Mark 54 LHT

Mark 54 MAKO Lightweight Torpedo
Mark 54 Torpedo aboard the USS Ross (DDG-71) in March 2008.
Type	Lightweight torpedo
Place of origin	United States
Service history
In service	2004–present
Used by	United States Navy Royal Australian Navy Indian Navy
Production history
Designer	Raytheon Systems
Designed	1999
Unit cost	US$839,320(FY2014)
Produced	2003
Specifications
Weight	608 lb (276 kg)
Length	106.9 in (2.72 m)
Diameter	12.75 in (324 mm)
Warhead	PBXN-103
Warhead weight	96.8 lb (43.9 kg)
Blast yield	238lb TNT
Engine	reciprocating external combustion
Propellant	Otto II (liquid)
Speed	>40 kn (74.1 km/h; 46.0 mph)
Guidance system	Active or passive/active Acoustic homing
Launch platform	Mark 32 Surface Vessel Torpedo Tubes, ASW Aircraft, RUM-139 VL-ASROC

The Mark 54 Lightweight Hybrid Torpedo (LHT) is a standard 12.75 inch (324 mm) anti-submarine warfare (ASW) torpedo used by the United States Navy.

The Mark 54 was co-developed by Raytheon Integrated Defense Systems and the U.S. Navy under the U.S. Navy's Lightweight Hybrid Torpedo program in response to perceived problems with the extant Mark 50 and Mark 46 torpedoes. The Mk 50, having been developed to counter very high performance nuclear submarines such as the Soviet Alfa class, was seen as too expensive to use against relatively slow conventional submarines. The older Mk 46, designed for open-ocean use, performed poorly in the littoral areas, where the Navy envisioned itself likely to operate in the future.

The Mk 54 was created by combining the homing and warhead portions of the Mk 50 and the propulsion unit of the Mk 46, improved for better performance in shallow water, and with the addition of commercial off-the-shelf (COTS) technology to further reduce costs. It shares much of the software and computer hardware of the Mk 48 ADCAP heavy torpedo, based around a custom PowerPC 603e chip.

Developmental testing began in July 1999, and a successful critical design review was completed in November 1999.

In April 2003, Raytheon was awarded a sole source contract for the production of the Mk 54. Full rate production began in October 2004. In March 2010 the Fifth Fleet requested improvements in the Mk 54's performance against diesel-electric submarines via an Urgent Operational Need Statement (UONS). This led to a software Block Upgrade (BUG) program which began testing in August 2011 and which continues, having been criticised by the DOT&E for using unrealistic proxies for threat submarines.

The Mk 54 can be fired from surface ships via the Mark 32 surface vessel torpedo tubes or the vertical launch anti-submarine rocket (ASROC) systems, and also from most ASW aircraft, although they are slightly different lengths and weights. The P-8 Poseidon uses the High-Altitude Anti-Submarine Warfare Weapons Capability (HAAWWC) GPS-guided parachute kit to drop torpedoes from high altitude.