Until now.

Programmed by Martin Scheweiger in his spare time, Orbiter is an astounding space flight simulation that not only matches Microsoft's venerable classics, but goes beyond it in many ways.

The game's highlights are many. Among other things, it accurately models planetary motion, gravitational effects, and flight dynamics of various spacecrafts. You can dock your shuttle at a space station or land on a planet surface or a spaceport. High-resolution planetary maps provide astounding visual effects, and the environment is completely configurable: you can add planets, space ships, and space stations to the default universe – or design a new solar system from scratch.

The game currently has limitations, such as the absence of missions, computer AI, or multiplayer. Basically, it allows you to fly around the solar system, and that is pretty much it. However, the game is already very stable and a lot of fun in its current state, although of course the author's planned upcoming features will make it even more promising and replayable. The graphics are simply breathtaking... I run the game on a laptop without any 3D cards, and the Direct3D graphics are already much better than most other games that use the same software mode. Overall, Orbiter is a definite must-have for any space sim enthusiast, and a Hall of Belated Fame inductee in my book. Newcomers to the genre may want to consult NASA's Basics of Space Flight guide (see Related Links below) before jumping into the game, as the learning curve is quite steep due to its complexity. Three thumbs up!

Note: the game has evolved heavily since 2001, with the latest edition having come out in 2016. Check link below.