Kerbal Space Program is a space flight simulation game developed by Squad, released in full in 2015 for PC, macOS, and Linux. Players design, build, and fly rockets and spacecraft for a space agency staffed by small green aliens called Kerbals, navigating real orbital mechanics to explore a solar system full of planets and moons.
Kerbal Space Program is one of the most celebrated simulation games ever made — a title that began as a passion project by Mexican developer Squad and spent years in early access before its full 1.0 release in April 2015. The game tasks players with building and operating a space program from scratch, designing rockets from modular components and launching them into orbit, to the Mun, and beyond. What sets it apart from other games is its commitment to authentic physics: every flight is governed by real orbital mechanics, and players must genuinely understand concepts like delta-v, transfer orbits, and gravity assists to succeed.
The game offers three main modes. Career mode challenges players to build a space agency from humble beginnings, earning funds through contracts and unlocking new parts through a research tree. Science mode strips out the financial management to focus on exploration and discovery. Sandbox mode gives unrestricted access to all parts and no objectives, freeing players to build whatever they can imagine.
Rocket construction takes place in the Vehicle Assembly Building or the Space Plane Hangar, where parts snap together with satisfying modularity. Engines, fuel tanks, command pods, landing legs, solar panels, and scientific instruments must be balanced and staged correctly to survive launch and reach the destination. The game simulates aerodynamics, thermal stress, and structural integrity — an unbalanced rocket will spin out; a poorly angled re-entry will incinerate the crew.
The Kerbal solar system is a scaled-down but richly varied playground. The Mun and Minmus orbit Kerbin (the Earth-analogue), while further destinations include the barren dunes of Duna, the giant canyon of Vall, and the dark surface of Eeloo at the edge of the system. Each body has a distinct gravity, atmosphere, and terrain that demands a purpose-built vehicle to explore.
Kerbal Space Program received strong reviews on PC, earning a Metacritic score of 88. Critics praised its extraordinary depth, the genuine sense of achievement that comes from a successful mission, and the rare ability to make complex physics intuitive and fun. It was championed by the science and engineering community for its educational value and was named to Edge magazine's 100 Greatest Games. HLTB data reflects the game's near-bottomless scope: the main story takes around 113 hours, with completionists logging over 600. It remains one of the highest-rated PC simulation games of its era, and its modding community has produced thousands of expansions, visual overhauls, and real-spacecraft recreations.