Taurus -----> Minotaur-C

Orbital Sciences Corporation * ATK Thiokol Propulsion

 

The Taurus is a ground-launched derivative of the Pegasus launch vehicle, which combines the Pegasus motors and avionics with a larger first stage.  This vehicle was developed to meet the requirements of DARPA's SSLV program, which emphasized rapid-response launch capability from an austere launch site. The SLV configuration of Taurus uses a government-furnished Peacekeeper missile first stage. After 1994 the contract was administratively transferred to the USAF.

Orbital Sciences Corporation  initiated development work on an upgraded version of the Taurus vehicle. This vehicle differs from the ARPA-Taurus  configuration primarily through the use of Thiokol's Castor 120 solid rocket motor for the first stage in place of the Peacekeeper stage (TU-903). The Castor 120 has the same diameter as the Peacekeeper, but is  longer to include more propellant. The stage has an added nozzle gimbal system for thrust vector control. The nozzle of the equivalent Pegasus stage was fixed because attitude control is provided aerodynamically.
Orbital  utilizes the following four-digit nomenclature to describe Taurus configurations (0000):

first Digit:              first stage motor
                                1 = Peacekeeper (TU-903)
                                2 = Castor 120
                                3 = Castor 120, stretched second stage
second Digit         fairing
                                1 = 63-in. diameter
                                2 = 92-in. diameter
third Digit              third stage motor
                                1 = Orion 38
                                2 = Star 37FM
fourth Digit           reserved

In early 2014, the Taurus brand was discontinued and replaced by the Minotaur-C, which is in fact a Taurus with Minotaur avionics.

Castor-120XL
This variant of the Castor-120 predecessor is used as a first or second stage in commercial launch vehicles and provides improved performance over the baseline configuration. A version of this motor was static tested for the U.S. Air Force as part of the Large Class Stage development program, however the motor is being updated to tailor burn rates and improve performance, as well as utilize common materials & processes to improve cost control for launch vehicle providers.
In addition to Athena family, Castor-120XL is in preparation for Minotaur-C (ex-Taurus family) and Minotaur-I (commercial version) which are in the process of being merged into one sub-family under Minotaur-I.