Gravity Engine 2
Contents
Gravity Engine 2¶
Version 9.0 (October 20, 2025)
Gravity Engine 2 is a Unity asset that provides gravitation simulation and orbital mechanics.
Gravity Engine 2 provides a complete toolkit for your space game physics.
create and configure orbits with editor and in-scene views
support for manual maneuvers, Hohmann and Lambert transfers
propagators for KEPLER, SGP4, ephemeris and PKEPLER motion
ability to use multiple evolution engines (no singletons!) in a scene
optional use of the Unity job system to offload physics calculations
clear separation between gravitational computation and the display of objects, optional multiple displays
simple, focused API
clear separation of world, physics and display scales
support for patched conic evolution
ability to build ALL of the solar system (planets, moons and small objects) in a sensible hierarchical model
rocket launch with ascent steering (pitch table, gravity turn, PEG)
circular three body evolution (cis-lunar etc.) with ability to import halo orbits from JPL
There are “quick tour” videos for the sample folders:
What’s New in 9.0¶
Extensive changes to the way rocket launches and atmospheric re-entry is added. This allows support for gravity turns and powered explicit guidance (PEG) ascent to a designated circular orbit. The changes required are not backwards comptablible with 8.0.
Creation of the KEPLER_COE propagator. This makes use of the COE and evolves in a way that allows propagation at times before the COE was specified. Propagation before the COE epoch can be designated to propogate to earlier times, hold the COE epoch position or remove the body and generate an event. See early propagate.
Allow use of KEPLER_COE, PKEPLER and SGP4_RAILS propagators for evolution times before the time at which their state was defined.
Support for specifying an “epoch time” for body initialization with COE or TLE initial data at a specific time in th epast or future. Prior versions required the COE to be describe the state at the time the body was aded. This also allows the time embedded in a TLE to be over-ridden.
Support the use of ephemeris files exported from NASA’s GMAT mission design tool. The ephemeris propagator now allows for a choice of interpolation algorithm (linear, cublic spline Hermite or Kepler).
Additional API enhancements and bug fixes can be found in the README.