Reactant Jetting in Unstable Detonation

We note the common existence of a supersonic jet structure locally embedded within a surrounding transonic flow field in the hitherto unrelated phenomena of unstable gaseous detonation and hypervelocity blunt body shock wave interaction. Extending prior results that demonstrate the consequences of reduced endothermic reaction rate for the supersonic jet fluid in the blunt body case, we provide an explanation for observations of locally reduced OH PLIF signal in images of the keystone reaction zone structure of weakly unstable detonations. Modeling these flow features as exothermically reacting jets with similarly reduced reaction rates, we demonstrate a mechanism for jetting of bulk pockets of unreacted fluid with potentially differing kinetic pathways into the region behind the primary detonation front of strongly unstable mixtures. We examine the impact of mono-atomic and diatomic diluents on transverse structure. The results yield insight into the mechanisms of transition and characteristic features of both weakly and strongly unstable mixtures

SHOCK INITIATION EXPERIMENTS ON THE LLM-105 EXPLOSIVE RX-55-AA AT 25?C AND 150?C WITH IGNITION AND GROWTH MODELING

Shock initiation experiments on the LLM-105 based explosive RX-55-AA (95% LLM-105, 5% Viton by weight) were performed at 25 C and 150 C to obtain in-situ pressure gauge data, run-distance-to-detonation thresholds, and Ignition and Growth modeling parameters. A 101 mm diameter propellant driven gas gun was utilized to initiate the explosive sample with manganin piezoresistive pressure gauge packages placed between sample slices. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement at 25 C with previously published data on a similar LLM-105 based formulation RX-55-AB as well as a slight sensitivity increase at elevated temperature (150 C) as expected. Ignition and Growth modeling parameters were obtained with a reasonable fit to the experimental data

Shock sensitivity of LX 04 at elevated temperatures

Hazard scenarios can involve multiple stimuli, such as heating followed by fragment impact (shock). The shock response of LX-04 (85 weight % HMX and 15 weight % Viton binder) preheated to temperatures hear 170C is studied in a 10.2 cm bore diameter gas gun using embedded manganin pressure gauges. The pressure histories at various depths in the LX-04 targets and the run distances to detonation at several input shock pressures are measured and compared to those obtained in ambient temperature LX-04. The hot LX-04 is significantly more shock sensitive than ambient LX-04. Ignition and Growth reactive flow models are developed for ambient and hot LX-04 to allow predictions of impact scenarios that a can not be tested directly

Initiation of Heated PBX-9501 Explosive When Exposed to Dynamic Loading

Shock initiation experiments on the heated PBX9501 explosive (95% HMX, 2.5% estane, and 2.5% nitro-plasticizer by weight) were performed at temperatures 150 C and 180 C to obtain in-situ pressure gauge data. A 101 mm diameter propellant driven gas gun was utilized to initiate the PBX9501 explosive and manganin piezo-resistive pressure gauge packages were placed between sample slices to measure time resolved local pressure histories. The run-distance-to-detonation points on the Pop-plot for these experiments showed the sensitivity of the heated material to shock loading. This work shows that heated PBX-9501 is more shock sensitive than it is at ambient conditions. Proper Ignition and Growth modeling parameters were obtained to fit the experimental data. This parameter set will allow accurate code predictions to be calculated for safety scenarios involving PBX9501 explosives at temperatures close to those at which experiments were performed

SHOCK INITIATION EXPERIMENTS AND MODELING OF COMPOSITION B AND C-4

Shock initiation experiments on the explosives Composition B and C-4 were performed to obtain in-situ pressure gauge data for the purpose of determining the Ignition and Growth reactive flow model with proper modeling parameters. A 101 mm diameter propellant driven gas gun was utilized to initiate the explosive charges containing manganin piezoresistive pressure gauge packages embedded in the explosive sample. Experimental data provided new information on the shock velocity versus particle velocity relationship for each of the investigated materials in their respective pressure range. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement with previously published data, and Ignition and Growth modeling calculations resulted in a good fit to the experimental data. These experimental data were used to determine Ignition and Growth reactive flow model parameters for these explosives. Identical ignition and growth reaction rate parameters were used for C-4 and Composition B, and the Composition B model also included a third reaction rate to simulate the completion of reaction by the TNT component. The Composition B model was then tested on existing short pulse duration, gap test, and projectile impact shock initiation with good results. This Composition B model can be applied to shock initiation scenarios that have not or cannot be tested experimentally with a high level of confidence in its predictions

