Orbiting Mun and Minmus, from Kerbin?

[strider3]

If you are departing from a Kerbin orbit, and you are going to orbit both the Mun and Minmus and return to Kerbin...does it make any difference in DV efficiency which you visit first?

[jimmymcgoochie]

Not really. Any differences due to the different orbital inclinations would be cancelled out by transferring between them at their relative ascending/descending nodes, though you may have to wait a while for that to happen at a time that also suits the departure burn. Any differences in Oberth effect for going to either moon first will disappear into the variations you get for different launch profiles, as would the difference from launching into the plane of Minmus (6 degrees) rather than the Mun (0 degrees).

[king of nowhere]

I'd add that the main cost is from LKO to reach either mun or minmus. after that, it's rather cheap. small differences in efficiency don't matter too much

[Blaarkies]

Luckily there is a tool for that https://ksp-visual-calculator.blaarkies.com/dv-planner

For the mission Kerbin(low orbit) -> Mun(elliptical orbit) -> Minmus(elliptical orbit) -> Kerbin(aerobraking low orbit) it costs
1063 m/s dv

For the mission Kerbin(low orbit) -> Minmus(elliptical orbit) ->Mun (elliptical orbit) -> Kerbin(aerobraking low orbit) it costs
1132 m/s dv

That's a difference of 69 m/s dv, so nothing much to worry about.

You will need to add the extra fuel if you want to go down to a landing on the surface and such, and if you do Apollo style landings you would save fuel by going to Mun first, because then you don't have to drag that fuel with you to Minmus anymore.

[Zhetaan]

15 hours ago, strider3 said:

If you are departing from a Kerbin orbit, and you are going to orbit both the Mun and Minmus and return to Kerbin...does it make any difference in DV efficiency which you visit first?

There is a difference, but not at a point that matters.  Since you intend to orbit both, there is no gravity assist to help you.  The only place to save delta-V, therefore, is in the braking burn on return to Kerbin.  That makes the Kerbin-Mun-Minmus-Kerbin route the better choice, because you'll be coming in from Minmus slightly faster and can shed more velocity for 'free' by aerobraking ... at which point, the mission's over anyway.