Ultrasonic Method Applied to Full-Scale Solid Rocket Motors

Assessment of the Performance of Ablative Insulators Under Realistic Solid Rocket Motor Operating Conditions

“…The transducer senses this reflected wave, and its propagation time is proportional to the distance between the transducer and the interface. In ablative materials, the ultrasonic wave reflects primarily from the char-virgin interface, so the char surface is not detected [39]. The propagation time, unfortunately, is also a function of the material temperature (both local value and gradients through the material) and the stress-strain distribution in the material, which is related to pressure [39].…”

“…In ablative materials, the ultrasonic wave reflects primarily from the char-virgin interface, so the char surface is not detected [39]. The propagation time, unfortunately, is also a function of the material temperature (both local value and gradients through the material) and the stress-strain distribution in the material, which is related to pressure [39]. Despite this complication, the ultrasonic technique has been used extensively for determining the regression rate of solid propellants [38] [40] [41] and hybrid fuels [42] with satisfactory results.…”

“…ablative materials: the pressure effect is negligible, while the thermal profile variation is important. In fact, the effect of the thermal profile variation is so strong that the heat flux into the material has as much effect on the propagation time of the ultrasonic wave as the material recession [39]. Therefore, in order to obtain real-time recession rate data for an ablative material via the ultrasonic method, the transient thermal profile through the ablator must be known [43].…”

Measurement of solid propellant burning rates by analysis of ultrasonic full waveforms

“…This system, which aims to determine the solid propellant burning rates as a function of pressure, consists of four major parts: 1) a closed bomb that can be pressurized up to approximately 4,000 psi; 2) an ultrasonic signal acquisition system including a normal beam ultrasonic transducer, an ultrasonic pulser/receiver, a high speed A/D conversion board (with a sampling rate of 100 MHz) and connecting cable; 3) a pressure data acquisition system composed of a pressure gauge, a charge amplifier and A/D converting board (with a sampling rate of 1 MHz); and 4) a control computer which uses a specially developed application software for acquisition and analysis of ultrasonic full waveforms and pressure data (in the pre-test and the burning test) in order to invoke the burning rate as a function of pressure. Due to the fact that the thermal profile has no significant effect on the burning rate, the pressure-induced stress effect (known as the "pressure effect") has to be taken into account in order to correct the burning rate values [6]. The major hardware components, such as the ultrasonic pulser/receiver and the A/D boards, were carefully chosen so that the total system can acquire ultrasonic full waveforms and pressure data up to 2,000 times in a second.…”

Novel burning rate measurement technique for solid propellant by means of ultrasonics

“…Linear burning rates under steady conditions are usually obtained with the break wire method in a strand burner or with a small motor method. ONERA (French National Aerospace Research Establishment) developed an ultrasonic technique called the "round-trip technique," which can yield the burning rate characteristics of solid propellants in a sophisticated manner, and their device, electronic device for ultrasonic measurements (EDUM), is widely spread in the world and used in combustion studies of solid propellants [1][2][3][4][5][6][7][8][9][10][11][12][13].…”