Kerbal Space Program

Kerbal Space Program is a multi-genre game where the player can create his own space program. In KSP, you must build a space-worthy craft, capable of flying it's crew out into space, without killing them. At your disposal is a collection of parts, which must be assembled to create a functional ship. Each part has it's own function and will affect the way a ship flies (or doesn't). So strap yourself in, and get ready to try some Rocket Science!

Main Features:

• The Vehicle Assembly Building. Allows players to build spacecraft out of any imaginable combination of parts.
• Fully-fledged, Physics-based Flight Simulation ensures everything will fly (and crash) as it should.
• Procedural Terrain delivers detailed terrain at a vast scale. The Kerbal Planet is 600km in radius!
• Mod-enabled, allows players to create new content and modify the game.
• Ship systems. Keep an eye out for engine temperatures and fuel levels, and try not to explode.
• Build ships with multiple stages, and jettison parts away as they burn out.
• Full control over the staging sequence allows for complex ships and advanced functionality.

The game is still in development, but it's already a lot of fun, and it can be downloaded for free. Below there are some videos of people doing it wrong. There are also videos of people doing well, but it's more fun to find out yourself how to build a good rocket.

I've so far failed at going orbital. It is definitely possible to orbit, use transfer orbits, and deorbit, as this video shows. There are also tips on the forum. I did manage to reach a virtual escape velocity, going vertically at 2800m/s, it did slowly tick down so I guess it would land again after weeks if not more of waiting :)

I really like building the rockets and also experimenting with silly designs. I love how the different stages detach and how rockets can spin out of control. PRO-TIP: In the assembly building there is a circle button on the top left which you can click to the desired symmetry and then the parts you attach will instantly be spaced that way.

The future of this game also looks bright with all the planned features, such as much more rocket parts, and all kinds of missions such as satellite deployment, or landing on the moon and other planets.