First Launches
Thor test launches were to be from LC-17 at Cape Canaveral Missile Annex. The development schedule was so compressed that plans for the Atlas bunker were used to allow the completion of the facility in time. Nevertheless pad LC-17B was just ready for the first test flight.
The first flight of the Thor IRBM was on January 25, 1957. The first airframe, number 101, was delivered in October of the previous year. The vehicle reached an apogee of 6 inches (150 mm) whereupon contamination destroyed a LOX supply valve causing the engine to lose thrust. The Thor slid backwards through the launch ring and exploded on contact with the thrust deflector. Serious pad damage occurred.
The second Thor flight (102) lasted 35 seconds after an April 1957 launch. It was ended by a range safety officer who destroyed the missile after seeing faulty data on a readout which indicated that the missile was heading inland over Florida.
Thor vehicle 103 (May 1957) exploded on the pad during tanking due to a faulty main fuel valve resulting in tank over-pressurization leading to tank rupture.
Thor vehicle 104 (August 1957) broke up after 92 seconds due to a loss of guidance.
Thor vehicle 105 (20 September 1957), 21 months after the start of construction, flew 1,100 miles (1,800 km) downrange. Estimated range without the extra load of the R and D instrumentation was 1,500 miles (2,400 km).
1957 saw five more flights, including a flight of 1645 miles (2647 km) by a stripped down Thor on 24 October. Phase II testing with the AC Spark Plug inertial guidance system began 7 December with the first successful flight on 19 December 1957.
Read more about this topic: PGM-17 Thor