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This paper describes the successful test of a multi-point fiber optic hydrogen sensor system during the static firing of an Evolved Expandable Launch Vehicle (EELV)/Delta IV common booster core (CBC) rocket engine at NASA's Stennis Flight Center. The system consisted of microsensors (optrodes) using a hydrogen gas sensitive indicator incorporated onto an optically transparent porous substrate. The modular optoelectronics and multiplexing network system was designed and assembled utilizing a multi-channel opto-electronic sensor readout unit that monitored the hydrogen and temperature response of the individual optrodes in real-time and communicated this information via a serial communication port to a remote laptop computer. The sensor packaging for hydrogen consisted of two optrodes --one doped with an indicator sensitive to hydrogen, and the other doped with an indicator sensitive to temperature. The multi-channel hydrogen sensor system is fully reversible. It has demonstrated a dynamic response to hydrogen gas in the range of 0% to 4% with 0.1% resolution and a response time of ≤15 seconds. The sensor package was attached to a custom fiber optic ribbon cable, which was then connected to a fiber optic trunk communications cable (standard telecommunications-grade fiber) that connected to the optoelectronics module. Each board in the expandable module included light sources, photo-detectors, and associated electronics required for detecting hydrogen and temperature. The presentation would discuss the sensor design and performance data under field deployment conditions.

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