Problem Apollo9 After phasing burn

[riclourenco]

hello

I'm having a problem in apollo9 after LEM Phasing Burn. After this burn and the null of the residuals, the LEM does not do the correct maneuver when I do V37E20E in the AGC. Comparing with file 16 (Before phasing burn) from the apollo9 scenarios folder after doing the burn:
Apollo 9 Scenarios Folder:

https://puu.sh/BJQzW/3dcd7dd741.png


My apollo 9 misson:

https://puu.sh/BJQmI/a7c9a63608.png


and it also happens in my mission that, during the phasing burn the AGS shuts off the engine 2 seconds before the burn time that is in the manuever pad. The burn is supposed to last 26 seconds and the AGS cuts the engine at 24 seconds. To get around this problem I inserted the vectors of burn into the AGS as if It were in orbit of the moon, so that I could turn off the engine manually at the right time. In both cases, after the burn, the LEM does not make the right maneuver after making V37E20E.
I've noticed that the orbit in my mission before the undocking is bit different from the orbit in the apollo9 scenario folder, as well as the values of the maneuver PAD. Can the problem be in the orbit before the undoking , because I did badly the burns with the SPS and the Docked LEM burn? Or could it also be some error in the values of the manuever pad? or maybe I have made a mistake in initializing LEM before undock?
I'm thinking in restarting a new apollo 9 mission. But I wonder if it's worth it, or if I can somehow fix the error by going back to a save file. Can you give me some help?

Thanks you

 

[indy91]

and it also happens in my mission that, during the phasing burn the AGS shuts off the engine 2 seconds before the burn time that is in the manuever pad. The burn is supposed to last 26 seconds and the AGS cuts the engine at 24 seconds. To get around this problem I inserted the vectors of burn into the AGS as if It were in orbit of the moon, so that I could turn off the engine manually at the right time. In both cases, after the burn, the LEM does not make the right maneuver after making V37E20E.

Remember that this is a manually throttled burn and might also slightly vary in DV. So of course it won't have the exactly planned burn time as compared to maneuvers using auto throttle. I'm not even sure the Maneuver PAD calculation uses the exact same throttle up time to 40% as the flight plan calls for (15 seconds after ignition). I wouldn't worry too much about this. As long as the burned DV is good.

I've noticed that the orbit in my mission before the undocking is bit different from the orbit in the apollo9 scenario folder, as well as the values of the maneuver PAD. Can the problem be in the orbit before the undoking , because I did badly the burns with the SPS and the Docked LEM burn? Or could it also be some error in the values of the manuever pad? or maybe I have made a mistake in initializing LEM before undock?
I'm thinking in restarting a new apollo 9 mission. But I wonder if it's worth it, or if I can somehow fix the error by going back to a save file. Can you give me some help?

I'm sure it can be fixed by going back to an earlier save file. The LM pointing at the CSM in P20 mainly depends on two things in the LGC: CSM state vector and LM state vector. The CSM state vector will have been uplinked some time before undocking. Later it has to be updated with P76 so that the LGC knows about the CSM sep burn. The LM state vector was also uplinked some time before undocking and will be unchanged until the phasing maneuver, which the LGC should be monitoring and incorporating the burned DV. If any of these haven't been done or not done properly then the LM of course can't find the CSM. In which case you shouldn't even bother attempting the rendezvous maneuvers, because all the calculations will be wrong.

Of course it could also be many other things, starting with the IMU alignment. Did the LM point directly up during the phasing burn?

 

[riclourenco]

Hello

Yes, the LEM points up during the engine burn. The LEM is apparently maneuvered into correct attitude after T - 2 min for phasing burn:

https://puu.sh/BL0yO/8d6770f131.png

https://puu.sh/BL0Ak/75a8275168.png


According what you say I should be able to correct the error by going back and restarting the LEM again before undocking!