Apollo 8 Flight Journal - Day 4: Lunar Orbit 7

Apollo Control here. The crew now is directly opposite the Earth. They're just west the Sea of Tranquillity, just south of the Imbrium Sea, southeast of the big crater Aristarchus, and directly east of the enormous Ocean Procellarum. They're only just a few miles north of a cluster of landing sites which are right along the lunar equator. They're about 8 degrees, 8 lunar degrees north of the sites, four of them that we consider prime sites in that central Apollo zone which is boxed in by an area of about 45 degrees west by 45 degrees east and running 5 degrees north and south of the lunar equator. And that's the area, of course, that the crew concentrated today on their optics check just as well as they're photographic efforts.

The PAD is interpreted as follows:

Purpose: The PAD is for an emergency burn to return to Earth at the end of Rev 8.
Systems: The burn would be made using the SPS engine, under the control of the Guidance and Navigation system.
CSM Weight (Noun 47): 45,701 pounds (20,730 kg).
Pitch and yaw trim (Noun 48): -0.40° and +1.57°.
Time of ignition (Noun 33): 85 hours, 18 minutes, 19.04 seconds.
Change in velocity (Noun 81), fps (m/s): x, +3,319.5 (+1,011.8); y, -126.7 (-38.6); z, +471.6 (+147.7). The large positive number in the X direction implies a large prograde component, essentially adding to their orbital velocity, exactly what would be expected from an escape manoeuvre.
Spacecraft attitude: Roll, 179°; Pitch, 8°; Yaw, 1°. The desired spacecraft attitude is measured relative to the alignment of the guidance platform which itself has been aligned per the LOI-2 REFSMMAT.
Expected apogee of resulting orbit (Noun 44): Not applicable. Being initiated around the Moon, the apogee of the resulting orbit around Earth is too large to register on the computer.
Expected perigee of resulting orbit (Noun 44): 18.7 nautical miles (34.6 km).
Delta-V_T: 3,355.2 fps (1,022.7 m/s). The total sum of the three velocity components.
Burn duration or burn time: 3 minutes, 11 seconds.
Delta-V_C: 3,335.5 fps. This figure will be entered into the EMS to allow it to shut down the engine as a backup in case the G&N system fails to do so.
Sextant star: Star 42 (Peacock, or Alpha Pavonis) visible in sextant when shaft and trunnion angles are 90.9° and 25.2° respectively.
Boresight star: Dschubba, or Delta Scorpii.
COAS Pitch Angle: Down 6.0°.
COAS X Position Angle: Left 4.2°.

The next five parameters all relate to re-entry, during which an important milestone is "Entry Interface," defined as being 400,000 feet (121.92 km) altitude. In this context, a more important milestone is when atmospheric drag on the spacecraft imparts a deceleration of 0.05 g.

Expected splashdown point (Noun 61): 3.73° north, 165° west; which is in the mid-Pacific.
Range to go at the 0.05 g event: 1,298.2 nautical miles. To set up their EMS (Entry Monitor System) before re-entry, the crew need to know the expected distance the CM would travel from the 0.05 g event to landing. This figure will be decremented by the EMS based on signals from its own accelerometer.
Expected velocity at the 0.05 g event: 36,256 fps. This is another entry for the EMS. It is entered into the unit's Delta-V counter and will be decremented based on signals from its own accelerometer.
Predicted GET of 0.05 g event: 146 hours, 46 minutes and 18 seconds GET.
GDC Align stars: Stars to be used for GDC Align purposes are Sirius and Rigel.
GDC Align angles: Roll, 129°; pitch, 155°; yaw, 10°.

There are two additional notes given in the PAD. An ullage burn of 15 seconds should be made by all four RCS quads to settle the contents of the half-empty SPS tanks prior to the burn. This is to minimise the chance of helium gas being ingested when the engine ignites. Also, the Moon's horizon should be lined up on the rendezvous window's 4° line at the moment of ignition.

Jim may be realigning the guidance platform after causing the computer restart. We believe he may have hit P01.

This is Apollo Control, Houston. You heard the last transmission from Frank Borman wherein he indicated that he planned a drastic reduction in activities in the next 4 revs. We've been noting and suggested earlier we had a tired crew. Certainly indicated in Lovell's voice. We heard very little crack from Bill Anders who is presently in a sleep period. It just could be that that will wind up our activities in lunar orbit. There is a conference going on, now, around the Flight Director's console, and it will be from that, that the ground will make up its mind on what, if anything, is needed or if anything we might suggest to Borman. And that will be the subject of a further conference if anything more was needed. Sounded to me like Frank was very definite that he wanted to wrap it up at this point and certainly let Lovell get some rest before Trans-Earth Injection burn. The Trans-Earth Injection burn is planned for 89 hours, 15 minutes. The major question in our minds on this particular console is whether the spouting off of activities will include the television transmission on the 9th rev. We don't have the answer to this yet. We should have the answer shortly. At 82 hours, 46 minutes into the flight; this is Apollo Control, Houston.

Apollo 8

Day 4: Lunar Orbit 7

Corrected Transcript and Commentary Copyright © 2001-2021 by W. David Woods and Frank O'Brien. All rights reserved.