The Mark 50 torpedo is a

U.S. Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage o ...

advanced lightweight

torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, ...

for use against fast, deep-diving

submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...

s. The Mk 50 can be launched from all anti-submarine aircraft and from torpedo tubes aboard surface combatant ships. The Mk 50 was intended to replace the Mk 46 as the fleet's lightweight torpedo. Instead the Mark 46 will be replaced with the

Mark 54 LHT The Mark 54 Lightweight Torpedo (formerly known as Lightweight Hybrid Torpedo, or LHT) is a standard anti-submarine warfare (ASW) torpedo used by the United States Navy. Development The Mark 54 was co-developed by Raytheon Integrated Defense ...

. The torpedo's stored chemical energy propulsion system uses a small tank of

sulfur hexafluoride Sulfur hexafluoride or sulphur hexafluoride (British spelling) is an inorganic compound with the formula SF6. It is a colorless, odorless, non- flammable, and non-toxic gas. has an octahedral geometry, consisting of six fluorine atoms attach ...

gas, which is sprayed over a block of

solid Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structur ...

lithium Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense soli ...

, which generates enormous quantities of

heat In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary. A thermodynamic system does not ''contain'' heat. Nevertheless, the term is ...

, which generates

steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporizatio ...

. The steam propels the torpedo in a closed

Rankine cycle The Rankine cycle is an idealized thermodynamic cycle describing the process by which certain heat engines, such as steam turbines or reciprocating steam engines, allow mechanical work to be extracted from a fluid as it moves between a heat sourc ...

, supplying power to a

pump-jet A pump-jet, hydrojet, or water jet is a marine system that produces a jet of water for propulsion. The mechanical arrangement may be a ducted propeller ( axial-flow pump), a centrifugal pump, or a mixed flow pump which is a combination of bot ...

. This propulsion system offers the very important deep-water performance advantage in that the combustion products—

sulfur Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...

and

lithium fluoride Lithium fluoride is an inorganic compound with the chemical formula LiF. It is a colorless solid, that transitions to white with decreasing crystal size. Although odorless, lithium fluoride has a bitter-saline taste. Its structure is analogous to ...

—occupy less volume than the reactants, so the torpedo does not have to force these out against increasing water pressure as it approaches a deep-diving submarine.

General characteristics, Mk 50

*Primary function: air and ship-launched lightweight torpedo *Contractor:

Alliant Techsystems Alliant Techsystems Inc. (ATK) was an American aerospace, defense, and sporting goods company with its headquarters in Arlington County, Virginia, in the United States. The company operated in 22 states, Puerto Rico, and other countries. ATK's ...

, Westinghouse *Length: *Weight: approx. *Diameter: *Speed: > *Power Plant: Stored Chemical Energy Propulsion System *Propulsion: Pump Jet *Guidance system: Active/passive acoustic homing *Warhead: high explosive

Comparable weapons

* Stingray torpedo * MU90 Impact

Notes

References

MK-50 Advanced Lightweight Torpedo
via FAS
Issues Related to the Navy's Mark-50 Torpedo Propulsion System, General Accounting Office, January 1989 - has diagrams showing internal general arrangement, retrieved December 18, 2012
{{Mark-series torpedoes Aerial torpedoes Torpedoes of the United States Military equipment introduced in the 1990s