Critical diameter RDX/GAP propellant

To type qualify the solid propellant D-07 according to the STANAG 4170 and the accompanying AOP-7, critical diameter has been determined. Two different methods have been applied. First, casted conical test items were tested, and then stepped cylindrical test items. Four conical charges were casted in polypropylene moulds with large diameter, 30 mm, and small diameter, 3 mm, and length 270 mm. The smallest diameter of these test items varied due to non-optimal filling during casting. Two of the charges were released from the mould while two were in the mould during testing. For all charges, the detonation reaction after initiation at the large end did not terminate before it reached the small end. The smallest diameters of the two confined charges were 3.8 mm and 4 mm. The smallest diameters of the two unconfined test items were 5.8 mm and 9.8 mm. Cylindrical charges with diameters from 5 mm to 2.3 mm were punched and glued together to stepped test items. They contained four cylindrical charges of different diameters. Three stepped test items were tested, and for all of them the detonation terminated in the cylinder with the second largest diameter (3.6-4.1 mm). Critical diameter was determined to be 3.6-3.8 mm. Both methods gave the same result, with a critical diameter for the solid propellant D-07 in the range 3.6-3.8 mm. However, the applied methods can give a slightly lower critical diameter than methods applying changes in detonation velocity.