Plastic optical fiber hydrogen detection sensor systems for harsh environment in aerospace application

This paper describes the 1st successful Plastic Optical Fiber (POF) cable and Glass Optical Fiber (GOF) hydrogen detection sensor systems developed for the Boeing Evolved Expandable Lunch Vehicle (EELV) Delta IV Launch Vehicle harsh environment of engine section. H 2 sensors are necessary to monitor the possible leak of rocket prior launch to avoid explosion, which can be highly dangerous. Due to harsh environment of launch vehicle, we developed the first combination of 100 m POF and glass fiber H 2 sensors. The hydrogen sensor consisted of optrodes distributed at multiple locations along a fiber optic cable-based network. These hydrogen sensors were used on the Common Booster Core (CBC) of Delta IV had to perform in temperatures between -18° C and +60° C. The hydrogen sensor sensitive chemistry was fully reversible and had demonstrated a response to hydrogen gas in the range of 0% to 10% with a resolution of 0.1 % and a response time of 5 seconds measured at a gas flow rate of 1 cc/mm. The optical signature of the optrode in the visible spectrum varied proportionally to the local hydrogen gas concentration. To qualify the POF and fiber optic cables, performed detail investigation for attenuation loss, thermal, humidity, temperature, vibration and accelerate testing for life expectancy. Extensive networking using LabView were carried out for lab and actual field demonstrations.