Investigation of the Feasibility of Measuring The Chamber Temperature of Solid Propellant Rocket Motors by Using Microwave Attenuation Measurements

摘要

The analysis of a plane wave propagating through a homogeneous plasma region of dimensions large compared to the signal wavelength has shown that the wave attenuation can be related to physical parameters of the plasma such as electron density, temperature, and pressure. In this report, the plasma in the combustion chamber of a small solid propellant rocket motor is used to investigate the feasibility of determining the temperature of the plasma by using microwave attenuation data. Potassium perchlorate is substituted for some of the ammonium perchlorate in the propellant to give an electron density that produces an easily measurable attenuation. The theoretical results show that for a known propellant composition and potassium perchlorate concentration, both the plasma temperature and chamber pressure at equilibrium may be found from one attenuation measurement. Also, for a known thermodynamic state of the plasma, the electron density may be found from the attenuation data. The method of microwave analysis is shown to be very useful in the study of transient phenomena in that no transducers are required; hence, the time response of the measurement is limited only by the microwave detection circuitry. This technique may be used to study localized disturbances within the plasma region. (Author)