Taurus

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 (Castor 100). 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, XL stage 1+2
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