OVERVIEW: The NT‑37E is a heavyweight, submarine-launched anti-submarine torpedo introduced in the 1980s as an export upgrade to the U.S. Navy’s Mk 37 series. It features Otto fuel propulsion, wire guidance, and enhanced digital electronics.

DETAILS: “NT‑37” denotes Northrop’s Otto-fueled upgrade of the Mk 37 electric torpedo; “E” indicates the third major retrofit in the 1980s. It retains a length of ~3.43 m, diameter of 19 in (with 21‑in guide studs), weighs around 650 kg, and carries a 150 kg HBX‑3 warhead. Mod E introduces solid-state digital guidance hardware and enhanced piezoelectric sonar transducers, matching prior Mod D but with further improved signal processing and reliability. Propelled by Otto Fuel II, it achieves ~36 kn speed and a maximum range of ~15 km, representing ~40% faster and ~150% further performance compared to Mk 37 Mod 0 . Guidance combines gyroscopic straight-run, mid-course wire control, and terminal active/passive homing, consistent with NT‑37 lineage.

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

FUNCTION: Launched from 19‑in tubes (with guide rails), it begins on a preset gyro course, receives mid-course updates via wire, and switches to active/passive sonar homing in the terminal phase. Its enhanced electronics and propulsion allow effective engagement of fast, deep-diving submarines in both deep and littoral environments.

NOTE:
IOC: Circa mid‑1980s (post-NT‑37E development period)
Manufacturer: Northrop Corporation / Honeywell Marine Systems, USA
Operators: Exported to allied navies (e.g., Israel, Netherlands) under NT‑37 program 
Platforms: Submarines equipped with 19‑in torpedo tubes (US and allied SSNs/SSKs)

SOURCE: Mark 37 torpedo (Wikipedia); Torpedoes USA post‑WWII (NavWeaps); Jane’s Naval Weapons Systems 2000‑2001; History of US torpedo upgrades (Naval‑Submarine League archives)