Flight Question AMSO Custom Launch Window Planning?

WillRak

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Hi everyone,

I have been flying some AMSO missions to new landing sites on the moon, however I find that when I am preparing for TEI, I always have a very long burn time (around 300s), and I have noticed that this is likely due to a rather high orbital inclination around the moon. I use IMFD and the AMSO autopilot to align the base, but it always does so at a very high inclination, and that must have its roots in my launch time from earth (It would waste a lot of CSM fuel changing the plane of these orbits, and I doubt that was the method used). I normally launch when the moon's orbital plane matches precisely the target orbital plane of the Saturn V, as this keeps the dV required for TLI low.

For anyone who has flown their own AMSO missions, how do you refine your launch window to make sure that your orbit plane around the moon does not stray into extreme latitudes, i.e, have a very high inclination?

Thanks a lot,

Will
 

2Copernicus

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I can only help regarding LunaTransfer MFD but hopefully it'll help. (Please Note I'm not an orbital physicist)

When launching for the moon using LTMFD there are a number of things you have to do. The first is to make sure that AMSO's launch azimuth (or azimutucor as it's called in the scenario file) is such that the Ein of LTMFD is as close to 0 as possible. So you have to correct for any Ein that you have at launch, and remember that the Saturn V only has 20 degrees azimuth to either side.

The next thing is regarding launch windows, there are 2 launch windows, one in the morning and one in the afternoon/evening. The morning one is used for Atlantic TLI's whereas the afternoon is good for TLI's over the pacific. The morning Window is to be used when you have a landing site south of the equator, whereas the afternoon window is for Landing sites North of the equator.

Another thing that you have to account for is ToA and PeT (time over site and time of lunar Periapsis for anyone who isn't aware). These numbers are a tad harder and you have to try and switch them up a bit to see what gives you the lowest inclination. It should be noted that you generally want the ToA to be around the time of your PDI, but if it comes with a ridiculous inclination than you may have to shift it and then engage in a plane change whilst in orbit.

All of these are good techniques to reduce the inclination within reasonable margins, unfortunately for some landings sites the inclination is still way too high despite controlling for all of this, and I've found no way around it. For those who want to lower the inclination to the minimum for these trouble sites. I'd recommend setting your TLI for an equatorial orbit around the moon, and then use AMSO's default autopilot to plane change to the correct point whilst in Lunar Orbit, and use the scenario editor to compensate for fuel burned in such a plane change. It's certainly unrealistic I know, but its the closest way I've found.

Anyways hope this helps you in planning Lunar Flights with Apollo, happy landings!

P.S This video from NASA in 1968 goes over the basics for Lunar Launch Windows, I found it helpful.

 
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