The game was released out of beta on 27 April 2015. The first public version was released digitally on Squad's Kerbal Space Program storefront on 24 June 2011, and joined Steam's early access program on 20 March 2013. The game features a realistic orbital physics engine, allowing for various real-life orbital maneuvers such as Hohmann transfer orbits and bi-elliptic transfer orbits. In the game, players direct a nascent space program, staffed and crewed by green humanoid aliens known as 'Kerbals'.
Kerbal Space Program, commonly abbreviated as KSP, is a space flight simulation video game developed and published by Squad for Microsoft Windows, macOS, Linux, PlayStation 4, and Xbox One.