This is the Loon, also called the JB-2 or KUW-1, an American copy of the German pulsejet-powered V-1 or "Buzz Bomb" of World War II. The Loon was designed to carry a 2,200 pound explosive payload to a range of 150 miles and could be launched from the ground, ships, or aircraft.
The Loon was first test launched in October 1944, but its development came late and it was not used in the war. However, the missile did provide invaluable experience to U.S. Navy and Army Air Force personnel in the handling of missiles. It was cancelled in 1950 and replaced by the faster and more powerful Regulus missile.
This Loon missile was transferred from the U.S. Navy to the Smithsonian Institution in 1971.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.