Thor was the first operational ballistic missile deployed by the U.S. Air Force (USAF). Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and September 1963 as an intermediate-range ballistic missile (IRBM) with thermonuclear warheads.
As Douglas' Chief Missiles Design Engineer, Max Hunter was the principal designer of the Air Force Thor intermediate range ballistic missile in the late 1950s. Fearful that the Soviet Union would beat the U.S. in deploying a long-range ballistic missile, the USAF began a crash program in January 1956 to develop the Thor, a 1,500 mile (2,400 km) intermediate-range ballistic missile.
There was a fierce competition between the Army's Jupiter ICRM under development by a team led by Wernher von Braun in Huntsville, Alabama and the Air Force's Thor contracted to Douglas Aircraft in Santa Monica. Max and Von Braun became acquainted during this period and later became friends and colleagues when Douglas was selected as the contractor for Von Braun's Saturn S-IV and S-IVB stages.
One of the advantages of the design was that, unlike the Jupiter IRBM, Thor could be carried by the USAF's cargo aircraft of the time, which made its deployment more rapid. The launch facilities were not transportable, and had to be built on site. The Thor was a stop-gap measure, and once the first generation of ICBMs based in the US became operational, Thor missiles were quickly retired. The last of the missiles was withdrawn from operational alert in 1963.
A small number of Thors, converted to "Thrust Augmented Delta" launchers, remained operational in the anti-satellite missile role as Program 437 until April 1975. These missiles were based on Johnston Island in the Pacific Ocean and had the ability to destroy satellites in low Earth orbit. With prior warning of an impending launch, they could destroy a Soviet spy satellite soon after orbital insertion. These missiles remain in storage, and could be reactivated, though the W-49 Mod 6 warheads were all dismantled by June 1976.
A large family of space launch vehicles—the Thor and its civilian counterpart Delta—were derived from the Thor design. The Delta II and Delta IV are still in active service in 2016 and, with the retirement of Atlas and Titan in the mid-2000s, are the last surviving "heritage" launch vehicles in the US fleet derived from a Cold War-era missile system.