FirePhysChem 3 (2023) 281–291 Contents lists available at ScienceDirect FirePhysChem journal homepage: http://www.keaipublishing.com/cn/journals/firephyschem/ A mathematical model for estimating the Gurney velocity of chemical high explosives Dany Frem FREM Co., Beirut, Lebanon a r t i c l e i n f o Keywords: Gurney velocity High explosives Fragmentation warheads Insensitive explosives Weapons a b s t r a c t The Gurney velocity is an important performance parameter that characterizes the metal pushing capability of conventional chemical explosives. Herein, this study proposes a mathematical model that aims to provide a simple and eο¬ective means by which the Gurney velocity of pure and mixed CHNO-based explosives can be accurately determined using as input information the volumetric heat of detonation, the parameter psi (πΉ ) and an adjustable parameter (π) that accounts for the type of the explosive being studied. The new model proved adequate for evaluating the Gurney velocity of sensitive and insensitive explosives of military interest, including melt-castable and plastic-bonded explosives (PBXs) and showed superior predicting performance compared to benchmark models. It is believed that the Gurney velocity obtained by the new method along with the Gurneytype equations would be very helpful for ordnance engineers for calculating the peak fragment deployment velocity from various warhead geometries, including omnidirectional and directed energy warheads for use in various weapons systems. 1. Introduction Chemical high explosives derive their unique properties from the ultrafast and energetic chemical decomposition reactions induced by external stimuli such as shock, friction, or heat. What makes explosives particularly useful is that these chemical reactions are always accompanied by a sudden volume change. For instance, the detonation of one kg of HMX liberates more than 900 liters of gaseous products within a short time of a few microseconds [1]. The expansion of the detonation products is fast enough to induce shock waves in the surrounding medium, leading to destructive eο¬ects on nearby materials and structures. When the explosive charge is in intimate contact with a piece of metal of suitable thickness, like in the case of fragmenting warheads, large numbers of high-velocity fragments are produced, capable of inο¬icting serious injuries even at very long distances from the epicenter of the detonation. In fact, fragmentation warheads have found an important role in air-, seaand land-based weapon systems whose purpose is to deter and neutralize stationary and moving soft non-hardened targets which include, combat equipment, drones and loitering munitions, radar and communication installations, lightly protected vehicles and aircraft in the open. The effectiveness and lethality of such warheads depend upon many factors, among which are, the type of explosive, fragments material, size, shape, number and mass, fragment spray angle, the initial ejection fragments velocity and the velocity at target impact [2,3]. Wave shaping and the method of initiation have also been cited as signiο¬cant factors that improve warhead performance [4]. Of particular importance, is the ability to produce optimal fragment size, shape and weight, tailored to the desired terminal eο¬ects. This requires means of controlling the breakup of the warhead casing which can be achieved, for example, by introducing grooves on the inner surface of the casing which weakens the structure and constitutes predetermined fracture points. Controlled fragmentation can also be readily obtained by using preformed fragments in the form of cubes or spheres made from steel or alloys of tungsten [5,6] placed in layers around the explosive charge in a polymer matrix. For a warhead designer, it is especially valuable to predict the velocity of the fragments ejected by a given warhead