PA/Manager, Apollo Spacecraft ProgramDEC 15 196767-PA-T-115APA/Chief, Apollo Data Priority CoordinationUrgent recommendation that CMC steering of the S-IVB be deleted
1. MSC and MSFC are currently operating in accordance with Headquarter's Apollo Program Directive No. 2A, dated September 1, 1966, which estab- lished the requirement for the command module computer (CMC) to be capable of guiding the S-IVB during the translunar insertion maneuver (TLI). The purpose of this memorandum is to recommend that action be taken to have this requirement deleted and to tell why we should do so. In summary, this recommendation is based on a conviction that the effort required to provide this capability is greatly out of proportion to the benefit to be gained by providing it. Its deletion would be just one more step in the current effort to simplify and clean up the overall Apollo program – eliminating niceties in order to concentrate our limited resources on those activities of greatest importance.
2. It is to be emphasized from the start that the CMC TLI steering can only back up a failure of the Saturn Launch Vehicle inertial platform occurring after insertion into earth orbit and prior to initiation of TLI. Reliability of this component of the IU has been estimated to be .996 at time of insertion into earth orbit. This is generally interpreted to mean that in four cases out of a thousand a platform failure will occur forcing deletion of the second S-IVB burn, resulting in a primary mission failure unless we provide this backup. The message here is that it is very un- likely we would ever use this capability even if it were provided. And perhaps of more importance, it is to be emphasized that crew safety is in no way involved.
3. It is generally agreed that this minute additional capability would be nice to have – provided the cost is not excessive. This is not the argu- ment nor is it questioned here and now that sufficient confidence could be developed in the backup system to permit its use. The basic point to be made is that the NASA and its contractual support is now operating at a fixed or decreasing level of effort and that the energy required to do this jon necessarily must be channeled from something else more important. Specifically, what are these various costs? It is the analysis and deliberations required of MIT people to determine the exact formulation of the CMC program. It is the actual programming and testing of that program integrated into the total flight software package. It is the analysis by MIT, MSDC and MSC to verify that the entire assembly – guidance and control system, propulsion system, structure, etc. – is dynamically qualified for flight. It is the planning, analysis and development of mission rules and procedures to carry out the real time systems evaluation and make the switchover decision in earth orbit. It is the development of crew procedures to initialize and monitor the back- up guidance mode during the TLI maneuver. It is the post-flight analysis to answer the question – how would it have worked if we had used it? It is the coordination of all this, and more, and endless explanations of how it all works. It is ten thousand meetings!
4. A rough estimate of the total cost of these things is given in the attached table. I am not listing them here because I am afraid that would divert your attention from the more important point. We have limited resources. The flight schedule is heavily upon us and there's an awful lot left to do for the nominal missions, the more likely contin- gencies and the situations involving crew safety. This low probability backup would demand attention of the same people who must do those jobs and we simply can't afford their involvement on it because its priority is too low in comparison. It's not just cost in terms of manhours and dollars but is something much more valuable – a drain on our straining resources.
5. The impetus for this campaign to delete CMC steering of the S-IVB came from discussions with some friends at MIT who expressed their concern regarding problems they still face in getting the program put together and flight qualified. They did not suggest that it be deleted, although they obviously concur with that idea. (It is to be emphasized that this program is not currently pacing delivery of the CMC lunar landing program [COLOSSUS] although there are some who expect it soon will. Nor is it absorbing an undue amount of computer storage.) I have recently polled a large number of other people and have found no champion for its retention, with one possible exception. That is, both systems and trajectory people of FCD, MPAD, G&C and ASPO and other interested parties, have all expressed a neutral position or, more often, concurrence that it should be deleted. Some members of the flight crew for the second and third manned missions still feel it would be nice to have, although it is my understanding there is no intention of using this capability in those missions. How could so many people be wrong?
6. In conclusion, I would just like to summarize by saying that the job of providing this backup can be done but the effort required is substantial, particularly if you weigh the fact that the particular talents involved are at a premium. The benefit to be gained is so small that to carry this job farther does not appear to be justified and it is strongly recommended that agreement be obtained at the earliest date for deletion of CMC guidance of the S-IVB during TLI, preferably before Christmas.
Rough, incomplete estimate of remaining effort required to provide CMC capability to steer the S-IVB.
a) Program Formulation (GSOP) Complete b) Program Coding 1 manmonth c) Level 3 and 4 Testing 3 1/2 manmonths d) Level 5 Testing and Documentation 1 manmonth e) Coordination MIT/MSFN/MSC 3/4 manmonth f) Development of Simulation Programs (MIT maintains they are g) Simulation and Analysis not going to do these jobs. if directed to do so, the CMC programs will slip.)
a) MPAD (See attachment 2) 6+ manmonths b) CAD SIVB/PNGCS Dynamic Simulation 1+ manmonths c) GCD, FCD, FCSD, FSD (Not estimated, not insignificant) (GCD must do “g.” above)
(See attachment 2) 34 manmonths
a) Provide MIT with math models of slosh, bending, (Not estimated, not rigid body propellant utilization. insignificant) b) Specify MIT analytic runs to be made. ” ” c) Review results of MIT work for accuracy and ” ” performance