3.5-Inch Forward Firing Aircraft Rocket

The 3.5-Inch Forward Firing Aircraft Rocket, or 3.5-Inch FFAR, was an American rocket developed during World War II to allow aircraft to attack enemy submarines at range. The rocket proved an operational success, and spawned several improved versions for use against surface and land targets.

Design and development
Following trials by the Royal Air Force of rocket-propelled, air-launched weapons for anti-submarine warfare during 1942, the United States Navy launched a high-priority project during the summer of 1943 for the development of an anti-submarine rocket of its own.

The resulting rocket was a simple design with four tailfins for stabilisation at the rear, powered by a rocket motor that had been under development by Caltech since 1943. No warhead was fitted; rather, the rocket's nose was a solid steel mass, weighing 20 lb, that was intended to puncture the pressure hull of a target submarine through the sheer kinetic energy of its flight; launched in a dive, the rocket's speed could exceed 800 mph, and it remained effective against submarine targets up to depths of 130 ft below water

Operational history
Following expedited development, the weapon, officially designated the 3.5-Inch Forward Firing Aerial Rocket, entered operational service with the U.S. Navy late in 1943; production of 10,000 rockets per month had been ordered that August. The FFAR's first "kill" of an enemy submarine took place in 1944. The rocket was originally only carried by the TBF Avenger torpedo bomber, due to the mass and drag caused by its rail launchers; tests determined that more streamlined "zero length launchers" could be used, allowing the rocket to be carried by a variety of carrier-based aircraft.

Although the rocket's accuracy was more than sufficient to allow usage against surface targets, the narrow body diameter restricted the size of any explosive warhead that could be fitted. Therefore, for use against ships and land targets, the rocket was modified with a warhead derived from a 5in/127mm anti-aircraft shell, producing the 5-Inch Forward Firing Aircraft Rocket.