Supersonic boom loudness remains a major obstacle in the adoption of over-land supersonic  
commercial transport. Varying atmospheric conditions as a function of weather, topology, and  
seasonal changes can increase the boom signature of an aircraft in excess of low boom  
requirements. Morphing aerospace structures can mitigate boom loudness in off-design  
conditions by modifying the outer mold line (OML) to better suit the off design condition while  
maintaining an acceptable level of aerodynamic efficiency and performance.  
Any actively morphing structure applied to a supersonic vehicle must be able to withstand the  
harsh environment of supercruise while not exceeding low boom requirements. The morphing  
structure must smoothly transition between target OML geometries and not feature sharp angles  
which can detrimentally affect the boom signature. The structure must be able to withstand  
temperature and vibration corresponding to the supercruise environment and efficiently transfer  
aerodynamic loads to the main structure of the vehicle.  
Active morphing structures must be driven by actuation systems. Morphing configurations are a  
tradeoff between boom reduction and reduced system-level performance due to the weight of  
actuation systems, including hydraulic pistons or electric motors and their associated  
components. The size of these conventional actuators hinders their integration into the structure  
of the vehicle, often requiring heavy transmission couplings or gearboxes to provide actuation  
where needed. Shape memory alloy (SMA) actuation systems offer a compact, electric actuation  
capability with high work density, reducing or eliminating the prohibitive trade-offs associated  
with conventional actuation systems. SMA actuation systems can be distributed throughout the  
vehicle, enabling morphing at different locations on the vehicle while not significantly impacting  
the underlying vehicle structure and systems.  
Texas A&amp;M University has partnered with Boeing Research &amp; Technology to investigate these  
morphing concepts and actuation systems as part of a NASA ARMD University Leadership  
Initiative. This work discusses challenges associated with designing an actuated, adaptive  
structure to meet the requirements of a low boom morphing OML concept. Examples of small-  
footprint actuation concepts driven by SMA will be presented with discussion on how these  
concepts are uniquely suited for integration within the skin of a supersonic aircraft. SMA driven  
actuation concepts will be traded against conventional actuation technologies in terms of  
expected size, weight, power, and complexity. Smooth outer skin morphing concepts will also be  
discussed, including kinematically linked rigid panels with elastomer filler and substrate. Proof-

of-concept demonstrations integrating controllable SMA actuation systems with morphing skin  
structures have also been developed and tested in a subscale laboratory environment.


Shape Memory Alloy Driven Actuation Concepts for Morphing Low-Boom Supersonic Aircraft Configurations

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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