FOSTRAD: An advanced open source tool for re-entry analysis

This work responds to the need of modeling the atmospheric re-entry of space debris, satellites, and spacecraft quickly, efficiently and with a reasonable reliability. The Free Open Source Tool for Re-entry of Asteroids and Debris (FOSTRAD) is a simulation suite that allows for the estimation of aerodynamics and aerothermodynamics of an entry object in a continuum or rarefied hypersonic flow by employing the local panel formulation. In this paper, the work done to integrate the tool within a comprehensive framework allowing the simulation of complex geometries using a mesh handler module, a 3DOF trajectory propagator, and a surrogate model generation function, is presented. In addition, a synchronous coupling with a 1D thermal ablation code has been implemented and tested. The mesh module allows operations such as surface local radius computation, surface facets visibility identification, and objects geometrical evolution due to the burn-up during the re-entry. In the continuum regime, the simplified aerothermodynamics are computed using a local radius formulation, while the tool employs a flat-plate based approach in the free molecular regime. A generalized nose radius-based bridging model has been introduced for the rarefied transitional regime. The tests have demonstrated that applying a local radius formulation along with the radius-based bridging model greatly improves the accuracy of re-entry heat-flux estimations. The integrated framework has been tested on two different examples of atmospheric re-entries: the ESA Intermediate Experimental Vehicle (IXV) trajectory optimization and the Stardust sample return capsule Thermal Protection System (TPS) burn-up recession; and the coupling between FOSTRAD and the thermal ablation code allowed to study a step-by-step trajectory evolution of Stardust TPS. The obtained results show good agreement with the literature.