In November 1955, three companies — Douglas, Lockheed and North American Aviation — were given one week to bid on a U.S. Air Force contract to build a missile that could hit the Soviet Union from the United Kingdom. On Dec. 23, 1955, the Air Force chose Douglas as the prime contractor for the missile’s airframe and integration, and North American’s Rocketdyne division for the engine, which would produce 135,000 pounds (600 kilonewtons) of thrust.

Thor, named after the Norse god of thunder, provided nuclear deterrence before intercontinental ballistic missiles (ICBM) were ready. It was designed to deliver a payload 1,500 miles (2400 kilometers), a range that allowed a U.K.-based missile to hit Moscow.

After several failures, Thor made its first successful flight on Sept. 20, 1957. It reached a speed of about 10,000 mph (16,093 kph) and attained an attitude of 1,100 miles (1800 kilometers) before the inert warhead splashed into the south Atlantic. Further testing ensued, and after 18 research-and-development launches, Thor was cleared for operational use.

Under the code name Operation Go Away, the first Thor missiles were deployed in the United Kingdom in September 1958, and by April 1960, four Royal Air Force squadrons had 60 missiles, all at above-ground launch sites.

More than 200 Thor missiles were built, but once the generation of ICBMs based in the United States became operational, Thor was no longer needed. It was deactivated in 1966.

Thor missiles lived on. Later, they were reconfigured as launch vehicles for the Air Force and NASA. They provided first the hardware, then the technology, for current Air Force and NASA launch systems, including the Delta family of launch vehicles that continues to send military and commercial satellites in to orbit.