Orbital Sciences Castor 4B

The Castor 4B solid-propellant rocket stage can also be used stand-alone as a single-stage suborbital rocket. Netween May 1991 and April 2017, at least 15 single-stage Castor 4B rockets have been launched. The first military use of this rocket were two U.S. Army launches in August 2005 as part of the CMCM-1 (Critical Measurements and Countermeasures Program, Campaign 1) missile defense tests. The U.S. Navy has used the Castor 4B as a target vehicle in 10 tests (between November 2005 and June 2012) of the Aegis ballistic missile defense system and the RIM-161 SM-3 missile. When used as target in missile defense tests, Orbital Sciences Corporation designated the Castor 4B rocket as the MRT (Medium-Range Target). The MRT could also be air-launched, using a cradle in the cargo space of a C-17 Globemaster III aircraft.

Photo: Orbital Sciences

Castor 4B MRT

Castor-M57A1

On 14 September 1999, the U.S. Air Force launched a two-stage rocket consisting of a Castor 4B first stage and an M57A1 (3rd stage of surplus Minuteman I/II missiles) second stage. The rocket launched the ait-2 (Atmospheric Interceptor Technology, Test Vehicle 2) mission, which conducted various experiments related to ballistic missile defense technology. The ait-2 vehicle was about 17.3 m (56 ft 10 in) long and weighed 14475 kg (31912 lb) at liftoff.

Specifications

Note: Data given by several sources show slight variations. Figures given below may therefore be inaccurate!

Data for Castor 4B (dimensions and weight without payload):

Main Sources

[1] Mark Wade: Encyclopedia Astronautica
[2] Jonathan McDowell: Launch Vehicles
[3] Gunter Krebs: Gunter's Space Page

Back to Directory of U.S. Military Rockets and Missiles, Appendix 4

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Last Updated: 19 October 2026