Capture Asteroid in Distant Retrograde Orbit Around Moon

[PeterMueller]

Hi folks!

I was reading the NASA Asteroid Redirect reference files and wanted to capture an asteroid NASA style! They plan to capture a fairly small rock and put it into a retrograde orbit around the moon. Later a SLS with an Orion spacecraft launches and rendezvous with the asteroid in moon orbit.

Here is a PDF for the capture process, scroll to page 9.

And here is a description of the rendezvous, on page 6.

My problem is to put the asteroid in the retroorbit. I simply don’t get the part with the lunar gravity assist. Each time I approach Mun I am confronted with 800+ Delta-v to compensate in order to not overshoot. Has anybody ideas about this grav assist?

Thanks a lot in advance!

[KerbMav]

I am not sure I understand your problem correctly.

You are approaching retrograde to Mun's orbit, not just retrograde to its rotation?

The 800+ dV would be needed to establish an orbit around Mun?

Although I think it is impossible to enter a stable orbit around a moon by a simple gravity assist

A gravity assist at a moon can lead to/help attaining/changing an/the orbit around the planet though.

This is what I think NASA wants to do, slingshot at Moon to fly further out and capture an asteroid, and then use Moon's gravity to slow down into a return trajectory to Earth.

[PeterMueller]

Ah, I’m stupid, I found my problem. I was trying to approach Mun heads-on, which resulted in those huge delta-v. As you said, a grav assist around Kerbin helped. Like this:

Thanks!

[r4pt0r]

wouldnt this have helped? http://forum.kerbalspaceprogram.com/threads/75488-Orbit-direction-indicator

[Vanamonde]

This how-to question moved to the how-to sub-forum.

[1D-1()T]

Does anyone else feel weird reading that pdf and realising that pretty much everything makes perfect sense?

[PeterMueller]

I think NASAs approach in the PDFs is very beautiful