Figure 7-1. - Definition of axes and positive rotations.
The availability of flight data from the instrumentation on the MS and the vehicle disturbances, the design features of the MS, the SAS, photographs taken in orbit, descriptions by the astronauts. and other information permit the following postulation of the probable sequence of events associated with the MS failure.
Figure 7-1 is furnished to indicate the pitch. roll, and yaw axes and directions of positive rotations. These axes are related to the position designations I, II, III, and IV as indicated on the sketch. A view of the shield and tunnel separating from the butterfly hinge, rotating outwardly, and producing roll torques is shown to provide initial orientation.
In figure 7-2 and 7-3, sketches and details of salient events are correlated to the roll rate data around the 63 second anomaly period. The events are designated on the figures by times which are consistent with the available data.
60. 12 Seconds - MS liftoff and local inflation in the vicinity of the auxiliary tunnel was indicated by a small shift in position of the torsion rod on the forward edge just to the left of the tunnel (see fig. 7-2).
61. 78 Seconds - Air entered the forward facing opening, raised the pressure under the shield and high mass flows escaped through the adjacent holes in the butterfly hinge. This flow produced reactive forces causing a gradual decrease in roll rate between 61. 78 seconds and 62.74 seconds.
62. 74 to 62.79 Seconds - Burst pressure under the auxiliary tunnel and adjacent MS caused a large tangential load on the forward section of the butterfly hinge, causing the whole hinge to unzip.
Fly around inspection indicated that the failure of the butterfly hinge occurred at the hinge line adjacent to the main tunnel.
The butterfly hinge was now completely broken. Aerodynamic drag on the M including the bulky auxiliary tunnel produced tension in the shield and pulled on the vehicle so as to roll it in the direction shown, that is, opposite to that noted earlier. The large area and mass of this metal "flag" induced a more rapid change in roll rate than the earlier jetting through the butterfly hinge. This process terminated as the MS started to wrap around and lift the SAS-2 wing.
62.79 to 62.90 Seconds - During this interval the shield was wrapping around SAS-2 wing producing a negative roll torque in the vehicle. At about 62.85 seconds the SAS-2 tie-downs were broken.
62.90 Seconds - Upon release of SAS-2, the tension in the shield was transferred to the trunnions, causing failure of the trunnion straps. Upon separation of this section of the shield, the negative roll torque ended.
62.90 to 62.95 Seconds - In this interval, the remaining section of the MS began unwinding, introducing a large positive roll torque.
63.17 Seconds - A large shock was detected by the Instrument Unit (IU) upper mounting ring vibration sensor due to the impact of the separated section of the MS upon the conical adapter between the OWS and the S-II stage.
63.7 Seconds - The MS continued to unwind and whip until 63.7 seconds when it reached SAS-1 wing. As the MS began to wrap around the SAS-1 wing, a negative roll torque resulted. The MS then ripped apart from top to bottom at the longitudinal joint adjacent to SAS-1, pulling a portion of the joint assembly over the SAS-1 wing as the MS section departed. From this point on the vehicle showed normal response to its roll control system. Figure 7-4 is a photograph taken by the astronauts which shows a portion of the MS that remained and how it was attached to the SAS - 1 wing.
Figure 7-1. - Definition of axes and positive rotations.
Figure 7-2. - Possible meteoroid shield motion from 60.12 to 62.74 sec.
Figure 7-3. - Sketches of possible shield dynamics during the 63 second anomaly.
Figure 7-4. - Photograph from orbit showing longitudinal aluminum angle bent over the SAS-1 wing. (This angle was later cut by astronaut and released the SAS-1 for full deployment. )
