# 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.
* A Mark 46 Mod 5A torpedo is inspected aboard the guided missile destroyer USS Mustin.
* A French Lynx helicopter carrying a Mk 46 torpedo.
* A P-8A Poseidon of VP-16 dropping a Mark 46 torpedo

## 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: Cheaper 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: 8 ft 6 in (2.59 m) tube launch configuration (from ship), 14 ft 9 in (4.50 m) with ASROC rocket booster
* Weight: 508 lb (230 kg) (warshot configuration)
* Diameter: 12.75 in (324 mm)
* Range: 12,000 yd (11,000 m)
* Depth: > 1,200 ft (370 m)
* Speed: > 40 kn (74 km/h; 46 mph)
* Guidance System: Homing mode: Active or passive/active acoustic homing
* Launch/search mode: Snake or circle search
* Warhead: 96.8 lb (43.9 kg) 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

* Australia
* Bahrain
* Belgium
* Brazil
* Canada
* Chile
* Colombia
* Croatia
* Ecuador
* Egypt
* France
* Germany
* Greece
* Indonesia
* Iran
* Israel
* Italy
* Japan
* Kuwait
* Mexico
* Morocco
* Netherlands
* New Zealand
* Norway
* Pakistan
* Peru
* Philippines
* Portugal
* Saudi Arabia
* South Korea
* Spain
* Taiwan
* Thailand
* Turkey
* United Arab Emirates
* United Kingdom
* United States