Thomas Weise

A 540 kJ modular capacitive pulsed power supply system for basic investigations on ETC-performance

The investigations of the electrothermal control of the combustion of solid propellants to be applied in electrothermochemical (ETC) guns requires pulsed power supply systems which provide a high flexibility in pulse shape adjustment. In order to support the ETC gun investigations to be performed within the German ETC-programme at TZN a modular capacitive pulsed power supply system was designed, set-up and tested by TZN and has been in operation since May 1997. The paper describes the design of the system in detail and reports about the results of the checkout tests. The system consists of 540 kJ capacitive discharge modules with a maximum charge voltage of 30 kV each. The modules are crowbared by 33 kV semiconducting diodes. Triggered vacuum switches are installed at each module in order to provide sequential firing capability. The pulse shape of each module can be adjusted by the selection of its capacitance in four steps as well as by the selection of six different inductance values which are provided by the pulse shaping inductors. Up to now about 300 experimental shots have been performed with the system supplying different closed vessel set-ups with charge chamber volumes from 45 ml to up to 6.51. By making use of the high degree of pulse shape flexibility of the pulsed power supply a large amount of scientific information has been obtained so far in order to understand the physical relations between electrical energy conversion and propellant combustion.

Light activated semiconductors for ETC pulsed power applications

The integration of a capacitive pulsed power supply system into a combat fighting vehicle with ETC weaponization requires the development of compact PPS modules with a high reliability of their energy storage and pulse forming components. To fulfill these requirements a variety of switch technologies have been investigated for many years. This paper gives first results of the investigations on a new type of a semiconducting switch which is activated directly by an optical trigger input. The attractiveness of this switch is its lower trigger power requirement, its compact set-up, and its high reliability. Integrated breakdown diodes prevent the switch from a damage in case of a malfunction of the trigger system of one wafer. A high voltage set-up of this switch technology was tested under ETC conditions. The paper presents the test set-up as well as the results obtained from the experiments. In the conclusion of the paper, the impacts of this switch technology on the development of future ETC gun PPS modules is discussed.

Basic investigations in a 70-mm firing simulator

The realization of proper interior ballistic performance in a large-caliber electrothermal-chemical (ETC) gun requires a well-defined interaction of the plasma ignition system with ETC-tailored propellants and charge designs. Before testing the interior ballistic cycle in a large-caliber gun, basic investigations in closed vessels and firing simulators have to be performed. In order to conduct these investigations, a 70-mm firing simulator has been designed and fabricated at Rheinmetall, Unterluess, Germany. The paper gives an overview on the setup of the 70-mm firing simulator. In the following, the design of the propellant charge to be tested is described briefly. Results obtained from preliminary interior ballistic simulations on the charge setup are presented. An overview on the test program is given and results of firings at different propellant temperatures are described and evaluated.