Human Systems/Subsystems Research

On-Board Oxygen Generation Systems (OBOGS) are currently monitored using oxygen sensors of the electrochemical variety. These sensors are subject to degradation with storage or use, and therefore require periodic recalibration or replacement. The newer zirconia sensors furthermore operate at 750C, generally require a reference gas, and do not measure oxygen at 100% concentration reliably. It is desirable to monitor to 100%, O2 cylinder gas, which is used at high altitude and as a back-up supply in case of OBOGS failure. Oxigraf proposes to use laser diode absorption spectroscopy in the visible spectrum to monitor oxygen concentration. The Oxigraf sensor in development for the past five years measures oxygen concentration in medical environments from 5 to 100% with +- 0.2% accuracy with fast 0.1 second response. This sensor can be perfected in Phase I to measure at aircraft altitude and be insensitive to vibration. In Phase II, the mean time between maintenance of the sensor can be extended from 1,000 to perhaps 15,000 hours using available improved laser diodes. In addition, aircraft packaging, electronic interfacing, and thermal, vibration, and other environmental testing can be achieved. In Phase III< Normalair-Garrett of Yeovil, England, an established supplier of aircraft oxygen systems, is prepared to pursue adoption on military aircraft systems provided the technology is perfected as proposed. A letter of support is attached on page 23 of this proposal.