An innovative method for Measurement of Insulation thickness of Fired Solid Rocket Motor

摘要

Thermal insulation system of a typical case bonded solid rocket motor consists of polymeric ablative material which is bonded on to the inside surface of the metallic/composite motor casing. A further coat of thin layer of liner is applied followed by the propellant which is cast in-situ. During the firing, insulator provides thermal insulation against high temperature combustion process inside the rocket chamber. Design of the insulation system is a complex job involving crucial assessment of ablative regression of the exposed insulator. Propulsion system designers carry out series of actual motor firings for monitoring the adequacy of thermal insulator. The design is validated by actual measurement of insulation thickness in unfired and fired rocket motor. Thereby fast and reasonably precise measurement of insulation thickness at various locations along the length and periphery of motor is of paramount importance in these experiments. Rocket motor was positioned on a lathe machine. Measurements were carried out using a suitably positioned dial gauge mounted on a boring bar which was further secured on the tool post. A mirror arrangement was also fitted at one end of the boring bar (near the dial gauge) to enable fast and easy read-out from the open end of the rocket motor. Methodology to carry out the measurement was developed and readings were taken at various positions along the length and periphery of the rocket motor. Comparisons were made with the readings and generally observed erosion (ablation) profile. The measured profile of the eroded (ablated) insulation was in line with the usually observed trend. Author(s) of this paper faced a number of engineering challenges which were overcome using simple and effective concepts and ideas which are discussed in this work.