Spearfish torpedo

The Spearfish torpedo (formally Naval Staff Target 7525) is the heavy torpedo used by the submarines of the Royal Navy. It can be guided by wire or by autonomous active or passive sonar, and provides both anti-submarine warfare (ASW) and anti-surface ship warfare (ASuW) capability.

It replaced the unreliable Tigerfish torpedo, which was withdrawn in 2004; the significantly higher speed of the Spearfish, for which development started in the 1970s, before the breakup of the Soviet Union, was intended to catch high-speed, deep-diving Soviet threats such as the Alfa-class submarine.

The torpedo is driven by a pump-jet coupled to a Hamilton Sundstrand 21TP04 gas turbine engine using Otto fuel II and hydroxyl ammonium perchlorate as oxidiser. The addition of an oxidiser improves the specific energy of the fuel by reducing the fuel-richness of the Otto fuel.

A microprocessor enables the torpedo to make autonomous tactical decisions during the attack. It has a powerful blast warhead, triggered by either contact detonation (against a submarine hull) or an acoustic proximity fuze (for under-keel detonation against ships). A standoff detonation under the keel enhances blast effects against surface ships through the amplification of stress resulting from the interaction of the explosion's products and the flexible structure of the ship. This can be seen in SINKEX video footage.