PA/Manager, Apollo Spacecraft ProgramOctober 2, 196868-PA-T-210APA/Chief, Apollo Data Priority CoordinationC Mission Techniques – are they being used?
As you suggested, I checked with Phil Shaffer – Chief, Flight Dynamics Officer on the C mission – to determine if the flight crew and flight controllers are following the mission techniques we developed. He is completely satisfied that everything is being done properly – at lease those things they are able to observe from the simulations. (There are some things the crew does that only a cockpit observer could check, of course.) For example, he says following each simula- tion there is a complete detailed discussion of such things as data source comparisons for rendezvous (TPI) and the crew is faithfully doing “right.”
Some things have been changed since our document was updated the last time, but only after discussion with all interested parties to the same extent as during the original Techniques Development. The point is, “spur of the moment” changes are not being made nor are changes based on someone's whim. Examples of changes are:
a. Use of the G&N to make a retrofire burn which must be delayed at the last moment – by recycling through the pre-thrust program (P30) and changing TIG – rather than using the SCS. (See paragraph 2.6, page 13 and logic page 33 of S-PA-8T-011, our latest Mission C Retrofire and Reentry Document, dated September 6, 1968.) Actually, this is what we always wanted to do – the crew resisted it because they didn't think they had enough time. Now they agree it's best.
b. Trimming ΔV residuals after retrofire is now done since it avoids having to recompute the entry pad data – i.e., it keeps the burn nominal and the pre-burn entry data remains right. We previously felt trimming was unnecessary and crowded the timeline when they should be separating the CM from the SM. Simulations have shown the new technique to be superior. Everyone agrees.