The 6555th, Chapter III, Section 4
The 6555th, Chapter III, Section 4
The Air Force Missile Test Center became involved with the THOR (Weapon System 315A) program in the fall of 1954, after ARDC ordered development of that missile "as soon as possible." The Wright Air Development Center sponsored the missile initially, and AFMTC hosted the THOR at Cape Canaveral. Following a series of meetings between AFMTC and Western Development Division officials in February and March 1955, support requirements were worked out for two launch pads, a blockhouse, a guidance site, one service stand, airborne guidance test equipment, housing and messing facilities. The THOR was given equal priority with the ATLAS in December 1955, and the Western Development Division became the missile's new sponsor at that time. The first THOR test missile was launched in January 1957, and, by that time, THOR launching facilities consisted of a blockhouse, one launching pad with a service tower (i.e., Pad 17B), a second partially finished launch pad (17A) and a 40,000-square-foot assembly building (Hangar M). The principal contractors were Douglas Aircraft Company (for the airframe), Bell Telephone Laboratories (for the radio-inertial guidance system), A.C. Spark Plug (for the more advanced all-inertial guidance system), General Electric (for the nose cone) and North American Aviation (for the rocket motors). The THOR weighed 110,400 pounds, and it was 62.5 feet long and 8 feet in diameter. It was propelled by a single rocket motor rated between 135,000 pounds and 150,000 pounds of thrust.14
 | COMPLEX 17 UNDER CONSTRUCTION - 1956 |
 | MISSILE ASSEMBLY BUILDING M (LEFT) AND STEEL STRUCTURE OF HANGAR L (RIGHT) - 1956 |
The first THOR was launched from Cape Canaveral on 25 January 1957. Engine ignition and main stage operation were normal at launch, but a liquid oxygen valve failed almost immediately after lift-off, and the missile slipped back through Pad 17B's launcher ring to explode on the deflector plate below. A low order explosion and fire destroyed the missile and damaged the pad, and the launch failure delayed the next launch until mid-April 1957. The second THOR launch, on April 19th, was more successful, but a third missile (Number 103) exploded on the pad on May 21st after its fuel tank ruptured five minutes before its intended launch. Once again, Pad 17B had to be refurbished, but Pad 17A was completed in July 1957, so 17A was used for the fourth THOR on August 30th. (That launch was successful, but the missile broke in half 93 seconds into the flight and plunged into the Atlantic about 20 miles from the launch site.) The fifth THOR was launched from Pad 17B on 20 September 1957, and it met all its test objectives. Unfortunately, Pad 17A received its own baptism in fire when the sixth THOR lost thrust on October 3rd, fell back through the launching ring and burned. Two other launches on October 11th and October 24th were successful, and they concluded the THOR's airframe/propulsion testing phase at the Cape. Guidance system tests began with a partially successful THOR flight from Pad 17B on 7 December 1957. A subsequent flight from Pad 17A tested the THOR's all-inertial guidance system on December 19th. It was completely successful.15
 | THOR NUMBER 101 ON LAUNCH STAND BEFORE LAUNCH |
 | THOR 101 LAUNCH FAILURE |
 | THOR 101 EXPLOSION |
 | REMOVING THOR 101 WRECKAGE |
 | THOR NUMBER 103 IN SERVICE TOWER, PAD 17B |
 | DAMAGE TO PAD 17B FOLLOWING EXPLOSION OF THOR 103 |
THOR nose cone separation tests began with a flight from Pad 17B on 28 February 1958, but the second launch in that series ended in another explosion and fire on Pad 17B on April 19th. The third nose cone test was flown successfully on June 13th, and a THOR tactical launcher performed well during a guidance system test launch offsite (e.g., Pad 18B) on 4 June 1958. Test flights to validate overall refinements in the THOR got underway on 5 November 1958, and five of those flights were launched from Pad 17B or 18B by the end of the year. Three of the five met their test objectives, and so did eight of the next nine THORs launched from 17B or 18B between 30 January and the end of June 1959. An 82-foot-long variant of the THOR, known as the THOR-ABLE, was also used in a dozen flights from Pad 17A between 23 April 1958 and 12 June 1959 to test two different ablative nose cone designs for the ATLAS program. Eleven out of 14 THORs met their flight test objectives in the last half of 1959.16
 | THOR-ABLE LAUNCH FROM PAD 17A |
Though contractors launched many THORs at Cape Canaveral, the Air Force conducted its ballistic missile Combat Training Launch (CTL) operations at Vandenberg Air Force Base. The first missile launched from Vandenberg was also the first THOR CTL operation, and it was completed successfully by a blue suit (SAC) missile crew on 16 December 1958. The British participated in THOR launches at Vandenberg and Cape Canaveral a little later on, and they increased their presence at Vandenberg and the Cape as blue suit and contractor support steadily diminished over the next two and one-half years. As testing continued at the Cape, THORs began to arrive in the United Kingdom in September 1958, and 60 THOR launch sites (assigned to four THOR squadrons) went on alert between June 1959 and April 1960. THOR launch operations were performed exclusively by Royal Air Force personnel after June 1961. Since the THOR's mission could be assumed by other weapon systems after 1962, the THORs were pulled out of Great Britain between November 1962 and August 1963, and they were returned to the United States. The THOR was matched with several different high energy upper stages in the late 1950s, and, as of this writing, the THOR booster continues to serve as the first stage of a space vehicle known as the DELTA II used for Global Positioning Satellite (GPS) and commercial space launch operations.17