This is a rather difficult challenge, in my opinion. The rules are simple: without any mods (stock), land a Kerbal on Duna, plant a flag, and get all Kerbals involved back home, safely, all without maneuver nodes.
It's just a challenge idea that I came up with when a friend of mine introduced me to KSP. He told me that maneuver nodes were 'essential' to any sort of space flight, so I wanted to prove him wrong. I have since landed (but not returned) on Duna without any maneuver modules, so it should be possible.
It's not a sort of competition; I just think that it would be cool to see all the different ways that everyone has of doing this. Even so, I think that the quicker you complete the challenge, the harder it is. Don't take use of bugs or glitches to get an infinite delta-V - you don't have to. Just persevere.
Good luck, you'll probably need it.
