A computer program called “42” simulates the attitudes and trajectories of multiple spacecraft flying in formation anywhere in the Solar System. The rotational dynamics are represented by high-fidelity models of spacecraft, each comprising as many as three connected rigid bodies and containing as many as four flywheel mechanisms for storing angular momentum for controlling attitude. The translational dynamics are represented partly by Encke’s method of orbit perturbation, which enables the use of a reference trajectory shared by multiple spacecraft and, in so doing, enables separation of gigameter-scale trajectory features from nanometer-scale formation adjustments to preserve the numerical accuracy needed for simulating precise multi-spacecraft formations.
Other models include planetary ephemerides and models for solar-radiation pressure, effects of the terrestrial magnetic field, effects of the terrestrial atmosphere, and non-spherical components of the geopotential. The program provides a graphical display that facilitates visualization of individual behaviors of, and interactions among, the spacecraft in a formation. Models of spacecraft sensors, control laws, and control-actuator dynamics are included; these models can be customized (this can include linking to real flight software) to enable high-fidelity simulation.
This program was written by Eric Stoneking of Goddard Space Flight Center.