| SM-75/PGM-17A Thor | |
|---|---|
 A Thor intermediate range ballistic missile. | |
| Type | Intermediate-range ballistic missile |
| Place of origin | United States |
| Service history | |
| Used by | United States Air Force (testing) Royal Air Force (operational deployment) |
| Production history | |
| Designed | 1957 |
| Manufacturer | Douglas Aircraft Company |
| Produced | 1959–1960 |
| No. built | About 225; peak deployment was 60 |
| Variants | Delta rockets Thor rocket family |
| Specifications | |
| Mass | 49,590 kilograms (109,330 lb) at start. |
| Length | 19.76 metres (64 ft 10 in). |
| Diameter | 2.4 metres (8 ft). |
| Propellant | kerosene and liquid oxygen |
Operational range | 2,820 kilometres (1,750 mi) |
| Flight altitude | 630 kilometres (390 mi). |
The PGM-17A Thor was the first operative ballistic missile of the United States Air Force (USAF). It was 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. Thor was 65 feet (20 m) in height and 8 feet (2.4 m) in diameter.
The first generation of Thor missiles were rushed into service, and design mistakes resulted in a 24% launch failure rate. The competing PGM-19 Jupiter missile saw more use, but both were quickly eclipsed by the Air Force's long range ICBM program, which could be fired from US soil. By 1959, with the Atlas rocket well on its way to operational status, both Thor and Jupiter programs became obsolete as delivery vehicles, yet continued to be built and deployed until 1963 for political reasons and to maintain aerospace industry employment.
The missile's lasting legacy continued as the Thor and later Delta families of space launch vehicles used boosters derived from the initial Thor missile, and continued on into the 21st century.