Castor (rocket stage)

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Diagram showing the use of a Castor as the second stage of a Scout-B vehicle

The Castor family of solid-fuel rocket stages and boosters were built by Thiokol and used on a variety of launch vehicles.^[1] They were initially developed as the second stage motor of the Scout rocket. The design was based the MGM-29 Sergeant, a surface-to-surface missile developed for the United States Army at the Jet Propulsion Laboratory.^[2]^[3]

[edit] Versions

Castor 1: The Castor 1 was first used for a successful suborbital launch of a Scout X-1 rocket on September 2, 1960.^[4]; It was 19.42 feet (5.92 m) long, 2.6 feet (0.79 m) in diameter, and had a burn time of 27 seconds. Castor 1 stages were also used as strap-on boosters for launch vehicles using Thor first stages, including the Delta-D. (A Delta-D was used in 1964 to launch Syncom-3, the first satellite placed in a geostationary orbit.) Castor 1 stages were used in 141 launch attempts of Scout and Delta rockets, only 2 of which were failures. They were also used on some thrust-assisted Thor-Agena launchers. The last launch using a Castor 1 was in 1971.^[5]
Castor 2: The Castor 2 was an upgraded version of the Castor 1. It was first used on a Scout in 1965, and continued to be used on Scouts until the last Scout launch, in 1994. Castor 2 stages were also used as the strap-on boosters for the Delta-E. It retained the same diameter as the Castor 1, and was from 5.96 m to 6.27 m in length.
Castor 4: The Castor 4, along with its A and B variants, were expanded to 1.02 m in diameter. They were used as strap-ons on some Delta, Delta II, Atlas IIAS, and Athena launch vehicles. They were also planned to serve as the first stage of the Spanish Capricornio booster, however, no such flights occurred before the project was cancelled.
Castor 120: An unrelated development, the Castor 120 is a derivative of the first-stage motor of the MX ("Peacekeeper") missile. "120" refers to the planned weight, in thousands of pounds, of the booster at project inception. The actual product turned out lighter than this, however. It was first used as the first-stage motor of Lockheed Martin's Athena I, and later the first and second stages of Athena II.^[6] After a test launch in August 1995, the first launch of a customer payload took place on August 22, 1997, when an Athena was used to launch the NASA Lewis satellite.^[7]