See list attachedOctober 29, 196969-PA-T-139APA/Chief, Apollo Data Priority CoordinationAGS licks PGNCS for RCS Insertion
Pete Conrad has discovered and, if necessary, intends to do something that Dan Payne and others around here got squared away a year or more ago. Unfortunately, due to the press of more urgent business, we failed to advertise it enough. This note is to make sure you know that the AGS does a better job than the PGNCS of guiding the LM into orbit using the RCS if the APS stops prematurely and can't be restarted. And, it should be used in this unlikely and horrifying event.
It may surprise you to learn that if the APS fails during the last minute of LM ascent, insertion may still be achieved using the RCS. For this specific case, a 4 jet RCS burn about 9 minutes long would be required to pick up the remaining 1,000 fps. (This obviously far exceeds the 85-second constraint currently limiting +X RCS operation, but who will quibble over that?)
The proper procedure for RCS insertion is to switch to AGS AUTO, since AGS will steer the vehicle automatically at RCS thrust acceleration levels while PGNCS will not. Meanwhile, the PGNCS velocity-to-be-gained display may be monitored to verify that AGS is performing adequately. When the PGNCS velocity-to-be-gained is small (i.e., less than 25 fps) control could be switched back to PGNCS and the standard velocity residual trim- ming procedures could be employed. Use of AGS AUTO relieves the crew of manually maintaining attitude such that the PGNCS display of total velocity- to-be-gained is along the X-axis during a long RCS burn. Also, AGS guidance has cross-range position control assuring insertion into the CSM plane while PGNCS does not.
As I said, Pete found all this out for himself and intends to act according with our blessing if this happens. This is another example of a low- probability contingency procedure cleared away. We'll have to be careful we don't carry this kind of effort too far or we'll be arrested for viola- tion of the law of diminishing returns!
tindallgrams02.pdf
