| Country: |
United States of America |
| Associated Country: |
United Kingdom |
| Alternate Name: |
SM-75 |
| Class: |
MRBM |
| Basing: |
Silo based |
| Length: |
19.81 m |
| Diameter: |
2.44 m |
| Launch Weight: |
49900 kg |
| Payload: |
Single Mk 2 RV |
| Warhead: |
Nuclear W49 1.44 MT |
| Propulsion: |
Single-stage liquid |
| Range: |
2700 km |
| Status: |
Obsolete |
| In Service: |
1958-1975 |
Details
The SM-75 Thor was a medium-range, silo-based, liquid propellant ballistic missile. It was the first US missile to reach the medium/intermediate-range category. However, the system was deployed in the United Kingdom, as it was impossible to strike the Soviet Union from Thor silos in the United States. Considered one of the most distinctive looking missiles ever developed by the United States, the missile’s blunt nose design made it look more like a first stage of a missile rather than a complete system. This was actually the missile’s commercial fate. After the military ceased its use, the primary contractor, Douglas (now McDonnell Douglas), used the Thor as the first stage for multi-stage space launch rockets.
The Thor, by today’s standards a theater missile, was intended for use against strategic targets. The high yield on its warhead made it an effective weapon for destroying cities, but the low accuracy of the guidance systems of the time prevented it from being effective at destroying anything but a soft target. The 60 Thor missiles placed in the UK were deployed to supplement the power of the Royal Air Force’s Bomber Command, which threatened targets in the western areas of the Soviet Union, mainly East Germany. They would most likely have been targeted upon large military installations or valuable strategic areas, although the possibility of nuclear strikes against Soviet satellite states would pressure Russia against launching an attack. The strategic value of the Thor was primarily to boost allied morale and deter Soviet nuclear strikes on US allies. Launched from silos, the missiles were safe from Soviet aerial attack and there was little threat from missile systems during this time.
The Thor missile had a range of 2,700 km (1,678 miles), though it reached test distances as far as 4,750 km (2,952 miles). It carried an Mk 2 reentry vehicle with the same W-49 1.44 MT warhead as the Atlas missile. The Thor was 19.81 m long, 2.44 m wide and had a launch weight of 49,900 kg. The accuracy of its inertial guidance system is unknown, but given the missiles of the time period, it was likely 1,000-2,000 m CEP. It used a single-stage liquid propellant motor.
The SM-75 Thor missile entered development in the 1950s, along with the Jupiter, Atlas, and Minuteman 1 projects. The Thor entered service in the US Air Force in 1958, with 60 missiles being transferred to the RAF Bomber Command between 1958 and 1959. The missiles were to be operated by RAF crews, but the warheads remained under US control and joint authorization was required for launch. In 1962, the US decided to concentrate on intercontinental-range missiles and withdrew maintenance support from the missiles, resulting in the Thor’s eventual retirement.
The Thor had a short rebirth in the 1970s as a satellite interceptor. The missiles were placed on remote ocean islands and put into position where they could intercept and destroy enemy satellites in time of war. In essence, this was a crude form of ICBM interception, using an extensive nuclear payload to destabilize satellites in orbit and make them non-functional. This form of missile defense has been technologically possible since the late 1950s, though only recent computer and navigation systems make it effective.(1)
Footnotes
- Jane’s Strategic Weapons Systems, Issue 46, ed. Duncan Lennox, (Surrey: Jane’s Information Group, January 2007) 606.
