[en] Low-velocity detonation (LVD) in a solid explosive from input shocks below the threshold for high-velocity detonation (HVD) had been previously reported for PBXN-109 in two gap tests with sample diameters of 36.5 and 73.0 mm. Similar phenomenon has now been observed for the highly insensitive PBXIH-140, whose critical diameter of ∼100 mm required an even larger gap test with a sample diameter of 178 mm. When just exceeding the critical gap for HVD, LVD propagated at similar velocities as in PBXN-109 and would punch clean holes in a witness plate like HVD. For somewhat greater gaps, there was enough shock reaction to drive LVD at constant but reduced velocities as the input shock decreased to ∼ ½ of critical. With a different formulation now exhibiting LVD, it may be more prevalent than previously realized. It is speculated to occur in various confinements when small percentages of easily detonable ingredients fail to initiate the remainder of less shock sensitive ingredients.

[en] The classical theory of detonation wave propagation has been highly successful in prediction of detonation dynamics based on a macroscopic, continuum-based approach, wherein the heterogeneity of the energetic material only enters the model via the reaction rate term (e.g., hot-spot based reaction mechanisms). The effects of spatial heterogeneity are rarely treated explicitly in detonation models. However, considerable evidence can be found that mesoscale phenomenon can influence the dynamics of the detonation front on scales larger than the heterogeneities. Two scenarios are identified that may result in spatial non-uniformity of the detonation front influencing the macroscopic dynamics of the wave propagation: (1) large-scale heterogeneities and (2) transverse or longitudinal instability of the front. This evidence is critically reviewed, and possible directions for modeling approaches that incorporate the spatial granularity (discreteness) of the energetic material are suggested.

[en] Short communication

[en] An uncomplicated explosive technique, in which a detonation wave is formed using a multipoint initiation, has interesting features. One of them is a complex cellular structure, which consists of nodes and cords. The reasons of these features and ways of their elimination are discussed in the work. The study was carried out using a high-speed camera with nanosecond resolution. Methods for smoothing a detonation wave formed with multi-point initiation are presented. (paper)

[en] An overall verification approach for the ESPROSE.m code is presented and implemented. The approach consists of a stepwise testing procedure from wave dynamics aspects to explosion coupling at the local level, and culminates with the consideration of propagating explosive events. Each step in turn consists of an array of analytical and experimental tests. The results indicate that, given the premixture composition, the prediction of energetics of large scale explosions in multidimensional geometries is within reach. The main need identified is for constitutive laws for microinteractions with reactor materials; however, reasonably conservative assessments are presently possible. (orig.)

[en] In the laser intensity range that the laser supported detonation (LSD) wave can be maintained, dissociation, ionization and radiation take a substantial part of the incidence laser energy. There is little treatment on the phenomenon in the existing models, which brings obvious discrepancies between their predictions and the experiment results. Taking into account the impact of dissociation, ionization and radiation in the conservations of mass, momentum and energy, a modified LSD wave model is developed which fits the experimental data more effectively rather than the existing models. Taking into consideration the pressure decay of the normal and the radial rarefaction, the laser induced impulse that is delivered to the target surface is calculated in the air; and the dependencies of impulse performance on laser intensity, pulse width, ambient pressure and spot size are indicated. The results confirm that the dissociation is the pivotal factor of the appearance of the momentum coupling coefficient extremum. This study focuses on a more thorough understanding of LSD and the interaction between laser and matter

[en] To achieve a higher thrust performance in the laser-driven in-tube accelerator operation, numerical analysises have been carried out. The computational code covers from the generation of the blast wave to its interactions with the projectile and the acceleration wall. The thrust history and the momentum coupling coefficient evaluated from the numerical simulation depend on the fill pressure and the projectile shape. The confinement effect can be clearly found using the projectile attached with a shroud

No abstract available

[en] The propagation of detonation waves in a channel filled with a bubbly liquid that suddenly widens is investigated. Possible scenarios for the dynamics of detonation waves after their transition to the widening part of the channel are analyzed. The influence of the volume content of a combustible gas and the geometric parameters of the channel on the propagation and breakdown of the detonation wave has been established.

No abstract available