Open UNSW course on introductory Mechanics: Motion, Forces, Energy and Gravity
The University of New South Wales is starting an online course on Coursera about mechanics. This will cover stuff you may find useful when planning missions in KSP with more precision than just building something, flying it up there and hoping for the best.
The course is free for anyone and its prerequisites are some basic knowledge of high school maths.
You can check it out and sign up at: https://www.coursera.org/course/particles2planets