Vent

—As the rate of combustion of the composition is independent of the pre ure of the gas in the bore, it follows, that if the size of the vent be contracted, the flow of gas through it will be accelerated. The strength of the case, and the friction of the gas, which increases as the vent diminishes, alone limit the reduction of the size of the vent. For vents of the same size, but of different shapes, that one which allows the gas to escape most freely will be most favorable to the flight of the rocket. A conical form of vent, with the larger orifice next to the bore, will allow the gas to escape more rapidly than one of cylindrical form.