The American Mk 54 lightweight torpedo has finally entered production. Costing less than a million dollars each, the Mk 54 is a cheaper, and somewhat less capable replacement for the Cold War era high tech Mk 50 and the old reliable Mk 46. The 750 pound lightweight torpedoes are used by helicopters and P-3 aircraft when hunting submarines. The three million dollar Mk 50 was in development for over two decades, to provide a deep diving, smart torpedo that was light enough to be carried by helicopters, and could go deep to kill Russian nuclear subs. But when the Mk 50 finally became available in the late 90s, the typical target was a quieter diesel-electric sub in shallow coastal waters. So the Mk 54 was developed, using cheaper, off-the-shelf, electronic components, some technology from the Mk 50 and larger Mk 48, as well as the simpler, but not deep diving, frame and propulsion systems of the older Mk 46 lightweight torpedo. Thus the ten foot long Mk 54 is a bit of a hybrid, created to save money, and also be more capable against quieter subs operating in shallower water. The Mk 54 has a range of about 10,000 meters and a top speed of about 20 meters a second. It has a built in sonar that can search for the target sub, as well as listening devices to pick up any sounds a sub might make. The Mk 54 also has an onboard computer and a data file of underwater noises and search tactics, which are used as it tries to find its target, and keep after it until it can hit the sub and destroy it with the hundred pounds of explosives in the warhead. In the last 40 years, some 25,000 of the older Mk 46 torpedoes were made, and at least a few thousand Mk 54s will be manufactured. Mk 50s will be kept in inventory to deal with the few hostile nuclear subs that are still out there, although the Mk 54 also has a capability of going deep, just not as deep as the more expensive Mk 50.