The two configurations of Taurus show the government version using a Peacekeeper stage (which will launch MTI) and the commercial version using a Castor 120 motor. Photo: Orbital

Orbital's Taurus rocket is a four-stage, ground-launched vehicle derived from the strong heritage of the Pegasus program. Taurus fills the cost and performance gap between our Pegasus rocket and the industy's much larger, more expensive launch vehicles.

Orbital designed the Taurus launch service to satisfy the varied requirements of our payloads, since the Taurus vehicle is simply a tool to enable the payload to accomplish its mission. Orbital offers a range of payload accommodations and interfaces to provide flexibility in designing a particular mission. In addition, Taurus ground and launch operations have been structured to streamline vehicle integration efforts. Originally designed for rapid response from austere launch sites for Department of Defense missions, the aspects of the Taurus launch system that enable these rapid operations have distinct advantages for commercial and scientific missions as well.

The Taurus launch vehicle can deliver satellites of up to 3,000 pounds into low-Earth orbit, or up to 900 pounds into geosynchronous transfer orbit. Like its Pegasus cousin, Taurus offers unprecedented operational flexibility for a ground-launched vehicle. It is fully transportable, capable of launching from austere sites, and able to be quickly assembled and tested to provide rapid response launches. Vehicle components can be delivered to virtually any unprepared area, then built and launched within one month from a simple launch pad.

Stage 0
The Taurus first stage (known as Stage 0) for the MTI mission is a leftover Peacekeeper missile Solid Rocket Motor (SRM) stage. For commercial launches, a Thiokol Castor 120 SRM is used instead of the reliable Peacekeeper first stage. The Castor 120 physical and performance characteristics are closely related to the Peacekeeper motor. Propellant binder, aluminum and solid content are the same, length and weight are increased modestly, and ballistics are reshaped slightly to create a more benign thrust profile and flight environment while achieving higher performance.

Stage 0/1 Interstage
An aluminum skin and stringer construction interstage extends from the forward skirt of the Stage 0 motor to the aft end of the Stage 1 motor, tapering from a 92 inch (2.3 m) to a 50 inch (1.3 m) diameter. This interstage is fabricated in two sections: the lower interstage, which remains with Stage 0, and the upper interstage, which flies with Stage 1. A field joint between the upper and lower sections of the interstage allows the Taurus upper stage stack to be mated to the Stage 0, while a linear shaped charge separation system severs the interstage sections at Stage 1 ignition. The lower interstage is designed to accommodate a hot-fire separation of Stage 1 through the incorporation of vent ports in the cylindrical portion of the structure. Aerodynamic panels covering the ports are jettisoned just prior to Stage 1 ignition. This hot-fire separation has been successfully demonstrated on all Taurus missions.

Stages 1, 2, and 3
The Taurus upper stages (known as Stages 1, 2 and 3) are the Alliant TechSystems Orion 50S, 50 and 38 SRMs, respectively. These motors were originally developed for Orbital's Pegasus program and have been adapted for use on the ground-launched Taurus vehicle. Common design features, materials and production techniques are applied to all three motors to maximize reliability and production efficiency. These motors are fully flight qualified based on heritage, design conservatism, ground static fires and multiple successful flights.

As an optional service, the Orion 38 Stage 3 can be replaced by a spinning upper stage using Thiokol's STAR 37FM motor.

Avionics Section and Boattail
The graphite/epoxy boattail structure provides the transition from the 50 inch (1.3 m) diameter of the Stage 2 motor to the 63 inch (1.6 m) diameter of the avionics skirt. The boattail is a sandwich structure constructed using a foam core and graphite epoxy facesheets. The avionics skirt, also a graphite/epoxy structure, supports the avionics shelf and carries the primary structural loads from the fairing and payload cone. The aluminum avionics shelf supports the third stage avionics. The shelf is annular in shape to maximize the use of available volume and enable the Stage 3 motor to be suspended from the payload cone through the shelf. This removes the Stage 3 motor from the primary structural load path and provides the flexibility for alternate upper stage configurations.

The MTI spacecraft as the protective payload fairing is installed inside processing building. Photo: Sandia National Laboratories

Avionics
The Taurus avionics system is an all-digital distributed processor design. Mission reliability is achieved by the use of simple designs, high reliability components, high design margins and extensive testing at the box, subsystem, and system level. The heart of the avionics system is a multiprocessor, 32-bit flight computer manufactured by SBS Embedded Computers. The flight computer communicates with all vehicle subsystems and the LSE using standard RS-422 digital serial data links. All avionics on the vehicle feature integral microprocessors to perform local processing and to handle communications with the flight computer. This RS-422 architecture is central to Taurus' rapid integration and test, as it allows unit-, stage- and system-level testing to be accomplished using only personal computers outfitted with commercially available interface cards.

Payload Fairings
Orbital offers one of two flight-proven Taurus payload fairings to encapsulate the payload and provide protection and contamination control during ground handling, integration operations and flight. Both fairings are bisector shells constructed of graphite/epoxy facesheets with an aluminum honeycomb core. The Taurus 63" diameter fairing, manufactured by Vermont Composites, was successfully demonstrated on Taurus' first and third missions while the larger 92" diameter fairing, manufactured by R-Cubed Composites, was successfully demonstrated on the second Taurus mission.