Here is how Randall Munroe, creator of xkcd, described it. One thing which is certain is that after you’ve spent some time with Kerbal Space Program you will develop an intuition about orbital mechanics which few people, even authors of “hard” science fiction, have. You can try building monster rockets for direct ascent missions to distant planets, explore innovative mission modes such as propellant depots, in-situ propellant production, flying probes in bodies with atmospheres, assemble complex space stations or interplanetary vessels with multiple launches, or just about anything that pops into your mind. When the player has unlocked all of the available technologies, visited every body in the Kerbol system, and collected all of the available science (which will take a long time), there are a multitude of other amusing things that can be done building upon a physics engine which is, within the somewhat odd universe it models, remarkably faithful. In career mode the player earns funds, reputation, and science points as goals are achieved, and these can be spent to advance through the game by obtaining access to new technologies, upgrading facilities, and recruiting additional crew.
![kerbal space program unmanned before manned kerbal space program unmanned before manned](https://farm8.staticflickr.com/7297/8734960166_3b1b175aa7_c.jpg)
The game can be played in a “sandbox” mode where all of the technology is available to the player from the start, in an intermediate “science” mode where completing scientific goals unlocks technologies, or in “career” mode where the player undertakes contracts to perform specific research and development tasks, such as testing an engine in flight or returning a surface sample from another world.
![kerbal space program unmanned before manned kerbal space program unmanned before manned](https://i.imgur.com/xu81OV3.png)
Just as in a real-world space program, it’s up to the player to decide whether to focus on robotic exploration, crewed missions, solid or liquid propulsion, rockets or air breathing engines, and expendable or reusuable launch hardware. Unlike many games, there is neither a well-defined path through the game nor a goal at which point the player has “won”. The space program is conducted on behalf of the Kerbals, inhabitants of planet Kerbin, and the player manages the space program, advancing in technological capability, ambitiousness of missions, and size and skill of the kerbonaut corps. Kerbal Space Program is a computer game in which the player can build spacecraft, aircraft, and spaceplanes to their own design and use them on missions, both robotic and with crews, to explore the planetary system of the star Kerbol.