Investigation Into the Internal Aerodynamic Design and Associated Errors in a Fast Descent Ducted Sonde for the Measurement of Atmospheric Pressure and Temperature (AMPARS Phase 2).
WEAPONS SYSTEMS RESEARCH LAB ADELAIDE (AUSTRALIA)
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This report investigates aspects of the atmospheric pressure and temperature measuring technique for a fast descent sonde. The sonde, which is drogue stabilized, is released from a rocket vehicle in the vicinity of the apogee which is 20 km. Low speed wind tunnel tests have been conducted to check any errors in the measurement of atmospheric pressure resulting from the positioning of the static tube mounted inside an internally ducted sonde. It shows that no errors occur for the chosen position up to an external airflow incidence of 30 deg. Errors owing to heat transfer into a centrally mounted thermistor are examined for various thermistor positions and incidence angles and the thermistor response time has been measured and compared with theoretical results. Overall it is shown that the duct design is suitable for a fast descent sonde with errors well below those specified by the Bureau of Meteorology for standard ascending meteorological sondes. Author