Speaker
Description
At the end of their lifespan, uncontrolled spacecraft eventually re-enter Earth’s atmosphere and demise, totally or partially, due to their interaction with the surrounding flow. The growing population of junk in Earth’s orbits induced space agencies to tackle the space debris issue by imposing increasingly stringent requirements over the years. The recently published standard ESA Space Debris Mitigation Requirements ESSB-ST-U-007 recommends Design for Demise (D4D) as the best choice among the possible end-of-life mitigation strategies that can be adopted to limit the risk of generating casualties on the ground. The D4D philosophy strongly advocates that, early in the design and development stages of a new space mission, careful evaluations of spacecraft buses, payloads, and structural components should be conducted to assess their potential to survive an uncontrolled re-entry.
Currently, the demise of spacecraft is assessed using low-fidelity engineering codes (object or spacecraft-oriented) that enable the simulation of the degradation of the satellite along the entry trajectory. Those engineering tools rely on strong hypotheses about heat flux prediction, ablation phenomena or structural failure of the spacecraft. Within the context of the ESA project DSMCFED (contract no. 4000135337/21/NL/MG), we are developing a high-fidelity design toolset to complement existing engineering tools. The methodology enables a more comprehensive understanding of spacecraft fragmentation through detailed modelling of the key aerothermodynamic, thermal, and structural phenomena contributing to such events. This is achieved by coupling high-fidelity physics-based numerical tools able to simulate the spacecraft aerothermodynamics in the rarefied/transitional regime and the thermo-structural behaviour of the spacecraft structure.
The SMURFS (Spacecraft Motion and behaviour Under Re-entry for Fragmentation Simulations) toolset integrates trajectory, flow, and thermo-mechanical computations. Based on a volumetric mesh of the spacecraft, the decomposition of the geometry into fragments during the trajectory is tackled by the toolset. The methodology employs a loosely coupled approach among the three modules. Steady-state aerothermodynamics evaluations at predefined altitude stations are combined with transient 6-DoF (Degrees of Freedom) trajectory analysis and quasi-static thermo-mechanical responses. This setup allows for the fragmentation assessment through predefined failure criteria, identifying potential breakup events with dedicated thermal and mechanical criteria. Thermal criteria are used to estimate fragmentation when the melting temperature is reached, and the mechanical properties are strongly degraded. Mechanical failure criteria are used in the second simulation step to detect fragmentation due to stress states. When fragmentation occurs, each resulting debris becomes independent from the others and is managed as a new simulation branch to compute further decomposition.
In this presentation, we will provide an update on the status of our developed toolset, the progress of ongoing initiatives, and the application to various test cases. We will outline the toolset's features, discuss the foundational assumptions, and offer guidelines for conducting simulations.