SHOCK INITIATION OF COMPOSITION B AND C-4 EXPLOSIVES; EXPERIMENTS AND MODELING

Shock initiation experiments on the explosives Composition B and C-4 were performed to obtain in-situ pressure gauge data for the purpose of providing the Ignition and Growth reactive flow model with proper modeling parameters. A 100 mm diameter propellant driven gas gun was utilized to initiate the explosive charges containing manganin piezoresistive pressure gauge packages embedded in the explosive sample. Experimental data provided new information on the shock velocity--particle velocity relationship for each of the investigated material in their respective pressure range. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement with previously published data, and Ignition and Growth modeling calculations resulted in a good fit to the experimental data. Identical ignition and growth reaction rate parameters were used for C-4 and Composition B, and the Composition B model also included a third reaction rate to simulate the completion of reaction by the TNT component. This model can be applied to shock initiation scenarios that have not or cannot be tested experimentally with a high level of confidence in its predictions

DYNAMIC LOADING OF TEFLON AT 200?C

Dynamic loading experiments were performed on inert Teflon (Polytetrafluoroethylene) samples, initially heated to the temperature of 200 C, to test its behavior under these conditions for its use in other heated experiments. Tests were performed in the 100 mm diameter bore propellant driven gas gun with piezo-resistive manganin pressure gauges imbedded into the samples to measure loading pressures. Experimental data provided new information on the shock velocity - particle velocity relationship for the heated material and showed no adverse effect of temperature on the insulating properties of the material

SHOCK INITIATION EXPERIMENTS ON THE HMX BASED EXPLOSIVE LX-10 WITH ASSOCIATED IGNITION AND GROWTH MODELING

Shock initiation experiments on the HMX based explosives LX-10 (95% HMX, 5% Viton by weight) and LX-07 (90% HMX, 10% Viton by weight) were performed to obtain in-situ pressure gauge data, run-distance-to-detonation thresholds, and Ignition and Growth modeling parameters. A 101 mm diameter propellant driven gas gun was utilized to initiate the explosive samples with manganin piezoresistive pressure gauge packages placed between sample slices. The run-distance-to-detonation points on the Pop-plot for these experiments and prior experiments on another HMX based explosive LX LX-04 (85% HMX, 15% Viton by weight) will be shown, discussed, and compared as a function of the binder content. This parameter set will provide additional information to ensure accurate code predictions for safety scenarios involving HMX explosives with different percent binder content additions

LOW AMPLITUDE SINGLE AND MULTIPLE SHOCK INITIATION EXPERIMENTS AND MODELING OF LX-04

Shock initiation experiments were performed on the plastic bonded explosive (PBX) LX-04 (85% HMX, 15% Viton binder) using single and multiple low amplitude shocks to obtain pressure history data for use in Ignition and Growth reactive flow modeling parameterization. A 100 mm diameter propellant driven gas gun was utilized to initiate the LX-04 explosive charges containing manganin piezoresistive pressure gauge packages placed between explosive discs. In the single shock experiments, the run distances to detonation at three shock pressures showed agreement with previously published data above 3 GPa. Even longer run distances to detonation were measured using 80 mm long by 145 mm diameter LX-04 charges impacted by low velocity projectiles from a 155 mm diameter gun. The minimum shock pressure required to cause low levels of exothermic reaction were determined for these large LX-04 charge dimensions. Multiple shocks were generated as double shocks by using a flyer plate with two materials and as reflected shocks by placing a high impedance material at the rear of the explosive charge. In both cases, the first shock pressure was not high enough to cause detonation of LX-04, and the second shock pressure, which would have been sufficient to cause detonation if generated by a single shock, failed to cause detonation. Thus LX-04 exhibited shock desensitization over a range of 0.6 to 1.4 GPa. The higher shock pressure LX-04 model was extended to accurately simulate these lower pressure and multiple shock gauge records. The shock desensitization effects observed with multiple shock compressions were partially accounted for in the model by using a critical compression corresponding to a shock pressure of 1.2 GPa. This shock desensitization effect occurs at higher pressures than those of other HMX-based PBX's containing higher HMX percentages

SHOCK INITIATION EXPERIMENTS ON PBX 9501 EXPLOSIVE AT PRESSURES BELOW 3 GPa WITH ASSOCIATED IGNITION AND GROWTH MODELING

Shock initiation experiments on the explosive PBX 9501 (95% HMX, 2.5% estane, and 2.5% nitroplasticizer by weight) were performed at pressures below 3 GPa to obtain in-situ pressure gauge data, run-distance-to-detonation thresholds, and Ignition and Growth modeling parameters. Propellant driven gas guns (101 mm and 155 mm) were utilized to initiate the PBX 9501 explosive with manganin piezoresistive pressure gauge packages placed between sample slices. The run-distance-to-detonation points on the Pop-plot for these experiments showed agreement with previously published data and Ignition and Growth modeling parameters were obtained with a good fit to the experimental data. This parameter set will allow accurate code predictions to be calculated for safety scenarios in the low-pressure regime (below 3 GPa) involving PBX 9501 explosive