ARDEC Solid Gun Propellant Shock Initiation Sensitivity Test

NOL large card gap test is not suitable to assess the shock sensitivity of granular propellant beds made of large grains. The result can be strongly influenced by the heterogeneity of the bed. A new small scale gun propellant shock sensitivity test has been developed at ARDEC. This test is a sensitive discriminator to assess gun propellant shock sensitivity. INTRODUCTION Shock-to-detonation sensitivity is one of the most important safety/hazard properties of energetic materials. Traditionally, this property is evaluated by the NOL large card gap test shown in the TB 700-2, the Department of Defense Explosive Hazard Classification Procedures. The large card gap test was developed to evaluate the shock sensitivity of homogeneous material such as a monolithic block of high explosive. This same test is now also used to evaluate the shock sensitivity of granular gun propellant beds which are highly heterogeneous. There have been some doubts In the safety community about the applicability of the large card gap test to assess the shock sensitivity of the granular gun propellants. As a part of ARDEC's gun propellant effort to investigate the basic material properties of gun propellants, the problem of using large card gap test to evaluate gun propellants, in particular for large caliber guns, was investigated, and an alternate new gun propellant shock sensitivity Is developed. The results of this study is reported in this paper. LARGE CARD GAP TEST DEFICIENCY Two test series were conducted to illustrate the deficiency of using the NOL large card gap test to assess the shock sensitivity of gun propellants. In the first test series, a large caliber gun propellant sample was loaded Into three large card gap test fixtures as shown in Figure I. in the first fixture, no special arrangement was made on the propellant bed. In the second fixture, the grains at the top most layer-were oriented sideways, and in the third fixture, the grains at the top most layer were oriented vertically. Additional grains were used to fill any void in the first layer in the second and the third fixtures. A small amount of grease was smeared on the top layer of grains and filled some of the voids among grains, to further improve the shock transmitting coupling between the pentolite booster and the grains in the second and the third fixtures. No cards were used in these tests. The results were very different. The fixture with grains oriented sideways which has the maximum contact area with the booster, had the most violent reaction: the witness plate was punctured and shattered. The fixture with the grains oriented vertically had a less violent reaction, a significant deformation of the witness plate occurred. The fixture with normal loading procedure had the least violent reaction, it only had Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE AUG 1994 2. REPORT TYPE 3. DATES COVERED 00-00-1994 to 00-00-1994 4. TITLE AND SUBTITLE ARDEC Solid Gun Propellant Shock Initiation Sensitivity Test 5a. CONTRACT NUMBER