The goal of "Kerbal Space Program" is to construct spacecraft and rockets and successfully launch them to their destinations. Players can choose from three different game modes that vary in their specific objectives.
Players construct rockets and spacecraft by putting together a set of components. When constructing a vessel, players need to consider complex orbital physics in order to successfully launch and deliver a craft to its target. Missions in the game vary somewhat in their objectives but generally require the player to either achieve orbit with a craft or to land on a planet or moon. Players must also ensure the safety of the titular Kerbals, the alien race who pilot the craft.
"Kerbal Space Program" has three different game modes to choose from. Sandbox mode allows players to select from any of the game's missions and use any craft they construct with little restriction on what components they can use. Science mode starts players with a very limited set of components and has them unlock more by successfully completing missions and performing research. Career mode adds further complexity to Science mode, with new aspects to manage such as a budget, an ongoing reputation based on mission results, and a need to drum up new contracts to stay funded.