Taking off near the north pole to orbit

[AeroGav]

I'm in the middle of a Duna & back challenge in a small spaceplane.   When coming in to land, I started following this valley/canyon hoping to find lower level/flatter ground.   I may have done, but this canyon took me close to the polar biome. 

Now the time has come to return to Kerbin.   However, when I take off due east, 90 degrees on the compass, I end up in a highly inclined orbit.   Am concerned that if I eject from Duna in such an orbit, I'll end up needing a massive ascending/descending node burn mid course correction on the way back to Kerbin.

What's my best option here?

1) fly due south in the atmosphere, at a slow, economic subsonic pace, before turning due east then gunning the engine and attempting to get to orbit

2) correct the inclination from orbit

3) don't bother trying to correct, just do the bare minimum to eject from duna SOI and correct your inclination/complete the transfer burn back to Kerbin from solar orbit?

 

[Plusck]

I'd say none of the above.

4. Include part of an inclination correction burn when you burn back to Kerbin. It won't be huge. It might even help you to capture.

5. Burn out to Ike on the way out of the system, catching it to give you a free inclination correction. Or if that isn't enough on its own, combine this with 4 above.

6. Choose a time to go when the inclination is aligned with your ejection path. So if the inclination is slanted retrograde towards the sun, you set off later than the ideal transfer date and your transfer will include a radial-in component; or if the inclination is slanted retrograde away from the sun, leave earlier and have the burn include a radial-out component.

7. Don't worry about the inclination of the transfer burn since in any event, you can pretty much choose when you meet Kerbin again and, if you get it opposite where you leave Duna, you'll encounter Kerbin fine (but at an angle, which just means reentry at an angle).

And in any event:

8. Wait on the surface until it's midday or midnight - your inclined orbit will end up being aligned prograde/retrograde and the inclination in sun orbit will not be huge anyway.

 

I'm pretty sure trying to correct the inclination while you're in Duna orbit - or burning minimally out then correcting in sun orbit - will be more expensive than any of those strategies.

Edited October 14, 2016 by Plusck

[Starhawk]

I don't like 1) at all.  There's not really such a thing as 'a slow, economic subsonic pace' when you're using non-air breathing engine(s).

I would use a variation on number three.  When your transfer window back to Kerbin comes up, zoom out in map view and check which direction Duna is moving.  Take off and head to a polar orbit which is aligned with the direction of movement of the planet when you look 'down' on it in map mode..  Then it doesn't really matter that your orbit is polar when you leave and you don't suffer any significant penalty for being in a non-equatorial orbit.

Happy landings!

 

[bewing]

I'm baslcally on board with #5. Use Ike on the way out -- more for the small gravity boost than for the plane change, though. And when you're at Kerbin, use a reverse gravity slingshot the Mun to wipe out another chunk of the inclination and excess velocity. ie. don't use fuel to do what a moon will give you nearly for free.

[HvP]

Have you tried it yet?

I admittedly haven't tried returning from Duna while in a polar orbit but I can take a guess how it would go. The inclination you get after circularizing around Duna is more relevant to your orbit around Duna, but not the Sun. When you escape the Duna system almost all of your orbital velocity remains in line with Duna's orbit and any vector you got from the polar orbit is a minor rounding error once you leave Duna's sphere-of-influence.

What will have a bigger affect on your return trajectory will be the relative inclination of Duna's orbit around the Sun compared to Kerbin's orbit and where that puts your ascending and descending nodes around the orbit of the Sun. And whether or not you burn to escape Duna when your prograde is in line with Duna's orbital path or at a wide angle from it. That latter will eat up a lot more delta-v.

Edited October 15, 2016 by HvP

[Guest]

Another vote for #5. 

The inclination change is minor compared to Duna's orbital velocity. It won't cost much to correct on the way back. Watch your return window and you'll be fine.