SV-FER 10.4 S-IVB second burn

[edit] 10.4.3 Control System Evaluation During Second Burn

S-IVB second burn pitch attitude error, angular rate, and actuator position are presented in Figure 10-9. Second burn yaw plane dynamics are presented in Figure 10-10. The maximum attitude errors and rates occurred following guidance initiation. Transients were also observed as a result of the pitch and yaw attitude controls at the termination of the Artificial Tau guidance mode (27 seconds before ECO).

A summary of the second burn maxlmum flight control parameter values is presented in Table 10-5.

The pitch and yaw effective thrust vector misalignments early in second burn (prior to MR shift) were 0.36 and -0.16 degrees, respectively. Following the MR shift the misalignments were 0.50 and -0.24 for pitch and yaw, respectively. The steady state roll torque during second burn was essentially zero as minimum impulse firings were observed at alternating sides of the roll deadband.

Normal propellant sloshing during second burn was observed on data obtained from the PU mass sensors. The slosh activity did not have any noticeable effect on the operation of the Attitude Control System.

[edit] 10.4.4 Control System Evaluation After S-IV Second Burn

The APS provided satisfactory orientation and stabilization from Translunar Injection (TLI) through the S-IVB/IU Passive Thermal Control (PTC) maneuver [Three-Axis Tumble Maneuver]. Each of the planned maneuvers was performed satisfactorily.

Significant events related to translunar coast attitude control were the maneuver to the in-plane local horizontal following second burn cutoff, the maneuver to the Transportation Docking and Ejection (TD&E) attitude, spacecraft separation, spacecraft docking, lunar module extraction, the maneuver to the evasive ullage burn attitude, the maneuver to the LOX dump attitude, the maneuver to the optimum lunar impact ullage burn attitude, the maneuver to the solar heating control attitude, the maneuver to the vernier lunar impact ullage burn attitude, and the PTC maneuver.

Figure 10-11 Pitch Plane Dynamics During Translunar Coast

The pitch attitude error and angular rate for events during which telemetry data were available are shown in Figure 10-11.

Following S-IVB second cutoff, the vehicle was maneuvered to the in-plane local horizontal at 12,059 seconds ((03:20:59) (through approximately -19.4 degrees in pitch and-0.2 degree in yaw), and an orbital pitch rate was established. At 12,809 seconds (03:33:29), the vehicle was commanded to maneuver to the separation TD&E attitude (through approximately 120, 40 and -180 degrees in pitch, yaw and roll, respectively).

Spacecraft separation, which occurred at 13,347 seconds (03:42:27), appeared nominal, as indicated by the relatively small disturbances induced on the S-IVB.

Disturbances during spacecraft docking, which occurred at 14,231 seconds (03:57:11), were less than on previous flights. Docking disturbances required 2,160 N-sec (485 lbf-sec) of impulse from Module 1 and 1,160 N-sec (261 lbf-sec) of impulse from Module 2. The largest docking disturbances on previous flights occurred on AS-510 and required 3,480 N-sec (783 lbf-sec) of impulse from Module 1 and 3,040 N-sec (683 lbf-sec) of impulse from Module 2. Lunar module extraction occurred at 17,102 seconds (04:45:02) with nominal disturbances.

At 17,520 seconds (04:52:00) a yaw maneuver from 40.3 degrees (TD&E attitude) to -40.0 degrees was initiated to attain the desired attitude for the evasive ullage burn. At 18,181 seconds (05:03:01) the APS ullage engines were commanded on for 80 seconds to provide the necessary separation distance between the S-IVB and spacecraft.

The maneuver to the LOX dump attitude was performed at 18,760 seconds (05:12:40). This was a two-axis maneuver with pitch commanded from 179.5 to 190.0 degrees and yaw from -40 to -19 degrees referenced to the in-plane local horizontal. LOX dump occurred at 19,460 seconds (04:24:20) and lasted for 48 seconds.

At 21,735 seconds (06:02:15) a ground command was received to perform a maneuver to the desired attitude for the APS ullage burn for lunar target impact. This was also a two-axis maneuver and resulted in a pitch maneuver change from 190.0 to 248.0 degrees and a yaw attitude maneuver change from -19.0 to -23.0 degrees referenced to the in-plane local horizontal. At 22,200 seconds (06:10:00) the APS ullage engines were commanded on for 98 seconds to provide delta velocity for lunar target impact.

At 22,664 seconds (06:17:44) a ground command was received to perform a maneuver to the solar heating attitude to assure proper solar heating conditions. This was a single-axis pitch maneuver and resulted in a pitch maneuver change from 248.0 to 161.0 degrees referenced to the in-plane local horizontal.

