euphOrbit 

euphOrbit version 1.0 is a simple tool designed to simulate the motions of planetary bodies in space. The primary design philosophy of this program was that it had to simulate asteroids speeding through our Solar System close to "true life".
astro solar orbit planet gravity asteroid newton kepler nasa inclination perihelium

Orbital Trader 

Earn millions of billions in this detailed planetary trading game. To build your economic empire you'll have to choose the most profitable goods, take the quickest paths between the revolving planets and buy planetary structures at the right time.
solar galaxia trader space trading game tycoon

Eagle Lander 3D 

Eagle Lander 3D (EL3D) is an authentic simulation of the Apollo lunar landings. EL3D includes accurate renditions of scenery, flight dynamics and the lunar module.
lunar landing simulator lm apollo moon p64 p66 flight historic space game dsky computer