The Competition between Tube Heating and Muzzle Velocity in Stick Propellant Gun Charges
Memorandum rept. Apr-Oct 1983
ARMY BALLISTIC RESEARCH LAB ABERDEEN PROVING GROUND MD
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In this report, NOVA, a one-dimensional, two-phase-flow, interior ballistic code, is used to examine in detail the trade-offs between one- and multi-bundle stick configurations and between calculated heating of the chamber and tube walls and calculated muzzle velocity. The system chosen for these calculations is a Navy 5-inch, 54-caliber gun firing the HIFRAG projectile and using a charge made up of nominal M31 propellant. The results provide the charge designer an appreciation of the tradeoffs between the hydrodynamic effects which on one hand increase muzzle velocity and on the other hand may seriously alter heat transfer processes. The tradeoffs between using a single bundle of slotted stick propellant compared with several two through five bundles were studied. It was anticipated that more bundles might lead to more movement of the propellant down the gun tube, in the manner of granular propellant. That would dissipate the anticipated heat over more of the chamber and gun tube. Thus, heating of the chamber at the origin of rifling would be reduced, and that would reduce critical barrel erosion. NOVA predicts that the sticks will move away from the breech as they burn, and that the multiple- bundle charges will spread out well past the origin of rifling before burnout. Nonetheless, as one goes from one long bundle of sticks to 5 short bundles, the maximum gun bore surface temperature at the origin of rifling is predicted to drop only 20K. If one adds a bit more propellant to the five-bundle charge in order to regain the ballistic performance of the one-bundle charge the heating at the origin of rifling rises. In the end, going from one long bundle to five reduces the predicted peak temperature at the origin of rifling only 11 K.