This is a paid asset, but now you can download Gravity Engine Free.
Detail this asset from Unity Store: Original Link
Gravity Engine v8.1 (Latest version)
Gravity Engine v7.0
Gravity Engine v6.1
Gravity Engine provides a complete toolkit for your space game physics.
– add stars, planets and spaceships that interact via gravitational N-body or “on-rails”
– design orbits by shape and see their paths in the editor and scene
– manual orbit changes with clickable handles
– orbit transfers/rendezvous from any orbit to any orbit
– rocket engines with staging
– model of Earth atmosphere
– solar system builder: add any object in the JPL database
– use real-world units (km/AU, kg)
– full support for particles
– highly accurate double-precision physics, with a choice of algorithm/Kepler evolution
– control of overall evolution speed, scale and CPU use
In-scene extensible command line console for development and debug
– change gravity to any force you design
No programming or math required.
Release Notes and DocsComplete source code provided.
Developed by a professional programmer with a PhD in astrophysics.