The Thor-Ablestar, or Thor-Able-Star, also known as Thor-Epsilon was an early American

expendable launch system An expendable launch system (or expendable launch vehicle/ELV) is a launch vehicle that can be launched only once, after which its components are destroyed during reentry or impact with Earth, or discarded in space. ELVs typically consist of s ...

consisting of a

PGM-17 Thor The PGM-17A Thor was the first operative ballistic missile of the United States Air Force (USAF). It was named after the Thor, Norse god of thunder. It was deployed in the United Kingdom between 1959 and September 1963 as an intermediate-range b ...

missile, with an Ablestar

upper stage A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own Rocket engine, engines and Rocket propellant, propellant. A ''tandem'' or ''serial'' stage is mounted on top of anoth ...

. It was a member of the

Thor Thor (from ) is a prominent list of thunder gods, god in Germanic paganism. In Norse mythology, he is a hammer-wielding æsir, god associated with lightning, thunder, storms, sacred trees and groves in Germanic paganism and mythology, sacred g ...

family of rockets, and was derived from the

Thor-Able The Thor-Able was an American expendable launch system used for a series of re-entry vehicle tests and spacecraft launches between 1958 and 1960. It was a two-stage rocket, consisting of a Thor IRBM as a first stage and a Vanguard-derived Abl ...

. The Ablestar second stage was an enlarged version of the

Able Able may refer to: * Able (1920 automobile), a small French cyclecar * Able (rocket stage), an upper stage for Vanguard, Atlas, and Thor rockets * Able (surname) * ABLE account, a U.S. savings plan for people with disabilities * Able UK, British s ...

, 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 and development of the stage took a mere eight months. 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. Thor-Ablestar 1 launches occurred from LC-17 at

Cape Canaveral Cape Canaveral () is a cape (geography), cape in Brevard County, Florida, in the United States, near the center of the state's Atlantic Ocean, Atlantic coast. Officially Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated ...

, and Thor-Ablestar 2 rockets were launched from LC-75-1 at

Vandenberg Space Force Base Vandenberg Space Force Base , previously Vandenberg Air Force Base, is a United States Space Force Base in Santa Barbara County, California. Established in 1941, Vandenberg Space Force Base is a space launch base, launching spacecraft from the ...

(now designated SLC-2).

Launches

Nineteen Thor-Ablestar 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. The first failure was the launch of Courier 1A, an experimental communications satellite, on 19 August 1960 when the first stage shut down 30 seconds earlier than planned and was destroyed by the

Range Safety Officer In rocketry, range safety or flight safety is ensured by monitoring the flight paths of missiles and launch vehicles, and enforcing strict guidelines for rocket construction and ground-based operations. Various measures are implemented to protect ...

. On 30 November, another launch involving a

Transit Transit may refer to: Arts and entertainment Film * ''Transit'' (1980 film), a 1980 Israeli film * ''Transit'' (1986 film), a Canadian short film * ''Transit'' (2005 film), a film produced by MTV and Staying-Alive about four people in countrie ...

satellite failed in practically identical fashion. This episode nearly created an international incident as parts of the Thor landed in

Cuba Cuba, officially the Republic of Cuba, is an island country, comprising the island of Cuba (largest island), Isla de la Juventud, and List of islands of Cuba, 4,195 islands, islets and cays surrounding the main island. It is located where the ...

. War was threatened. Cuban leader

Fidel Castro Fidel Alejandro Castro Ruz (13 August 1926 – 25 November 2016) was a Cuban politician and revolutionary who was the leader of Cuba from 1959 to 2008, serving as the prime minister of Cuba from 1959 to 1976 and President of Cuba, president ...

subsequently sold off the Thor's engine to the Soviets and the Chinese received its thrust vectors, which ended up proving valuable to the latter's development of a ballistic missile capability. To prevent this from happening again, future Thor Ablestar launches had their flight paths modified to avoid passing over Cuba. The launch of a

satellite on 22 February 1961 was successful, but its companion Lofti satellite failed to separate from the second stage. On 29 June 1961, a Thor-Ablestar successfully inserted a Transit-4A into orbit, but two hours later the Ablestar exploded for unknown reasons into hundreds of pieces, which remained in orbit. This is the first known artificial object to break up unintentionally in space. The third launch failure occurred on 24 January 1962 when the second stage produced insufficient thrust to achieve orbital velocity for several piggybacked satellites. The fourth and final failure was the launch of an Anna geodetic satellite on 10 May 1962 when the second stage completely failed to ignite.

References

{{Thor and Delta rockets Thor (rocket family) Spacecraft that broke apart in space

Launches

See also

References