Advances in developing a signal processing tool for rocket motor measurements

Solid rocket propellants are critical components in weapons, automobile airbag, and satellite technologies. The instantaneous rate at which a propellant burns is an essential design parameter in all of these applications. While existing formulas accurately predict burn rates for most solid engine propellants, these standard equations assume that the burn is homogeneous along an axis parallel to the burning surface. This assumption is not valid for solid fuel ramjets (SFRJ) and certain advanced solid rocket motors (SRM). For this reason, Aerojet Corporation is developing a novel ultrasound technology to measure burn rate directly during live-fire tests. This paper describes recent progress on the design of algorithms to identify the location of the burning propellant surface from noisy ultrasound time-series data. The key challenges are to identify the ultrasound echo corresponding to the burning surface for each measurement pulse and to isolate a single point within this echo which is consistent across pulses. We describe a new algorithm for this purpose. Using data sets from both live-fire and laboratory experiments, we compare predictions based on this algorithm to those based on alternate approaches. Also described is the redesign of a prototype human-computer interface that is used to record and display burn rate data