The burning rate of propellants plays a vital role among the parameters controlling the operation of solid rocket motors, therefore, it is crucial to precisely measure the burning rate in the successful design of a solid rocket motor. In the present review, a brief description of the methods for the determination of the burning rate of solid rocket propellants is presented. The effects of various parameters on the burning rate of solid propellants are discussed and reviewed. This review also assesses the merits and limitations of the existing different methods for the evaluation of the burning rate of solid rocket propellants.

Various Methods for the Determination of the Burning Rates of Solid Propellants : an Overview

This article illustrates the application of an ultrasonic pulse–echo technique to determine the burning rate of a composite solid propellant as a function of pressure. An evaluation of the measurement uncertainty of the method is also presented. Unlike the more traditional strand burner techniques, where dozens of constant pressure tests are necessary, the ultrasonic technique measures the burn surface position thousands of times per second as the pressure varies. This reduces the number of tests necessary to determine the ballistic characteristics of the propellant by an order of magnitude. This work presents new methods to characterize the changing speed of sound in the propellant and quantitative estimates of the measurement uncertainty in the burning rate measurement. The results of the uncertainty analysis showed that the measurement is accurate to around 4%. The propellant samples were tested in a closed-combustion vessel, under pressurization rates of up to 15.8 MPa/s. The data obtained with the cl...

Direct ultrasonic measurement of solid propellant ballistics

The development of an ultrasound technique for precisely measuring the instantaneous regression rate of a solid-rocket propellant under transient conditions is reviewed. The technique is used to measure the burning-rate response of several solid propellants to an oscillatory chamber pressure with a frequency of up to 300 Hz. This measurement is known as the propellant's pressure-coupled response function and is used as an input into rocket stability prediction models. The ultrasound waveforms are analyzed using cross-correlation and other digital signal processing techniques to determine burning rate. Digital methods are less prone to bias and offer greater flexibility than other techniques previously used. The resulting data are corrected for compression effects. The effects of a changing thermal profile on the measurement are discussed. Other phenomena that may corrupt the measurement, such as surface roughness, are also covered. Results of the experiments are compared to data from two other measurement techniques: a T-burner and a magnetic flowmeter.

Evaluation of ultrasound technique for solid-propellant burning-rate response measurements

Review of ultrasonic technique for steady state burning rate measurements

A method of solid-propellant burning rate measurement by ultrasonic technique using small cylindrical specimens was developed for routine measurements required in the solid-propellant manufacturing industry. The measurement procedure is discussed in detail. Emphasis is given to accuracy in measurements, ease of operation, minimization of manpower, and savings of cost and time. With this in view, new adaptations in specimen preparation, test procedure, and data processing are incorporated. Burning rates of more than 300 batches of aluminized ammonium perchlorate/hydroxyl-terminated polybutadiene composite propellant of three different compositions were measured. The results showed that the standard deviation in the measurements for a propellant batch was less than 1%. It was also demonstrated that the performance of full-size solid motors can be predicted with good accuracy by these burning rates with a small augmentation factor.

Industrial Adaptation of Ultrasonic Technique of Propellant Burning Rate Measurement Using Specimens

The instantaneous burning rate of an aluminized composite solid propellant in a ballistic evaluation motor was measured continuously using an ultrasonic pulse-echo technique. The motor was designed to operate over a range of pressure from 2.5 to 4.5 MPa during its burning period. Hence, the burning-rate data could be obtained at different pressures directly from a single motor  ring itself, and the data were used to determine the pressure dependence of the burning rate. Thus, the technique is shown to overcome the need for carrying out several strand tests or ballistic evaluation motor tests, each at a different pressure, for characterizing a solid propellant burning rate.

Determination of Pressure Dependence of Burning Rate in Solid Motors Using Ultrasonic Technique

With the use of the ultrasonic pulse-echo technique, local burningrates aremeasured at different radial locations across the web during static tests of center-perforated solid propellant rocket motor grains. The measurement shows a higher burning rate in the midweb region and a lower burning rate toward the port and motor case. The measured motor pressure history could be very well simulated by using the measured local burning rates. Thus, direct evidence is provided that the variationof the burning rate across the web is the cause of themidweb anomaly in chamber pressure widely reported in solid motors with center-perforated grains.

Direct Evidence of Spatial Burning Rate Variation as Cause of Midweb Anomaly

The ultrasonic pulse-echo technique has been applied for the measurement of instantaneous burnrate of aluminised composite solid propellants. The tests have been carried out on end-burning 30 mmthick propellant specimens at nearly constant pressure of about 1.9 MPa. Necessary software forpost-test data processing and instantaneous burn rate computations have been developed. The burnrates measured by the ultrasonic technique have been compared with those obtained from ballisticevaluation motor tests on propellant from the same mix. An accuracy of about +- 1 per cent ininstantaneous burn rate measurements and reproducibility of results have been demonstrated byapplying ultrasonic technique.

http://publications.drdo.gov.in/ojs/index.php/dsj/article/download/3899/2240

M. S. Padmanabhan

Papers

Determination of Pressure Dependence of Burning Rate in Solid Motors Using Ultrasonic Technique

Direct Evidence of Spatial Burning Rate Variation as Cause of Midweb Anomaly

Application of Ultrasonic Technique for Measurement of Instantaneous Burn Rate of Solid Propellants .