Mark 46 torpedo. The Mark 46 torpedo is the backbone of the United States Navy's lightweight anti-submarine warfare torpedo inventory and is the NATO standard. These aerial torpedoes are designed to attack high-performance submarines. In 1989, an improvement program for the Mod 5 to the Mod 5A and Mod 5A(S) increased its shallow-water performance. The Mark 46 was initially developed as Research Torpedo Concept I (RETORC I), one of several weapons recommended for implementation by Project Nobska, a 1956 summer study on submarine warfare.

Design details

Variants 
 Mod 0: One of the original versions of 1960 (production started 1963). Solid propellent piston engine. Gyro/wire guidance with passive/active homing.
 Mod 1: Based on Mod 0. 1967. Uses liquid Otto fuel piston engine. Laminar search guidance. Phase 1 of 1968 uses stronger hull to resist deeper waters. Phase 2 of 1971 uses a new homing program able to detect submarines near the surface.
 Mod 2: Based on Mod 1 phase 2. More powerful Mk 103 Mod 1 warhead. Improved computer with snake search pattern capability. Known to have been captured by China in 1978.
 Mod 4: Version for use as Mark 60 CAPTOR mine payload.
 Mod 5: 1979 upgrade kit for Mod 2, also known as NEARTIP (near-term improvement program). New passive/active sonar, liquid fuel and two speed engine for low speed search and high speed attack.
 Mod 5A: Cheapter NEARTIP upgrade kit for Mod 1 and Mod 2 with improved shallow-water performance. 1980s.
 Mod 5A(S): Variant of 5A that allows use in water as shallow as 40 m.
 Mod 5A(SW): Latest variant from 1996 Service Life Extension Program. Boasts improved counter-countermeasure performance, enhanced target acquisition, provides a bottom-avoidance preset, and improved maintainability and reliability.
 Mod 6: Version for Mark 60 CAPTOR, with some NEARTIP components.
 Mod 7: Cancelled. Not funded by Congress.

For most variants there is also an inert REXTORP (recoverable exercise torpedo) version.

Specifications 
 Mark 46, Mod 5
 Primary Function: Air and ship-launched lightweight torpedo
 Contractor: Alliant Techsystems
 Power Plant: Two-speed, reciprocating external combustion; Mono-propellant (Otto fuel II)
 Length:  tube launch configuration (from ship),  with ASROC rocket booster
 Weight:  (warshot configuration)
 Diameter: 
 Range: 
 Depth: > 
 Speed: > 
 Guidance System: Homing mode: Active or passive/active acoustic homing
 Launch/search mode: Snake or circle search
 Warhead:  of PBXN-103 high explosive (bulk charge)
 Date Deployed: 1967 (Mod 0); 1979 (Mod 5)

Yu-7 variant
The Chinese Yu-7 torpedo is said to be based on the Mk 46 Mod 2. The Chinese Navy used the Yu-7 ASW torpedo, deployed primarily on ships and ASW helicopters, but it started to be replaced by the Yu-11 in 2012.

Operators

See also
 Advanced Light Torpedo Shyena
 CAPTOR mine (a sea mine which incorporates a Mk 46 torpedo)
 MU90 Impact torpedo
 Mark 50 torpedo
 Mark 54 MAKO Lightweight Torpedo
 Stingray torpedo

References

External links
 DiGiulian, Tony, Navweaps.com: USA Torpedoes
 Unofficial U.S. Navy Site: MK-46 Torpedo
 FAS: MK-46 Torpedo

Aerial torpedoes
Cold War anti-submarine weapons of the United States
Military equipment introduced in the 1960s
Torpedoes of the United Kingdom
Torpedoes of the United States