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    The PGM-17A Thor was the first operational ballistic missile of the USAF. Named after the Norse god of thunder, it was deployed in the United Kingdom between 1959 and 1963 as an intermediate-range ballistic missile (IRBM) with a thermonuclear warhead. Development of the Thor began in 1954. The goal was a missile system that could deliver a nuclear warhead over a distance of 1,150 to 2,300 miles with a CEP of 2 miles. This range would allow the targeting of Moscow from almost any location in Europe. On 30 November 1955, three companies were given one week to bid on the project: Douglas, Lockheed, and North American Aviation. The requirement was that the missile was to use existing technology, skills, abilities, and techniques to expedite its entry into service. On 27 December 1955, Douglas was awarded the prime contract for the airframe and integration. The Rocketdyne division of North American Aviation was awarded the engine contract, AC Spark Plug the primary inertial guidance system, Bell Labs the backup radio guidance system, and GE the nose cone/reentry vehicle. The program proceeded quickly in spite of a number of setbacks. The first launch, conducted at Cape Canaveral on 25 January 1957, was a spectacular failure, lifting a few feet, then falling back onto the launch pad and exploding as all of the fuel mixed with all of the oxidizer simultaneously. More failures and explosions followed. In fact, of the first eight launches, only one ended with a successful flight test. The Cape was not the only location of disasters. On 30 July 1958, six Douglas technicians were severely burned, three fatally, when a LOX valve failed at the Thor static test stand in Sacramento, CA. Finally, after several more successful flight tests, Thor was declared operational and testing began at Vandenberg AFB. The first missile to be launched from that base was a Thor, by a SAC crew, on 16 December 1958, and it was successful. From that point, the program proceeded quickly, but deployment of the IRBM fleet to Europe proved more difficult than expected because no NATO members other than the UK accepted the offer to have Thor missiles stationed on their soil (Italy and Turkey both agreed to accept Jupiter missiles). Unlike the Jupiter missiles, Thors could be carried by the USAF’s cargo aircraft of the time, which resulted in a more rapid deployment. Thor arrived in the UK beginning in August 1958 under the code name “Project Emily.” All 60 of the Thor missiles deployed in the UK were based at above-ground launch sites. The missiles were stored horizontally on transporter-erector trailers and covered by a retractable missile shelter. To launch the weapon, the crew used an electric motor to roll back the missile shelter, essentially a long shed mounted on steel rails, then used a powerful hydraulic launcher-erector to lift the missile to an upright position for launch. Once it was standing on the launch mount, the missile was fueled and could then be fired. The entire launch sequence, from starting of shelter roll-back to engine ignition, took approximately 15 minutes. Total flight time from launch to target impact was approximately 18 minutes. The 60 missiles were operated by 20 squadrons of RAF Bomber Command under US-UK dual-key control. The first active unit was No. 77 Squadron at RAF Feltwell in 1958, with the remaining units becoming active in 1959. Once the first generation of U.S.-based ICBMs became operational, the IRBMs were quickly retired. The last of the Thor missiles was withdrawn from operational alert in 1963.
    But that was not the end of the Thor. A small number of them with "Thrust Augmented Delta" boosters and nuclear warheads remained operational in an anti-satellite (ASAT) missile role known 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. Several patches in this album date from the Thor’s ASAT era.
    Thors were also used in some nuclear tests at Johnston Island during 1962, but only one such test proved successful: On 8 July 1962, Thor missile 195 launched a Mk4 reentry vehicle containing a W49 thermonuclear warhead to an altitude of 250 miles--outer space! The warhead detonated with a yield of 1.45 MT. This was the Starfish Prime event of the nuclear test series called Operation FISHBOWL. Seventeen days later, during a Thor launch for Bluegill Prime in the same test series, the Thor launch vehicle and its nuclear payload were destroyed on the launch mount, contaminating the pad and surrounding facilities with plutonium. An extensive, and expensive, clean-up operation followed.
    Despite being retired from service as an IRBM just a few years after deployment, the Thor found widespread use as a space launch vehicle (SLV) in subsequent years, putting many hundreds of satellites into orbit. It was the first in a large family of SLVs—the Delta rockets. The last remaining direct descendant of the Thor, the Delta II, was retired in 2018.
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