Re-entry flight clearance

The objective of the research was to identify and evaluate promising mathematical techniques for re-entry flight clearance. To fulfil this objective, two mathematical methods were investigated and developed: μ analysis for linear models and interval analysis for both linear and non-linear models. The stability of re-entry vehicles in the presence of model uncertainties was chosen as the clearance criterion, which is represented by two mathematical criteria: worst-case eigenvalues (linear) and the Lyapunov stability (non-linear). Two vehicle models including flight control systems were developed and used as case studies for the evaluation of the clearance techniques. These models are based on the DART (Delft Aerospace Re-entry Test Demonstrator) and SPHYNX (Subscale Precursor Hypersonic X) re-entry vehicle models. The suitability of the two mathematical techniques for re-entry flight clearance was evaluated based on the results of the clearance application on these models. Non-linear simulations were also performed to verify the clearance results generated by the two techniques. Non-linear interval analysis has been found to be the most reliable method of all other methods investigated in this research, because it could perform the clearance for the non-linear dynamic models of the re-entry vehicles with uncertainties, and the results were confirmed by the non-linear simulations