Nulka is an electronic warfare decoy, jointly developed by the navies of the United States and Australia. It is a rocket-propelled radio transmitter that projects a radar signature similar to that of a large warship as well as a significant infrared plume.
After launch, the decoy flies to a predetermined point then begins using its rocket motor to hover, maintaining the decoy longer than simple chaff or flares would. Its primary purpose is to divert anti-ship missiles away from their intended targets. Because the Nulka rocket itself is so small, the probability of an anti-ship missile striking it directly is pretty small. Because of this, it is capable of drawing away multiple missiles. It can be used to provide decoy coverage for another ship as well as for the launching platform. This allows it to be useful in convoy defense, preventing situations like the missile attack that sunk MV Atlantic Conveyor during the Falklands war.
The name comes from an Australian aboriginal term meaning 'quickly'. It is standard equipment aboard all Australian and US frigates, destroyers and cruisers. The US also uses it aboard amphibious assault ships, aircraft carriers and supply ships.