U.S. Anti-Aircraft Gunners Practice Jet-Propelled Targets -- Jot-propelled rocket targets streak into the air, cutting bands of light in the sky and leaving luminous clouds of dust on the ground, as they are ejected from specially constructed carriages to give U.S. anti-aircraft gunners practice in aiming at fast-. moving planes. Used at an Army camp in the Southern U.S., the rocket targets have an initial speed of 450 miles an hour. American gunners track the targets with .50-caliber machine guns and 20 and 40 mm. cannon. April 06, 1944. (Photo by U.S. Office of War Information Picture).