Proof-of-concept Study of Smart Panel for Space Structures

Verification of a spacecraft structure is a process in which the structural mathematical model, usually finite element model, is compared with the test results to confirm the validity of the structural design. The ultimate structural requirements with the high accuracy and the high stability motivate space engineers to evaluate the structural issues, such as micro-vibration and zero thermal expansion, more precisely on the ground tests. In addition, it would be significant to verify the structural design using the data obtained on orbit since the ground test environments cannot be perfectly equal to the space environments. Author proposed "Sensor Integrated Smart Panel for Space Structure" to enable both the precise structural measurements and the verification on orbit. In this study, fiber optic sensors were integrated with a honeycomb sandwich panel, which consist of CFRP skins and Aluminum honeycomb core. The size of the panel is 300 mm x 300 mm and the weight is approximately 500 grams including mechanical inserts. Four sensor lines with over 30 FBGs were integrated between the CFRP skin and the honeycomb core in the process of bonding. The most remarkable feature of the panel is the design of the optical fiber interface at the edge of the panel. Optical connectors were also integrated with the panel and user (e.g. satellite integrator) can easily access to the FBGs with FC/APC interface without any special tools. Then, the panel was tested in the thermal vacuum chamber to evaluate the durability and the performance of the sensors under the space environment. As a result, the smart panel could endure high vacuum (below 10(-5) Pa) and low temperature (below 200K). The sensor output was very stable and low noise, 0.6 mu epsilon in standard deviation within 1 degrees C temperature variation in 30 minutes.