design. It comes as no surprise that the higher initial velocity corresponds to the higher kinetic energies of the fragments for target penetration. Higher kinetic energies also widen the lethal fragment range of the projectile [7]. During the 1940s, physicist Ronald W. Gurney provided simple equations from which the peak fragment velocity (π0 ) of explosively driven cylinders and spheres can be obtained [8]. In deriving these equations, Gurney’s assumed that a ο¬xed amount of chemical energy released during the explosive detonation is converted into the kinetic energy of the fragments and the expanding detonation products. It is also assumed that these products have uniform density and linear velocity proο¬les from the center of the explosive/metal system to the interface with the metal. The Gurney model predicts the velocity of the fragments √ in terms of the charge-to-metal ratio (πΆβπ) and the Gurney velocity ( 2πΈG ). Other investigators have extended and applied the Gurney model to include complex metal/explosive geometries used in practical applications. Some of E-mail address: frem.dany@gmail.com https://doi.org/10.1016/j.fpc.2022.11.002 Received 17 August 2022; Received in revised form 8 November 2022; Accepted 13 November 2022 Available online 14 November 2022 2667-1344/© 2022 Xi’an Modern Chemistry Research Institute. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) D. Frem FirePhysChem 3 (2023) 281–291 using simple correlations and analytical models [9–14] or the output of complex thermochemical codes [15–17]. However, these methods have varying degrees of success and many of these will generally fail to predict the Gurney velocity when applied to certain classes of explosives, especially insensitive ones such as 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) or 3-nitro-1,2,4-triazol-5-one (NTO). List of symbols π½ πΆ πΆE πΆβπ π· Δπ»f0 πΈc πΈG πΈ7π£0 πΉ (π) π √π₯ 2πΈG (πΌ) π π πT πΏ π π πarb πw π πarb πE ππ Φπ πΉ πΉπ πΉmix π πarb ππ πmix π π 0 π e π πcu ππ π0 π0 (π) π£βπ£0 π7π£0 Model parameter that accounts for gas leakage Mass per unit length of the explosive charge (kg) Eο¬ective weight of explosive C (kg) Charge-to-metal ratio Detonation velocity (km/s) Standard heat of formation (kcal/mol) Speciο¬c cylinder energy [(mm/μs)2 /2 or MJ/kg] Gurney energy (MJ/kg) Speciο¬c cylinder energy at seven volumes expansion [(mm/μs)2 /2 or MJ/kg] Modiο¬cation factor Velocity reduction coeο¬cient Gurney velocity (km/s) A factor that accounts for gas leakage between preformed fragments Covolume of the ith detonation product Coeο¬cient of tamping material Rod length (cm) Adjustable parameter (π = 0.25 or 0.5) Mass per unit length of the metal case (kg) Average molecular weight of gaseous detonation products calculated using the [H2 O–CO2 ] arbitrary decomposition assumption (g/mol) Molecular weight of the explosive (g/mol) Weight of tamper N (kg) Number of moles of gaseous detonation products per gram of explosive calculated using the [H2 O–CO2 ] arbitrary decomposition assumption (moles/g) Eο¬ective weight of tamper N (kg) Number of moles of the ith detonation product Mass fraction of the ith energetic component in the mixture Parameter psi (mol2 βÅ3 /g) Parameter psi of the ith energetic component in the mixture (mol2 βÅ3 /g) Parameter psi of the explosive mixture (mol2 βÅ3 /g) Heat of detonation (kcal/g or kJ/g) Heat of detonation calculated using the [H2 O–CO2 ] arbitrary decomposition assumption (cal/g) Heat of detonation of the ith energetic component in the mixture (kcal/g or kJ/g) Heat of detonation of the explosive mixture (kcal/g or kJ/g) Radius from the center of the warhead to the outermost ring of rods (cm) Radius of the explosive charge (cm) Radius of the center core explosive (cm) Loading density (g/cm3 or kg/m3 ) Density of the copper cylinder (8.94 g/cm3 ) Radius from the center of the warhead to the ith ring