Advanced Space Flight is a realistic space simulator for interplanetary and interstellar travel. It is the only space simulator available that takes into account relativistic effects during interstellar flight.
Besides simulating space flight this app can also be used as a planetarium, with all known planets shown in real scale with their accurate keplerian orbits. It can also be used as a star chart and exoplanet explorer, showing all solar systems with confirmed exoplanets within 50 light years from the Sun.
This is the only app where you can get a sense of the true scale of the Universe, zooming out throught thousands of galaxies and galaxy clusters until you see the entire observable universe in your screen.