CSM Computer seems stuck PROG light and Actv light on solid

sw34669

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During my trip down onto the moon, i've kept an eye on the CSM checklist wise , not much to but made sure it was upto date.

Getting ready for liftoff, i get the vec update for the LM completed ok but when I switch to the CSM to do the same, I notice the PROG light is on (last command run on CSM was v45e)
and the COMP ACTV light is also on solid. Never seen this condition before not sure what it means. I've tried hitting reset and then P00ing it. The ACTV light stays on and the CSM state vector update gives an OP ERR light.

Not sure what's gone wrong i've only run the few items that appeared in the checklist for the CSM during time on the moon.
 

sw34669

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ok i may have found a bug . i went back to one of my saves just to make sure it wasnt me.

I wait in the LM for the uplink, the message LM: ready for uplink shows. I check the CSM and the computer is idling in p00 no prog or OP ERR
I come back to the LM and carry out the uplink , it shows, CSM State Vector has been updated
I switch back to the CSM and now the PROG ACT light is on solid
 

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Thespacer

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My observation is similar - the Comp Acty light stays solid. I’ll let others chime in as to whether this is buggy or not (whether as a result of NASSP or the AGC itself), but it strikes me that there is a pattern: it tends to happen when the CSM has been either idle for quite some time, or has completed some other intensive process, and it simply takes a lot longer to stop integrating. Perhaps your experience is different, but it eventually does stop integrating for me (perhaps after several minutes), and I am able to proceed with an uplink.

I have observed this behavior in other parts of the mission too (perhaps to a much lesser degree).
 

sw34669

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when i switch to the CSM a few mins later an uplink comes in and says it's updating CSM and LM state vector but nothing gets uplinked (no flashing uplink light)

Is it possible that these 2 uplinks are the wrong way round ? What i dont understand is why uplinking the LM: uplink, to the LM: a) shows CSM SV updated and b) all of a sudden causes the computer on the CSM to go into solid calc mode.
 

sw34669

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Here's my scenario just before it
 

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sw34669

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it takes 15 minutes, for the CSM ACT light to go out, which now reduces the time available for prep and the uplink message has gone as the man pad has come in over the top of it

tried this a few times, even when the CSM accepts its uplink I get an OPR Err at the end
 

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Thespacer

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When was the last time you did V37E 00E in the CSM? Even though the CMC generally remains idle (P00) while you’re focused on LM activities, every now and then it seems (to me) to help to re-enter P00 every now and then. Now I’m not sure if there is a more specific and technical reason for the stuck comp acty light, but FWIW I have not seen it as bad as that.
 

sw34669

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When was the last time you did V37E 00E in the CSM? Even though the CMC generally remains idle (P00) while you’re focused on LM activities, every now and then it seems (to me) to help to re-enter P00 every now and then. Now I’m not sure if there is a more specific and technical reason for the stuck comp acty light, but FWIW I have not seen it as bad as that.
I did it a few times, also re-ran from further back, doing a p00 on csm earlier, but, ended up in the same place, LM uplink ok, CSM uplink gives solid ACTV and OP ERR.
 

indy91

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Ok, so for the program alarm, that is alarm code 114. You can check that with V05 N09E and then you can reset the program alarm with the RSET button on the DSKY. Alarm 114 is "more marks made than desired". That alarm should only happen in P22, I think, maybe you did too many marks during a P22 earlier? When you press the mark button in P00 or so then it tends to give alarm 122 "marking not called for", which is different. Both alarms types are harmless and shouldn't have anything to do with the stuck computer activity light.

Ok, small lecture on how P00 works. Every once in a while (that time is variable) the CMC checks the current time of the CSM state vector. When that state vector is outdated it integrates both the CSM and the LM state vector to present time. Now, a few hours earlier you did V44, which told the CMC that the LM is on the surface. This inhibits the integration of the LM state vector, as that would be pointless, the LM isn't coasting in space anymore. And then, a while before LM liftoff, the flight plan calls for V45, which reset the lunar surface flag again and allows the integration of the LM state vector. But that means the LM state vector hasn't been brought to present time since the time of landing, so it's many hours old. And this is what takes the CMC so long to process, it tries to take the 20 hour old LM state vector to present time. The coasting integration routine is slow. I'm pretty sure it's a coincidence that the COMP ACTY light went on at about the same time as the LGC uplink. You simply did the V45 not long ago and then the next time the CSM state vector is outdated it will take both to present time, which takes forever for the LM one.

And here is how that went down during the actual mission:

122:31:43 Collins: Yes sir. Keep it that way. (Long Pause) Columbia is coming up on a Verb 45, Enter to reset the surface flag.
122:32:15 Evans: Columbia, Houston. Negative. Standby on the Verb 45.
122:32:52 Evans: Columbia. Roger. We copy. (Long Pause) Columbia, Houston. We've got a couple more vectors to send up to you. They'll be coming up shortly and then you can do the Verb 45 after you get those in. Over.

So they uplinked a new LM (and CSM) state vector before Collins did the V45. As that is a predicted LM state vector with a time tag after insertion of the LM the very long calculation in the CMC is prevented.

And for NASSP, I will check for the timing of the V45 and the uplinks to the CMC. The uplinks should really come first. I'll adjust the checklists accordingly.

What you can always do is a V96 which stops the P00 integration. Just do that and then let it do the uplinks of the state vectors to the CMC. That should prevent any problems.
 

sw34669

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Advanced Higher lecture thank you, all points noted and understood. I wondered about SV's aging and how this was managed. You're correct it's of course just a timing thing.

As Columbo would always say as he walked away, "Just one more thing".....

Playing around this afternoon, I noticed that regardless of the timings, when updating the SV on the CSM I get an OP ERR . Is that OP ERR due to already processing, is what you're saying? Unlike fine wine, the SV gets worse with age (entropy).

thanks, great summary.
 

indy91

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Yeah I think the operator error is due to the permanent state vector being integrated. It probably sets some flag that doesn't allow it to be interrupted (aside from V96).
 

sw34669

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right , i'm off to fire this tin can up and see if i can get back upto the csm. thanks again for the insight.
 
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