Flight Question Going to the moon - prograde or retrograde orbit?

[EternalFrustration]

Hi everyone, I'm pretty new to Orbiter, and I'm loving it since I've been a space nerd since I was a little kid playing Project Space Station.
I finally managed to make it to lunar orbit after buying the farm a few times. My question is this - I'm in a prograde orbit, though most tutorials I've seen wind up in a retrograde orbit. Is there any advantage to orbiting one way versus the other?
Thanks for any advice!

 

[agentgonzo]

The moon rotates so slowly that it doesn't make a lot of difference. You'll save a slight bit of fuel by going the prograde route.

Most people enter in a retrograde orbit as this is the way it was done on the Apollo missions. The reason for this is that if you target a retrograde orbit and something goes wrong en-route, there is only a slight change* required to allow you to perform a retrograde sling around the moon and be on a free-return trajectory to the Earth. If you did this in a prograde manner, the sling would fling you off into solar orbit.

*Apollo missions started off on a retrograde-sling/free-return trajectory and when they checked everything was hunky-dorey on the way to the moon then performed a mid-course-correction to target lunar orbit.

---------- Post added at 13:53 ---------- Previous post was at 13:47 ----------

Oh, and welcome! and congratulations! and all the normal probe nonsense.

 

[C3PO]

Oh! And Probe is not nonsense!!! :nono:

 

[agentgonzo]

Told you

 

[Belisarius]

When you've mastered that, the challenge is direct trajectory, blasting directly towards the surface without orbit injection first, then braking for a soft landing.

That's when you find out how the craters got on the moon.

 

[EternalFrustration]

When you've mastered that, the challenge is direct trajectory, blasting directly towards the surface without orbit injection first, then braking for a soft landing.

That's when you find out how the craters got on the moon.

Yeah, that's not going to happen anytime soon. I took a couple of times around to get my perilune and apelune decent, and another couple of times around to get lined up with the base. I'm playing with infinite fuel for now until I get the hang of things, lord knows I don't need anything else to worry about yet...

 

[Wishbone]

Infinite fuel is not a friend of yours. Quicksave and re-do are your allies, though.

 

[C3PO]

Infinite fuel is not a friend of yours. Quicksave and re-do are your allies, though.

You can refill the tanks on the fly with the scenario editor. It's a much better option then using infinite fuel.

 

[dgatsoulis]

You can refill the tanks on the fly with the scenario editor. It's a much better option then using infinite fuel.

@EternalFrustration
As C3PO and Wishbone allready stated... That's the way to go. An infinite fuel source, will not help you learn anything. But a finite one, will! You can start by counting the number of times you had to "refill"... and then come down to a percentage of a fuel tank.

 

[EternalFrustration]

And out of curiosity, how would I change from a prograde orbit to a retrograde one if I wanted to?

 

[Wishbone]

If you are still far away from the Moon, by using RCS. If very close to it, by landing on the Moon and taking off, or otherwise expending a humongous mass of fuel.

 

[Izack]

What Wishbone said. Once you're there, you're stuck where you ended up until you leave.

If you're still far from the Moon, IMFD's Base Approach program can help you.

 

[EternalFrustration]

Okay, another newbie question - How do I get back to Earth from lunar orbit? :lol:

 

[agentgonzo]

TransX, IMFD or LTMFD. It can't be done with the built-in TransferMFD.

 

[Belisarius]

Try IMFD Base Approach. Set the source to Moon, target a place on Earth with Lat and Long, or use a base name.
Wait for the correct ejection time, usually when you're on the far side of the moon. If it looks like you're going to thrust directly into the Moon surface, something's wrong. Don't burn, check it again.