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Help changing an orbit


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Hey folks, I've got a probe in HKO and I'm trying to change it's orbit to a very specific one for a Fine Print mission. I've matched the orbital plane, but I'm not quite shure how to get it to match exactly.

O7uCIqD.png

The Teal line is my current orbit. Orange dotted line is my next planned maneuver, and the green line is the orbit I'm trying to change to. The blue line is irrelevant - ignore it :P

So how do I shift it over?

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Try burning "up" (away from Kerbin). To visualize this, pull out the blue pull-thing (what are these things called) in the maneuver node editor facing away from Kerbin. I'll edit in a screenshot in a second. Added.

This button thingamajig:

6wo6daO.png

See if that fixes your problem.

Edited by Save Ferris
Added Photo.
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Done a few of these, so I got a basic four step procedure:

1: After getting into orbit, change inclination to roughly the same as the target orbit where the two intersect.

2: At where closest to the Ap or Pe of the target orbit (whichever I get to first), I make a maneuver node to get the opposite Ap/Pe at same altitude as the targets opposite Ap/Pe.

3: At the same maneuver node I then jiggle the Radial nodes to make the opposite Ap/Pe hit perfectly with the targets opposite Ap/Pe - make them overlap.

4: After doing the burn for the maneuver node set up in steps 2 and 3, I make a new maneuver node where the now overlapping Ap/Pe markers are on the opposite side. This just to extend or shrink my orbit to make it overlap on both Ap/Pe markers.

And that does the trick so far. Remember you also got some margins of error, usually between 5% and 10% so no need to achieve a perfect match of orbits. Eyeballing it is sufficient.

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Good tips, but I'd recommend changing one a little:

  Zylark said:
Done a few of these, so I got a basic four step procedure:

1: After getting into orbit, change inclination to roughly the same as the target orbit where the two intersect.

Try launching roughly into the right inclination straight away (wait for KSC to cross the point where the orbit intersects with the equator then launch so you are roughly pointing in the right direction) - I'll screenshot this later as it's not clear. It probably won't be perfect, especially if you are eyeballing it, but it will save you delta-v, rather than doing an expensive plane change in LKO from 0 degree inclination.

Also, it's worth doing the plane change AFTER you have raised your AP and PE. It's cheaper to do plane changes higher so you aren't fighting Kerbins gravity well.

Also, as others mentioned, do use the radial maneuvre node vectors. They are essential for fine tuning your orbit. (Sometimes Fineprint can be really finicky, other times you don't even have to be anywhere near, even at the same degree of accuracy.)

Edited by severedsolo
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I would do two burns to sort that out. Burn prograde at the point where the two orbits are furthest apart and your current orbit is higher than the target orbit. This will push the other side of your current orbit higher up. Stop the burn when it matches your target orbit.

Complete 180 degrees of your current orbit to the point where you have just matched the two orbits, and burn retrograde to bring the other side down to match as well.

No messing about with manoeuvre nodes, or burning radial/anti-radial.

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