Jehan Dastoor
(Advisor: Prof. Mavris)
will propose a doctoral thesis entitled,
Calibration of Data-Driven Reduced Order Models to Heterogeneous Data with an Entry Vehicle Application
On
Friday, August 1st at 8:00 a.m. 
Collaborative Visual Environment (CoVE)
Weber Space Science and Technology Building (SST II)
And
Join the meeting now
Abstract
Entry, Descent, and Landing (EDL) is one of the most crucial phases of a space mission, involving flight from atmospheric interface, deceleration through an atmosphere, and ultimately delivering a payload to a bodies surface. Due to the exorbitant cost of flight tests, EDL aerodynamicists rely on ground-based tests and Modeling and Simulation (M&S) to understand aerodynamic phenomena. The culmination of possibly up to a decade of testing is an aerodynamic database, which characterizes the vehicle's aerodynamics at each flight condition of interest. These databases combine multiple sources of aerodynamic information and uncertainties to provide a single prediction at each point along a trajectory. However, these databases are often costly and time consuming to construct, as well as limited in their ability to capture dynamic responses.
Reduced Order Models (ROMs) have been suggested as an alternative to traditional databases, where instead of predicting aerodynamic coefficients, the entire surface pressure and shear field is predicted. These models have been shown to produce similar results to higher-fidelity CFD solutions with a lower online computational cost, allowing them to be used in trajectory simulations and dispersion analysis. However, aerodynamic ROMs currently only utilize data from CFD solutions, which are known to have discrepancies when compared to experimental data. 
This motivates the research objective of this thesis: to calibrate a ROM using experimental measurements from a ballistic range, which is often considered the most trusted ground source of dynamic data for entry capsules. This is made challenging by the fact that surface pressure fields are not currently experimentally measured for entry capsules and therefore, heterogeneous data must be utilized. Ultimately, this led to the selection of a Bayesian calibration methodology due to its ability to handle heterogeneous data, model discrepancies between numerical models and experimental data, and propagate uncertainties. 
This thesis develops the calibration methodology by addressing how calibration parameters should be defined, whether trajectory data can be utilized to calibrate aerodynamic forces and fields, and how discrepancies between numerical and experimental results can be accounted for using a discrepancy function. An experimental plan is proposed to address these questions, utilizing previously generated CFD-in-the-loop trajectories for the Genesis Sample Return Capsule. 
Committee
•    Prof. Dimitri N. Mavris – School of Aerospace Engineering (advisor)
•    Prof. Graeme J. Kennedy – School of Aerospace Engineering
•    Prof. Lakshmi N. Sankar – School of Aerospace Engineering
•    Dr. Bradford E. Robertson – School of Aerospace Engineering
•    Dr. Christian Perron – School of Aerospace Engineering
•    Dr. Hisham M. Shehata – Atmospheric Flight Entry Systems Branch NASA LaRC, Analytical Mechanics Associates