To support development of atmospheric balloons and gossamer structures, NASA requires a capability for real-time, dynamic strain measurement in thin polymeric membranes during deployment and flight. This capability will provide quantitative test data to inform balloon design efforts, as well as enable real-time monitoring of material state during flight. Existing technologies include wired or wireless electrical or fiber-optic strain gauges, impractical to implement on a thin membrane; photogrammetric techniques that require multiple cameras, detailed knowledge of nominal balloon geometry, and significant post-processing computation; and exotic optical techniques that are unsuited for large scale, dynamic balloon testing and flight. We will develop a completely novel measurement system based on an optically-interrogated thin-film elastomer strain gauge that will provide sensitive, real-time, two-component strain measurement in balloon gores. A large number of the low modulus, thin-film sensors distributed across the balloon will be interrogated remotely at high frequency with a single camera that can be mounted on the payload.
Given the high cost of payload launch, NASA often develops lightweight technologies. These include membrane systems such as balloons, solar sails, inflatable booms, and parachutes, along with thin structures such as solar panels, spacecraft skins, and pressure domes. In each case, our novel low modulus, remotely interrogated strain gauge will be of value for both testing and development along with in-service control feedback and health monitoring.
Because of its unique properties such as low elastic modulus, ease of application, and remote interrogation, we anticipate that this novel sensor will have a broad array of applications. It will find commercial use in testing of flexible structures such as sails, balloons, tents, and architectural panels. It might also be used in novel scientific applications, such as measuring the strain in human skin during locomotion or tree limbs under wind load.