This paper describes the design of a nonlinear robust adaptive controller for a flexible air-breathing hypersonic vehicle model. Because of the complexity of a first-principle model of the vehicle dynamics, a control-oriented model is adopted for design and stability analysis. This simplified model retains the dominant features of the higher-fidelity model, including the nonminimum phase behavior of the flight-path angle dynamics, the flexibility effects, and the strong coupling between the engine and flight dynamics. A combination of nonlinear sequential loop closure and adaptive dynamic inversion is adopted for the design of a dynamic state-feedback controller that provides stable tracking of the velocity and altitude reference trajectories and imposes a desired set point for the angle of attack. A complete characterization of the internal dynamics of the model is derived for a Lyapunov-based stability analysis of the closed-loop system, which includes the structural dynamics. The proposed methodology addresses the issue of stability robustness with respect to both parametric model uncertainty, which naturally arises when adopting reduced-complexity models for control design, and dynamic perturbations due to the flexible dynamics. Simulation results from the full nonlinear model show the effectiveness of the controller.

Nonlinear Robust Adaptive Control of Flexible Air-Breathing Hypersonic Vehicles

https://engineering.purdue.edu/~aae519/BAM6QT-Mach-6-tunnel/reviewpapers/cone-scram-blt-review-pas-feb04.pdf

Hypersonic laminar–turbulent transition on circular cones and scramjet forebodies

The status and some recent developments in computational modeling of flexible multibody systems are summarized. Discussion focuses on a number of aspects of flexible multibody dynamics including: modeling of the flexible components, constraint modeling, solution techniques, control strategies, coupled problems, design, and experimental studies. The characteristics of the three types of reference frames used in modeling flexible multibody systems, namely, floating frame, corotational frame, and inertial frame, are compared. Future directions of research are identified. These include new applications such as micro- and nano-mechanical systems; techniques and strategies for increasing the fidelity and computational efficiency of the models; and tools that can improve the design process of flexible multibody systems. This review article cites 877 references. @DOI: 10.1115/1.1590354#

https://hosting.umons.ac.be/html/mecara/grasmech/PaperWasfyNoor.pdf

Computational strategies for flexible multibody systems

It is well known that the high levels of noise present in conventional hypersonic ground-test facilities cause transition to occur earlier than in e ight. Flight measurements of incoming noise are reviewed and compared with measurements in ground-test facilities, of both conventional and quiet design, at hypersonic and high supersonic speeds. The low noise present in e ight is apparently the reason for the very large transition Reynolds numbers sometimes measured in e ight, when roughness, crosse ow, and other factors are controlled. Design will usually involve consideration of the trend in transition when a parameter is varied. The effect of facility noise on these trends is reviewed. In some cases, the trend of conventional-tunnel data is opposite to the trend in quiet-tunnel data. Thus, transition measurements in conventional ground-test facilities are not reliable predictors of e ight performance, except perhaps in special cases.

Effects of High-Speed Tunnel Noise on Laminar-Turbulent Transition

This paper reviews the state of phosphor thermometry, focusing on developments in the past 15 years. The fundamental principles and theory are presented, and the various spectral and temporal modes, including the lifetime decay, rise time and intensity ratio, are discussed. The entire phosphor measurement system, including relative advantages to conventional methods, choice of phosphors, bonding techniques, excitation sources and emission detection, is reviewed. Special attention is given to issues that may arise at high temperatures. A number of recent developments and applications are surveyed, with examples including: measurements in engines, hypersonic wind tunnel experiments, pyrolysis studies and droplet/spray/gas temperature determination. They show the technique is flexible and successful in measuring temperatures where conventional methods may prove to be unsuitable.

https://www.mdpi.com/1424-8220/8/9/5673/pdf

Thermographic Phosphors for High Temperature Measurements: Principles, Current State of the Art and Recent Applications

Boundary-layer trip devices for the Hyper-X forebody have been experimentally examined in several wind tunnels.Fivedifferenttripconegurationswerecomparedinthreehypersonicfacilities:theNASALangleyResearch Center 20-Inch Mach 6 Air and 31-Inch Mach 10 Air tunnels and in the HYPULSE Reeected Shock Tunnel at the General Applied Sciences Laboratory. Heat-transfer distributions, utilizing the phosphor thermography and thin-elm techniques, shock system details, and surface streamline patterns were measured on a 0.333-scale model of the Hyper-X forebody. Parametric variations include angles of attack of 0, 2, and 4 deg; Reynolds numbers based on model length of 1.2 ££ 10 6‐15.4 £ 10 6 ; and inlet cowl door simulated in both open and closed positions. Comparisons of boundary-layer transition as a result of discrete roughness elements have led to the selection of a trip coneguration for the Hyper-X Mach 7 eight vehicle.

