Study of Solid Hydrogen Pellet Speed in a Gas Gun–Type Injector

Based on the ideal gas gun theory (IGT) approximation, an analytical study of solid hydrogen pellet motion in a gas gun–type pellet injector has been performed. A parametric investigation has been conducted to study the pellet speed dependence on the gun characteristics and the propellant conditions. The calculations have been verified by applying various experimental data reported from the literature. Experimental results are within 70% to 90% of the ideal IGT and are in line with global predictions. Calculations indicate that the speed of the pellet has a strong dependence on the propellant pressure and its mass, and a weak dependence on the length of the gun barrel. In addition, the effects of shock waves due to the sudden opening of the propellant valve and some nonideal effects, such as the effect of friction at the propellant pellet–wall interface, have been studied. The results of the calculations have been verified by applying them to the experimental results.