Apollo 16 MCC-1 RTCC Calculation

Wedge313

Active member
I'm in the early stages of the Apollo 16 mission, running the RTCC calculations for MCC-1. Another learning opportunity presents itself.

I'm using Option #4. The initial calculation comes up with a 7 fps maneuver, but it gives me an LOI burn time of 74:56:35. The Flight Plan shows LOI at 74:28:38. If I adjust the F23 constraint times and move the LOI burn closer to the flight plan time (I ended up with 74:28:55) the required dV jumps up to 28.6 fps.

How important is it to get the LOI to agree with the flight plan at this point? I'd imagine being off by 27 minutes would have a huge effect on the resulting orbit. But will later MCC's give me more efficient opportunities? How do I set up the RTCC to look at the dV's that might be required later? Just by adjusting the TIG? Or is there a way to see all the MCC's at once to find the more optimal solutions? Thanks.

BTW I'm using NASSP v8-1833 this time. I like the new FDAI and the Checklist MFD EXEC ON/OFF feature. Constantly improving an already impressive product.

indy91

I'm using Option #4. The initial calculation comes up with a 7 fps maneuver, but it gives me an LOI burn time of 74:56:35. The Flight Plan shows LOI at 74:28:38. If I adjust the F23 constraint times and move the LOI burn closer to the flight plan time (I ended up with 74:28:55) the required dV jumps up to 28.6 fps.

How important is it to get the LOI to agree with the flight plan at this point?

Quite important. The later missions really wanted to follow the flight plan closely.

I'd imagine being off by 27 minutes would have a huge effect on the resulting orbit. But will later MCC's give me more efficient opportunities? How do I set up the RTCC to look at the dV's that might be required later? Just by adjusting the TIG? Or is there a way to see all the MCC's at once to find the more optimal solutions? Thanks.

No, there is no display for TIG vs. DV. The general rule for the midcourse corrections is that earlier is cheaper. Only if you calculate a very early maneuver (before normal MCC-1 time) would the DV be larger, mostly due to the optimization having trouble finding the optimal solution though.

The preferred point to do the MCC is MCC-2 actually. Only if MCC-2 becomes too large would they have done MCC-1. I'm not too happy with your 28.6 ft/s for MCC-1 already (could be caused by many things), MCC-2 is going to be even a bunch more DV. But I think it is still small enough that you could wait until MCC-2 and skip MCC-1. But in any case I would try to get the LOI GET within about a minute of the flight plan time.

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