NOAA KLM User's Guide
The Propulsion and Reaction Control Subsystem is a hybrid solid/ liquid/cold-gas system consisting of a solid propellant for orbit (apogee) injection and a dual Reaction Control Equipment (RCE) system using both pressure-regulated cold-gas nitrogen thrusters and hydrazine monopropellant thrusters. This subsystem primarily provides separation from the Titan II booster, ascent-phase attitude control (three-axis stabilized) and orbital velocity trim for the satellite. Figure 1.2.3-1 provides a functional schematic of the RCE.
The hydrazine RCE consists of four thrusters and two spherical storage tanks The hydrazine thrusters are used for maneuvers requiring large control torques and for all velocity change maneuvers, i.e., spacecraft separation from the booster and orbit circulation trim, as well as pitch and yaw control during the AKM burn. After completion of the orbital velocity trim burn, pyrotechnic valves at the outlet of each hydrazine propellant tank may be fired to isolate the hydrazine thrusters from the propellant tanks and render the system inoperative.
The cold-gas nitrogen RCE consists of eight thrusters and two spherical storage tanks of usable nitrogen. The nitrogen thrusters are used for three-axis control during ascent (except during AKM burn), Earth acquisition after handover and as a backup for momentum unloading in normal orbit mode control. Four of the thrusters provide roll control through Ascent Guidance Software (AGS), and are operated, under software control, in coupled pairs. The remaining four thrusters are operated individually to provide AGS pitch and AGS yaw control.
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