/pdf/hypersonic-boundary-layer-trip-development-for-hyper-x-1typxzigf3.pdf

Hypersonic Boundary-Layer Trip Development for Hyper-X

/pdf/numerical-analysis-of-convection-transpiration-cooling-27b4pky7ud.pdf

Numerical Analysis of Convection / Transpiration Cooling

Computational e uid dynamics tools have been used extensively in the analysis and development of the X-43A Hyper-X Research Vehicle. A signiecant element of this analysis is the prediction of integrated vehicle aeropropulsive performance,which includes an integration of aerodynamic and propulsion eoweelds. Thedevelopment of the Mach7X-43Arequiredapree ightassessmentoflongitudinalandlateral-directionalaeropropulsivecharacteristics nearthetargeteight-testcondition.Thedevelopmentofthispree ightdatabasewasaccomplishedthroughextensive aerodynamic wind-tunnel testing and a combination of three-dimensional inviscid airframe calculations and cowlto-tail scramjet cycle analyses togenerate longitudinal performance increments between mission sequences. These increments were measured directly and validated through tests of the Hyper-X e ight engine and vehicle e owpath simulator in the NASA Langley Research Center 8-Foot High Temperature Tunnel. Predictions were reened with tip-to-tailNavier‐Stokescalculations,which alsoprovidedinformation onscramjetexhaustplumeexpansion inthe aftbody region. A qualitative assessment of lateral-directional stability characteristics was made through a series of tip-to-tail inviscid calculations, including a simulation of the powered scramjet eight-test condition. Additional comparisons with wind-tunnel forceand momentdataas well as surfacepressuremeasurements from theHyper-X e ight engine and vehicle eowpath simulator model and wind-tunnel testing were made to assess solution accuracy.

/pdf/integrated-aeropropulsive-computational-fluid-dynamics-5892lnlb1g.pdf

Integrated Aeropropulsive Computational Fluid Dynamics Methodology for the Hyper-X Flight Experiment

The NASA X-43 Hyper-X hypersonic research vehicle will be boosted to a Mach 7 flight test condition mounted on the nose of a Pegasus launch vehicle. The separation of the research vehicle from the Pegasus presents some unique aerodynamic problems, for which computational fluid dynamics has played a role in the analysis. We describe the use of several computational methods for investigating the aerodynamics of the research and launch vehicles in close proximity. Specifically addressed are unsteady effects, aerodynamic database extrapolation, and differences between wind-tunnel and flight environments.

Computational Fluid Dynamics Prediction of Hyper-X Stage Separation Aerodynamics

The NASA X-43 "Hyper-X" hypersonic research vehicle will be boosted to a Mach 7 flight test condition mounted on the nose of an Orbital Sciences Pegasus launch vehicle The separation of the research vehicle from the Pegasus presents some unique aerodynamic problems, for which computational fluid dynamics has played a role in the analysis This paper describes the use of several CFD methods for investigating the aerodynamics of the research and launch vehicles in close proximity Specifically addressed are unsteady effects, aerodynamic database extrapolation, and differences between wind tunnel and flight environments

/pdf/prediction-of-hyper-x-stage-separation-aerodynamics-using-3oirbrgyze.pdf

Arthur D. Dilley

Papers

Hypersonic Boundary-Layer Trip Development for Hyper-X

Numerical Analysis of Convection / Transpiration Cooling

Integrated Aeropropulsive Computational Fluid Dynamics Methodology for the Hyper-X Flight Experiment

Computational Fluid Dynamics Prediction of Hyper-X Stage Separation Aerodynamics

Prediction of Hyper-X Stage Separation Aerodynamics Using CFD