| In order to better predict the erosion rates of carbon-cloth phenolic (CCP) nozzle material along the surface of solid rocket motor (SRM) nozzles, it is necessary to improve the understanding of the thermochemical and mechanical erosion processes of CCP nozzle material under realistic motor operating conditions. To this end a subscale SRM with an aluminized composite solid propellant has been used to examine nozzles constructed of CCP material. A main feature of the subscale SRM is an X-ray translucent test section. This allowed a real-time X-ray radiography (X-ray RTR) system to capture a sequence of images of the nozzle during the operation of the SRM. Overall, four CCP nozzle test sample configurations were investigated: 45° ply-angle MX-4926N, 45° ply-angle LR1406, 70° ply-angle MX-4926N, and 70° ply-angle MX-4926. Upon enhancement and analysis of image sequences captured with the X-ray RTR system, the recession behavior of the entire nozzle surface, near throat erosion rate, and char/virgin interface location of these nozzles samples was examined. From the time variation of instantaneous nozzle surface location, it was observed that the converging portion of the CCP nozzle regressed at much higher erosion rates than the throat region. In addition, examination of the deduced throat height variation with time showed a period of contraction of the nozzle throat. This period was followed by a nearly constant recession of the nozzle throat. However, in many cases the erosion rate did vary over the course of the test firing and, in a few, dramatically. The largest difference in CCP material performance was between the LR1406 and the other materials (MX-4926N and MX-4926) independent of ply-angle. While, the effects of ply-angle variation were difficult to establish by examination of MX-4926N nozzle samples at the two ply-angles studied (45° and 70°). |
