Orbiter is a free space flight simulator of Dr. Martin Schweiger. The flight paths of the "objects" (like e.g. the spaceships) are computed by a realistic physics engine in real time and do not behave not after so-called "star Wars physics" like most Weltraumballerspiele, which is unrealistic in the space flight. The additional ADD Ons is developed by one ever more largely becoming Community of freiwilliger programmer. As ADD Ons e.g. the complete Apollo program, the space shuttle as well as numerous futuristic and material spaceships are free of charge available. In the standard simulation the entire solar system with all its larger planets and moons is contained.