Well, I had gone to and landed on Duna a few times, but I never made it back. Then I decided I would make two separate ships, a tug and a lander/return pod. Everything went great until after I docked them and tried to intercept Duna. I was really off and wasted too much fuel trying to get an intercept. After I orbited the sun for a thousand times and finally intercepted it, I had no fuel left in the tug. I didn't pack my lander with any parachutes for landing on Duna, (I had bad experiences trying to land with parachutes, I always tore my ship to shreds, and at the time I didn't know you could repack parachutes) so I had to land rockets blazing. So a) I suck at landing, so I wasted fuel, and I wasted even more getting into orbit around Duna. Anyway, I landed, planted a flag, whatever, and then went back into orbit... or tried to. Ran out of fuel and crashed back into Duna.