild of older Mk 46 torpedoes. The other torpedo in development is the Mk 54 Lightweight Hybrid Torpedo (LHT). The Mk 54 uses the Mk 46 propulsion system with the sensor package of the Mk 50. The warhead system used has not been revealed, but either system would suffice against a smaller boat like a Kilo or a Type 209 (the two diesel-electric submarines that are most numerous). The older Mk 46 still has a new lease on life, though. The Mk 46 Mod 7 is a torpedo with a new kind of target: Other torpedoes. It will be launched from surface vessels, used as a hard-kill system to prevent torpedoes from hitting American vessels.
The British have their own lightweight torpedo, the Stingray. A mature system in service from the 1980s (pre-production units were sent to the Falklands, and four were lost onboard HMS Antelope), Stingray was in service prior to the Mk 50. Its warhead is a shaped charge, to punch through the tough hull of some of the late-model Soviet submarines. Stingray, though, was also designed to handle shallow-water sub threats as well. The French, Germans, Australians, Poles, and Italians use the MU-90, called the Impact. It has a 100-pound shaped charge, and is roughly comparable to the Mk 50.
The Russian ASW torpedoes are usually 400mm (just under 16 inches) as opposed to the smaller NATO torpedoes (there is a reason these torpedoes are all the same size NATO standardized). Their most modern ASW torpedo is the APSET-95, with a 132-pound warhead, a range of 30 kilometers, and a speed of 92.6 kilometers per hour. This torpedo is designed to kill the most-capable sub in the U.S./NATO arsenals, the Seawolf-class attack submarine. The other major ASW torpedoes currently in the Russian arsenal are the APR-2 (two-kilometer range, 115-kilometer per hour speed, and a 220-pound explosive charge) and the APR-3 (a lighter version of the APR-2 with a 168-pound warhead).
Future air-launched lightweight torpedoes will probably follow the mold of the Mk50, Stingray, and MU-90. Shallow-water capability will be emphasized, with a shaped-charge to ensure penetration of a submarines hull. How submarines will adapt to this is a matter to determine what is going on. Harold C. Hutchison (firstname.lastname@example.org)
The air-launched torpedo has evolved over the past 65 years. Once the primary ship-killer for all the major naval powers, it has now evolved into a specialized anti-submarine weapon of deadly efficiency.