apolllo 11 mcc-3 in gimbal lock zone

[patio]

Flying apollo 11 with mcc enabled

my mcc1 and mcc2 were scrubbed

but I get the following mcc-3 in gimbal lock zone

It is the first time I see this
Is that supposed to happen with mcc ?

P30 MANEUVER
MCC-3 PURPOSE
SPS/G&N PROP/GUID
+63272 WT N47
+000.73 PTRIM N48
-000.32 YTRIM
+00053 HRS GETI
+00054 MIN N33
+053.71 SEC
-0003.2 DVX N81
+0000.5 DVY
+0001.2 DVZ
XXX252 R
XXX162 P
XXX271 Y
+9999.9 HA N44
-0411.8 HP
+0003.5 DVT
XXX0:01 BT
X0000.5 DVC
XXXX16 SXTS
+079.80 SFT
+16.500 TRN
XXX000 BSS
XX+00.0 SPA
XXX+0.0 SXP
+000.00 LAT N61
+000.00 LONG
+0000.0 RTGO EMS
+00000 VI0
000:00:00 GET 0.05G
SET STARS: Vega, Deneb
RALIGN 007
PALIGN 144
YALIGN 068
Remarks:
LM weight is 33773.

 

[indy91]

Hmm, this is something the MCC doesn't properly support yet. Quite unlucky to get a yaw angle that's actually so far into gimbal lock. The proper procedure would be to use a preferred REFSMMAT (all zero IMU angles at ignition) for the burn and then go back to the PTC REFSMMAT afterwards. If the MCC wants to support this it would have to remember that it has to uplink the PTC REFSMMAT again. That's a bit tricky in terms of the schedule of MCC calculations, so probably why I didn't implement it yet.

My suggestion is to do a P52 option 1 using the P30 burn target. Have you done that procedure during Apollo 7 or 9? You do P30 after the uplink, then enter P40, but only on the first display of it. Exit P40 and then you do the P52 option 1.

Then do the burn at 0,0,0 angles with that REFSMMAT. There isn't really an easy way to get the right PTC REFSMMAT back, so you could simply stay with that wrong REFSMMAT until before MCC-4. Then you will get a new REFSMMAT from MCC anyway.

 

[patio]

Thanks

I will do that