Speaker
Description
At the end of their operational lifespan, uncontrolled spacecraft re-enter Earth's atmosphere and undergo total or partial destruction through interaction with the surrounding flow. The growing population of debris in Earth's orbits has prompted space agencies to address the space debris issue by imposing increasingly stringent requirements over the years. The published ESA standard Space Debris Mitigation Requirements (ESSB-ST-U-007) recommends Design for Demise (D4D) as the preferred end-of-life mitigation strategy for limiting the risk of casualties on the ground. The D4D philosophy advocates that, early in the design and development stages of a new space mission, careful evaluations of spacecraft buses, payloads, and structural components be conducted to assess their potential to survive an uncontrolled re-entry.
Currently, spacecraft demise is assessed using low-fidelity engineering codes (object or spacecraft-oriented) that simulate satellite degradation along the entry trajectory. These tools rely on strong simplifying assumptions regarding heat flux prediction, ablation phenomena, and structural failure. Within the framework 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 by modeling the key aerothermodynamic, thermal, and structural phenomena that drive such events. This is achieved by coupling high-fidelity, physics-based numerical tools capable of simulating spacecraft aerothermodynamics in the rarefied and transitional regimes together with the thermo-structural behavior of the spacecraft structure.
The SMURFS toolset (Spacecraft Motion and behaviour Under Re-entry for Fragmentation Simulations) integrates trajectory, flow, and thermo-mechanical computations. Starting from a volumetric mesh of the spacecraft, the toolset progressively decomposes the geometry into fragments along the trajectory. A loosely coupled approach is adopted across the three modules: steady-state aerothermodynamic evaluations at predefined altitude stations are combined with transient 6-DoF (Degrees of Freedom) trajectory analyses and quasi-static thermo-mechanical responses. This framework enables fragmentation assessment through dedicated failure criteria — thermal criteria flag fragmentation when melting temperatures are reached, and mechanical properties are strongly degraded, while mechanical criteria, applied in a subsequent simulation step, detect fragmentation driven by the resulting stress states. When fragmentation occurs, each debris piece becomes independent and is propagated as a new simulation branch to compute its further decomposition.
This presentation provides a status update on the SMURFS toolset, summarizing recent developments, ongoing activities, and applications to representative test cases. We outline the main features of the toolset, discuss its underlying assumptions, and offer practical guidelines for setting up and running simulations. The maturity of the code has advanced significantly, culminating in the first official release to ESA, which includes a regression-test suite to ensure reliability across versions. Complementary developments include a graphical user interface (GUI) that streamlines case setup and execution, as well as a dedicated post-processing toolchain for visualizing and analyzing simulation results. We then describe mesh-erosion techniques that preserve the geometry's watertightness throughout the fragmentation process. Finally, we demonstrate the toolset's capabilities on a series of representative test cases, including multi-material CubeSats and the AVT reference model.