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Thor Able Star with Transit VBN-2 Dec 5 1963.jpg
Launch of a Thor-Ablestar 2 with a Transit satellite
Function Orbital carrier rocket
Manufacturer Douglas/Aerojet
Country of origin  United States
Height 29 metres (95 ft)
Diameter 2.44 metres (8 ft 0 in)
Mass 53,000 kilograms (117,000 lb)
Stages 2
Payload to
1100km LEO
150 kilograms (330 lb)
Associated rockets
Family Thor
Comparable Delta
Launch history
Launch sites LC-17, Canaveral
LC-75-1, Arguello
Total launches 19
Successes 12
Failures 5
Partial failures 2
First flight 13 April 1960
Last flight 13 August 1965
First Stage - Thor
Engines 1 MB-3-1
Thrust 760.64 kilonewtons (171,000 lbf)
Specific impulse 285 sec
Burn time 164 seconds
Fuel RP-1/LOX
Second Stage - Ablestar
Engines 1 AJ-10
Thrust 36.02 kilonewtons (8,100 lbf)
Specific impulse 280 sec
Burn time 296 seconds

The Thor-Ablestar, or Thor Able-Star, also known as Thor-Epsilon[1] was an early American expendable launch system consisting of a PGM-17 Thor missile, with an Ablestar upper stage. It was a member of the Thor family of rockets, and was derived from the Thor-Able.

The Ablestar second stage was an enlarged version of the Able, which gave the Thor-Ablestar a greater payload capacity compared to the Thor-Able. It also incorporated restart capabilities, allowing a multiple-burn trajectory to be flown, further increasing payload, or allowing the rocket to reach different orbits. It was the first rocket to be developed with such a capability.[2]

Nineteen Thor-Ablestars were launched between 1960 and 1965, of which four failed, and a fifth resulted in a partial failure, as only one of two payloads separated from the upper stage.[2] Two versions were built; the Thor-Ablestar 1, with a DM-21 Thor, and an AJ-10-104 second stage engine, and the Thor-Ablestar 2, which had a DSV-2A Thor first stage, and an uprated AJ-10-104D engine on the second stage.[1] Thor-Ablestar 1 launches occurred from LC-17 at Cape Canaveral, and Thor-Ablestar 2 rockets were launched from LC-75-1 at Point Arguello, which has since become part of Vandenberg Air Force Base and is now designated SLC-2.

See also[edit]


  1. ^ a b Krebs, Gunter. "Thor Able-Star". Gunter's Space Page. Retrieved 2008-11-30. 
  2. ^ a b Wade, Mark. "Delta". Encyclopedia Astronautica. Retrieved 2008-11-30.