The excitement of the Artemis II mission has renewed interest in the mechanics of space flight and planetary exploration. We will review the basic astrodynamics of lunar and Martian missions, including flybys, orbiters, and landers. We’ll use the Kerbal Space Program (KSP) software package to experience realistic physical simulations of these missions in real time, giving us the ability to consider and execute on numerous distinct command decisions and identify potential outcomes.