Yesterday I worked on a couple of crafts for my 100 kerbal to Duna mission. The interplanetary stage has to have enough thrust and delta-V for nearly 200 tons of landers. I think I finally managed it, with a 140 ton core, that has nearly 10,000 vacuum delta-V without the cargo and enough thrust to actually be able to lift off from kerbin. It's powered by 9 NERVAs. Each 25 kerbal lander weighs 45 tons, I am also including a few single kerbal landers, though I am having difficulty finding a way to put both a docking port and a parachute on it. Next, I've got to build, test, rebuild, retest, rebuild, an ascent stage to get the lander to orbit. A rather large assumption that I am making with my big landers is that the atmosphere and a few Mk-16 XL parachutes will eat a significant portion of the velocity on the way down and allow me to save fuel for a hypothetical return. Does anybody have some specific numbers for how much delta-V you need when landing on Duna? Come to think of it, this will be the first time I will have landed on a body with atmosphere...