Upthread: Results of the February 18 Apollo Spacecraft Software Configuration Control Board (ASSCCB) meeting (Feb 20, 1969)
Downthread: Software for the AAP CSM spacecraft computer (Feb 12, 1970)
See list belowOctober 21, 196969-FM-T-131FM/Deputy ChiefApollo Spacecraft Software Configuration Control Board meeting number 32
On October 9 Chris Kraft convened the first Software Configuration Board meeting since June 5 at MIT. We had a real pot full of PCR's to discuss, some of which were approved for Apollo 13, some for 14, and some were put in a category in which MIT was to continue development to a point where their value could be assessed, perhaps for Apollo 14 implementation.
This memo is to document briefly what happened there:
1. COLOSSUS Apollo 12
PCR 960 – In case you weren't aware, a 49-word erasable memory program has been developed which will permit the CMC to start Time Base Six (TB6) in the S-IVB. This relieves the crew of a somewhat dangerous manual setting channel bits, if they ever encounter this absolutely impos- sible-to-encounter S-IVB inertial reference failure.
2. COLOSSUS Apollo 13
There were seven program changes approved for this program, some of the more interesting ones were:
PCR 936 – This change relieves the crew of the task of keying in TIG when he needs to apply an out-of-plane component as part of the CSI or CDH burn. The LM program was fixed this way too.
PCR 949 – Software fix for the split pulse problem in the VHF ranging equivalent to the fix for the two radars on the LM.
PCR 966 – This makes Option 3 the nominal option in P52. This saves the crew some DSKY key strokes.
PCR 967 hopefully will fix the pulse torquing program so that it will execute a 90° REFSMMAT change three time faster than it currently does and without screwing the FDAI ball around like a drunken sailor's Augekugle.
3. COLOSSUS Apollo 14
About 14 program changes were approved for Apollo 14 (that's fitting, isn't it?). Some of the more interesting ones are:
PCR 869 provides rate-assisted optics for the landmark tracking program (P22) which should be especially useful in the low orbits currently planned.
PCR 868 consists of several cis-lunar navigation program (P23) changes, some of which are probably useful since they help the crew orient the spacecraft to get good star/horizon observations. One improvement involves making the altitude of the horizon a function of range which doesn't leave me particularly warm. I would suggest that Math Physics Branch take a look at that.
PCR's 822, 917, 916, and 857 were all deletions yielding a total of about 700 words. Specifically, they are the stroking test, P31, TPI search (P17/P77), and a chunk of the pre-flight performance test flight program.
PCR 867 makes it possible to carry out orbit rate torquing with any roll attitude using R64.
4. COLOSSUS Off-line Assemblies
The two programs in the development hopper are PCR 876, a new pre- launch technique, and PCR 927, the Universal pointing routine which will be needed by at least Apollo 16 to support the CSM experimental package.
5. LUMINARY Apollo 13
About 9 changes were approved for LUMINARY, including:
PCR 882 to replace the DSKY display of horizontal velocity during P66 with the horizontal velocity component in the spacecraft X and Z plane.
PCR 285, submitted by yours truly, to remove the check for the auto throttle discrete. Essentially this change eliminates program P67 and makes it possible for the crew to use the manual throttle at any time during descent. It also makes the program insensitive to failure of the auto throttle discrete. (CCK requested that MIT look into making the LGC com- manded thrust a DSKY display as a part of this PCR.)
6. LUMINARY Apollo 14
Approximately 11 changes have been approved for Apollo 14, including:
PCR 896, which not only saves about 50 words, but should increase descent navigation accuracy by centering the readout of landing radar velocity at PIPTIME.
PCR 892, which deletes the rendezvous radar automatic acquisition capability during ascent. It is already inoperable during descent and descent aborts. Deletion of R29 frees 390 words of memory. Incidentally, Routine 29 does not work in the Apollo 12 program and will not be fixed for Apollo 13. In other words, it never worked and never will!
7. LUMINARY Off-line Assemblies
There is some interesting development work going on with LUMINARY. The one that appeals to me the most is Delta Guidance (PCR 969), which I have written about in another memo. Work on a landing radar pre-filter (PCR 941) and addition of a simple lunar terrain profile (PCR 940) are also under consideration for descent program changes. The so-called co- ordinated turn during a manually controlled lunar landing (PCR 884) is still in the mill.
PCR 888 is under consideration to modify the DAP control authority model to include the effect of RCS plume deflectors.
PCR 890 is supposed to improve the slosh stability of the LM DAP to be used when docked with the CSM.
A very interesting endeavor underway at MIT that you should be aware of is an attempt to develop a CSM rendezvous program which will operate as nearly automatically as is possible. If the off-line program proves dramatically successful in the crew simulations, the efforts may be expanded to other computer programs including those in the LM.
Another substantial effort at MIT has been devoted to recoding the CSM program much more efficiently than COLOSSUS. This effort has been completed, resulting in a program called Artemis which they have in their hands now, but which has not been tested. It provides at least 2,700 words of avail- able memory and with some program deletions could cough up as much as 4,300. Since we have no foreseeable need for this extra storage and we don't want to give up the considerable confidence we have in the current operationally proven COLOSSUS program, MIT was directed to discontinue further work on Artemis. Incidentally, no equivalent effort has been done on LUMINARY and no such work is planned now. It was stated, however, that the LUMINARY savings potential is estimated to be much less than for COLOSSUS.