2 The abnormal attitude of the 1st stage was everything.

    Looking at the time history of attitude control from the 1st stage through the 3rd stage, the attitude of the vehicle was normal except for the last phase of the 1st stage. From 250 seconds after liftoff, the scheduled 90 deg. roll control was carried out to keep the quality of telemetry signal. And, from 360 seconds, the turn over control to prepare the satellite separation was successfully performed.

    Figure 2 shows the history of pitch, yaw and roll of the 1st stage. You can see in this figure the abrupt increase of pitch angle at 55 seconds, and then the delayed sudden divergence of yaw angle accompanying the revolution of roll angle. The pitch became very high two times reaching 120 deg. from hirizon at the maximum.

Fig.2   Attitude Time History of M-V-4

    The pitch and yaw of the 1st stage are controlled by swinging the nozzle. To compensate the motion of the nozzle with the a pressure increase in the combustion chamber during burning, a potentiometer is installed at the opposite side of respective TVC actuators across the nozzle.

    The 1st stage pitch command, the answer and the output of the potentiometer are shown in Fig. 3. You can see the command to hold down the pitch divergence after 53.57 seconds, but the answer was zero, i.e. the actuator did not work. And the output of the potentiometer was lost almost at the same time. The status showed the loss of pitch control. The loss continued till the 2nd stage ignition (75 seconds). The yaw control was lost at 69.59 seconds.

Fig.3   Pitch Command Time History of M-V-4

Next

0 Top-page

1 How did M-V-4 fly?

2 The abnormal attitude of the 1st stage was everything.

3 What caused the abnormal attitude?

4 Damage of Graphite

5 Current Situation

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