How to get a good interplanetary encounter?

[Yobobhi]

So, I have a recurring problem. Whenever I go interplanetary, for example on my last Duna mission, I can never get the encounter down below about 25000km. I pack Delta-V to compensate for this, but it's annoying how elliptical my initial orbits end up being. Any tips on how to cut down distance on interplanetary encounters?

[Hodari]

Once you have your initial encounter, try doing very small maneuvers in each direction(prograde, retrograde, normal/anti-normal, radial/anti-radial) and keep adjusting until you get closer.  If you still can't get close enoguh, try again a bit later on your approach to the planet when you're coming from a different angle and see if that helps.  Also, you can set the target planet as focus and zoom in on that planet in the map view to see exactly what your encounter path will be, then use that to help you adjust it.

[Warzouz]

First, did you left Kerbin LKO at the correct window (as described here : http://ksp.olex.biz/) ?

Set Duna as "target" to ease encounter

Then you need to be gentle on your transfer orbit to Mars orbit (don't cross orbits).

You should alway encounter your target on the other side of the Sun (or other central body).

If your Duna orbit is not good enough, no problem, do a small course correction burn (preferably at AN/DN if you can).

 

I would recommend using some user-friendly node tweaking tool mod (such as "Precise Node", or MechJeb "Node Editor" feature)

[Plusck]

In addition to the above comments:

- there is no point making any adjustment in the normal/antinormal directions as you leave Kerbin. The destination is on the far side of your orbit, so normal and antinormal will merely twist your point of arrival. At most, if you aren't doing a perfect transfer (i.e. you are not meeting the planet directly opposite, but looping around the other side of its orbit) you will be able to make a difference but at the cost of huge amounts of fuel.

- heading outwards from the sun (such as to Duna) adjustments get cheaper after the half-way mark. The reverse is true if you're going inwards. So drop your adjustment maneuvre node somewhere in the halfway to three-quarters-way mark, preferably on AN/DN or as close as you can get to it (without getting too close to your destination though), focus on duna, turn the map around so you can click on the maneuvre node again and play around with the sliders.

- prograde/retrograde and radial in/out are quite closely coupled. You'll find that a small adjustment to one of the pairs gives much the same result as a larger change to the other pair. What is different between the two sorts of adjustment, though, is the change it has on your time of arrival. You can use this to catch (or miss) Ike at exactly the right point in its orbit.

[Nich]

move your burn node forwards and backwards slightly as ejection angle is very important

Edited March 25, 2016 by Nich