Alkali Seeded Propellant for ETC: Closed Vessel Experiments

The report describes experimental work within Electrothermal-Chemical launch (ETC) with the ambition to improve the performance of guns. ETC is a launch technology in which electric energy is used to ignite andlor stimulate the combustion of the propellant charge in a gun. In the present work is investigated if it is possible to stimulate the combustion by conducting a current through the flame itself. To improve the electric conductivity of the flame it has been necessary to develop new propellant compositions with alkali additives. These new propellants may prove useful in other ETC-principles by making it easier for the plasma to survive. Testing of the recently developed propellants is carried out in a closed vessel, a bomb, which for the ETC experiments is connected to an electric pulsed power supply. A fast burning booster charge raises the pressure to a desired level. The propellants subjected to the test have been prepared in the shape of a fairly thick, homogeneous slab, making them bum a comparatively long time and thus facilitates the study of the burning characteristics. This report describes the ETC bomb used for the experiments and a few propellants that were prepared with alkali additive. Thermochemical calculations and estimation of flame conductivity are presented as well as experiences from experiments performed so far. The experimental equipment and measurement technology are found to be suitable for studies of how the burning rate of a homogeneous propellant slab can be affected by an electric current supplied through the flame zone or through the combustion products at a preselected pressure level.