Addressing the risk of the atmospheric re-entry of space debris is progressively becoming more and more pressing due to the increase in the number of orbiting objects and the consequent higher frequency of re-entry. The prediction of the re-entry process is impacted by the fragmentation of the re-entering objects as a result of the severe aerothermal loads. Improved modelling and simulation of the aerothermodynamically-induced fragmentation is paramount to design systems for safe demise and assess the associated risk.
Accurate modelling of such break-up mechanism is challenging due to its complexity and multi-disciplinary nature. The unsteady changes in the object shape and in the aerodynamic environment consequent to the relative motion of fragments will affect the aerothermal loads in the first instants after the separation. Existing modelling and simulation capabilities are still based on simplifying assumptions that cannot address in a consistent manner the break-up process resulting in substantial uncertainty.
In order to reduce the uncertainty on the demise process, it is proposed to:
- develop an approach based on high-fidelity methods with adaptive meshing to model the aerothermodynamics of the initial instants of fragmentation;
- use advanced models for fragmentation and detachment leading to changes in the topology of the computational domain;
- couple the high-fidelity with a 6 DoF model of the object's motion to account for the impact of separation on the dynamics of fragments.
The high-fidelity model of the few seconds before and after the break-up will be coupled with an existing low-fidelity model of atmospheric re-entry and descend. The expensive but accurate high-fidelity method will be used only in the few instants before and after fragmentation. A low-fidelity approach will be used to simulate the rest of the process. An optimal trade off between computational cost and accuracy will be achieved reducing the uncertainty on the demise process.
