AiMT Advances in Military Technology Vol. 6, No. 1, June 2011 Geometric Coefficients Modifications of Surface Non-Treated Seven-Perforated Nitrocellulose Powder J. Štrba1* and J. Kusák2 1 University Pardubice, Institute of Energetic Materials, Pardubice, Czech Republic 2 Prototypa-ZM, Brno, Czech Republic The manuscript was received on 19 December 2010 and was accepted after revision for publication on 15 February2011. Abstract: Calculating of the interior ballistics characteristics using seven-perforated nitrocellulose powder in cartridge assemblies can be used in special techniques and in special projectile sets. Accuracy of interior ballistics characteristics calculations influences construction solutions of special techniques and ammunition; main utilization is in armed forces special techniques and ammunition for country defence. Originally derived relations make geometric coefficients solution of non-treated seven-perforated powder more accurate and easier to use. Keywords: Interior ballistics, interior ballistics characteristics, ammunition, gun, nitrocellulose powder. 1. Preparing Gun and Ammunition Using seven-perforated nitrocellulose powder in substantial range different calibres cartridge sets is a long-term common routine, which has been a worldwide practice of ammunition producers for about 80 years. In technical literature the powder combustion process description differs author to author and is not always practically applicable. In a factory, which produces heavy artillery weapons, it is a common practice to substitute seven-perforated grains by single-perforation grain in interior ballistic computations using conversion of its weight by means of a specific coefficient. We have conducted an experiment when a total of 18 shots from a fully charged 122 mm H D-30 gun using projectile filled with an inert charge was shot. The barrel of the gun was equipped with six strain gauges, as follows [1, 2]: * Corresponding author: Halalovka 46, 911 08 Trenčín, Slovak Republic, phone: +421 902 989 811 or +421 903 478 701, E-mail:
[email protected] 48 J. Štrba and J. Kusák 1 piece on the chamber, 1 piece just beyond the transition cone, 1 piece in a place where the bullet is supposed to be in the time of reaching the maximum pressure and other 3 pieces uniformly placed towards the end of the barrel. Fig. 1 122 mm H D-30 gun provided with strain gauges Fig. 2 Powder charge Powder charge contained units relatively to the total weight of the charge as follows: black powder 0.73 %, 49 Geometric Coefficients Modifications of Surface Non-Treated Seven-Perforated Nitrocellulose Powder 49 locking powder 1.93 %, single-perforation nitrocellulose powder 5.07 %, seven-perforated nitrocellulose powder 92.27 %. Surface of nitrocellulose powder was not treated and the test