Normal and antinormal maneuver nodes are handled really badly

[THX1138]

When I want to plan a change of inclination of my orbit and I pull the normal or antinormal maneuver node handle, it doesn't take into account the fact that the position of normal and antinormal changes during the burn. It practically renders the maneuver node planning useless for anything but slight changes where the change in normal/antinormal orientation during the burn will be minimal. This really ought to have been addressed years ago. Perhaps there's an explanation for it that I'm not aware of?

[stibbons]

Maneuver nodes have only ever described an instantaneous change in velocity. I don't think it would be appropriate for the game to try to guess at how accurately or how much thrust you're going to put in to a burn to try to "correct" the node.

[Gaarst]

What @stibbons said. Manoeuvre nodes assume an instantaneous burn, calcuating a continuous burn accounting for the mass loss, orbital velocity and stuff would be much more complicated (KSP can't even properly predict a burn time). For most situations, the instantaneous burn assumption works pretty decently but there might be situations in which it doesn't, for example a large inclination change.

The best way to get around this, if you don't want to write a mod that properly plans manoeuvres, is trial and error: with time you'll get used to doing these manoeuvres and they will not be a problem anymore.

[septemberWaves]

In any case, if you're doing major inclination changes it's best to do them at the apoapsis of a highly elliptical orbit. That way you'll lose the least fuel from inefficiently calculated nodes, and just inefficiency in general.

[PT]

26 minutes ago, Gaarst said:

...The best way to get around this, if you don't want to write a mod that properly plans manoeuvres...

Or just use MechJeb Maneuver Planner function?

[Rocket In My Pocket]

1 hour ago, Gaarst said:

(KSP can't even properly predict a burn time)

Snark's got ya covered on that! I highly recommend his Better Burn Time mod.

In regards to the OP's question, is your problem that pulling the normal/anti normal node doesn't just rotate the existing orbit around the planet while keeping it at the same Ap/Pe? If so you need to add some retrograde in there, this is something I found counter intuitive at first as well. But boosting off in the normal/anti normal direction without any effort spent on circularizing will do the same thing boosting off in any one direction will, it will throw you out of your orbit.

Edited July 17, 2016 by Rocket In My Pocket