See list belowNOV 09 196767-FM-T-103FM/Deputy ChiefMIT/MSC review of LUMINARY Descent Programs
1. On November 2, 1967, a team of Flight Crew, G&C and FCD people met with MIT to discuss the lunar landing descent programs. We have recently been reviewing these programs at MSC and it has become evident that many of the displays and associated computations which we had listed as require- ments early in the year are not. That is, apparently insufficient thought was given at that time as to how the system would actually be used. We did not intend to insist upon changes that would make the MIT schedule situation more critical but rather to identify those things we were confident we would not need and would then leave it to MIT to decide whether to delete them from the first edition of the LUMINARY program or not. There was a strong impression that MIT would probably make most of the possible deletions, but we asked them to take as much time as necessary to review the situation and tell us what they intend to do, formally, in writing. I personally felt that the meeting was very worthwhile and should result in a much better program requiring considerably less MIT effort to complete.
2. Several items were discussed extensively which I thought might be worth recording for my own records and perhaps your information. The remainder of this memo will be devoted to them.
3. One of the items we spent the most time on had to do with crew procedures associated with the out-of-plane situation existing during descent. Pro- posals had been made to display quantities to the crew prior to initiation of breaking which would enable him to plot the approach trajectory on a strip chart of the lunar surface, taking into account the existing out-of-plane situation. There was considerable skepticism during our discussion that visual monitoring of the lunar surface as it streams by would be of much value in determining performance of the systems, need for abort, or for any other really useful function. The situation is somewhat equivalent to a low altitude pass over an unfamiliar desert at Mach-3 with lots of other interest- ing things going on inside the cockpit. Pete Conrad was going to review this whole business with FCSD people and the Astronaut Office to make sure the action we proposed at ??? was okay, namely make the display of delta R a requirement—to be computed exactly as now formulated in the MIT program. Specifically, delta R is the perpendicular distance of the landing site position vector from the LM orbital plane. This quantity is displayed in P-63, prior to DPS ignition, and may serve as an indicator to the crew of reduction in hover time they can expect due to use of propellant for plane change. And it may also be useful for some sort of lunar surface ????? chart initiation. It was noted that following Conrad's review we may recommend deletion of the entire 3-register display format containing delta R at MIT's option. We definitely don't want to change the defini- tion of delta R from that given above.
4. In response to my question regarding the computer's test to determine whether or not to use landing radar data, MIT stated that it was made on the computed value of altitude based on the spacecraft navigation starting prior to DOI. Considering the flat approach trajectory and the possibility of relatively large error in computed altitude due to uncertainty in the lunar radius and degraded MSFN performance, it is possible that radar data may be accepted much earlier or later than it should be. This is just a remark about a situation which perhaps deserves some investigation. It is not a proposal to change anything at this time.
5. It is understood that the delta V monitor program in the LGC will only send an engine off command in one of the P-40 series thrust program. In the other thrust programs—ascent, descent and abort—it will only issue a program alarm since erroneous engine off commands in these time critical mission phases could be catastrophic.
6. The P-64 Spacecraft Computer Descent Program provides the capability for redesignating the landing site location with the hand controller. Pete Conrad was concerned that the stick could be deflected accidentally causing the targeted landing site position to be moved unintentionally. In order to avoid having a “hot stick” when it may not be needed at all, it was decided to slightly modify P-64. To be consistent with standard PNGCS operations, the P-64 display will be made a flashing display, thus, requiring the crew to hit Proceed if he wants to redesignate the landing site. It is only after this crew input that stick motion would be regarded as a legiti- mate request for landing site relocation. Following the input of Proceed the display stops flashing and the stick remains hot thereafter. The crew would only hit Proceed if he wants to redesignate, of course.
7. Another item on which we spent a considerable amount of time dealt with “Delta V Margin.” MIT proposed to provide an on call display which was the LGC's prediction of delta V remaining at touchdown converted into hover time margin. Its primary use was to inform the crew of the fuel cost they have incurred by redesignating the landing site. The discussion brought out that this computation is really not particularly accurate. Furthermore, it was anticipated that allowable landing site redesignation would probably be governed by mission rules. However, this lengthy discussion revealed that it should be possible to make a fairly accurate prediction of how much fuel is required from present time until touchdown including the effects of landing site redesignation. This display could be made to automatically appear after each LPD action. The crew could compare this with the fuel gauge, which is considered to be fairly accurate, giving him an indication of whether or not he had sufficient fuel to complete his landing as currently specified. It was agreed that this parameter should be added into the P-64 program display format provided there was no schedule impact, excessive storage requirement or any program development trouble. At first incident of any of them it would be dropped. It will be displayed in units of “percent” fuel in order to be compatible with the fuel gauge and will take the place of Delta V Margin previously requested.
8. At one time it was proposed that when the crew detected there was no relative velocity of the spacecraft with the moon's surface, they would input this fact to the computer which would zero the velocity state vector. This was included in Chapter 5 if the LUMINARY GSOP but not in Chapter 4. It was determined that this was not a computer program requirement and will be deleted from Chapter 5.