Physics educational software for high school, college and university students and teachers. May also be of interest to the amateur astronomer and physicist.With Orbit Xplorer orbit simulator you can do lab exercises in gravitational physics. Study elliptical orbits, double stars, escape velocity, Kepler's third law, Lagrange points, the three-body problem and more.

from ScienceMan

Current version is 2.0

With Orbit Xplorer orbit simulator you may:

Calculate and plot the orbits of up to 10 gravitationally interacting bodies.
Easily create, run, save and print your own orbit simulation.
View time, distance, velocity, acceleration and energy.
Create graphs of distance, velocity, acceleration and energy versus time.
Run up to four simultaneous simulations.

Some of the features:

29 simulations with on-screen activities in html format included.
Sample activity 1 . Sample activity 2 . Sample activity 3.
Uses actual pictures of planets.
Project the orbits into one of three planes or view them in 3D.
Tutorial and context-sensitive help..

Use it for:

Learning.
Teaching.
Experimenting
Solutions to textbook problems.
Fun.

System requirements:

Windows 95/98/Me/NT/2000/XP. Also works on a Mac PC emulator.
Pentium processor (at least 400 MHz recommended).
32 MB RAM.
16 bit color or better.

The pictures on the left show (click to enlarge):
Satellite orbit with acceleration vectors.
A double star.
A three-dimensional view of the inner solar system with orbit projections.
Two bodies in the orbit of the Moon, one of them in the Lagrange point L4.
A satellite orbiting Lagrange point L4 of the Moon.