Temperature sensitivities of energetic binder propellants

Abstract

The temperature sensitivity of several MURI Phase II propellants have been measured using the ultrasonic burning rate measurement technique. The results presented here are for the two Thiokol Phase IIBAMMO/AMMO propellants and the two Alliant baseline propellants. One propellant from each set was metallized. The BAMMO/AMMO propellants contained AP. The Alliant propellants had HTPE binders and AP and AN as oxidizers. The BAMMO/AMMO propellants exhibited higher temperature sensitivities that the HTPE/AP/AN propellants. Nomenclature a, b Constants characterizing the speed of sound as a function of pressure C Speed of sound E Propellant Thickness P Pressure T Propagation time ap Propellant temperature sensitivity r Temperature Introduction The Multidisciplinary University Research (MURI) program on Novel energetic Materials to Stabilize Rockets includes a task to measure propellant combustion characteristics. Thiokol Corp. supplied a total of 11 mixes of biplateau propellant for this study the first year. These propellants are known as MURI phase I propellants. CSD, Alliant, and Thiokol have provided additional propellants for this effort. The CSD and Thiokol propellants are known as 'Student ^Member 5 Associate Member Copyright © 2000 by Marlow D. Moser Published by the American Institute of Aeronautics and Astronautics, Inc., with permission. This work was sponsored partly by the University of Alabama in Huntsville and partly by the Caftech Multidisciplinary University Research Initiative under ONR Grant No.~N00014-95-l-1338, Program Manager Judah Goldwasser. Phase II propellants and the Alliant propellants are known as Phase in propellants. Two Thiokol Phase n propellants which are BAMMO/AMMO binder with AP and the two Alliant baseline propellants were tested and the results presented here. The burning rates were measure with the ultrasonic technique at temperatures of 24 and 60°C. The burning rates and temperature sensitivities are presented. Procedure The ultrasonic pulse-echo technique has been developed by ONERA in the 80's and utilized at several other places'''. It has been used at UAH for several years to measure steady state burning rate6, temperature sensitivity7, and propellant response function. Ultrasonic Technique: The ultrasonic technique is utilized in these propellant tests. This technique is highly effective for measuring the instantaneous thickness of the propellant The ultrasonic transducer emits a sound pulse that propagates through the propellant to the propellant surface where it is then reflected back down to the transducer. The same transducer then detects the returning pulse. By measuring this propagation time and knowing the speed of sound through the propellant, the instantaneous thickness can be determined for each pulse emitted by the ultrasonic transducer. The burning rate is determined by taking the time derivative of the instantaneous thickness. The process is shown schematically in Fig. 1 along with a typical waveform. The ultrasonic transducer sends a pulse through the coupling material, which is typically epoxy, and to the propellant. Wherever an impedance mismatch exists an echo is produced. Care is taken to match the impedance of the coupling material and propellant to minimize this echo. The propellant/buming gas interface produces (c)2000 American Institute of Aeronautics & Astronautics or Published with Permission of Author(s) and/or Author(s)' Sponsoring Organization.