Bug NASSP Issue with AGC clock sync

[Messierhunter]

Hi all, I'm in the process of recording a real-time simulation of the entire Apollo 8 mission to sync up to the audio archives and play back during a webcast on the 50th anniversary in December. In doing a practice run with the Apollo 8 MCC scenario I found that the AGC's reported mission elapsed time by verb 16 noun 65 was several minutes off from the time shown by the checklist mfd and mission timer just after launch. I really don't want to get halfway through my real-time play through and have this happen, so is there any known cause of this bug and is there anything I can do to avoid it or fix it?

I should mention I'm using orbiter 2016 with the latest beta.

 

[indy91]

Not a known bug, pretty unusual. Any idea when it started diverging? Was it gradual or instantly? Not sure what could cause it, maybe excessive time acceleration or loss of power for a few minutes.

The AGC clock time can be fixed by a clock update, the Project Apollo MFD can do that. But it shouldn't have diverged in the first place, so, I'd rather figure out why it even happened. With an AGC clock that is several minutes off you can't fly a mission. None of your maneuvers would be accurate.

 

[Messierhunter]

Not a known bug, pretty unusual. Any idea when it started diverging? Was it gradual or instantly? Not sure what could cause it, maybe excessive time acceleration or loss of power for a few minutes.

The AGC clock time can be fixed by a clock update, the Project Apollo MFD can do that. But it shouldn't have diverged in the first place, so, I'd rather figure out why it even happened. With an AGC clock that is several minutes off you can't fly a mission. None of your maneuvers would be accurate.

Yeah, I don't know when it happened but it seemed pretty sudden; prior to launch it was just fine, I saved the scenario about 30 minutes after the launch and shut down. When I came back to the scenario later I noticed it was several minutes off. I reloaded it several times just to make sure. The only time acceleration I did during or after the launch was to set it to 0.1x for a bit during post-launch checklists to try to get caught up on some items. Not sure if that could have thrown things off.

Also, I realize the mid-flight scenarios might be hold-overs from an earlier version and therefore broken, but it seems like every time I try to run the Apollo 8 re-entry scenario I bounce off the atmosphere after peaking at about 6 g's. Maybe I'm doing something wrong in the entry checklist, it's been a long time since I've used NASSP, but I don't recall ever having this problem back when v7 was in beta. I ran through an entire Apollo 8 playthrough back then even when it wasn't fully supported and it ran fine. I'm assuming though that in this case it's just an older version of the scenario and it's just broken.

For my real-time playthrough I will not be using any time acceleration, I'm recording all 147 hours of the mission bit by bit and re-syncing the audio archives to my captured footage. Hopefully if it's a time acceleration issue I'll simply avoid it by default. So far I'm a couple hours into pre-launch, which is some of the most tedious work audio-wise. None of the gaps between PAO remarks are preserved on the original tape, so I have to manually separate each remark out and place it on the correct part of the launch timeline. Once the mission gets off the ground the audio is pretty much complete from start to finish on the mission (save for one missing 3 hour tape for which Honeysuckle Creek has some backed up audio) so it should be less tedious.

 

[indy91]

Yeah, I don't know when it happened but it seemed pretty sudden; prior to launch it was just fine, I saved the scenario about 30 minutes after the launch and shut down. When I came back to the scenario later I noticed it was several minutes off. I reloaded it several times just to make sure. The only time acceleration I did during or after the launch was to set it to 0.1x for a bit during post-launch checklists to try to get caught up on some items. Not sure if that could have thrown things off.

No, that shouldn't cause any issues. What can happen with time acceleration is that you accidentally press T too often and end up with 1000x or so, which can destroy the frame rate and then maybe cause the time issue. But that was just my theory and seems unlikely.

Also, I realize the mid-flight scenarios might be hold-overs from an earlier version and therefore broken, but it seems like every time I try to run the Apollo 8 re-entry scenario I bounce off the atmosphere after peaking at about 6 g's. Maybe I'm doing something wrong in the entry checklist, it's been a long time since I've used NASSP, but I don't recall ever having this problem back when v7 was in beta. I ran through an entire Apollo 8 playthrough back then even when it wasn't fully supported and it ran fine. I'm assuming though that in this case it's just an older version of the scenario and it's just broken.

Yeah, the Mission Scenarios for Apollo 7 and 8 that come with NASSP are still the same as in the NASSP 7 release. There are lot of minor things broken in those scenarios, but you encountered the main issue: the Auto RCS Enable relays are diabled. They were moved to a different subsystem since the 7.0 release and that's why the AGC won't have rolled your CM around during the reentry and you skipped off. It's a fairly easy fix and with that these older scenarios are quite usable: SECS Arm circuit breakers in, then RCS CMD to On. That should make the RCS properly work again.

For my real-time playthrough I will not be using any time acceleration, I'm recording all 147 hours of the mission bit by bit and re-syncing the audio archives to my captured footage. Hopefully if it's a time acceleration issue I'll simply avoid it by default. So far I'm a couple hours into pre-launch, which is some of the most tedious work audio-wise. None of the gaps between PAO remarks are preserved on the original tape, so I have to manually separate each remark out and place it on the correct part of the launch timeline. Once the mission gets off the ground the audio is pretty much complete from start to finish on the mission (save for one missing 3 hour tape for which Honeysuckle Creek has some backed up audio) so it should be less tedious.

The only issue with time acceleration should be that the frame rate can become really bad, which in turn could cause some issues. And there is one small restriction right now with the LVDC++, that it can't handle more than 50x time acceleration. So don't do that between liftoff and CSM separation after TLI. Other than that it shouldn't be an issue.

Seems like quite the project you are attempting. I hope we figure out what goes on with your AGC clock somehow and that you don't have any more issues with that. Maybe you have a scenario saved just before launch and can try the ascent again? And check every so often if the clock is still accurate?

 

[Messierhunter]

Yeah, the Mission Scenarios for Apollo 7 and 8 that come with NASSP are still the same as in the NASSP 7 release. There are lot of minor things broken in those scenarios, but you encountered the main issue: the Auto RCS Enable relays are diabled. They were moved to a different subsystem since the 7.0 release and that's why the AGC won't have rolled your CM around during the reentry and you skipped off. It's a fairly easy fix and with that these older scenarios are quite usable: SECS Arm circuit breakers in, then RCS CMD to On. That should make the RCS properly work again.

Got it, thanks, that makes sense. I might try that scenario again then just for kicks.

Seems like quite the project you are attempting. I hope we figure out what goes on with your AGC clock somehow and that you don't have any more issues with that. Maybe you have a scenario saved just before launch and can try the ascent again? And check every so often if the clock is still accurate?

Yeah I'm going to keep a close eye on it with my real-time play through and see if it happens again. I'm saving the scenario about every hour and it's still fine so far, but if it messes up during the launch again then I'll definitely have to find a fix. I don't think I went past 10x time acceleration before launch on my previous playthrough where it messed up, but if there's some other cause then it could happen again this time.