ENGINE GIMBALLING SYSTEM Gts
The Saturn V engine gimballing system positions the gimballed engines of the active stage to provide the thrust vectors required for vehicle control. In performing this function, the gimballing system is controlled by commands initiated by the attitude control and stabilization function. (Refer to Paragraph 20-35.)
The engine gimballing system steers the vehicle along its trajectory by providing engine thrust vectors for pitch, yaw, and roll control (except for the S-IVB stage). The system is active during the ascent and the translunar trajectory phase of the mission (throughout S-IC stage, S-II stage, and S-IVB stage powered flight). As the vehicle ascends, in addition to the region of high aerodynamic pressure (35, 000 to 50, 000
feet), it may encounter other disturbances such as thrust misalignments and winds. The external forces produced on the vehicle by such disturbance are counteracted by gimballing the engines of the active stage providing thrust vectors which minimize vehicle structural loading and maintain the vehicle on trajectory.
After the S-IC stage has expended its useable propellants, the stage is separated from the vehicle and the gimballing system operation is switched to the gimballed engines of the S-II stage. When the S-II stage engines are cutoff at propellant depletion, the stage separates from the vehicle and the S-IVB stage engine performs the gimballing system functions. When the S-IVB stage and payload have obtained orbital velocity, and altitude, the S-IVB stage engines are cut off. The system is inactive during the earth orbital phase of the mission. The gimballing system is reactivated during the translunar trajectory phase during S-IV-B stage second burn. The system ceases to function after Apollo payload separation.
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