How to fine-tune interplanetary transfers?

[phemark]

Hi,

I managed to land on Duna and back two times. First time took ages, but for second time I used Alarm to tell me when planets will match, and then do the nodes myself. Which worked ok. However, I still dont know how to fine tune the approach to planets from far away.

1) How to focus on the intersection point of the map, i.e. so that I can zoom in there while creating nodes - that way I could see how close I am to the planet while adjusting nodes much easier.

2) How to fine-tune the approach to planet from far away? I can do it once I can see the planet in the map, but that take a lot of Delta, however MechJab can do it from half of Kerbol system with 20deltaV. Can this be done manually?

Thanks!

[Epthelyn]

1) Yes, see below. You can click on any PE or AP marker (both from real trajectories or ones created by maneuver nodes) to lock it onto the screen; you will no longer have to mouse-over it to display the altitude and it will continue to display as the altitude changes provided you don't end of up a collision course. It's a little tricky sometimes depending on where the marker is.

2) Anything MechJeb can do can be done manually. Anything. MechJeb is not a magical cheating tool, it's an autopilot. The further you are from a part of an orbit you want to change, the more any burn at your current position will change it.

The easiest way to do it manually is to, ideally, do that thing from my (1) and then very slightly burn in any direction. If the altitude or close encounter or whatever you want moves closer to where you want it to be, continue to burn very slowly in that direction until it stops getting closer. At this point change direction and repeat. The idea behind "very slightly" is that you're trying to save as much dV on the encounter as possible, and don't really want to lose much effectively guessing your way to an improvement - since fine adjustments will make huge changes to an orbit at a distance even 0.1m/s can be enough to tell you whether or not you're going in the right direction.

That's the way I do it, anyway. I suppose there must be some way to determine more or less where you need to burn without so much guesswork, but before someone says "Scott Manley has a tutorial on it", he used this strategy as part of Interstellar Quest a couple of episodes back

I'm sure someone can explain this far more succinctly than I can, but that's the general idea.

Edited April 12, 2014 by Epthelyn
Correction made, credit to FenrirWolf :)

[FenrirWolf]

@Epthelyn: The ARM update actually added new functionality to the map view that makes your first point much easier to accomplish. Now when you click on a planet, there's a button to focus the map view on it. When you do so it automatically changes the conics to mode 0 so you can see your path relative to the planet's SoI. Then putting the focus on your ship again sets the conics back to mode 3 like normal.

Edited April 12, 2014 by FenrirWolf

[Epthelyn]

This update can't be real. It's far too good to be.

Post #2 edited.

EDIT (@below):

That's true, but it seemed reasonable to provide an example to show that even 'The Man(ley)' doesn't have some magical trick beyond guesswork when quickly adjusting an encounter

Edited April 12, 2014 by Epthelyn

[FenrirWolf]

Then when it comes to your last point, the Man(ley) did indeed release a video about this exact subject a day or two ago

[phemark]

Then when it comes to your last point, the Man(ley) did indeed release a video about this exact subject a day or two ago

Could I have a link to this video please?

I understand how to guess my approach, but I still dont know how to zoom on the intersect with another planet, while doing so. I wanna see what my guesses will do to the orbit when I arrive from close up, and not from Kerbol system view..

[cantab]

Like Fenrir said, in map view hit tab until it says you're focussed on the planet you want to encounter, then zoom in with the scroll wheel. There should be your flyby.

And if you need to make small adjustments with a big engine, right click the engine and drag the thrust Limiter down to 5%. It acts as a multiplier so 10% throttle on a 5% limiter gives you 0.5% of the usual full throttle.

[phemark]

Thanks will try this.

(Very useful tip with engine too!)

[magnemoe]

You can also use RCS for the 0.1 m/s adjustments, benefit that you don't have to turn to burn the other way.

To check if you arrive at an equator orbit see how much your orbit is offset then it leaves the planet, if you leave in solar system plane you will stay in an orbit around equator, this is mostly interesting if going to Jool,

[That guy who builds stuff]

Could I have a link to this video please?

Here you go.