Fixing planet intercept

[zapman987]

Trying to intercept 2 planets, each have a different problem.

Set up for one before I entered Sol orbit. Had it according to pathing, perfect. Got to Sol orbit, now its portraying opposite where it was. WTF? Note I was not "sped up" at all between the SOI change. That said, I was not actively watching the SOI transition.

Second ship/intercept, Im 45000km from, at closest approach (no periapsis). Orbital Plane is within 0.1 degree. Any ideas how to close the gap?

Edited February 12, 2014 by zapman987

[Vanamonde]

To answer your second question, closing the gap would depend on the exact alignment of your path to the planet's orbital path. Could you perhaps post a screenshot of mapview? Meanwhile, put a manuever node at the halfway point of that transit and tug on the markers to see the results and how you might arrange an intercept.

[zapman987]

Got a good way to focus on the intercept point? Otherwise its not gonna show much.

[Vanamonde]

If you go to your settings file and change

CONIC_PATCH_DRAW_MODE = 3

to

CONIC_PATCH_DRAW_MODE = 0

it will display your projected path next to the planet itself. Then you can tab to focus on that planet and watch the result of your manuever node fine-tuning.

[Awaras]

For the first problem, sometimes the game will show a wildly incorrect path for a little while just after a SOI change. When that happens, it goes back to normal after 10 seconds or so...

[alexmun]

You can try to walk the intercept in by slowly burning along the three major axes (prograde, normal, and radial). The axis to start with depends on your situation. If you have closest approach markers (and they look to be in about the right place) and are around 180 degrees from your target, start with the prograde/retrograde axis. Burn a little prograde and see if the approach gets closer. If not burn retrograde instead until the closest approach hits a minimum. Then switch to another axis (radial in/out or normal/anti-normal) and burn until the distance is minimized for that axis. Repeat for the last axis then start over again until you get an encounter. If you're closer to 90 degrees until intercept, start with the radial axis. If you don't have closest approach markers at all, start by burning normal/anti-normal until either the ascending or descending node marker (whichever was closer) intersects the target orbit at the point where you expect to intercept the planet. That should give you the closest approach markers so you can adjust the other axes.

Walking the intercept in manually like that will usually work but it's not very efficient and can be time consuming. If you happen to be using a mod that gives you your orbital elements (like Kerbal Engineer Redux, MechJeb, or Telemachus) or you're willing to fish around in the persistent.sfs file for them, you can use my Launch Window Planner calculator (see link in my sig) to generate a precise correction burn. Just click "Add Body" next to the origin selection, enter in the orbital elements of your vessel, select your destination and it will generate a pork chop plot of all the possible transfers from your orbit to your target. If you're close to an intercept already, this plot will look like a diagonal blue/green line from top left to bottom right. You may want to zoom in on the line a bit to get a better fix on when to do your burn, then you can get the details for your midcourse correction by clicking on the info icon next to the "ejection burn delta-v" value. It will give you the prograde/radial/normal delta-v values for making a maneuver node as well as the pitch and heading of the burn if you'd rather do the burn that way. Do note that the burn it gives you will probably put you on a collision course with the planet so you may want to cut it short once you see your periapsis hit the level you want.