23rd international symposium on ballistics, Tarragona, Spain 16-20 April 2007.The artillery projectile range can be increased by decreasing the aerodynamic drag by means of ejecting hot gas from a base-bleed unit into the base flow of the projectile.
A new base-bleed/hollow-base construction is suggested. In this concept, a hollow chamber in the projectile base is closed at some point of the intermediate ballistic phase and subsequently, the in-captured high pressure propellant gas is leaked out through small holes.
The out-bled mass flow is estimated to last only the first few kilometers of the flight. However, the first kilometers are the most important from the point of view of extended range, and the new concept is believed to be a promising choice, especially taking into account the minimal effect on the dispersion of rounds. No fragile propellant unit is present and the technical risk is in finding out the proper valve mechanism to keep the captured gas in the chamber.
Some preliminary computations are made to estimate the potential of the new unit to extend the range. The gas leakage efficiency is assumed to be of the same order as in case of an ordinary unit. However, the high-velocity jets might provide a way to control the main flow pattern around the base region and in this way, somewhat higher drag reducing efficiency might be obtained. Some CFD computations are needed to verify this assumption, but these are outside the scope of this preliminary study.
