V-1 Missile : German in full Vergeltungswaffen-1 (“Vengeance Weapon 1”), also popularly called flying bomb, buzz bomb or doodlebug, German jet-propelled missile of World War II, the forerunner of modern cruise missiles.

More than 8,000 V-1s were launched against London from June 13, 1944, to March 29, 1945, with about 2,400 hitting the target area. A smaller number were fired against Belgium. The rockets were launched from the Pas-de-Calais area on the northern coast of France and subsequently from other sites in German-occupied western Europe. (For contemporary accounts of the bombings of London)

The V-1 was about 8 metres (25 feet) long, exclusive of the long tailpipe of its jet engine, and had a wingspan of about 5.5 metres (20 feet). It was launched from catapult ramps or sometimes from aircraft. It carried an 850-kilogram (1,870-pound) explosive warhead at about 580 km (360 miles) per hour and had an average range of 240 km (150 miles).

The first practical cruise missile was the German V-1 of World War II, which was powered by a pulse jet that used a cycling flutter valve to regulate the air and fuel mixture. Because the pulse jet required airflow for ignition, it could not operate below 150 miles per hour. Therefore, a ground catapult boosted the V-1 to 200 miles per hour, at which time the pulse-jet engine was ignited. Once ignited, it could attain speeds of 400 miles per hour and ranges exceeding 150 miles. Course control was accomplished by a combined air-driven gyroscope and magnetic compass, and altitude was controlled by a simple barometric altimeter; as a consequence, the V-1 was subject to heading, or azimuth, errors resulting from gyro drift, and it had to be operated at fairly high altitudes (usually above 2,000 feet) to compensate for altitude errors caused by differences in atmospheric pressure along the route of flight.

The missile was armed in flight by a small propeller that, after a specified number of turns, activated the warhead at a safe distance from the launch. As the V-1 approached its target, the control vanes were inactivated and a rear-mounted spoiler, or drag device, deployed, pitching the missile nose-down toward the target. This usually interrupted the fuel supply, causing the engine to quit, and the weapon detonated upon impact.

Because of the rather crude method of calculating the impact point by the number of revolutions of a small propeller, the Germans could not use the V-1 as a precision weapon, nor could they determine the actual impact point in order to make course corrections for subsequent flights. In fact, the British publicized inaccurate information on impact points, causing the Germans to adjust their preflight calculations erroneously. As a result, V-1s often fell well short of their intended targets.

Following the war there was considerable interest in cruise missiles. Between 1945 and 1948, the United States began approximately 50 independent cruise missile projects, but lack of funding gradually reduced that number to three by 1948. These three—Snark, Navaho, and Matador—provided the necessary technical groundwork for the first truly successful strategic cruise missiles, which entered service in the 1980s.