See list attachedOctober 16, 196868-PA-T-224APA/Chief, Apollo Data Priority CoordinationC’ Earth Orbit and TLI Mission Techniques Open Items
It appears we have the Earth Orbit and TLI Mission Techniques for the C' pretty well under control. The only two significant open items that I know of deal with the optics check and the crew procedures for pro- tecting against an SIVB engine cutoff failure during TLI.
The problem with the optics check is that no one has really established what they are trying to accomplish by doing it. My own personal opinion, of course, is that it is not really necessary. That is, we will be willing to do TLI with the optics busted, whatever that means, since we should be able to align the platform using the COAS good enough to perform the return to earth maneuver. Although, I guess, we really haven't proven that to everyone's satisfaction yet.
How the crew should backup the SIVB IU engine cutoff signal has been a sticky wicket (I believe that is the expression). I think we have now gotten through the emotional phase of this one and have zeroed in on two possible techniques, both of which seem pretty good. The one I personally favor was proposed by Charley Parker. Its merits are simplicity and the fact that it gives the IU the greatest chance to perform its job, if it is going to. Basically, no crew action would be taken until after an elapsed burn time is equal to that expected from a 3 sigma low performing engine. This would be like 10 seconds past the nominal burn duration. At that time, the crew would manually shut the engine down as soon as the GNCS indicated the targeted inertial velocity has been achieved as readout from their DSKY display. Of course, if we really have had an IU failure, the GNCS would indicate that we have already exceeded that velocity at that time and so the crew would take immediate action by turning the abort handle to shut down the engine and return it to its neutral position to avoid automatic separation of the spacecraft from the SIVB. (Note that the EMS ΔV counter plays no role in this procedure.) In the event the IU has truly failed to send the cutoff command when everything else is perfectly normal, this procedure would result in an overspeed of about 500 or 600 fps which would require a 2,000 to 3,000 fps return-to-nominal midcourse maneuver three hours after TLI. This does not preclude going into lunar orbit.
The alternate proposal is precisely the same as that, except than an addi- tional period permitting manual crew engine cutoff is included – namely, that period containing all burn durations possible with a 3 sigma performing engine. This would be a 20 second period centered about the nominal cutoff time. During this period, the crew would send a manual engine off command if both the GNUS and the EMS ΔV counter indicated the desired cutoff velo- city had been achieved.
Studies are continuing on both these techniques and a crew preference will also be obtained hopefully leading to resolution within the next couple of weeks. Since there is no crew simulation facility capable of faithfully simulating the TLI maneuver, it will not be possible to base the decision on experience gained in that way.