Technical Overview
Software
- Written in Java
- Uses the Java Bindings for OpenGL for the 3D visualization
Physical Model
- Earth's gravity is modeled as a spherical-harmonic gravitational model using the coefficients from the Joint NASA GSFC and NIMA Geopotential Model: EGM96.
- Earth's atmosphere is modeled as a composite of three atmospheric models: U.S. Standard Atmosphere (1976) from 0 km to 25 km altitude, CIRA-72 for 25-500 km altitude, and CIRA-82 with Tinf=1000 K for 500-1000 km altitude.
- Earth's orientation is measured relative to the J2000 frame by calculating the Greenwich sidereal-time (precession, nutation, and polar motion will be implemented in the future).
Orbital Maneuvering
- The employed orbital maneuvers are continuous-thrust maneuvers derived from Gauss' form of the [orbital element] variational equations and agree with classical impulsive-thrust maneuvers if massive instantaneous thrusts were to be used aboard each spacecraft.
- The terminal rendezvous autopilot employs a steady-state, Linear-Quadratic-Controller applied to the linearized equations of motion for a "docking" spacecraft in the vicinity of a "station" spacecraft in a circular orbit (Clohessy-Wiltshire equations of motion).
Numerics
- The numerical integration of the equations of motion are calculated using the Runge-Kutta-Fehlberg adaptive step-size algorithm.
- The Linear-Quadratic-Controller is calculated using a customized linear algebra library for Java.