If you are into such things, do take a look at the orbiter project (http://orbit.medphys.ucl.ac.uk/) and the NASSP add-on (http://nassp.sourceforge.net/wiki/Main_Page). I spent many an after-school night flying to the moon by punching codes on a keyboard. It was amazing.

edit: Here's a video https://www.youtube.com/watch?v=7VDV6Gdxakc