Apollo 12 Powered Descent/LR Issue

Max-Q

99 40
Addon Developer
Joined
Jul 5, 2021
Messages
765
Reaction score
1,178
Points
108
Location
Cislunar Space
Website
www.orbiter-forum.com
Another thing I noticed on the return trip:
TEI was nominal. VERY nominal as it turned out, all three MCCs on the way home were scrubbed and I hit right in the middle of the entry corridor!
Anyway, there was an issue when MCC tracking went to calculate my MCC-5. Obviously it would normally show "Thread Started" then "Thread Completed", then show "MCC-5 has been scrubbed". In my case, the sim hung after "Thread Completed" and I ended up having to restart Orbiter. It did it again 2 more times, and I ended up disabling MCC tracking and calculating MCC-5 myself with RTCC. The dVs were really small, I decided the maneuver was scrubbed, and once well past MCC-5 I reenabled MCC tracking after resetting the substate. The problem didn't reoccur for later MCCs, they showed the normal "MCC-# has been scrubbed" message and gave me the SV uplink. MCC worked nominally for the rest of the TEC and entry phase.
Here's the odd thing: It printed a nonsense MCC-5 pad in the MCCPreAdvisoryData.log file that never showed on the screen because the sim hung. Attached is a scenario just before MCC-5 and the nonsense PAD. Looks like maybe a divide by zero error or something.
 

Attachments

  • MCC Bug.scn
    134.5 KB · Views: 64
  • MCC-5 Not-A-PAD.txt
    767 bytes · Views: 64

rcflyinghokie

LM Junky
Addon Developer
Joined
Jun 4, 2016
Messages
605
Reaction score
325
Points
78
Location
Colorado
Just out of curiosity, is there any chance a copy of FP7 still exists in some archive somewhere or could it be reconstructed? Obviously a massive project, just curious.
We have no idea, certainly something we are hunting for! But if we had the listing like FP6 or 8 we could certainly get it working.
 

indy91

Addon Developer
Addon Developer
Joined
Oct 26, 2011
Messages
1,223
Reaction score
579
Points
128
Ah I think I know what was going on with MCC-5. It didn't even calculate the maneuver. The calculation happened in the lunar SOI (30 minutes before crossing over) while MCC-5 will be already in the Earth SOI. And the logic was checking what SOI the state vector was in. It saw the Moon and aborted the calculation, leading to some random behavior, usually just the burn being scrubbed. I'll implement some improvements there so that the logic checks the SOI at TIG and not the input state vector (= current time).
 
Top