It's my fault, I admit it. I already have 3 long challenges running, but I stumbled over the speedrun challenge and couldn't resist picking it up. As the name says, the purpose is to complete all objectives in career as fast as possible That's quite a lot of stuff to do, but most of that is irrelevant because it can be done simultaneously. The slowest thing is the mission to Eeloo. Now, I know from having done it in my DREAM BIG mission, it is possible to make the Eeloo-Kerbin t