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Launch of the Transit 1A satellite on a Thor-Able II
Function Expendable launch system
Sounding rocket
Manufacturer Douglas/Aerojet
Country of origin  United States
Height 26.9 metres (88 ft) - 27.8 metres (91 ft)
Diameter 2.44 metres (8 ft 0 in)
Mass 51,608 kilograms (113,776 lb)
Stages 2-3
Payload to 640km LEO 120 kilograms (260 lb)
Associated rockets
Family Thor
Derivatives Thor-Ablestar
Comparable Luna
Launch history
Launch sites LC-17A, Canaveral
Total launches 16
Successes 10
Failures 6
First flight 24 April 1958
Last flight 1 April 1960
Notable payloads Pioneer
First stage - Thor
Engines 1 LR79-7
Thrust 758.71 kilonewtons (170,560 lbf)
Specific impulse 282 sec
Burn time 165 seconds
Fuel RP-1/LOX
Second stage - Able
Engines 1 AJ-10
Thrust 34.69 kilonewtons (7,800 lbf)
Specific impulse 270 sec
Burn time 115 seconds
Third stage (optional) - Altair
Engines 1 X-248
Thrust 12.45 kilonewtons (2,800 lbf)
Specific impulse 256 sec
Burn time 38 seconds
Fuel Solid

The Thor-Able was an American expendable launch system and sounding rocket used for a series of re-entry vehicle tests and satellite launches between 1958 and 1960. It was a two stage rocket, consisting of a Thor IRBM as a first stage, and a Vanguard-derived Able second stage. On some flights, an Altair solid rocket motor was added as a third stage. It was a member of the Thor family, and an early predecessor of the Delta.[1][2]


Sixteen Thor-Ables were launched, nine on sub-orbital re-entry vehicle test flights, and seven on orbital satellite launch attempts. Six launches resulted in failures, in which three of those failures were the result of an Altair upper stage added to the rocket to allow it to launch the spacecraft onto a trans-lunar trajectory. All sixteen launches occurred from Cape Canaveral Air Force Station Launch Complex 17A.[3]


The Thor-Able vehicle had a stronger airframe than the standard Thor IRBM and had the inertial guidance system replaced by a radio guidance package mounted on the Able stages. It saw its first test on April 24, 1958 when Vehicle 116 was launched with dummy upper stages. 146 seconds after liftoff, it exploded from a turbopump failure. The second and third tests on July 10 and 23 were successful, after which Vehicle 127 was prepared for launch with the world's first lunar probe. This flight, broadcast live on television, took place on August 17 but ended embarrassingly when the Thor exploded 77 seconds into the launch due to another turbopump malfunction. After an Atlas missile test a month later also failed due to the turbopumps, the Air Force Ballistic Missile Division quickly replaced the pumps in all of their missiles and this problem did not repeat itself again.

On October 10, Pioneer 1 was launched on Thor 130. The second stage shut down too early and the probe did not have sufficient velocity to escape Earth's orbit. It reentered the atmosphere and burned up 43 hours after launch.

Pioneer 2 was launched November 8 and reentered the atmosphere less than an hour after launch when the third stage failed to ignite.

The next six Thor-Able flights were suborbital tests for the Air Force (January 23, February 28, March 21, April 8, May 20, and June 11, 1959). All of these were successful except the first one, which failed to stage due to an electrical problem and fell into the Atlantic Ocean.

On August 7, Explorer 6 (a scientific satellite) was launched on Vehicle 134 and successfully orbited.

On September 17, Transit 1A failed to orbit due to the third stage again failing to ignite.

On November 3, Pioneer 5 was successfully launched. Intended originally as a Venus probe, technical delays caused it to be launched after the 1959 Venus window had closed so that it was instead sent into heliocentric orbit.

The final Thor-Able launch orbited Tiros 1 on April 4, 1960.

The Able upper stage name represents its place as the first in the series, from the Joint Army/Navy Phonetic Alphabet.[4]

See also


  1. Krebs, Gunter. "Thor Able". Gunter's Space Page. Retrieved 2008-11-10.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  2. Wade, Mark. "Delta". Encyclopedia Astronautica. Retrieved 2008-11-10.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  3. Lethbridge, Cliff. "Thor-Able Fact Sheet". Cape Canaveral Rocket and Missile Programs. Spaceline. Retrieved 2008-11-10.<templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>
  4. Helen T. Wells, Susan H. Whiteley, and Carrie E. Karegeannes. Origin of NASA Names. NASA Science and Technical Information Office. p. 5. <templatestyles src="Module:Citation/CS1/styles.css"></templatestyles>

External links