Well, even with a small planet it takes a long time to complete an orbit. But there's a nice workaround to let the time run up to 20 times faster. As this could cause crashes I'll post it here as a spoiler... First, you need a tool named Cheat Engine available at http://www.cheatengine.org/.After Installation, start Cheat Engine and KSP. Go to Cheat Engine and press the button in the top left corner ('Select a process to open') (Be careful, strange things may happen if you do this with an important system process). Find KSP and press 'Open'. Now check the box 'Enable Speedhack' on the right side of the window. Enter a number from 1 to 20 and press 'Apply'. Done!