OVERVIEW: The Mk 46 Lightweight Torpedo Mod 1 is a U.S. Navy air- and surface-launched anti-submarine weapon introduced in 1967 as a major upgrade to the original Mod 0. It employs liquid monopropellant propulsion and active/passive acoustic homing to effectively engage submarine targets.

DETAILS: “Mod 1” marks the conversion from the Mk 46’s Mod 0 solid-fuel piston engine to a liquid monopropellant (Otto fuel II) piston engine, introduced in 1967 for improved maintainability and deeper operational depth (>400 m). It retains the 12.75‑in diameter and 8‑ft length, weighing approximately 508 lb (231 kg), with a 45 lb PBXN-103 warhead. Guidance uses gyro stabilization plus active/passive sonar in a laminar search pattern, providing robust target detection to about 460 m. Mod 1 included two upgrade phases: Phase 1 (1968) introduced a strengthened hull; Phase 2 (1971) enhanced homing to detect near-surface submarines and extended range to ~8–11 km at ~40 kn.

TYPE: Lightweight ship/air‑launched acoustic homing torpedo

FUNCTION: Upon launch from Mk 32 tubes, aircraft, or ASROC, it uses initial gyroscopic launch stabilization followed by programmed laminar search in active/passive mode. Upon finding a submarine, it homes-in at ~40 kn and explodes its PBXN-103 warhead on contact.

NOTE:
IOC: 1967 (Mod 1 entry; hull reinforcement Phase 1)
Manufacturer: Naval Ordnance Test Station Pasadena; Aerojet-General; Honeywell, USA
Operators: United States; exported under Military Assistance Program
Platforms: Surface vessels (Mk 32 tubes), ASW aircraft and helicopters, vertical launch ASROC
Conflict used in: No confirmed combat deployment

SOURCE: Mark 46 torpedo (Wikipedia); A Brief History of U.S. Navy Torpedo Development – Part 2 (Jolie, 1978); Mark 46 torpedo data (Weaponsystems.net)