of rods (cm) Peak fragment velocity (km/s) Peak velocity of the preformed fragment at a distance r from the charge centerline (km/s) Volume expansion ratio Cylinder test wall velocity at seven volumes expansion (km/s) 2. A new model for predicting the Gurney velocity In this section, a model is proposed by which the Gurney velocity can be estimated for sensitive and insensitive explosives including nitrogenrich compositions with minimal calculation eο¬ort. For a given explosive with the general formula Ca Hb Nc Od , the composition of the formed detonation products can be obtained by applying a set of rules and decomposition pathways (Fig. 1) as dictated by the oxygen balance of the studied explosive [23]. It is then easy to show that the heat of detonation (π) can be computed using the expression [24]: [∑ ( ) ( )] 0 0 − π π=1 ππ Δπ»f detonation product π − Δπ»f explosive π= (1) πw where πw is the molecular weight of the explosive, Δπ»f0 (detonation product)π and ππ are the standard heat of formation and the number of moles of the ith detonation product, respectively. The heat of detonation is not only an important property of explosives but also a major factor used to determine the detonation velocity (π·) and pressure (π ) [25–27]. Furthermore, Akst [28] has shown that the volumetric heat of detonation (ππ) directly aο¬ects the metal-propelling ability of an explosive as measured in the cylinder expansion test. Xiong [23] introduced the parameter psi (πΉ ) as a very useful parameter along with the heat of detonation for deriving an empirical equation for estimating the detonation velocity of explosives. Considering the signiο¬cant impact of the volumetric heat of detonation and the parameter psi on the performance of explosives, the trial-and-error approach was employed to ο¬nd and optimize a model for predicting the Gurney velocity using (ππ) and (πΉ ) as key parameters: √√ √ ( ) 3 2πΈG kmβs = πΉ ππ − π (2) πΉ= π 1 ∑ ππ πw π=1 π π (3) where (π) is the loading density of the explosives in g/cm3 , while (π) is the heat of detonation in kJ/g, ππ and π π are the number of moles and the covolume (Table 2) of the ith detonation product, respectively. In order to reproduce the experimental Gurney velocities, it was necessary to include an additional variable (π) into the model, which can take two values: 0.25 for hydrazinium nitrate-containing compositions and seriously deο¬cient explosives (Type IV and V) and 0.5 for Type I, II and III explosives. For explosive mixtures with or without additional additives like waxes, binders and plasticizers, the heat of detonation (πmix ) and the parameter psi (πΉmix ) of the mixture are calculated as follows: πmix = π ∑ π=1 πΉmix = π·π π π π ∑ π=1 π·π πΉπ (4a) (4b) where (π·π ), (ππ ) and (πΉπ ) are the mass fraction, the heat of detonation and the parameter psi of the ith energetic component in the mixture. An energetic component is deο¬ned as any compound bearing at least one energetic moiety such as nitro, nitramine, furazan, furoxan, tetrazine, etc. Table 3, shows how (π) and (πΉ ) can be calculated from the heat of formation and the stoichiometry of the explosive. these √ Gurney-type equations are shown in Table 1. The Gurney velocity ( 2πΈG ) appearing in each of these equations is a characteristic of the explosives and varies with their loading density. There exist several approaches and methods by which the Gurney velocity can be estimated 282 D. Frem FirePhysChem 3 (2023) 281–291 Table 1 Gurney-type equations for peak fragment deployment velocity prediction of various warhead conο¬gurations. Warhead type Fragment velocity formula Preformed fragments [18] √ π0 = 2πΈG ( 12 + Center core rod [19] π0 = Jellyroll [20] √ π0 = 2πΈG [ Forward-Firing [21] π0 (π) = √ 2πΈG √ √ (1+ π e πΏ π0 = π½ = 0.5 (for cylindrical rod fragments) π½ = 0.56 (for rectangular rod fragments) πΆ π π e βΆ radius of the center