Dynamic stability of deployable aeroshells at supersonic speeds
File(s)
Author(s)
Innocenzi, Pietro
Type
Thesis or dissertation
Abstract
This thesis investigates the dynamic stability of a deployable aeroshell using two complementary approaches: Computational Fluid Dynamics simulations and experimental testing in a supersonic wind tunnel.
The computational study addresses limitations in current formulations of pitch damping for entry vehicles. Rather than depending only on the instantaneous vehicle state, the pitch damping derivative is proposed to depend on the history of the wake flow. An instantaneous formulation is introduced in which the pitch damping coefficient is expressed as a function of variables linked to the present and past wake state, including pitch angle, pitch rate, Mach number, Reynolds number, and Strouhal number. Free-oscillation Detached Eddy Simulations of a deployable aeroshell are performed in the pitch degree of freedom, and the damping derivative is evaluated over these parameters. The study not only proposes a more comprehensive characterisation of pitch damping, but also identifies the physical mechanisms driving the instability. In particular, the stabilising forebody and destabilising aftbody contributions are shown to respond differently to variations in the governing non-dimensional parameters, revealing previously undocumented trends.
The experimental study investigates the pitch--roll coupled instability observed in the 2018 ADEPT SR-1 flight test vehicle. Free-oscillation tests of a deployable aeroshell model are conducted in a blow-down tunnel at M = 2 using a spherical air bearing that enables near zero-friction rotation in roll, pitch, and yaw. Motion is measured using non-invasive photogrammetry. The experiments reveal a precessional instability previously reported only for slender bodies in high-hypersonic regimes, demonstrating that severe instabilities can arise when roll rates approach the natural frequency of the pitch oscillations, potentially explaining the instability experienced by the ADEPT vehicle.
The computational study addresses limitations in current formulations of pitch damping for entry vehicles. Rather than depending only on the instantaneous vehicle state, the pitch damping derivative is proposed to depend on the history of the wake flow. An instantaneous formulation is introduced in which the pitch damping coefficient is expressed as a function of variables linked to the present and past wake state, including pitch angle, pitch rate, Mach number, Reynolds number, and Strouhal number. Free-oscillation Detached Eddy Simulations of a deployable aeroshell are performed in the pitch degree of freedom, and the damping derivative is evaluated over these parameters. The study not only proposes a more comprehensive characterisation of pitch damping, but also identifies the physical mechanisms driving the instability. In particular, the stabilising forebody and destabilising aftbody contributions are shown to respond differently to variations in the governing non-dimensional parameters, revealing previously undocumented trends.
The experimental study investigates the pitch--roll coupled instability observed in the 2018 ADEPT SR-1 flight test vehicle. Free-oscillation tests of a deployable aeroshell model are conducted in a blow-down tunnel at M = 2 using a spherical air bearing that enables near zero-friction rotation in roll, pitch, and yaw. Motion is measured using non-invasive photogrammetry. The experiments reveal a precessional instability previously reported only for slender bodies in high-hypersonic regimes, demonstrating that severe instabilities can arise when roll rates approach the natural frequency of the pitch oscillations, potentially explaining the instability experienced by the ADEPT vehicle.
Version
Open Access
Date Issued
2026-03-09
Date Awarded
2026-08-01
Copyright Statement
Attribution-NonCommercial-ShareAlike 4.0 International Licence (CC BY NC-SA)
Advisor
Bruce, Paul
Navarro-Martinez, Salvador
Publisher Department
Department of Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)