knowledge me about trajectories

[putnamto]

as you can see in this picture im aproaching the mun with an equatorial trajectory, and if i dont circularize my escape will put me in an equatorial orbit of kerbin.

what im trying to understand is that when setting up my nodes, the return trajectory will shift through a bunch of different orbits(usually all the way to a polar orbit)

what causes this? IRL and in KSP.
and is their a way i can take advantage of this? maybe a cheaper way to reach a polar kerbin orbit?(i doubt it, but ill ask)

[Goody1981]

Nice Hohmann work

I would imagine that it’s due to tiny deviations in your trajectory where you are having a huge impact over that much travel time. Like unless you enter the mun’s sphere of influence EXACTLY aligned with the equatorial, then any tiny (even a fraction of a degree) difference north or south will compound on the journey back to Kerbin. 

You can definitely use this to achieve polar orbits but obv going to the mun first makes it more expensive dV-wise than just launching into a polar orbit. If you were already in equatorial orbit around Kerbin and wanted to plane change 90 degrees, then I think you could work it so the mun assist would be cheaper... give it a crack!

[HvP]

That's mainly due to the fact that when you're traveling long distances very small changes in the initial conditions will have a large effect on the far end.

It's practically impossible to launch into a perfectly zero-inclination orbit in relation to your target. There will always be some small degree of relative inclination, and even if it was perfect your aim when making your transfer burn will almost certainly introduce some small error. For a path that extends for thousands of kilometers even a very slight bias towards the normal/anti-normal directions can project your path far above or below the equatorial plane of your target. Imagine shining a laser beam onto a target a mile away. You would probably have a hard time even aiming at the target because tiny movements in your hand will cause the laser to jump all over the place at the far end.

This error gets compounded when the same path loops around both bodies more than once because each near approach will further disrupt the arc of your orbit.

You can use this to your advantage to enter a polar orbit by burning normal or anti-normal very early in your transfer long before you enter the sphere-of-influence of your target. This requires far less delta-v than would a plane change while in orbit of the target.

Edited May 11, 2018 by HvP

[putnamto]

5 minutes ago, Goody1981 said:

Nice Hohmann work

I would imagine that it’s due to tiny deviations in your trajectory where you are having a huge impact over that much travel time. Like unless you enter the mun’s sphere of influence EXACTLY aligned with the equatorial, then any tiny (even a fraction of a degree) difference north or south will compound on the journey back to Kerbin. 

You can definitely use this to achieve polar orbits but obv going to the mun first makes it more expensive dV-wise than just launching into a polar orbit. If you were already in equatorial orbit around Kerbin and wanted to plane change 90 degrees, then I think you could work it so the mun assist would be cheaper... give it a crack!

thanks, now that i read your answer, it seems kind of obvious lol, tiny changes have big impact over long distances. i should have noticed this when accidently launching slightly north or south on the navball and being waaaay off of east/west by the time i reach horizontal.

thanks dude.

 

[Goody1981]

1 minute ago, putnamto said:

thanks, now that i read your answer, it seems kind of obvious lol, tiny changes have big impact over long distances. i should have noticed this when accidently launching slightly north or south on the navball and being waaaay off of east/west by the time i reach horizontal.

thanks dude.

Haha no problem

@HvP ...jinx?