Bally Ribbon Mills (BRM) is working on a novel approach to structural health monitoring (SHM) for potential use on inflatable habitat structures being developed for NASA space missions. The new method uses sensors embedded in the flexible structural restraint webbing layers to capture data on stress, strain, creep, and micrometeoroid impacts.
The work is being done in partnership with Luna Innovations, Inc., an American developer and manufacturer of fiber-optics and terahertz-based technology products for aerospace.
BRM has been working with Luna since 2007, when Luna’s NASA contact suggested the partnership to provide a sample that could be used to demonstrate Luna’s technology capabilities. Undertaken as part of the Small Business Innovation Research (SBIR) program, the project aimed to demonstrate the integration of optical fiber sensing technology into composites to monitor the vacuum assisted resin transfer molding (VARTM) process.
BRM successfully wove the material and passed it along to Luna. Fast-forward 15 years, and Luna came back to collaborate with BRM on a NASA multistage grant award examining whether the embedded sensor technology could survive all the required manufacturing processes for use in inflatable habitat structures being developed for upcoming space missions. The long-term goal was to be able to measure stress, strain, and temperature, as well as pinpoint the location of strain. For example, if a micro meteorite hits the shell fabric and causes point source stress, scientists could know where it hit and be able to gauge the potential for failure.
BRM successfully produced the material, overcoming two key webbing manufacturing process challenges along the way: ensuring that the sensor is not damaged during the weaving; and ensuring that the weave design is precise enough to place sensor ingresses and egresses in the proper locations within the weave structure’s surface.
Luna Innovations then tested the fiber optic sensors woven into the flexible structural restraint layer webbings on an inflatable test article with a diameter of 0.61 meters (2 feet) fabricated from Vectran®, a manufactured filament fiber with a liquid-crystal polymer chemistry. Experiments successfully demonstrated creep sensing, pressure sensing, and detection of damage location and magnitude. NASA has also been conducting hypervelocity impact tests on the inflated habitat.
Currently, a one-third scale, 2.74 meter diameter (9 feet) inflatable with embedded structural health sensors is being used for creep and burst testing at NASA’s Johnson Space Center to validate the bench-top engineering and design of the habitat’s structural components. The plan is to build four one-third scale models and one full-scale model to validate the system for human space flight.
While the goal is to complete the project by 2023, the final schedule will be based on successful orchestration of raw material supply, component procurement, manufacturing, assembly, testing, test-facilities scheduling, and funding. Based on previous success with the prior phases and benchmarks, BRM is currently contracted to produce the next set of sensorized webbing.
The new sensor-based technique for monitoring the health of the flexible softgoods restraints on inflatable living structures shows great promise. If the embedded sensing technology proves to be successful, it could be included in future space mission habitation structures, including the Lunar Gateway or Mars missions.