The Mark 50 torpedo is a U.S. Navy advanced lightweight torpedo

Torpedo

The modern torpedo is a self-propelled missile weapon with an explosive warhead, launched above or below the water surface, propelled underwater towards a target, and designed to detonate either on contact with it or in proximity to it.The term torpedo was originally employed for...

 for use against fast, deep-diving submarine

Submarine

A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...

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

Mark 46 torpedo

Designed to attack high-performance submarines, the Mark 46 torpedo is the backbone of the U.S. Navy's lightweight ASW torpedo inventory, and is the current NATO standard. These aerial torpedoes, such as the Mark 46 Mod 5, are expected to remain in service until the year 2015...

 as the fleet's lightweight torpedo. Instead the Mark 46 will be replaced with the Mark 54 LHT

Mark 54 LHT

The Mark 54 Lightweight Hybrid Torpedo is a standard 12.75 inch antisubmarine warfare torpedo used by the United States Navy.- Development :...

.

The torpedo's Stored Chemical Energy Propulsion System uses a small tank of sulfur hexafluoride

Sulfur hexafluoride

Sulfur hexafluoride is an inorganic, colorless, odorless, and non-flammable greenhouse gas. has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule. Typical for a nonpolar gas, it is poorly soluble in water but soluble in...

 gas

Gas

Gas is one of the three classical states of matter . Near absolute zero, a substance exists as a solid. As heat is added to this substance it melts into a liquid at its melting point , boils into a gas at its boiling point, and if heated high enough would enter a plasma state in which the electrons...

 which is sprayed over a block of solid

Solid

Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...

 lithium

Lithium

Lithium is a soft, silver-white metal that belongs to the alkali metal group of chemical elements. It is represented by the symbol Li, and it has the atomic number 3. Under standard conditions it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly...

, which generates enormous quantities of heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

, in turn used to generate steam

Steam

Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...

 from seawater. The steam propels the torpedo in a closed Rankine cycle

Rankine cycle

The Rankine cycle is a cycle that converts heat into work. The heat is supplied externally to a closed loop, which usually uses water. This cycle generates about 90% of all electric power used throughout the world, including virtually all solar thermal, biomass, coal and nuclear power plants. It is...

, supplying power to a pump-jet

Pump-jet

A pump-jet, hydrojet, or water jet, is a marine system that creates a jet of water for propulsion. The mechanical arrangement may be a ducted propeller with nozzle, or a centrifugal pump and nozzle...

.

General characteristics, Mk-50

• Primary function: air and ship-launched lightweight torpedo
• Contractor: Alliant Techsystems
  Alliant Techsystems
  Alliant Techsystems Inc., most commonly known by its ticker symbol, ', is one of the largest aerospace and defense companies in the United States with more than 18,000 employees in 22 states, Puerto Rico and internationally, and 2010 revenues in excess of an estimated...
  
  , Westinghouse
• Length: 2.84 m (112 in)
• Weight: 340 kg (750 lb)
• Diameter: 324 mm (12.75 in)
• Speed: > 40 kn
• Power Plant: Stored Chemical Energy Propulsion System
• Guidance system: Active/passive acoustic homing
• Warhead: approximately 45 kg (100 lb) high explosive (shaped charge
  Shaped charge
  A shaped charge is an explosive charge shaped to focus the effect of the explosive's energy. Various types are used to cut and form metal, to initiate nuclear weapons, to penetrate armor, and in the oil and gas industry...
  
  )