1. POLITECNICO DI TORINO I FACOLTA’ DI INGEGNERIA TESI DI LAUREA SPECIALISTICA IN INGEGNERIA AEROSPAZIALE Studio sul comportamento strutturale di un veicolo da rientro atmosferico in fase di ammaraggio Relatori Prof. Giulio Romeo – Politecnico di Torino Ing. Roberto Ullio – Thales Alenia Space Candidato Maurizio Coltro

2. Part of ESA’s Future Launchers Preparatory Programme has been devoted to optimizing a long-term European roadmap for in-flight experimentation with atmospheric re-entry enabling systems and technologies. Thesis activity The Intermediate eXperimental Vehicle (IXV) project is the next core step of this effort. This work has been developed within the IXV project and with closed collaboration of TAS-I and ESA. Many thanks to ESA and TAS for their support. Thanks also to Altair Engineering for providing the software suite for the analysis.

3. The IXV Project Technology platform Intermediate element of technology-effective and cost efficient European roadmap Prepare future ambitious operational system developments with limited risks for Europe Project objectives Design, development, manufacturing, on-ground and in-flight verification of autonomous European lifting and controlled re-entry system Critical technologies of interest Advanced instrumentation for aerodynamics and aerothermodynamics Thermal protection and hot-structures solutions Guidance, navigation and flight control Success of IXV mission Correct performance of re-entry Safe landing and recovery with its experimental data 1/17

4. Experimental measurements Mockup representative of external shape inertial properties scale factors Physical quantities accelerations pressures Test facility electromagnets to release vehicle high frequency cameras high pool dimension to perform impact 2/17

5. Modeling methodology Hypermesh Hypercrash Preprocessor Radioss BLOCK V10 Solver Hyperview Postprocessor Explicit solution tecnique Drawbacks Suited for problems short duration high velocity highly nonlinear nature 3/17

6. IXV numerical model STRUCTURE CONFIGURATION Fuselage components Flaps assembly MODELING ASSUMPTIONS External dimensions taken into account Bidimensional rapresentation of surfaces Rigid body description RIGID BODY INERTIAL PROPERTIES MassJxxJyyJzz [kg] 27,821,174,524,31 4/17

7. Fluid numerical model FLUID DESCRIPTION LAW37 Biphas ALE approach MODELING ASSUMPTIONS Gas volume extensionLiquid volume extension 5/17

8. Fluid numerical model HORIZONTAL EXTENSION Limited front dimensions to avoid wave reflection VERTICAL EXTENSION Limited in-deep dimensions to lighten fluid model WATER BASIN COMPARISON Deep water modelShallow water model Horizontal1,22 x 2,14 [m] Vertical0,8 [m]0,4 [m] N Elements335265189317 CPU Time8413 [s]5077 [s] 6/17

9. Characteristic elements dimension Finest mesh normal to phenomenon Sensitivity analysis 2D ELEMENTS (VEHICLE) 3D ELEMENTS (AIR) 3D ELEMENTS (WATER) HEIGHT 20 [mm] WIDTH 20 [mm] DEPTH /10 [mm] N ELEMENTS 356478324287188 7/17

10. Fluid-structure interface SENSITIVITY ANALYSIS PERFORMED FLUID STRUCTURE INTERFACE TYPE18 STFAC Interface stiffness GAP Activation distance Single TYPE18 interface to represent sensors separately PRESSURE PROBES INTERFACE 8/17

11. Boundary-initial conditions Atmospheric pressure to water free surface DYREL dynamic relaxation for convergence Gravity load to water volume Lateral/bottom surfaces locked FLRD = 1 upper surface WATER BOUNDARY CONDITIONS Initially locked in all DOFs Gravity load to master node Initial velocity to master node Initial distance from free surface VEHICLE BOUNDARY CONDITIONS 9/17

12. Numerical - Experimental Correlation Impact angle 35 deg Flaps position 0 deg Vertical velocity 3,4 m/s FIRST LOADCASE Impact angle 19 deg Flaps position 0 deg Vertical velocity 3,4 m/s SECOND LOADCASE Impact angle 51 deg Flaps position 21 deg Vertical velocity 3,4 m/s THIRD LOADCASE Impact angle 35 deg Flaps position 21 deg Vertical velocity 3,4 m/s FOURTH LOADCASE All loadcases computed from 0 to 200 ms 10/17

13. First Loadcase AX - COG AZ - COG Numerical Experimental 11/17 All curves normalized to 1

14. Second Loadcase AX - COG AZ - COG Numerical Experimental 12/17 All curves normalized to 1

15. Third Loadcase AX - COG AZ - COG Numerical Experimental 13/17 All curves normalized to 1

16. Third Loadcase 19 deg Sensor 35 deg Sensor 51 deg Sensor NumericalExperimental NumericalExperimental 14/17

17. Correlation results summary Main outcomes from acceleration results very good correlation at COG in X and Z directions satisfactory correlation at NOSE and REAR parts Main outcomes from pressure results good correlation impact event chronology pressure time history signature satisfactory correlation pressure peak values Correlation process model updating activity improvement of modelling approaches correction of individual parameters 15/17

18. Remarks and further developments Fluid LAW51 Multimaterial with outlet treatment SPH method Structure Deformable body Alternative modeling methodology 16/17 Experimental numerical results deviation Flexible body behaviour Statistic data dispersion Exposed impact areas and mathematical model

19. Thanks for your attention 17/17