The Poly‐Rho Test as a Screening Tool for Explosive Performance

Abstract

A screening test was developed at Los Alamos National Laboratory [1] that can be used to decide if a newly synthesized/ formulated explosive might warrant further development. The test consists of firing a rate-stick composed of 12.7 mm diameter by 12.7 mm high pellets of different densities ordered from lowest to highest, initiated by a detonator at the low-density end of the stick. This poly-rho test yields detonation velocities over a range of densities using only the small amount of the explosive typically generated by the synthetic organic chemist at an early stage of the scale-up process. The amount of material required is far less than that required for the typical rate-stick series. This paper presents results on poly-rho tests that were conducted on three explosives commonly used at Los Alamos National Laboratory, namely PBX 9501, PBX 9502 and PETN. The results are compared with empirical detonation-theory predictions and existing explosive experimental data, with good agreement in all cases.

Properties and Promise of Catenated Nitrogen Systems As High-Energy-Density Materials

“…202 Further modification with oxone converts this to the bis-N-oxide (51). The acid nitrate and perchlorate salts of these compounds were studied for their detonation properties using the experimental poly rho approach 27 rather than using thermodynamic computational codes. The perchlorate salts of the guanidinotetrazine (50) shown in Scheme 23 and the bis-N-oxide (51) had the best properties, with measured VoD extrapolated to 8540 and 7580 m/s at TMD, respectively.…”

“…It is normally prepared by reaction of picramic acid with nitrous acid (eq 30). 166 Azole-containing diazo complexes are common isolable variants, such as 2-diazo-2H-imidazole-4,5-dicarbonitrile 168−170 (27), which was originally prepared by diazotization of the 2-aminoimidazoledicarbonitrile with nitrous acid: 168 Despite its low oxygen balance of −111%, this compound is remarkably sensitive to explosion, 168−171 diagnostic of the instability of diazo molecules.…”

“…The location where the two failure fronts of the fuse loop meet is compared to the center point of the loop and may be used to calculate the VoD of the unknown. Other methods to measure VoD include the rate stick test, 26 the poly rho method, 27 and direct measurement by high speed cameras. 28 Because VoD is so difficult to determine experimentally, it is most often predicted via calculations using heavily parametrized equations or software codes.…”

Engineering the Microstructure and Morphology of Explosive Films via Control of Interfacial Energy

“…These properties, among others, dictate detonation characteristics of the explosive, 1−4 enabling parametric study of grain-scale material effects on initiation and detonation propagation. It is well established that explosive density impacts detonation pressure and velocity 5 and that specific surface area affects the critical detonation diameter. 4,6 Qualitatively similar trends in deto-nation behavior have also been observed in vapor-deposited explosives; however, the microstructure can also have more subtle effects on initiation and failure of the explosive, especially at sub-millimeter length scales.…”

“…These properties, among others, dictate detonation characteristics of the explosive, − enabling parametric study of grain-scale material effects on initiation and detonation propagation. It is well established that explosive density impacts detonation pressure and velocity and that specific surface area affects the critical detonation diameter. , Qualitatively similar trends in detonation behavior have also been observed in vapor-deposited explosives; however, the microstructure can also have more subtle effects on initiation and failure of the explosive, especially at sub-millimeter length scales. − During the deposition process, interfacial effects on microstructure evolution are not well understood and can result in drastically different energetic material properties. Limited work has been done to investigate the morphology evolution of vapor-deposited organic films, especially those relevant to energetics.…”