Best hope for Polar Orbital Insertion (the Mun)

[paul_c]

What's the best (nearest 90deg, polar) inclination you'd normally hope to achieve if going from Kerbin to the Mun? I've done it a few times, initially not deliberately because my starting orbital plane on Kerbin was no where near zero (and it was just luck or lots of excess fuel to make the trip in the first place) but I deliberately wanted one this time, and achieved it:

 

38.4 degrees......could I hope for more? 90??

Edited November 13, 2020 by paul_c

[king of nowhere]

11 minutes ago, paul_c said:

What's the best (nearest 90deg, polar) inclination you'd normally hope to achieve if going from Kerbin to the Mun? I've done it a few times, initially not deliberately because my starting orbital plane on Kerbin was no where near zero (and it was just luck or lots of excess fuel to make the trip in the first place) but I deliberately wanted one this time, and achieved it:

 

38.4 degrees......could I hope for more? 90??

yes, you can get a mun insertion at 90 degrees, and it's not even very expensive. you don't even need to start from an inclined orbit either, that would be expensive.

just, when you make the intercept burn, fiddle with the normal/antinormal (pink direction) until you are not pointing at the equator but at the poles.

here is an image. do notice the directions in the manuever. it ended up costing 60 m/s more than a normal equatorial insertion.

 

But it's even better to make a course correction along the way, as shown here

the first manuever was a normal, all prograde manuever. the second manuever, in violet in the upper side of the image, is mostly normal to push your trajectory up, plus a little bit of radial to go exactly over the pole, and it is only 36 m/s. the cheapest place to make those manuevers is around halfway, and you can be more accurate.

[Kerbart]

When you set up your navigation node you can click on mun in the map to make it the focus of your view; just aim for the dead center.

then a mid course correction in normal/anti normal will cost just a few m/s DV to set up an apoapsis at, say, 50 km

[paul_c]

Many thanks - I didn't think of deliberately setting the periapsis to the centre of the Mun (but it makes sense now!) I tend to prefer free return trajectory ones, although the one in the OP was a hybrid anyway (I think that's the term? It had the encounter with the mun then an escape from kerbin's influence later on). I guess its 6 and half a dozen, you have LOCV either way if the engine doesn't start for the mid-course burn!

[vv3k70r]

On 11/13/2020 at 12:32 PM, paul_c said:

What's the best (nearest 90deg, polar) inclination you'd normally hope to achieve if going from Kerbin to the Mun?

By manipulating insertion time with a slight inclination to da Mun. The point where You get int the gravity will decide Your inclination. For higher inclination its easier to start from KSC to the west and insert on the front of da Mun. You can get same result by folowing Mun on a huge circular orbit.

But generaly it is cheaper to get any reasonable high insertion and then alter it by manouver normal/antinormal.

 

 

[paul_c]

I think that will be my strategy for now. I tried the "aim for the centre, Pe isn't even there" and all it meant was a fair mid-course burn. I figure the best way, is to get a tight as Pe as terrain will allow, straight from the prograde burn from Kerbin, then do the minimal retro burn to capture the Minmus orbit, then once at the top, do any gross correction of inclination there. Then once at Pe again, circularise to a lowish orbit ready for a landing try.