High Quality Content by WIKIPEDIA articles! The Hydra 70 rocket is a weapon derived from the 2.75 inch (70 mm) Mk 4/Mk 40 Folding-Fin Aerial Rocket developed by the United States Navy for use as a free-flight aerial rocket in the late 1940s. The Hydra 70 family of WAFAR (Wrap-Around Fin Aerial Rocket), based around the Mk 66 universal motor was developed from the previous 2.75 inch Mk 40 motor-based FFAR (Folding Fin Aerial Rocket). The Mk 40 was originally used during the Korean and Vietnam wars, beginning a rich history of providing close air support to ground forces from about 20 different firing platforms, both fixed-wing and armed helicopters, by all U.S. armed forces. Today, the OH-58D(R) Kiowa Warrior and AH-64D Apache Longbow, as well as the Marine Corp's AH-1 Cobra carry the Hydra rocket launcher standard on its weapon pylons. To provide some stability the four rocket nozzles were scarfed at an angle to impart a slight spin to the rocket during flight.