Reentry analysis and experiment of space debris considering dynamical separation process

Abstract

Recently, Tiangong-1 space lab, China's first space station, reentered and burned up in the atmosphere over the southern Pacific Ocean on April 1. This issue brought a serious alert to the public in the world, regarding collision risks of the orbiting object and a possibility of a consequent threat to the survivability when the object survives and impacts human. In this study, reentry analysis and experiment of space debris considering dynamical separation process have been investigated. The contents of this study are threefold. Firstly, the experiments to analyze the separation process of reentry space debris were conducted using a shock tunnel in a Mach 6 flow. Iron or acetal models with different shapes and sizes were considered. By varying the size, shape, and number of models, the lateral velocity and the separation behaviour were measured and analyzed. Furthermore, a new equation to account for the lateral velocity of the multi-spheres was proposed. Secondly, an integrated system for the orbit, orbital lifetime, and reentry survivability estimation modules of space debris has been developed for the first time. To ensure the reliability of the system, each module was compared and validated with results of the well-known existing codes. Finally, the developed integrated system was combined with the presented experimental data to analyze the reentry trajectory and survivability of space debris. The results showed that the separation process leads to large discrepancies in survivability, downrange, and ground footprint prediction because it causes a change in ballistic coefficient, heat of ablation, and lateral velocity. Caution should therefore be exercised in the reentry trajectory and survivability analysis when the effect of separation induced due to fragmentation is not considered.