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The challenges of space shuttle orbiter reaction control subsystem development began with selection of the propellant for the subsystem. Various concepts were evaluated before the current Earth storable, bipropellant combination was selected. Once that task was accomplished, additional challenges of designing the system to satisfy the wide range of requirements dictated by operating environments, reusability, and long life were met. Verification of system adequacy was achieved by means of a combination of analysis and test. The studies, the design efforts, and the test and analysis techniques employed in meeting the challenges are described.

The Space Shuttle RCS (reaction control system) is required to provide propulsion thrust for precise attitude control and three-axis translation. This capability must be provided for external tank separation, on-orbit operation, deorbit, and reentry. In order to meet these requirements a bipropellant, pressure-fed system utilizing monomethylhydrazine as fuel, and nitrogen tetroxide as oxidizer has been selected. The RCS engines include 38 primary thrusters rated at 870 lbf thrust and 6 vernier thrusters rated at 25 lbf thrust. The system is divided into three removable modules (one forward and two aft) to achieve maintenance and turnaround requirements. In order to provide additional mission flexibility, the aft modules can be connected together or interconnected with the OMS (orbital maneuvering system).