Kerbal Space Program is multi-genre game in which you create your own space program, starting with building  a space-worthy craft out of a collection of parts. Still under development it is being taken seriously - both in the classroom and by NASA.

Since its launch in 2011 Kerbal Space Program (commonly abbreviated to KSP) has attracted a large following and has been sold on Steam, as well as on it's own website, for almost a year. There's also demo version that is, and will remain, free to download.

KSP comes from Mexico-based Squad, a marketing company that recruited its creator , Felipe Falanghe, because they needed a 3-D modeler to both virtually design and physically build installations for advertising campaigns.

As reported by Charlie Hall on Polygon, it was when Falanghe, who had had enough of being on the road working on the construction aspect of the job, tried to hand in his resignation, that his bosses told him that if he stayed with the company they would help him with the game he wanted to build. Although Squad still has a marketing agency, Kerbal is now a substantial part of its business

The storyline for the game involves a humanoid race of small, green, would-be astronauts, called Kerbals, who have constructed a spaceport (Kerbal Space Center, or KSC) on their homeworld Kerbin. Gameplay consists of constructing rockets and spaceplanes out of a provided set of components and launching them.

This video, which is the first of a set of tutorials to get new users started, gives you an overview:

Note that this video relates to an earlier version of the software. There's also a short update on the site that covers recent changes.

To call Kerbal Space Program (commonly abbreviated to KSP)  a game is to underestimate it. Better to think of it a rocketry simulator that relies on complex physics and this is the reason that it is being adopted in the classroom and by NASA. It makes use of the Unity game engine and if you know how to program Unity you can build add-on modules for the game.

Together with TeacherGaming, which has already brough an education version of Minecraft to classrooms, Squad is working on KerbalEdu, a mod of the existing problem with UI improvements, premade lessons and other features to make the game fit with the school curriculum. In the meantime educational discounts are available for schools that want to be involved in the pilot program.

On this occasion xkcd has got it wrong it seems KERBAL is very welcome at NASA. More cartoon fun at xkcd 

According to Charlie Hall, KSP is already on NASA's radar. He quotes Doug Ellison, a visualizations producer at the Jet Propulsion Lab as saying:

"I knew KSP was something special when I watched a young kid — probably less than 8 years old — playing KSP and using words like apogee, perigee, prograde, retrograde, delta-v; the lexicon of orbital mechanics. To the layperson orbital mechanics is a counter-intuitive world of energy, thrust, velocity, altitude that this kid — just by playing Kerbal — had managed to get his head around."

Hall also reports that NASA and Squad have plans for a joint venture - a downloadable mission pack, that will allow players to put Kerbals on an asteroid. Players will first have to launch a spacecraft to fly alongside the asteroid. Then they will have to push the giant rock into a stable orbit around the Kerbal's home planet without creating an extinction-level impact below. Finally, they'll need to safely land on it. It's all a matter of applied physics.

NASA itself hopes to land humans on an asteroid by 2025 and it seems that  Kerbals will manage it more than a decade before their real-life counterparts.