See listDEC 22 196666-FM1-188FM/Deputy Chief, Mission Planning and Analysis DivisionDAP initialization simplification
Ken Cox, Rick Nobles, Charley Parker and I got together to see what could be done about reducing the number of crew displays and inputs associated with the digital auto pilot (DAP). As you recall, the DAP's require ini- tialization by the crew who specify the spacecraft configuration, choice of RCS quads to be used, dead-band, RCS jet failures, etc. These quan- tities are displayed to the crew prior to each maneuver and must be over- ridden if unsatisfactory. We see no way around those displays and inputs.
It was our desire to attempt to reduce or eliminate the requirement for input of additional quantities such as spacecraft weight, moments of iner- tia, initial engine gimbal angle settings, etc., prior to the initiation of main engine maneuvers. It has been noted on numerous occasions that all of these parameters could be determined by the computer itself to well within the degree of accuracy required. For example, it should be suffi- cient that the final engine trim angles experienced during the previous maneuver be used at the start of the next; the weight and moments of in- ertia are more-or-less dependent upon the amount of main engine propellant which has been expended. A running account of the propellant expended could be continuously carried in the computer probably based on ΔVm, which is computed during each maneuver. Ken Cox has prepared curves of each of these quantities as functions of weight which can be used to prepare linear approximations as functions of the summation of ΔVm to be supplied to MIT.
It is to be emphasized that the only reason these parameters need be com- puted on board is to provide a backup for communication failure or lack of a ground station at the time it is needed since it is the intention of the Flight Control Division to update these parameters from the ground rou- tinely. Therefore, it is our desire that these quantities be computed and stored away in the computer at the conclusion of each main engine maneuver rather than just before the next so that the ground supplied data is not wiped out by the less accurate values computed on-board.
It is our intention to tell MIT that there is no requirement to display these quantities to the crew, and the program will be designed that way unless we are informed that this is unacceptable by representatives of the flight crew. If they feel it's necessary to see these displays, then it must be with the understanding that there will be no special automatic up- dating of these quantities. Rick Nobles is going to check this out.
MIT was requested to prepare an MDRB based on a description of the require- ments noted above given to them over the phone on December 19. We'll attempt to get it in AS-258 but if the schedule impact is too great (as it probably will be) we'll get it in AS-504.