Speaker
Description
The latest data from 2022, shows a record number of satellites were launched and re-entered Earth’s atmosphere compared to previous years. Current projections that account for the growing prevalence of satellite constellations and launch rideshares, suggest that these numbers will continue to rise. This increase in atmospheric re-entry events shows the growing adherence to space debris mitigation measures, that mandate the removal of satellites from over-populated orbits at the end of their operational lives. However, as more satellites opt for disposal via atmospheric re-entry, the precise simulation of re-entry becomes increasingly important to assess the trajectory and associated risk of any surviving fragments.
Simulating re-entry scenarios is a complex process, involving the modelling of atmospheric, aerothermodynamic, structural and flight dynamics amidst shock wave interactions and high-temperature, non-equilibrium flows. Accurately modelling scenarios involving multiple interacting fragments also poses a distinct challenge to re-entry simulations. Current re-entry tools typically neglect the effects of fragment interactions, including the possible physical collisions and flow feature interactions. Neglecting these features may alter the profile of the fragment cloud post-breakup, subsequently influencing the trajectories and ground impact footprint predictions of re-entry simulations.
A re-entry tools ability to accurately simulate re-entry is dependent on the fidelity level of its models, particularly in the case of the fragmentation, aerodynamics and aerothermodynamics. Most re-entry tools rely on low-fidelity expressions for aerothermodynamics and aerodynamics, as well as pre-defined criteria for fragmentation, prioritizing computational efficiency over accuracy. In comparison, high-fidelity methods capable of resolving the complexities of re-entry are often considered computationally impractical when analysing full re-entry trajectories or in design for demise processes.
The re-entry analysis tool TITAN (TransatmospherIc flighT simulAtioN) addresses the aforementioned challenges of re-entry modelling through its collision model to simulate the physical interactions of fragments and its multi-fidelity capabilities for aerodynamics, aerothermodynamics and structural dynamics. This approach enables the use of high-fidelity models at critical phases of the re-entry trajectory to minimize the error of predictions. The collision model in TITAN allows for elastic collisions that accounts for the impact of object contact in the respective trajectory and risk analysis.
In this study, the destructive atmospheric re-entry of the Delta-II second stage is simulated with TITAN, with the collision model and multi-fidelity capabilities incorporated. The impact of including these models will be analysed with respect to the resulting prediction of the trajectory and ground footprint of the surviving Delta-II second stage debris. The results of the study will be assessed with respect to the Delta-2 rocket debris recovery locations to quantify the impact of the respective modelling methods on the accuracy of the predictions.
