See list belowAPR 23 196868-PA-T-84APA/Chief, Apollo Data Priority CoordinationDescent Orbit Insertion (DOI) monitoring and abort procedures are proposed
1. Something rather interesting came out of Floyd Bennett's April ?? Descent Mission Techniques meeting that I would like to pass around. It has to do with monitoring the DOI maneuver.
2. Previously, in discussions with Ed Lineberry's mission planning people, it had been proposed that if an abort should be necessary within the first 10 minutes or so after DOI, the best technique was not to go through an entire coelliptic rendezvous sequence, but rather was to thrust back directly toward the CSM with sufficient delta V to unsure closure and to go straight into the standard breaking procedures. The delta V required to do this is in the order of 100 fps to be applied directly along the line-of-sight. At the time of our discussion on this, no one had thought of any reason for aborting in that short period and so I did not include this technique in my “Lunar Rendezvous Abort Summary” memorandum, which had already grown too long. However, when we considered monitoring DOI, such an abort situation became readily apparent. Specifically, we concluded if an LM PGNCS and/or DPS failure occurs during DOI – particularly if we have either overburn or underburn – we should use the abort procedures noted above. The alternate is to delay the abort action and accept a LM rendezvous from above with either the LM PGNCS or DPS not working properly.
3. The systems available for monitoring the PGNCS controlled DOI burn are obviously the AGS and the clock. The latter of course is very crude since it only takes an overburn of 13 fps on a nominal 70 fps DOI to result in lunar impact and this sort of dispersion would occur within two or three seconds at half thrust. If the AGS or the burn duration indicate PGNCS has commanded an erroneous burn magnitude, it is only necessary to pitch the LM to acquire rendezvous radar lock-on to find out what's up. Since the CSM is located directly ahead of the LM during this retrograde maneuver, the range-rate indication is all that is needed to determine if the proper delta V had been attained or not. We also considered use of the CSM VHF ranging devise in this monitoring, but quickly concluded that since it does not directly range-rate, it would probably not be very useful. Of course, DOI occurs behind the moon so MSFN is out of the picture.
4. In the event of a DOI failure, the LM crew should align the vehicle along the CSM line-of-sight and thrust until a closing rate of about ?? fps is displayed on the rendezvous radar range-rate readout. It may be desirable to make this maneuver by staging and using four jet RCS with the interconnect open.
5. Obviously, detailed procedures and systems utilization was only in the preliminary design phase on all this. On the other hand, the concept described here is better than anything else we could think of and is certainly feasible. I wanted to make you aware of it and solicit your thoughts.