Prediction of Orbit Decay for Large-Scale Spacecraft considering Rarefied Aerodynamic Perturbation Effects

The growing risk of falling debris from outer space as well as the atmospheric interaction effect makes the orbit decay prediction of large spacecraft in very low earth orbit (VLEO) increasingly significant. Focusing on the aerodynamic perturbation effects under multiscale and nonequilibrium states on the orbit decay of the large spacecraft in VLEO at the end of its lifetime, we developed a novel perturbation prediction model covering the entire altitude range before reentry to perform long-term and short-term predictions of the large-scale spacecraft. A unified local rapid engineering algorithm for aerodynamic force and moment coefficients covering all flow regimes is proposed. The orbit perturbation models, combining the components of aerodynamics solved by the engineering algorithm, are built for the large-scale spacecraft. For altitudes ranging from 350 km to 250 km, which we defined as the slow descending stage (SDS), the two-line orbital elements (TLEs) and simplified general perturbation 4 (SGP4) model were used for long-term prediction, whereas for altitudes from 250 km to 120 km, which we defined as the rapid falling stage (RFS), Kepler two-body motion dynamics with acceleration perturbations were applied. All the relevant orbital elements were analytically solved and numerically simulated by the Runge–Kutta integration method. Thus, the decay orbit for large spacecraft from 350 km to 120 km altitudes can be evaluated by the platform we built. All the predicted results were broadly consistent with the measurement data. The findings in this paper can be further applied into the orbit determination of noncooperative spacecraft.