FREE app for Windows and MAC OS X – travel along with current space missions, go to planets, moons, and asteroids. Additional modules include real-time Earth climate data, and exoplanet system explorer.
Free From: https://eyes.nasa.gov
Companion Website: NASA’s Solar System Exploration: https://solarsystem.nasa.gov
A virtual Universe you can explore on your Windows computer. You can travel from star to star, from galaxy to galaxy, landing on any planet, moon, or asteroid with the ability to explore its alien landscape. You can alter the speed of time and observe any celestial phenomena you please.
The Steam version has downloadable content (DLC) which models solar system bodies using hi-resolution NASA imagery.
Kerbal Space Program
Take charge of the space program for an alien race known as the Kerbals – you’ll have access to an array of parts to assemble fully-functional spacecraft that fly (or don’t) based on realistic aerodynamic and orbital physics.
Launch your Kerbal crew into orbit and beyond (while keeping them alive) to explore moons and planets in the Kerbol solar system, constructing bases and space stations to expand the reach of your expedition.
Universe Sandbox is a powerful space and gravity simulator that lets you create and destroy on a scale you’ve never before imagined.
Realistically model our solar system or bend the laws of physics, speed up time and watch stars evolve till they supernova, manipulate Earth’s seasons or twist its orbit outward and freeze the oceans solid, then spawn a nearby galaxy to rip apart the Milky Way.
A complete rewrite of the original by a team that now includes an astronomer, a climate scientist, and a dedicated physics programmer, this sequel opens doors to more exploration and interaction. Vive VR support now included!
An oldie, but a goodie! Celestial is a free space simulation that lets you explore our universe in three dimensions.
Celestia runs on Windows, Linux, and Mac OS X.
Free From: https://celestia.space