Spaceflight Simulator is a game that allows players to experience the process of designing and launching a rocket. The game is split into two parts: the building of the rocket and the launching of the rocket. The game is designed to be realistic, and players will need to use physics to design their rockets. The game is currently in early access, and many features are not yet available. However, the game does have some good tutorials that walk players through the basics of orbit, docking, and landing on the moon.

Kerbal Space Program

Kerbal Space Program is a game about building and flying rockets. You have to design your own rockets, and then fly them to see if they work. The game is very physics-based, so you really have to know what you're doing if you want to succeed.

Orbiter

Orbiter is a flight simulator with a focus on realistic space physics. You can fly around in realistic spacecraft, and experience what it would be like to pilot one. The game has a very steep learning curve, but it's worth it if you're interested in spaceflight.

Universe Sandbox

Universe Sandbox is a space simulator that lets you play with the laws of physics. You can create and destroy planets, stars, and galaxies, and see how they interact with each other. It's a great way to learn about astrophysics, and have some fun at the same time.

Celestia

Celestia is a 3D space simulator that lets you explore the universe in real-time. You can fly to any location in the solar system, and even beyond, and see what it looks like. The game is very detailed, and includes accurate data about stars, planets, and other astronomical objects.

EVE Online

EVE Online is a game set in space in which players can battle, trade, and explore. The game is incredibly vast and complex, and offers players a great deal of freedom.