How much dV am I wasting using a 605km parking orbit?

[Kasuha]

I use an eccentric parking orbit for this reason; periapsis at around the 120km mark, apoapsis out scraping my geosynchronous satellites. It makes for a roughly 3 hour orbit, so not too long to hit a window, and gets about 3500m/s down at the bottom to take advantage of Herr Oberth's math.

-- Steve

If you know where you will need that periapsis when the window comes up, you can definitely pull that apoapsis almost to SOI limits and eventually do some inclination fixes while you're there. But I found planning that a bit too complicated with vanilla game.

If you just place the periapsis somewhere, there's pretty good chance it won't be where you need it.

Another thing to consider is when using LV-N nuclear and Ion engines burn times can be quite long. If you start a burn 10 mins before AP in LKO you will end up deorbiting the craft if you are using maneuvre nodes. A higher parking orbit reduces this effect.

That can be avoided just by putting the orbit a bit higher, such as 75 km instead of 70. And even getting as low as 60 km won't usually hamper your burn significantly.

I have much more serious problems with the maneuver node being misleading - when I burn exactly how the maneuver tells me, I end up going somewhere completely else. I have already learned to stop following navball marker at certain phase and match the SOI exit point (position and time) instead. It may be not 100% precise but it works way better than navball.

Edited December 10, 2013 by Kasuha

[Anton P. Nym]

If you know where you will need that periapsis when the window comes up, you can definitely pull that apoapsis almost to SOI limits and eventually do some inclination fixes while you're there. But I found planning that a bit too complicated with vanilla game.

That's definitely too fiddly to do with just maneuver nodes... which is part of why I only do it out to geosynch or a bit more. (Also making sure I don't get an unplanned slingshot by the Mun or Minmus in there, and keeping the orbit period low enough so that the bird's at periapsis during the window.) It's not optimised, but it is enough (or seems so anyway) to help. The added bonus of having a "flatter" arc to the burn, reducing wastage when following a maneuver node marker, is nice to have too.

-- Steve

[codepoet]

I use an eccentric parking orbit for this reason; periapsis at around the 120km mark, apoapsis out scraping my geosynchronous satellites. It makes for a roughly 3 hour orbit, so not too long to hit a window, and gets about 3500m/s down at the bottom to take advantage of Herr Oberth's math.

-- Steve

I have been doing aload of work on interplanetary burs with ion engines. My approach is like yours - an ecentric parking orbit, built up over several orbits, and then I adjust the Ap to be able to time a mun slingshot, to get a bit of extra delta-v to compensate for not being able to do the full interplanetary burn at 72km. As I pass the mun, I burn away and raise the AP up to Jool or wherever. Often I will raise it most of the way, but wait until I have left the kerbin SOI, and then finish the job at the exact moment of transfer window to get an optimum transfer.

[The Ideal Gas Lawyer]

...The added bonus of having a "flatter" arc to the burn, reducing wastage when following a maneuver node marker, is nice to have too.

-- Steve

I usually avoid that (and the accidental reentry problem to some degree) by setting up the maneuver node so that I know how much dV I need but then burning towards the prograde marker instead of the blue node marker. It avoids wasting fuel by burning off-angle and it slowly moves to be coincident with the maneuver node at T-0 and then beyond it in the second half of the burn. So long as you monitor the ejection angle in map view to make sure that it ends up where it needs to be it works quite well.

[The Ideal Gas Lawyer]

...how do I change this thread to [Answered]?

[Anton P. Nym]

...how do I change this thread to [Answered]?

Go to the initial post, click "edit" then click the "go advanced" button in the edit window. That should show you an option to change the thread tag.

-- Steve

[The Ideal Gas Lawyer]

Ah, I missed the advanced button