At 39,760 seconds (11:02:40) a ground command was received to perform a maneuver to the desired attitude for the second lunar impact APS ullage burn. This maneuver was a two-axis maneuver and resulted in a pitch maneuver change from 161.0 to 121.0 degrees and a yaw attitude maneuver change from -23.0 to -11 degrees referenced to the in-plane local horizontal. At 40,500 seconds (11:15:00) the APS ullage engines were commanded on for 102 seconds to provide delta velocity for a more accurate lunar target impact.

The command to initiate the PTC maneuver was received at 41,510 seconds (11:31:50). This maneuver consisted of commanding the vehicle +31 degrees in the pitch, yaw and roll axis. After vehicle angular rates of approximately -0.3 degree/second pitch, -0.3 degree/second yaw, and 0.6 degree/second roll were established, a ground command was received (Flight Control Computer Power Off B) at 41,532.5 (11:32:12.5) to inhibit the IU Flight Control Computer leaving the vehicle in a three-axis tumble mode.

APS propellant consumption for attitude control and propellant settling prior to the APS burn for lunar target impact was lower than the mean predicted requirements. The total propellant (fuel and oxidizer) used prior to the first ullage burn for lunar target impact delta velocity was 51.8 kilograms (114.2 lbm) and 52.9 kilograms (116.7 lbm) for Modules 1 and 2, respectively. This was approximately 35 percent of the total available propellant in each module (approximately 147 kilograms [330 lbm]). APS propellant consumptlon is tabulated in Section 7, Table 7-4.

[edit] 10.5 INSTRUMENT UNIT CONTROL COMPONENTS EVALUATION

The control subsystem performed properly throughout the AS-S12 mission. All ST-124M Stabilized Platform Subsystem (SPS) factors remained within previously experienced limits. The eouipment temperatures increased as expected when the water sublimator operation was inhibited (Section 14.4.1).

[edit] 10.5.1 Gimbal Angle Resolvers

Proper vehicle attitude was indicated by the gimbal angle resolvers until the PTC maneuver was initiated at approximately 41,500 seconds. As on AS-511 the positive yaw gimbal mechanical stop was contacted for short periods of time. This was expected. No vehicle perturbation or hardware failure was evident as a result of the contacts.

[edit] I0.5.2 ST-124M Power Supplies

All power parameters were within specification limits. Deviation from nominal occurred while the water sublimator operation was inhibited. The 4.8 KHz voltage increased while the 400 Hz voltage decreased, but in each case no specification limit was exceeded.

[edit] 10.6 Separation

[edit] 10.6.1 S-IC/S-II Separation

Figure 10-12 AS-512 S-IC/S-II Separation Distance

The AS-512 S-IC/S-II stages separated as planned with no known anomalies. Clearance distance between the stages was approxiamtely 2.4 meters (eight feet) more than required at S-II Engine Start Command (ESC) as shown in Figure 10-12. Separation distance was approximately 15.2 meters (50 feet) at J-2 engines main propellant ignition.

During the first n@@@ separation period (160 to 166 seconds), the maximum roll attitude and angular rate were approximately -2.7 degrees and +2.5 degrees per second, respectively. Maximum pitch and yaw attitude @@@@@@ and -0.7 degrees, respectlvely. Corresponding maxiumum @@@@@ rates at this tlme were -0.2 and -0.1 degrees per second.

[edit] 10.6.2 @@@@ond Plane Separation

@@@@ond plane separation was performed as planned. No significant transients in vehicle attitudes or rates were identified that would have caused this separation to be other than nominal.

[edit] 10.6.3 S-II/S-IVB Separation

Nominal accelerations were observed on the flight vehicle during the S-II/S-IVB separation. Vehicle dynamics were as predicted and well within staging limits.

[edit] 10.6.4 CSM Separation

At 12,810 seconds (03:33:30) a maneuver to the TD&E attitude was initiated to assure proper lighting and communication conditions for spacecraft separation, docking, and lunar module ejection. The vehicle was commanded to pitch 120 degrees, yaw 40 degrees, and roll -180 degrees. This attitude was held inertially until the beginning of the evasive maneuver. The vehicle motion during the maneuver was close to predicted with maximum vehicle rates of 0.75 deg/sec, 0.95 deg/sec, and -0.80 deg/sec in the pitch, yaw, and roll axes, respectively.

Transients due to spacecraft separation at approximtely 13,348 seconds (03:42:28) appeared nominal. Separation disturbances caused five APS Module 1 pitch firings within 10 seconds following separation. A negative roll disturbance was controlled by 6 roll firings within 15 seconds following separation.

All attitude errors remained within the 1 degree deadband during the separation process.

Saturn V Launch Vehicle Flight Evaluation Report - AS-512 - Apollo 17 Mission , (PDF), Marshall Space Flight Center, Feb 28, 1973, NTRS Accession Number: 73N33822; Document ID: 19730025089; Report Number: MPR-SAT-FE-73-1, NASA-TM-X-69534. The original NASA material is copyright-free. Edits (and errors) by Eric Hartwell are licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 license.