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15 July 1993 Nonintrusive cryogenic propellant sensing with millimeter-wave/EM beams
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Proceedings Volume 1874, Infrared and Millimeter-Wave Engineering; (1993)
Event: OE/LASE'93: Optics, Electro-Optics, and Laser Applications in Scienceand Engineering, 1993, Los Angeles, CA, United States
In this paper experimental results of cryogenic tankage mass measurements and descriptions of level sensors using optical and millimeter wave signal beams are presented. The discussed results are based on a 100 GHz frequency modulated radar mass sensor. Test results are compared with a similar system which makes use of a laser beam and a frequency modulated microwave subcarrier. In addition the performance of a laser triangulation level sensor is presented which is suitable for normal gravity applications. Performance prediction in terms of the resolution and measurement accuracy are discussed with emphasis on the measurement difficulties encountered while using liquid hydrogen under normal gravity conditions. For a mass sensor the small 11% refractive index change between an empty and a filled tank of hydrogen causes a loss of measurement accuracy by a factor of ten, as compared to a level sensor. This loss is common to all mass propellant sensing systems, including the conventional capacitance probe sensor. Special processing techniques are indicated. Extensions of the presented millimeter wave mass sensor concept for micro and zero gravity cryogenic systems and for other special space related propellant conditions such as slush hydrogen are discussed.
© (1993) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
J. Martin Osterwalder and T. W. Nyland "Nonintrusive cryogenic propellant sensing with millimeter-wave/EM beams", Proc. SPIE 1874, Infrared and Millimeter-Wave Engineering, (15 July 1993);

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