title: Invited article: Time accurate mass flow measurements of solid-fueled systems.
abstract: A novel diagnostic method is described that utilizes a thrust stand mass balance (TSMB) to directly measure time-accurate mass flow from a solid-fuel thruster. The accuracy of the TSMB mass flow measurement technique was demonstrated in three ways including the use of an idealized numerical simulation, verifying a fluid mass calibration with high-speed digital photography, and by measuring mass loss in more than 30 hybrid rocket motor firings. Dynamic response of the mass balance was assessed through weight calibration and used to derive spring, damping, and mass moment of inertia coefficients for the TSMB. These dynamic coefficients were used to determine the mass flow rate and total mass loss within an acrylic and gaseous oxygen hybrid rocket motor firing. Intentional variations in the oxygen flow rate resulted in corresponding variations in the total propellant mass flow as expected. The TSMB was optimized to determine mass losses of up to 2.5 g and measured total mass loss to within 2.5% of that calculated by a NIST-calibrated digital scale. Using this method, a mass flow resolution of 0.0011 g/s or 2% of the average mass flow in this study has been achieved.
authors.affiliation: Department of Aerospace and Mechanical Engineering, University of Southern California, Los Angeles, California 90089, USA.
authors.forename: Jordan D
authors.initials: JD
authors.lastname: Olliges
authors.forename: Taylor C
authors.initials: TC
authors.lastname: Lilly
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Joslyn
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Ketsdever