Frequency Selective Surfaces for Passive, Unpowered, Wireless, and Non-Contacting Softgood Structural Health Monitoring

A key enabling technology for the future of crewed habitation systems is developing inflatable softgood materials and structures to provide larger habitat volumes with a lower structural mass. NASA requires technologies to mature inflatable softgoods via integration of sensing capabilities for structural health monitoring (SHM) for deployment of these devices as part of future space habitation systems.  Texas Research Institute (TRI) Austin and The Missouri University of Science and Technology (MST) propose the development of frequency selective surface (FSS)-based structural health monitoring capabilities for inflatable softgood material systems to monitor the structural performance of these materials in situ. This technology provides the ability to measure load/strain on softgood components, detect damage, and potentially predict further degradation/potential failures via a non-contacting, passive, and unpowered system.  TRI and MST will couple this technology to a commercial-off-the-shelf vector network analyzer to allow NASA to acquire, process, and make use of this data in real time as an important risk mitigation mechanism for potential structural failure modes.  In Phase I, TRI and MST will demonstrate the validity of this system via proof of concept and preliminary testing on representative inflatable softgood structures in the creep strain range of interest (0.1-0.5% strain, or 1,000-5,000 microstrain).  This technology can be incorporated into softgood structures as either a “stand alone” add on (built on a substrate and implanted/adhered into the layer of interest in the structure), or as a “built in” piece of the inflatable (such as by using conductive textiles), as the FSS can be illuminated and the response designed specifically to transmit through a dielectric material, or a series of dielectric materials.

FSS-type sensors can be applied to current/future pressurized vehicles, including launch vehicles to sense strain changes for warnings from impacts or potential leaks, providing additional safety for both flight and ground crews. FSS sensors can be embedded in habitat structures for the ISS and Lunar/interplanetary exploration. These low mass, wireless, unpowered, passive, and non-contacting sensors are easily incorporated into metallic or inflatable habitat structures without increasing mass, power requirements, cost, or EM environment.

The U.S. faces a backlog of infrastructure inspections. FSS sensors can provide long-term monitoring for deformations in structures, such as bridges and dams, and can be applied to structures in areas subject to natural disasters (hurricanes and earthquakes). As the aerospace industry adopts more composites, FSSs can be incorporated into aerospace structures such as fuselages or wing skins.

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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