Operation Chastise On 26 Feb 1943, the new "Upkeep" bomb was approved for use against German dams. "Upkeep" was designed by Barnes Wallis. It was a drum-shaped bomb designed to be carried by aircraft. When released at a low altitude, they spun at the rate of over 500 RPM (revolutions per minute) backwards, which... http://ww2db.com/battle_spec.php?battle_id=211