Rendezvous question

[uncle_jew]

I am trying to do orbital rendezvouz without having to do dozens of orbit change maneuvers. The rendezvous target is my spacecraft launched earlier into a 200x100km elliptical orbit above Kerbin.

I launch into an equatorial orbit. Then I change the orbit inclination to match the orbital inclination of the target spacecraft. From there, I can do 2-3 orbit change maneuvers and get myself into an orbit crossing the target orbit and having a close encounter (5-15km) with the rendezvous target. So far so good.

Now, when I get to the encounter point, I need to execute a burn to place myself into the same orbit as the target spacecraft. And I can't figure out the correct burn direction and duration.

I tried constructing this maneuver in the map view (by combining prograde/retrograde and radial burns), but it doesn't work very well, because orbits always become misaligned by a few km. The screen resolution is simply not enough to see how closely the orbits match each other. So I have to execute several follow-on burns to iron out these inaccuracies, which eats fuel and time.

Is there any simple trick to figure out the exact burn needed to change from orbit A to the orbit B at their intersection point?

Thanks

Edited October 19, 2015 by uncle_jew

[Reactordrone]

When the navball is in target mode, burning retrograde to kill your velocity relative to the target will adjust your orbit to match the target and the closer the intersection with the target the better the two orbits will be aligned after the burn.

Edited October 19, 2015 by Reactordrone

[Alshain]

Yeah, as Reactordrone said, stop looking at map mode once you get your closest approach. Make sure the NavBall is in target mode (should happen as you approach automatically, but sometimes it may not) and then burn retrograde to slow your relative speed to the target. The act of stopping relative velocity is the same as matching orbits... though technically not perfectly matched, to do that you would have to be inside the target.

Understanding the relationship of the target NavBall and matching orbits is crucial if you ever want to learn the best way to rendevouz. To do that, wait till your target is just coming over the desert shoreline to launch from KSC. You can get the intercept while suborbital. Then as you slow relative velocity to the target you establish an orbit somewhat automatically on approach. (Be warned, using this method the target comes at you a lot faster so be ready to slow down in a hurry)

Edited October 19, 2015 by Alshain

[Mighty1]

You should try to get a closest encounter below 5 km. Then, at closest approach try to match orbits as you described but put your velocity indicator on "relative to target" (click on the speed just above the navball) when you get to 0 m/s relative motion you have succeeded. Then burn directly towards your target ASAP to close your distance and finally dock.

EDIT double ninjad while typing.

Edited October 19, 2015 by Mighty1

[uncle_jew]

Got it, thanks