My first Duna return trip: It consisted of a Main orange tank + NERVA + 2 manned capsule, and a basic empty one man lander. So I entered Duna orbit transferred a kerbal into the lander and dropped it on Duna. Suddenly I noticed another body orbiting Duna. It was from a previous Duna mission that had run out of fuel with a single lone kerbal on board. It was planned that I would land on Duna, then go into orbit, rendez-vous with the main ship (no docking needed), transfer the kerbal from the lander and head back to kerbin without the lander. But now I had a new passenger that I had to rescue, so I did the rendez-vous with the stranded old ship, transferred a last bit of fuel it had and the lone kerbal. Then I did a rendez-vous with the lander. Docked and headed back to Kerbin with the first Kerbal that stepped on Duna having to do the whole trip on the single manned lander capsule. That really made me happy! Unfortunately I screwed the whole thing on Kerbin reentry... Oh well...