Altitude and directional effects on debris lifetimes in low Earth orbit

The early post-fragmentation evolution of low-Earth-orbit debris is investigated using a reduced planar dynamical model including the Earth’s central gravitational field, the J 2 zonal harmonic, and altitude-dependent atmospheric drag. Fragmentation is represented by an impulsive velocity perturbation whose direction is described through a tangential–radial decomposition while maintaining a constant impulse magnitude. A large ensemble of fragment trajectories is propagated for up to 200 days over breakup altitudes ranging from 200 to 800 km , allowing the statistical response of orbital lifetime to be characterized as a function of fragmentation direction.The results reveal a clear transition from drag-dominated to drag-limited orbital evolution with increasing breakup altitude. At low altitudes, atmospheric drag rapidly removes most fragments regardless of fragmentation direction, whereas at higher altitudes orbital persistence progressively increases as atmospheric dissipation weakens. Statistical characterization based on the median lifetime and interquartile range demonstrates that fragmentation direction primarily modulates the variability of orbital lifetime through the redistribution of the impulsive velocity between the tangential and radial directions rather than producing a unique deterministic orbital response.The observed lifetime distributions are consistently explained by the combined effects of atmospheric drag, impulsive orbital energy redistribution, and the resulting perigee evolution. The proposed framework provides a physically interpretable and computationally efficient methodology for investigating the early evolution of fragmentation clouds and contributes to a better understanding of short-term debris persistence in low-Earth orbit.