core explosive (cm) )(1+ 2πΆπ ) πΆ π πΆ 0.5(1+ π ) ] 1 2 π ( π π ) ππ βΆ is the radius from the center of the warhead to the ith ring of rods (cm). π : is the radius from the center of the warhead to the outermost ring of rods (cm) √ πΆ 3 πΉ (π) π 2πΈG [ [(πΉ (π) LEFPa [22] Remarks 1 π −2 ) π½πΆ πΆ 2 πΆ ) +5πΉ (π)( π π √ 1+π΄3 2πΈG [ 3(1+ + π΄) πE πΆE π΄2 + )+4] 1 2 1 π −2 ] πΆE ] πΉ (π): (1 − π΄= π(πΌ) 2 ) π 0 1+2 πΆπ 1+2 E πE πΆE πE = πT π a LEFP: Linear Explosively Formed Projectile. Fig. 1. Assumed detonation products based on the type of explosive with the general empirical formula Ca Hb Nc Od . Table 2 The covolumes of the detonation product species. Species π π a H2 O 250 CO2 600 CO 390 N2 380 H2 214 O2 350 CH4 528 pansion is observed with a rotating mirror streak camera or its velocity is directly measured using Photonic Doppler Velocimetry (PDV) technique [30]. The wall velocities are reported at a radial displacement of 6 mm, 12.5 mm and 19 mm corresponding to volume expansion ratios (π£βπ£0 ) of 2, 4, and 7, respectively [31]. the 2 and 7 volume ratios are a ο¬gure of merit in explosive applications because it has been shown that for detonations impinging head-on against metals all the energy is transferred to the metal by the time the detonation products reach an expansion ratio of 2 while for grazing detonation the explosion products continue to eο¬ectively transfer energy until they reach a volume expansion ratio of 7 [32]. Moreover, the velocity at seven volumes expansion (π7π£0 ) is generally assumed to be the terminal wall velocity since at this volume expansion the wall velocity can be reliably obtained before the test breaks up [33,34]. The Gurney velocities collated in Table 4 were primarily obtained from Dobratz & Crawford [35], however, for many other compositions it is the speciο¬c cylinder energy (πΈc ), wall velocity or the Gurney energy (πΈG ) that are reported in the literature. All of these quantities were evaluated at π£βπ£0 = 7 and the Gurney velocity at the cor- C(s)a 46 C(s) stands for solid carbon. 2.1. Source of Gurney velocity data The Gurney velocity of solid and liquid explosives is routinely obtained from the cylinder expansion test. The test is the standard method that provides key hydrodynamic performance information on an explosive’s metal-pushing ability. A typical one-inch cylinder test consists of a fully annealed, oxygen-free high-conductivity (OFHC) copper tube 11.8inch long (300 mm) with a 1 inch inner diameter (25.4 mm) and a wall thickness of 0.1 inch (2.54 mm) [29]. The cylinder is ο¬lled with 250– 300 gs of explosive [30] and detonated at one end. The radial wall ex283 D. Frem FirePhysChem 3 (2023) 281–291 Table 3 Equations for the calculation of (π) and (πΉ ) for diο¬erent types of explosives [23]. Explosive type Type I (π − 2π − 2π ≥ 0) Type II (π − 2π − 2π < 0) Type III (π − 2π − π ≤ 0) Type IV (π − 2π ≤ 0; π ≥ π ) Type V (π − 2π ≤ 0; π < π) π (kcal/g)a πΉb 28.9π+94π+Δπ»f0 250π+37.5π+190π+175π πw πw 2.365π+52π−10π+Δπ»f0 πw 1.772π+52π−10π+Δπ»f0 πw 54.37π−10π+Δπ»f0 πw 57.8π−31.4π+Δπ»f0 πw 3. Results and discussion 3.1. Explosive compositions with π = 0.5 Table 4 lists Gurney velocity values for more than ο¬fty compositions of pure and mixed explosives many of which are currently used, or have the potential to be used in future ordnance programs. More importantly, the studied compositions have a wide range of loading densities, thermal stabilities and sensitivities toward external insults such as heat, impact, shock, friction, and electrostatic charge. Several interesting models were used to predict the Gurney velocity and their results were compared to the experimental data. The Keshavarz method [9] provides a simple means to obtain the Gurney velocity of an explosive at any loading density with a little computation time while requiring very few or no experimental parameters as input information: √ ( ) 2πΈG kmβs = 0.404 + 1.020π − 0.021π + 0.184(πβπ ) + 0.303(πβπ) (10) 46π+9.95π+190π+277π πw 46π+36.75π+190π+277π πw 46π+107π+190(π+π) πw 354π+107π+190π+36π πw a The heat of formation (Δπ»f0 ) is in kcal/mol. To apply Eq.