PAD for S-IVB restart sequence
The timings for events relating to the launch vehicle are defined relative to a number of time bases, each of which start with a particular event. This allows controllers to move complete sequences of events relative to the overall mission time. The restart sequence for the S-IVB's single J-2 engine is tied to time base 6. When TB-6 begins, all subsequent events to restart the engine such as tank repressurisation, engine chilldown, ullage, etc., follow on, leading to the engine start command 9 minutes, 30 seconds later, and ignition 8 seconds after that.
The crew also have tasks to perform in the minutes leading up to the TLI burn and they use their event timer to help them. Around 002:40:23, TB-6 begins and this is shown by both the 'Uplink Activity' and 'S-II Sep' lamps coming on. The former is illuminated for ten seconds, the latter for 38 seconds. At 9 minutes to ignition, the point at which the 'S-II Sep' lamp is extinguished, Dave will start the event timer counting up, having previously set it to 51:00. This will give a visual count-up to and beyond ignition to aid the crew in sequencing their final tasks before and during TLI. Items in the checklist are therefore shown with times from 51:00, through (1:)00:00 and upwards. (ap15fj)
The PAD is interpreted as follows.
| TB-6 predict light | This comes on at 002:40:23, which implies that TB-6 begins at 002:40:31 and that Tig (time of ignition) will be at 002:50:01. |
|---|---|
| Attitude for TLI | 180°, 45°, 001° in roll, pitch and yaw respectively. This attitude is with respect to the local vertical/local horizontal. Duration of burn: 5 minutes, 55 seconds. |
| Delta-Vc' | 10,401.1 fps (3,170.3 m/s) will be entered into the EMS to allow the crew to monitor the remaining velocity to be added. |
| VI | Indicated velocity at engine cut-off is 35,599 fps (10,850.6 m/s). |
| Separation attitude | The correct attitude for separation of the CSM from the launch vehicle is 359°, 77°, 320° in roll, pitch and yaw respectively with respect to the local vertical/local horizontal. Among the criteria for adopting this attitude is solar illumination of the LM to assist the docking procedure. |
| Extraction attitude | The correct attitude for extraction of the LM from the S-IVB is 301°, 257°, 40° in roll, pitch and yaw respectively. |
| R2 align | 045.0. |
| R2 ignition | 038.0. |
| ORDEAL Start | Relative to the count-up on the event timer, the ordeal should be started at 56:45. [see: Orb-rate explanation] The ORDEAL (Orbital Rate Display - Earth And Lunar) drives the FDAI (Flight Director Attitude Indicator, or "8-ball") to make it display the spacecraft's attitude relative to the ground below. |
| Yaw | 001 |
| LM extraction | The LM will be extracted from the top of the S-IVB stage by the docked CSM at 4 hours, 16 minutes GET. |