Wedge313
Well-known member
Hello, I'm running Apollo 17, I'm currently in a 170 x 51 orbit around the moon after LOI. It looks like the orbit has me passing pretty much over the intended landing site. I'm trying to use the RTCC to plan the DOI-1 burn. Another learning opportunity for me, both in how to use the RTCC and in orbital mechanics.
Following the RTCC MFD Input Reference Guide, it looks like Apollo 17 did things a little differently than the others. The DOI procedure refers me to the "common functions" section. I've set up the General Purpose Maneuver as instructed (TYP=Apogee and Perigee Change, PNT=Time, GET=93:13:08 (from the flight plan), REF=Pad/LS, ApA=60.0, PeA=13.17). It then says to tweak the GET until LONG P is 31.36.
I'm unable to get LONG P to 31.36. Playing around with the GET, right around 93:12:36 I get a strange result. If I use 93:12:36.3 my LONG P is 33.10 E. If I go to 93:12:36.4 (only 0.1 sec later) the LONG P jumps to 68.16 W.
I don't understand what's going on here. Is my current orbit so far off that it's a case of "you can't get there from here"? Why is the LONG jumping about 90 degrees?
Going forward, should I go with the DOI-1 burn with LONG P of 33.10 E and hope my LM DOI-2 can correct for it? Or is there a better way I can plan this first DOI burn?
Hoping to better understand what's going on here.
I've attached a .scn of my current state.
As always, thanks for the help.
Following the RTCC MFD Input Reference Guide, it looks like Apollo 17 did things a little differently than the others. The DOI procedure refers me to the "common functions" section. I've set up the General Purpose Maneuver as instructed (TYP=Apogee and Perigee Change, PNT=Time, GET=93:13:08 (from the flight plan), REF=Pad/LS, ApA=60.0, PeA=13.17). It then says to tweak the GET until LONG P is 31.36.
I'm unable to get LONG P to 31.36. Playing around with the GET, right around 93:12:36 I get a strange result. If I use 93:12:36.3 my LONG P is 33.10 E. If I go to 93:12:36.4 (only 0.1 sec later) the LONG P jumps to 68.16 W.
I don't understand what's going on here. Is my current orbit so far off that it's a case of "you can't get there from here"? Why is the LONG jumping about 90 degrees?
Going forward, should I go with the DOI-1 burn with LONG P of 33.10 E and hope my LM DOI-2 can correct for it? Or is there a better way I can plan this first DOI burn?
Hoping to better understand what's going on here.
I've attached a .scn of my current state.
As always, thanks for the help.