(2), the calculated (π) value in kcal/g needs to be. converted to kJ/g by multiplying it by the constant 4.184. b If π = 0, πΉ ′ = 1.25πΉ . If π = 0, πΉ ′ = 1.06πΉ (except Type I). If π = 0, and π = 0, πΉ ′ = 1.06πΉ (for Type IV). If π = 0, and π = 0, πΉ ′ = 1.04πΉ (for Type V). where a, b, c and d are the number of carbon (C), hydrogen (H), nitrogen (N) and oxygen (O) atoms in the explosive composition. The model developed by Locking [12] was chosen for the current analysis simply because the experimental detonation velocities for the majority of the studied explosives are readily available. The Locking model is simple and easy to apply, requiring only two input parameters, the detonation velocity and the loading density of the explosive: responding expansion ratio were calculated using Gurney’s equation for cylindrical geometry: √ √ 2πΈG = π7π£0 1 + 0.5 πΆβπ πΆβπ β‘ β€ β’ β₯ π 1 πΆβπ = β’ ( ) β₯ 2 β’ OD − 1 β₯ πcu β£ ID β¦ √ (5) πΈ7π£0 = 1 π 2 7π£0 (6) √ (7) 0.5 2.2. Models performance evaluation The performance and accuracy of the new model as well as other models in estimating the Gurney velocity of explosives were evaluated by mean absolute percent error (MAPE) and root-mean-square error (RMSE) [36]. π 1 ∑ || π¦π − π¦Μπ || × 100% π π=1 || π¦π || 0.5 (12) (13) where π = πarb (πarb ) (πarb ) . One interesting point to note is that the majority of the studied compositions belong to Type III explosives whereas, PETN is the sole pure compound that has enough high oxygen balance to be classiο¬ed as Type II. Moreover, LX-09 and Composition C-3 incorporate small amounts of energetic additives like bis(2-ο¬uoro-2,2-dinitroethyl) formal (FEFO) and mononitrotoluene (MNT) belonging to Type II and Type IV energetic materials, respectively. From the analysis of the data in Table 4, it can be seen that the Gurney velocities calculated using Eq. (2) with π = 0.5 are in good agreement with the experimental results in which 83% of the estimated values lie within ±3% of the actual values while the rest (17%) deviate by no more than ±5% (sample calculations can be found in the Appendix section). An important aspect of the new model is its ability to accurately predict the Gurney velocities of √ insensitive explosives. For example, using Eqs. (10)–(13) to estimate ( 2πΈG ) of known insensitive materials like DNAN, NTO, SK TNBI, TATB and PBX-9502 will result in large deviations which, in some cases, amount to more than 16% (Eq. (10), PBX-9502 and pressed DNAN) whereas the Gurney velocities values obtained from Eq. (2) were within ±3% of the experimental results. Table 4 also shows that compared to the other models, Eq. (2) demonstrates superior prediction performance and better accuracy which is reο¬ected in lower MAPE and RMSE scores of 1.67% and 0.05 km/s, respectively. Gurney energies at π£βπ£0 = 7 were determined graphically from the curves of (πΈG ) as a function (π£βπ£0 ). MAPE = √ ( ) 2πΈG kmβs = 0.6 + 0.54 1.44ππ (π» − πΎ ) and √ ( ) 2πΈG kmβs = 0.887π0.5 π0.4 (πΎ − πΉ ) )2 √ √ π √1 ∑ ( )2 RMSE = √ π¦ − π¦Μπ π π=1 π (11) where (π·) is the detonation velocity (in km/s), (π) is the loading density (in kg/m3 ) and ππ₯ is the velocity reduction coeο¬cient. Hardesty & Kennedy (H-K) [14] and later Kamlet & Finger (K-F) [13] have related the Gurney velocity to the loading density and to Kamlet’s (π) parameter [64] which in turn depends on the number of moles of gaseous detonation products per gram of explosive (πarb ), the average molecular weight of these gasses (πarb ), and on the heat of detonation (πarb ) (in cal/g), all calculated using the√[H2 O–CO2 ] arbitrary decomposition assumption. The expressions for ( 2πΈG ) are as follows: where (OD), (ID) and (πcu ) are the outside diameter, internal diameter, and the density of the copper cylinder, respectively, and (π) is the density of the explosive. The relationship between (πΈ7π£0 ) and the wall velocity (π7π£0 ) at seven volumes expansion is: ( β‘ 1 + 1.3π β€ ( ) π· 1000 β₯ 2πΈG kmβs = and πx = 18.0467 β’ β’ π0 . 