Help getting more precisely to the moon!

[Zatnikitelman]

Well, I've finally gotten out to the lunar neighboorhood using IMFD! WOOHOO! However, I can't get it to give me a lunar Periapsis of anything reasonable. On my most recent trip, I made a Planet Approach burn just after leaving Earth's SOI (as indicated on IMFD's map display) then again shortly before entering the moon's SOI, both times, I shot for a periapsis of 100k and an inclination of 65* (a bit above Brighton Beach). However, the map display indicated I still had a periapsis of 17M, I was able to get that down to around 12M with some manual burns and a lot of fuel expended. Is there some sort of problem with Planet Approach that doesn't compute a burn to give a small Periapsis? I'm working on the moon base so I don't have a huge fuel margin like I would with a Delta Glider.
Thanks for any help!
Zat

 

[Urwumpe]

I remember that I always arrived at the moon in 500km distance, but don't ask me now how I did it. Was flying in LEO too long. I think you can aim for the desired arrival already.

But don't worry - Apollo did their capture burn in 9000km distance, when I remember correctly.

 

[Quick_Nick]

I doubt it would make much difference, but since there may be a chance, try a retrograde orbit around the moon.(Inc: 115*) Also, if it is actually showing a periapsis of 1.7M and not 17M, a PeD around 1.7M is the same as a PeA of low altitude.(ex:100km) However, I think you'd be able to tell the difference between 1.7M and 17M when you are at perilune.

 

[Zatnikitelman]

I'm trying a retrograde orbit, but not much seems to affect the 19M PeD/17MPeA. I'm going from a quicksave, I'll try redoing the mission, but at this point not much seems to be doing anything.

 

[MJR]

Retrograde burn at periapsis, but make sure your periapsis is high enough because sometimes that goes down too. There is this one tutorial that tells you how to get to the Moon's orbit and it tells you how to lower it and everthing. I beileve it is "Go Play in Space." It can also apply toother vehicles too.

 

[V8Li]

Funny, I just went to the Moon and landed on a Brighton Beach pad with only the Orbit MFD and Map MFD 5 minutes ago, must be karma . I do only one injection burn and only one correction burn when in Moon's SOI. The burn is not prograde nor retrograde wrt the orbit around the Moon. Instead a burn at a perpendicular direction on the orbit around the Moon (and that's a prograde or retrograde in Sun's orbit or Earth's) so that I get ahead or behind the Moon at intersection point, depending on what I want: orbit insertion or free return. Simply rotate the ship so that the Moon is 90 deg to your left or right and burn, you will see the Pe decreasing fast. So when you want to do a capture it won't help burning retrograde only at Periapsis. If the Periapsis is too high use the technique above, lower it and burn retrograde to lower Ap.

To change the iclination burn at the nodes. You know that by using the Orbit MFD, ref Moon.

 

[V8Li]

Retrograde burn at periapsis, but make sure your periapsis is high enough because sometimes that goes down too.

Get in a retrograde direction and deactivate the autopilot. Then yaw (ie pitch up and down) to compensate for the PeT difference since that happens if you burn way before the Pe, maybe because you want to get captured and you have to bleed alot of energy. And that means you're not paralel to the surface (you can't, the orbit is elliptic and using the retrograde autopilot will point you in an upward direction). Vectors, just link in the physics class...

Sorry for the double post...

 

[Zatnikitelman]

Lol, I figured it out. Apparrently the reference was set to Earth in Planet Approach so IMFD was acting as if I was trying to engage a 100k orbit around Earth! There was no label or whatever on IMFD so by chance, I zoomed out till I could see where I was in relation to the random grey circle on the screen and realized that I was looking at Earth.
I was finally able to make it partially down to the moon, but due to all the correction burns, I ran out of fuel! So thanks guys!!! I'll be writing my experiences down in the next few days so other IMFD newbies can hopefully figure it out.

 

[tblaxland]

Apparrently the reference was set to Earth in Planet Approach so IMFD was acting as if I was trying to engage a 100k orbit around Earth! There was no label or whatever on IMFD...

IIRC, there is a label "Ref" in the bottom left hand corner of the MFD. I'm at work at present so I can't check. Well done on getting to the Moon.

 

[ar81]

In the last version of my IMFD tutorial I added something about slingshot around Moon to go back to Earth.
[ame="http://www.orbithangar.com/searchid.php?ID=3403"]Tutorial: Concepts for Interplanetary MFD 4.2.1[/ame]
This tutorial refers to 4.2.1 since 5.1 is still under construction.

It also explains what SRC, TGT and REF are.
Understanding these is important to plan trajectories.

 

[mrspacely]

i like using transfer mfd for earth to moon, then imfd for moon to earth... always works for me

 

[polaris149Tiberius]

Try my tutorial

You can also try my tutorial for help doing this. Check the section on TLI.

"From the Earth to The Moon" an AMSO 1.17 Apollo 11 Full Mission Tutorial Using IMFD

I shot for a periapsis of 100k and an inclination of 65*

Could you explain how you made IMFD shoot for the inclination of 65*?
I would love to know how to do this.
Thanks in advance.