FA?DIrector of Flight OperationsMAR 2 196767-FM1-19FM/Deputy Chief, Mission Planning and Analysis DivisionProgress Report – RTCC program development reduction – Review of requirements for the AS-502 mission
On February 17th we held a meeting in our continuing effort to reduce the program development demands on the Real Time Computing Complex. In this instance, a group of FCD, FSB and MPAD people reviewed requested modifi- cations to the AS-501 RTCC program in preparation for the AS-502 mission. I could briefly summarize the results by saying eight of the changes requested were not considered mandatory and were deleted. There were three items which seemed so important that a concerted effort will be made to add them into the AS-501 program for use on that flight as well as AS-502. There will be four modifications required in the telemetry and command systems which were unavoidable due to changes in the space vehicles themselves between AS-501 and AS-502. In fact, it's quite like- ly that these four will be the only differences in the AS-501 and the AS-502 programs.
1. The following new requirements were deleted:
a) (hp vs Vp) on X-Y plotboard. (Will be displayed elsewhere, if needed.
b) (? vs V) on projection plotboard. (Displayed elsewhere).
c) Use AGC low speed telemetry vector in orbit phase for trajectory updates. (High speed vectors can be used and, if necessary, low speed can be used by a somewhat awkward procedure).
d) Add Residual Summary Display II. (Not needed).
e) Major modifications in the live plots of CSM SPS fuel and oxidizer remaining. (Not needed).
f) Addition of two summation computations for radiation surface dose and depth dose. (Not needed for flight control).
g) Display number of events from the AGC on TV rather than on lights. (Not needed).
h) RSDP GMTLO command update. (Not needed).
2. It is our intention to add the following three items in the AS-501 program for support of both missions, if possible. Jim Stokes, in con- junction with IBM, intends to determine their impact on the schedule for releasing the AS-501 program and, assuming it is no more than about two or three weeks, it will be our recommendation to make them. As I under- stand it, the likelihood of launch schedule slippage is great enough that this should be acceptable.
a) (φ vs λ)EI on projection plotboard. This capability is being added for a rather remote contingency situation which involves some change of Flight Controller action causing the spacecraft to impact somewhere in the United States. The Flight Dynamics people had requested that the latitude and longitude at 400,000 feet (the co-called entry interface) be predicted and displayed during large maneuvers. As I understand it, the SIVB must have failed and the SPS must not be under complete control for this display to be useful. However, the modifications requested were considerably simplified such that either the projection plotboard spotter or scriber would be used to display this pre- dicted “impact” point on the standard 10 x 20 would map in place of present position. Since (φ and λ)EI are already routinely computed, this capability should not be particularly difficult to provide. The request to scribe the nominal plot of these parameters was deleted.
b) The capability of initializing the RTCC program for the actual loaded propellant weights in the SIVB during the prelaunch countdown based on measurements made during the loading was added. Previously, the program assumed full tanks which intro- duced a considerable error of display of LOX and LH2 remaining.
c) The computation to compute He remaining in the SIVB is being completely redone. It will use a cryogenic type computation vis the old ambient temperature type computation which introduced a considerable error in the determination of this critical para- meter which is used in conjunction with a mission rule for deter- mining whether or not the SIVB may be reignited.
3. There are four changes in the telemetry and command systems which do not apply to AS-501 but which are essential for AS-502 due to vehicle modifications.
a) The definition of the IU coordinate system will be changed which must be reflected in the RTCC program.
b) The granularity and number of LVGC downlink parameters will be changed which influence the computations of GRR, TB4 start, orbital mode word, etc. The Guidance Officer considers this change mandatory if he is to make a reasonable decision as to whether or not to send a navigation update to the SIVB. He maintains that without this improvement his computations would be sufficiently in error that he would have no choice but to send one every time.
c) The SLV time base update will be modified to make it a double precision output vis single precision.
d) A new command format, the SLV navigation update, will be added.
4. There is one orbital phase display requested by the Flight Dynamics people – namely, perigee height vs velocity – upon which we haven't made final resolution. The Flight Controllers maintain that the special char- acter of the AS-502 maneuvers make the AS-501 displays inadequate. For example, a plot used to monitor one of the maneuvers goes completely off scale. On the other hand, if we're able to eliminate this request, the orbit phase could be made identical for the AS-501 and AS-502 missions. Our action on this item is for the Flight Controllers and MPAD people to determine if the other displays can support whatever job is to be done by the Flight Controllers adequately and also to determine if the requested display would be even adequate, since there is some question about that. Jom Stokes has assured us that if a decision is available by March 15th we should be able to add it without schedule impact.
I felt this was one of the best meetings yet. There was a true spirit of cooperation among all participants in trying to get the job done, and I felt that the compromises arrived at were really very good. The Flight Controllers freely abandoned their requirements where at all possible and the Flight Software people are making an extra effort to not only provide the capabilities identified as essential for AS-502, but where suitable will also make them available in the AS-501 system. The point is, I feel we have improved the product as well as significantly reducing the work which must be performed in getting it ready.