ULTRASENSITIVE INTERFEROMETRIC DETECTION OF LAUNCH VEHICLE POLLUTANTS

The 1990 Clean Air Act Amendments list nearly two hundred toxic materials that must be regulated. Among these are hydrazines, compounds that are used as rocket fuels. Air Force compliance with Environmental Protection Agency (EPA) regulations will dictate the investigation and careful monitoring of the emissions of hydrazines to the atmosphere, particularly during the fueling and launching of rocket vehicles. However, current techniques to monitor atmospheric pollutants are not sensitive and specific enough to hydrazines to satisfy future EPA requirements. To fill this need, Science Research Laboratory (SRL) proposes to develop a portable interferometric pollution monitor (IPM) with the capability of measuring hydrazine and other pollutants in situ and continuously at the parts-per-trillion (ppt) level. The basis of this instrument is the interferometric measurement of the optical-path change that occurs immediately after a pulsed carbon-dioxide laser beam is absorbed by the pollutant present in one arm of the interferometer. An instrument that utilizes a line-tunable, pulsed carbon-dioxide laser can be tuned through the near-infrared absorption spectrum of hydrazines to determine their concentration in the presence of other absorptive species. An IPM will be sensitive to a concentration of several parts per trillion, orders of magnitude better than instruments based on other approaches to detect such toxic species. Such an instrument will be ideal for monitoring compliance with EPA regulations and for continuous measurement of the effectiveness of control processes that minimize the emission. The proposed Phase I feasibility study will be followed by a Government-sponsored proof-of-principle Phase II demonstration.