Page:NASA Launch Vehicle Handbook.pdf/11

SCOUT Guidance and Control System

Guidance of the Scout vehicle is obtained by a conventional three-axis "strapped down" gyro system combined with a three-axis control system. In this system, guidance is confined to the pitch plane only, with azimuth and roll orientation maintained during flight at essentially the initial reference attitudes established at the time of launch. The guidance system is based on three body mounted miniature integrating gyros (MIG's), three rate gyros (GNATS), and the pitch axis programmer.

In the lift-off configuration, the vehicle is aerodynamically stable. A proportional control system featuring a combination of jet vanes and aerodynamic tip control surfaces operated by hydraulic servo actuators is used to control the vehicle throughout the entire first-stage burning period. These controls operate in pairs for pitch and yaw control. The jet vanes provide the majority of the control force during the thrusting phase and the aerodynamic tip controls provide all the control force during the coasting phase following burnout of the first stage.

After separation of the first stage all succeeding stages are aerodynamically unstable. Because of this, the second stage is not separated until 130,000 feet altitude is reached. This reduces the effect of the unstable aerodynamic air loads on the control system. Control during second-stage burning is provided by hydrogen peroxide reaction jets which are operated as an on-off system within a small deadband. Second-stage nominal deadband values are as follows:

Fitch Xaw oll

Position

Rate

+o.8 ° 0.9° °

2°/sec +2.25°/sec "5°/sec

Control of the third stage is also provided by hydrogen peroxide reaction jets. Two modes of control operation are provided. The thrusting phase controls consist of four 44-pound reaction jets for pitch and yaw control and four 14-pound jets for roll control. After burnout, when possible thrust-induced upsetting moments are zero, a switch is made to the coasting phase controls by a programed signal from the timer which also turns off the pitch and yaw jets. Yaw and roll control during coast is combined in the four roll Jets that have been reduced from 14 pounds to a level of approximately 3 pounds by means of a restrictor orifice. Pitch control is maintained with a switch in pair of 2-pound Jets. The same roll and yaw deadbands are utilized for the second and third-stage coast periods; however, the pitch deadband is reduced during third-stage coast to 0.3° position and 0.75° per second.