OVERVIEW: The NT‑37C is a heavyweight anti-submarine torpedo derived from the U.S. Navy’s Mk 37 series, redesigned in 1975 for extended range and speed. It uses a liquid monopropellant engine, passive/active acoustic homing, and offers wire-guided mid-course updates.

DETAILS: “NT” denotes Northrop Torpedo upgrade; “37” references the Mk 37 lineage; “C” marks the first full conversion from electric battery to Otto Fuel II propulsion. It measures approximately 3.43 m in length, 533 mm diameter, and weighs about 650 kg, carrying a 150 kg HBX‑3 warhead. Speed increased by over 40% and range by ~150%, achieving ~36 kn and ~15 km range, compared to the original’s 26 kn and 9 km. Its guidance includes initial gyroscopic run, wire mid-course control, and passive/active terminal homing using improved acoustic transducers . Entered service circa 1973–1975, it retained operational relevance into the 1990s with allied navies using it into the early 2000s .

TYPE: Heavyweight submarine-launched wire-guided acoustic homing torpedo

FUNCTION: Launched from 19‑inch submarine tubes (with 21‑inch guide rails), the NT‑37C begins with a straight run then receives mid-course steering via wire link. In terminal phase it deploys passive/active sonar homing at ranges of ~0.6 km to intercept deep or fast submarine targets.

NOTE:
IOC: Circa 1973–1975
Manufacturer: Northrop Corporation (later Honeywell) / Naval Ordnance Station Forest Park, USA
Operators: United States; Netherlands; Israel; other NATO allies 
Platforms: Submarines equipped with 19‑inch tubes (U.S. and allied SSNs/SSKs)

SOURCE: Mark 37 torpedo (Wikipedia); Torpedoes USA post‑WWII (NavWeaps); Northrop Mark 37 upgrade history (Jane’s Naval Weapons Systems); NT‑37C specification data (cmano‑db); Mark 37 torpedo technical evolution (Naval Submarine League archive)