On the Development and Testing of a 120 mm Caliber Double Pulse Motor (DPM)

This report summarizes the major results of a 120 mm caliber Double Pulse Motor (DPM) development and testing program conducted at Co. Bayern-Chemie/Protac, Germany. The design of the rocket motor was kept relatively simple in order to be able to concentrate efforts on DPM testing and the functional proof of critical motor components such as Pulse Separation Device (PSD), internal thermal insulation of the Pulse 1 motor, and nozzle-throat material. A test series of two singleand four double-pulse test-firings was conducted with pulse separation times of 1 s and 30 s, and motor soak-temperatures ranging from ° 30...C to +65...C. All conducted test firings have been successful, without any failure, and highly repeatable in terms of motor and component performance. The PSD with consumable Aluminum burst-diaphragm did not only satisfy the requirement of being a hotgas pressure seal during pulse 1 operation, but also worked reliably during pulse 2 pressurization and subsequent diaphragm burst. Most importantly, the consumption of the open Aluminum diaphragm by the pulse 2 hot gases did not lead to the formation of ejecta. Also, the pulse 1 insulation and nozzle throat material were found to withstand the first thermal loading of pulse 1, the intermediate cool-down phase, and the second thermal loading during pulse 2 operation.