- Date: Jul 21 1966
- From: FM/Deputy Chief, Mission Planning and Analysis Division
- Subject: AS-204 computer program status
During the week of July 4, 1966, the prime and backup crews for the AS-204 mission attended briefings at MIT, which, among other things led to their request that four changes be made in the spacecraft computer program for that mission. This request triggered off a considerable amount of activity which I would like to record here, indicating the final outcome of it all.
In discussing the overall AS-204 computer program situation with MIT people on July 14, 1966, I was told that a flight-worthy program would probably not exist on August 8, the date we had established for the release of the flight program tape for rope manufacture. That is, according to the best MIT estimate, the program would still contain bugs and would not have satisfactorily completed its flight acceptance verification. They felt that delaying delivery of this program two weeks–that is, until August 22–was necessary to assure flight readiness. They also indicated that three of the four pilot requested program changes could be made with little or no impact during this period of time. These changes are as follows.
- Choice of heads-up or heads-down spacecraft attitude during SPS maneuvers.
- Display of latitude and longitude after completion of reentry guidance.
- Display of the sensed retrograde maneuver–three ΔV’s in the IMU platform coordinates system.
They estimated that the fourth change–providing a pilot choice of displays during launch powered flight and immediately after insertion into orbit–would delay tape release an additional week beyond the August 22 date.
My personal view of this situation is somewhat different than MIT’s. Considering our experience in the past, I question whether a truly flight-worthy program can be delivered on August 22, even without changes, and I’m certain that any attempt to make changes will only reduce our chances. The people who are currently carrying out the program checkout would have to make these changes, so obviously some of their effort must be diverted.
In addition to that, these program changes would certainly make further program checkout necessary and would tend to nullify some of that work which has already been carried out. Furthermore, although it would be nice for the crew to have these additional capabilities, there does not seem to be any technical justification for classifying them as mandatory. Accordingly, it was my recommendation, supported by a number of other MSC people, that none of the crew recommended changes be made in the AS-204 program. This recommendation was accepted by the G&N Subsystem Manager and the Apollo Program Manager. And, that is how the situation stands now.
One item of particular concern to the crew was the apparent lack of well established crew procedures for making a GO NO-GO decision onboard the spacecraft following S-IVB shutdown. Although the ground is primary for this function, as it has been on past manned programs, it would certainly be highly desirable to have this onboard capability, particularly recognizing the somewhat poor ground monitoring and communications available during Apollo launch. Furthermore, such a capability is very nearly within our grasp, which makes it even more tantalizing. In reviewing the status of the work going on in support of this onboard function, I find that sticking to the current onboard displays will somewhat delay availability of charts for the crew to use in this mission phase. Specifically, this work, which has been primarily directed toward development of the RTCC/MCC capability, is now estimated to be within about four weeks of completion and crew charts could have been made available at about that time if V, ?, and h were displayed onboard the spacecraft. However, since special charts will be needed for use with the parameters to be displayed to the crew, an additional one or two weeks will be needed for their preparation. Therefore it is estimated that they will be available on about September 1.
In summary, MIT feels the earliest date a flight-ready program could be delivered for AS-204 is about August 22, and MSC is authorizing delay of the flight program tape release at least until that date. In order to give greater assurance that the program will be flight-ready on that date, no program changes are being authorized. In the absence of the most desirable of these onboard computer program changes, specifically the provision of displays onboard the spacecraft for making GO NO-GO decision after launch booster shutdown, special charts must be prepared, which will take about two weeks longer than if the changes were made, but should be ready on about September 1.