Astrodynamics Java Project

About

A orbital mechanics project originally created while I was in Aerospace Engineering graduate school. Orbit tools is a Java class which has functions that are useful in creating astrodynamic Java programs. It was used in a program I created while working at the Space Environment Center. A separate class, planetary elements, calculates the orbital elements for a planet at a given time. These three applets based on these two classes are on this site the Julian Date Converter, Planetary Elements Applets and Direct Trajectory Calculator.

Applets

Julian Date Converter

About

Simple applet to convert from a Julian Date to normal time and normal time to Julian Date. Julian Dates are commonly used in orbital mechanics. Note: normal time is Greenwhich Mean Time (GMT)

Orbit Tools: Julian Date Converter
Java applets no longer work in browsers. Images coming soon.

Planetary Elements

About

Gets the orbital elements at the Julian Date inputted. It also converts the orbital elements into position and velocity vectors relative to the sun. (Coordinate system is mean ecliptic of J2000)

Orbit Tools: Planetary Elements Applet
Java applets no longer work in browsers. Images coming soon.

Direct Trajectory

About

You put in the planets you want to travel between, how long you want to take and what dates to look at and it gives which day is best to leave. It also gives position and & velocity vectors for leaving the departure planet and arriving at the target planet and the heliocentric orbital elements of the transfer orbit when leaving the departure planet. This information can be input into mission design programs as the starting point. It is based on what is commonly called the zero-patched-conic method (aiming from the center of one planet to the other ignoring everything except the Sun's gravity). HEV is the hyperbolic excess velocity (aka V infinity).

Orbit Tools: Interplanteary Trajectory Applet
Java applets no longer work in browsers. Images coming soon.

OrbitTools Functions


Future Work

Updated: 10/15/2025