Mark 37 torpedo

• Name — Mark 37 torpedo • Origin — United States • Type — Acoustic torpedo • Is Ranged — yes • Is Explosive — yes • Is Missile — yes • Service — 1956 -1972 • Used By — United States Navy Israeli Navy Royal Netherlands Navy • Designer — Westinghouse Electric Underwater Sound Laboratory, Harvard University Ordnance Research Laboratory, Pennsylvania State University • Manufacturer — Naval Ordnance Station Forest Park • Design Date — 1946 • Variants — Mark 37 Mod 1 Mark 37 Mod 2 Mark 37 Mod 3 NT37C NT37D NT37E NT37F • Weight — 1430 lb • Length — 135 inch • Diameter — 19 inch (21-inch guide rails) • Range — 23000 yards at 17 knots, 10000 yards at 26 knots • Filling — Mk 37 Mod 0, HBX-3 • Filling Weight — 330 pounds • Detonation — Mk 19 contact exploder • Engine — Electric • Speed — 17 knots, 26 knots • Guidance — Gyroscope (initial), passive sonar (cruise) and Doppler active sonar homing (terminal) • Launch Platform — Submarines

Its engineering development began in 1946 by Westinghouse. It was largely based on the concept of the passive homing Mark 27, with added active homing system tested on modified Mark 18s, and a new torpedo body. Between 1955 and 1956, thirty torpedoes were produced for development testing, with large-scale production commenced shortly afterwards. Due to its electric propulsion, the torpedo swam smoothly out of the launch tube, instead of having to be ejected by pressurized air, therefore significantly reducing its acoustic launch signature. To allow for water flow around the torpedo while swimming out, several 1 in-thick guide studs were attached to the torpedo, which although 19 in in diameter was designed to be used only from 21 in torpedo tubes. The guidance of a Mk37 mod 0 torpedo was done by a gyroscope control during the initial part of its trajectory, where the gyro control achieved a straight run, a passive sonar homing system, and at the last 700 yards by a Doppler-enabled active sonar homing, with magnetostrictive transducers operating at 60 kHz. The electronics was based on miniature vacuum tubes, later on solid-state semiconductor devices.

• Illustration — A Mark 37 Mod 1 torpedo at The Submarine Force Museum, Argentina. • Illustration — Israeli Mark 37E torpedo The mod 1 torpedoes were longer, slower and heavier than mod 0, but offered better target acquisition capabilities and higher ability to intercept agile submarines. They used wire-guidance. In 1967, the mod 0s started being refurbished as mod 3, and mod 1 as mod 2. These modifications involved many changes including replacement of magnetostrictive transducers with piezoelectric ones, and resulted in target acquisition range increased from 700 yd to 1000 yd without loss of sensitivity with increasing depth. The torpedoes used Mark 46 silver oxide batteries. These had a known tendency to overheat, occasionally igniting or exploding. Training torpedoes used rechargeable secondary batteries. The efficiency of Mk 37 torpedoes was high for targets with speed lower than 20 kn and depth less than 1000 ft. As submarines with higher speeds and operating depths appeared, new torpedoes were developed. Of them, the export models NT37C, D, E, and F are based on the Mk37 design. For a long time, the Mark 37 was a primary U.S. submarine-launched ASW torpedo. It was replaced by the Mark 48 starting in 1972. The remaining inventory was then rebuilt and sold to several countries, including Israel, as the NT-37C after the vacuum tube guidance systems were replaced by solid-state electronics and the electric propulsion was replaced with a liquid monopropellant.

The Mk 67 submarine launched mobile mine is based on a Mark 37 torpedo body. It entered service in 1983 and is capable of swimming as far as 10 miles through or into a channel, harbor, shallow water area and other zones which would normally be inaccessible to the vessel laying it. After reaching the target area it sinks to the sea bed and acts like a conventionally laid influence mine. The exploder in the Mk 67 warhead is computerised and incorporates magnetic, acoustic and pressure sensors.

section • Illustration — A Mark 37 exhibit in Tonijn, at the Dutch Navy Museum. • Power plant: Mark 46 silver-zinc battery, two-speed electric motor • Length: 135 in (mod.0), 161 in (mod.1) • Weight: 1430 lb (mod.0), 1660 lb (mod.1) • Diameter: 19 in • Range: 23000 yards at 17 knots, 10000 yards at 26 knots • Depth: 1000 ft • Speed: 17 knots, 26 knots • Guidance system: active/passive sonar homing; passive until about 700 yards from target, then active; mod.1 with wire-guidance • Warhead: 330 lb HBX-3 high explosive with contact exploder • Date deployed: 1957