Deviating from MCC uplinked LOI-1 burn

MrFickles

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I'm currently flying Apollo 10 with MCC enabled and following Checklist MFD. I've noticed that my time of arrival at the moon (and all subsequent events) is approximately 20 minutes late.

I've flown the mission until the initial LM activation steps at ~81h MET, and I'm starting to get annoyed by this +20min offset. I decided it would be best if I reverted back to before LOI-1, ignoring the MCC LOI-1 PAD values and generate my own using RTCC MFD.

My plan is to put the spacecraft in an orbit slightly lower than 60x170nm in order to gain back 20 minutes between LOI-1 and LOI-2. How would I go about computing such a maneuver in RTCC MFD? Or do I have to go back further and gain back the 20 minutes in the trans-lunar coast?
 

indy91

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Orbital period after LOI-1 is about 2:08:39.5 (Apollo 12 operational trajectory value). After LOI-2 it is 1:58:43.3. So if there are two orbits between LOI-1 and LOI-2 then you might want to skip LOI-2 entirely and get into the 60x60 orbit with LOI-1 already. The new LOI targeting is pretty well documented in the RTCC MFD manual now (under Doc\Project Apollo - NASSP). I guess you just need to change the HA from 170 to 60 and calculate your solution.
 

MrFickles

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Yea, I kind of figured I'd need to go directly into a low orbit. I compared the orbital period of a 60x170 vs a 60x60 orbit and noticed it was almost exactly 10 minutes difference.

I personally would not like to skip LOI-2, so I reverted to MCC-3 and sped up my arrival at the moon.
 

indy91

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You kind of need to go non-free return to have any control over arrival time at the Moon. I do want to look at the Apollo 10 TLI targeting parameters again soon though, I'm certain something is wrong with them and contributes at least 10 minutes of late arrival time at the Moon.
 

MrFickles

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I'm okay with going into a non-free return trajectory. Completely skipping a major burn is where I draw the line.
 
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