Kerbal Space Program (KSP) is a space flight simulation video game developed and published by Squad for Microsoft Windows, macOS, Linux, PlayStation 4, and Xbox One. In the game, players direct a nascent space program, staffed and crewed by green humanoid aliens known as "Kerbals". The game features a realistic orbital physics engine, allowing for various real-life orbital maneuvers such as Hohmann transfer orbits and orbital rendezvous.