Thor IRBM Development History
The origins of the Air Force IRBM program can be traced back to the Matador (TM-61), a subsonic, tactical-range missile. In 1951 the Air Force's Wright Air Development Center (WADC) located at Wright-Patterson Air Force Base (AFB), Ohio, became concerned that the Matador, which followed a relatively slow and predictable course toward its target, could be readily intercepted in flight. Searching for an alternative to the air-breathing missile, WADC recommended that the Air Force develop a tactical-range ballistic missile (TBM). The Tactical Air Command endorsed the concept, and Air Force Headquarters ordered the Air Research and Development Command to formulate a development plan for the TBM by June 1, 1955. The goal was to have the new missile flying by 1960.
In mid-1954 ARDC selected four contractors (the Glenn L. Martin Company, Douglas Aircraft, Lockheed Aircraft, and General Electric) to perform design studies on the TBM. As outlined in the December 1954 General Operational Requirement (GOR), the mission of the TBM was the destruction of surface targets within a range of 600 to 1,000 miles. The GOR stressed that the new missile needed to combine the merits of simplicity, mobility, and flexibility to operate in all parts of the world. Late the following year the Air Force increased the required range to between 1,200 to 1,500 miles and changed the name to Medium-Range Ballistic Missile (MRBM). Shortly thereafter, the Air Force set up the MRBM program office at WADC.
Events outside of Wright-Patterson, however, soon changed the face of the missile program. The impetus for change came from two sources. The first was the Air Force's burgeoning intercontinental ballistic missile (ICBM) program. In May 1954 the Air Force escalated the ICBM to its top research and development priority and established a powerful program office, called the Western Development Division (WDD). Located in Inglewood, California, a suburb of Los Angeles, the WDD quickly emerged as the focal point of the Air Force's long-range ballistic missile development effort.
The second factor that changed the nature of the MRBM was the Killian Report. The report was prepared by the Killian Committee, a high-level government study group directed by President Eisenhower to determine how to use new and emerging technologies to reduce the risk of a surprise attack on the United States. In the February 1955 report the committee urged that in addition to the ICBM, the United States should also develop a new class of 1,500-mile IRBM to counter a similar program thought to be under way in the Soviet Union. Anticipating that the IRBM would be far easier to build than the ICBM, the committee feared that the Soviets would deploy their IRBMs before the American ICBMs were ready. Not only would that be a blow to American prestige, it would also allow the Soviets to intimidate U.S. allies in Europe and Japan.
To counter the Soviet missile program, the committee recommended that the United States develop both land- and sea-based IRBMs. President Eisenhower endorsed the committee's recommendations, and by the fall of 1955, all three services proposed to build and operate IRBMs. The interservice competition was keen. Unable to decide which service would develop the IRBM, in November the Joint Chiefs of Staff recommended that the Air Force develop the land-based IRBM and the Army and Navy jointly develop the sea-based version.
Initially the Air Force was reluctant to begin yet another missile program. Its hesitation sprang from the WDD's concern that diverting engineers and equipment to the IRBM would delay the ICBM program. However, with the prospect of losing the mission to the Army or Navy, the Air Force decided it had to build an IRBM of its own. At first the Air Force proposed developing the IRBM as a derivative of the ICBM, but after a Department of Defense study panel showed that approach to be impractical, the Air Force elected to develop a new missile, the Thor (SM-75).
Anxious to integrate the IRBM program within the broad outlines of the ICBM program, in May 1955 the Air Force transferred responsibility for the IRBM from Wright-Patterson to the WDD. Throughout the summer and early fall, the WDD refined its development approach and solicited preliminary IRBM designs from a variety of airframe manufacturers, industrial concerns, and the Army Ordnance Department's Redstone Arsenal.
After evaluating the prospective contractors, on November 30, 1955, the WDD invited three to bid: Douglas Aircraft, Lockheed Aircraft, and North American Aviation. The WDD gave the firms a week to prepare their proposals. At the end of December the Air Force awarded a contract to build the Thor airframe and then assemble and test the missile to Douglas, the California aircraft manufacturer.
To expedite the new program the Air Force sought to use existing ICBM components wherever possible. Thor's engine was one-half of an Atlas ICBM primary booster; its guidance system and reentry vehicle also came from the Atlas program. The only components Douglas had to design and develop were the airframe and the ground support equipment.
The availability of off-the-shelf components made developing the IRBM less challenging than building the ICBM, but these advantages were offset by the Air Force's fervent desire to stage Thor's first test flight in January 1957, a mere 13 months after it awarded Douglas the contract. Although the Air Force was ostensibly racing to beat the Russians, in reality the air service saw the Army's IRBM, the Jupiter (SM-78), as the more immediate threat. Both services were racing to be the first to develop an operational IRBM, a step each saw as crucial in winning control of the IRBM mission.
Initially the Army missile program had a substantial lead over the Thor program. The Army had already built ample missile test facilities, and its Redstone tactical-range missile provided an effective test platform for Jupiter's components. In contrast, in January 1956 the Air Force had yet to complete any of its test facilities. Progress, however, came rapidly. By March 1956, construction of the engine and captive missile test stands was under way at Edwards AFB, California, as was the construction of the Thor launch facilities at Cape Canaveral on Florida's east coast. Also in March 1956, Douglas and the WDD completed the airframe design, and Douglas began setting up the Thor production line at its Santa Monica, California plant.
The engine test stands at Edwards were completed in July 1956, and from then until November, Rocketdyne and Douglas engineers worked three shifts a day, 7 days a week to test the engine and integrate the powerplant into the airframe. The first two Thor test vehicles were flown to Patrick AFB in the late fall of 1956. To keep pace with the Army, the Air Force was very anxious to stage a successful flight as quickly as possible, and was willing to accept a substantial risk to do so. The WDD classified Thor as a “maximum risk” program, meaning the WDD set minimum performance and reliability requirements for the initial test flights.
Thor flight testing began inauspiciously. In January 1957 the first flight ended in a cataclysmic explosion within a few feet of the launch pad. On the second test flight, conducted in late April, the missile appeared to be on its way to a perfect test flight when the Air Force range safety officer (RSO) destroyed it in mid-air. Soon afterward the Air Force found that the missile's tracking transponder had been installed backwards. As a result, although observers standing outside the blockhouse could see the missile was heading out over the ocean, on the RSO's monitor it appeared to be flying inland, and he had to destroy it. A month later a third test flight ended in a sheet of flame on the launch pad.
Despite the string of failures, the Air Force and Douglas were able to fx the problems fairly quickly, and at the end of August, a Thor staged a partially successful test flight. Finally, on September 20, the fifth test vehicle logged a successful test flight of 1,300 miles.
The successful test came not a moment too soon. In early October the Soviet Union placed the world's first artificial satellite, the famous Sputnik, into orbit. Within a week President Eisenhower ordered Thor into full production, and at the end of December the President announced that the United States would deploy four squadrons of IRBMs overseas. In early February 1958 the United States and Great Britain reached an agreement to deploy the missiles in that island nation. Under the terms of the agreement the missiles would be operated by Royal Air Force (RAF) crews, but the warheads would stay under American control.
In mid-December 1958 a Strategic Air Command (SAC!) crew fired a Thor from an operational test facility at Vandenberg AFB, California, and the following April an RAF crew fired a missile from the same installation. In June 1959 the Air Force placed its first Thor squadron on operational alert, and by the following April it had activated the remaining three.