Ballistic Criteria for Propellant Grain Fracture in the GAU-8/A 30 MM gun
Abstract
From plots of the square of the muzzle velocity compared to peak pressure (proportional to the piezometric efficiency) versus temperature derived from multiple GAU-8 gun firings over the temperature range minus 50 degrees Centigrade to plus 70 degrees Centigrade, it is possible to derive criteria for propellant grain fracture during the ballistic cycle. Propellants which do not undergo loss of mechanical integrity show a linear relationship between the square of the muzzle velocity compared to peak pressure and temperature, with negative slopes. In this study it has been found that the single base propellants, CIL 3532 and CIL 3331, the current USAF GAU-8/A propellant (GAU-8 extract) and three high performance, cool burning candidate propellants for the GAU-8/A gun (IH.3, IH.5 and ABL 20/21) do not show detectable grain breakup during the ballistic cycle. Propellants which undergo grain fracture during the ballistic cycle exhibit marked reduction in piezometric efficiencies and consequent deviations from the usual linear relationship between the square of the muzzle velocity compared to peak pressure and temperature. Subambient temperature brittle fracture is usually also accompanied by marked scatter of the square of the muzzle velocity compared to peak pressure values leading to high standard deviation error estimates. Such behavior has been observed in this study for all the triple base propellants Nos. 24, 34, 35, 46, 50/51/52 and 55. However, a triple base propellant (M30 MOD) containing ground nitroguanidine (as opposed to the unground nitroguanidine contained in the other triple base propellants investigated) exhibited a marked improvement in low temperature brittle fracture properties.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 01, 1982
- Accession Number
- ADA118376
Entities
People
- Bertram K. Moy
- Clifford W. Fong