NASA ULI

Adaptive Aerostructures for Revolutionary Civil Supersonic Transportation

2017 - 2022

Project Overview

This NASA ULI project considered the feasibility of distributed structural adaptivity on a supersonic aircraft for maintaining acceptable en-route sonic boom loudness during overland flight. The ULI team involved a large group of industry and university partners working to develop and implement the systems and tools necessary to accomplish this goal.

As a member of the Utah State University AeroLab, my work on the ULI project included:

Low-fidelity supersonic aerodynamic and sonic boom analysis
Sonic boom loudness optimization via localized vehicle OML changes
Wave drag analysis
Sonic boom minimization tool development and integration
End-of-project demonstrator management, integration, and implementation

Open-source Github repositories I have contributed to:

Python wrapper for sBOOM: https://github.com/usuaero/rapidboom

Additional project links:

Texas A&M Project Page: https://supersonic.tamu.edu/overview/

NASA ULI TechPort: https://techport.nasa.gov/view/96121

Sonic Boom Minimization Technical Demonstrator

One of the major deliverables for the ULI project was an end-of-project technical demonstration. This demonstration showcased the physical hardware, material design, software tools, and sonic boom minimization results that were produced over the 5 year project.

The USU team proposed and managed much of the tool and system integration necessary for this technical demonstration. My own contributions to the project included:

Managed the design and integration of the technical demonstrator framework
Developed a Python wrapper for supersonic flight simulation using FlightGear
Established a data transfer and management server using Python based TCP protocols
Developed and integrated a kinematics model of the physical hardware design

Equivalent Area Optimization

The equivalent area representation of a supersonic aircraft provides a lower-order method for optimizing the pressure signature for loudness reduction. Much of my work on the ULI was focused on using equivalent area representations for design space exploration and optimization. Some of the studies we performed and results we found include:

Studied how small OML deformations, modeled as equivalent area changes, could be used to reduce the perceived loudness (PLdB) of supersonic aircraft
Found that larger, more distributed area changes, were necessary for larger PLdB ( up to 5 dB) changes
Multiple regions on both the NASA 25D concept aircraft and C608 (X-59) were found to be candidates for active OML adaptation
Optimal morphing regions were consistent over different atmospheric profiles but varied slightly with flight conditions (Mach and angle-of-attack)
The PLdB reduction was highly sensitive to deformation amplitude and location

Wave Drag Prediction Methods

Linear supersonic analysis methods are commonly used in preliminary aircraft design. Perhaps the most common method for estimating the wave drag of a supersonic body is the Harris wave drag code or its more modern implementation found in the NASA OpenVSP software. These tools are limited to predicting the volume component of wave drag, but can still be expected to show useful trends in a design space. I have recently published a conference paper considering the accuracy of these wave drag prediction methods relative to high-fidelity inviscid CFD. Some details of this research include:

Studied axisymmteric geometries (Sears-Haack bodies) over a range Mach numbers and R/L ratios (radius to body length)
Revisited the analytic and numerical developments for estimating the wave drag of a supersonic body
Performed grid convergence studies for the analytic, linear numerical, and inviscid CFD methods
Generated contour plots of the difference in solutions throughout the design space
Identified regions in the design space where the "slender body" assumption is likely being violated

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