4 β₯ πx β£ β¦ (8) (9) where π¦π , π¦Μπ and N are, respectively, the observed (or experimental) value, the predicted value, and the number of the considered data. The closer RMSD and MAPE are to zero the closer the predicted value of the model is to the experimental value. 284 D. Frem FirePhysChem 3 (2023) 281–291 Table 4 Predicted Gurney velocities for 52 explosive compositions at various loading densities as compared to experimental data. Percent deviations are shown in parentheses. Compositions PETN TNT TNT Tetryl HMX RDX HNS HNS NM DNAN (melt) DNAN (pressed) SK TNBI DAAF NTO NTO TATB FOX-7 Composition A-3 Composition-B Composition-B Composition C-3 Composition C-4 RDX/TNT (50/50) Cyclotol 75/25 Octol 75/25 Cyclotol 77/23 Octol 78/22 RDX/wax (94/6) HMX/wax (96/4) RDX/wax (95/5) PETN/Viton (95/5) LX-09 LX-10 LX-14 PBX-91C PBX-9404 PBX-9501 PBX-9502 QRX080 (FOX-7)vit CL-14/Viton A (97/3) NTO/FOX-7/Kel-F 800 (67/30/3) DNAN/RDX/NTO (40/20/40) TNT/RDX/NTO (40/20/40) KH 30 KH 50 NTO/DAAF/Kel-F 800 (67/30/3) PAX-60-MD PAX-63-MD AFX-521 RX-45-AA AmPicCC RMSE (km/s) MAPE (%) π (g/cm3 ) Δπ»f0 (kcal/mol)a √ 2πΈG (km/s) (Exp.)a √ 2πΈG (km/s) (Eq.(2)) √ √ π· (km/s)π½ 2πΈG (km/s) (Eq.(11)) √ 2πΈG (km/s) (Eq.(12)) √ 2πΈG (km/s) (Eq.(13)) 1.76 1.63 1.2 1.62 1.89 1.77 1.6 1.2 1.14 1.45 1.52 1.55 1.691 1.77 1.855 1.854 1.78 1.59 1.71 1.717 1.60 1.60 1.64 1.754 1.821 1.754 1.821 1.65 1.780 1.650 1.710 −128.7 −16.0 −16.0 4.67 17.93 14.71 18.7 18.7 −27.0 −44.61b −44.61b −98.95c 106.12d −24.07b −24.07b −36.85 −32.00b 2.84 1.28 1.28 3.74 3.33 −0.21 3.21 2.78 3.48 3.17 3.10e 4.40f 4.53f −47.58 2.93 2.37 2.16p 2.50 2.97 2.93 2.53q 2.18q 2.41 2.00r 2.02r 2.14c 2.63s 2.37t 2.47s 2.38u 2.66v 2.63 2.70 2.71 2.68 2.66w 2.57t 2.79 2.83 2.79x 2.83x 2.73e 2.93y 2.72y 2.76y 8.26 6.93u 5.470 7.415π 9.11 8.70 6.950 5.740 6.436π 5.690 5.960 6.690 8.020 7.940 8.188 7.675 8.325 7.884π 8.068π 8.094π 7.63 7.917π 7.610 8.340π 8.595π 8.356π 8.622π 8.390 8.730 8.390 8.080 2.93 (0) 2.40 (1.27) 2.12 (−1.85) 2.62 (4.80) 2.95 (−0.67) 2.88 (−1.71) 2.47 (−2.37) 2.20 (0.92) 2.29 (−4.98) 2.04 (2.00) 2.08 (2.97) 2.15 (0.47) 2.51 (−4.56) 2.39 (0.84) 2.44 (−1.21) 2.40 (0.84) 2.64 (−0.75) 2.61 (−0.76) 2.69 (−0.37) 2.70 (−0.37) 2.63 (−1.87) 2.62 (−1.50) 2.61 (1.56) 2.78 (−0.36) 2.82 (−0.35) 2.79 (0) 2.83 (0) 2.70 (−1.10) 2.82 (−3.75) 2.72 (0) 2.81 (1.81) 2.97 (1.37) 2.42 (2.11) 1.98 (−8.33) 2.41 (−3.60) 2.95 (−0.67) 2.87 (−2.05) 2.26 (−10.67) 1.85 (−15.14) 2.43 (0.83) 2.28 (14.00) 2.35 (16.34) 2.29 (7.01) 2.43 (−7.60) 2.70 (13.92) 2.79 (12.96) 2.66 (11.76) 2.93 (10.15) 2.65 (0.76) 2.68 (−0.74) 2.69 (−0.74) 2.60 (−2.99) 2.66 (0) 2.57 (0) 2.78 (−0.36) 2.85 (0.71) 2.79 (0) 2.86 (1.06) 2.73 (0) 2.89 (−1.37) 2.74 (0.74) 2.92 (5.80) 2.77 (−5.46) 2.37 (0) 2.02 (−6.48) 2.54 (1.60) 2.99 (0.67) 2.91 (−0.68) 2.39 (−5.53) 2.12 (−2.75) 2.40 (−0.41) 2.01 (0.50) 2.08 (2.97) 2.32 (8.41) 2.72 (3.42) 2.65 (11.81) 2.70 (9.31) 2.53 (6.30) 2.78 (4.51) 2.72 (3.42) 2.72 (0.74) 2.73 (0.74) 2.63 (−1.87) 2.72 (2.26) 2.60 (1.17) 2.80 (0.36) 2.85 (0.71) 2.80 (0.36) 2.86 (1.06) 2.86 (4.76) 2.91 (−0.68) 2.86 (5.15) 2.73 (−1.09) 2.84 (−3.07) 2.42 (2.11) 2.16 (0) 2.55 (2.00) 2.92 (−1.68) 2.85 (−2.73) 2.41 (−4.74) 2.17 (−0.46) 2.37 (−1.66) 2.21 (10.50) 2.25 (11.39) 2.42 (13.08) 2.59 (−1.52) 2.57 (8.44) 2.62 (6.07) 2.57 (7.98) 2.74 (3.01) 2.63 (0) 2.68 (−0.74) 2.68 (−1.11) 2.63 (−1.87) 2.65 (−0.38) 2.60 (1.17) 2.75 (−1.43) 2.79 (−1.41) 2.76 (−1.08) 2.80 (−1.06) 2.70 (−1.10) 2.80 (−4.44) 2.71 (−0.37) 2.73 (−1.09) 2.90 (−1.02) 2.38 (0.42) 2.10 (−2.78) 2.55 (2.00) 2.98 (0.34) 2.90 (−1.02) 2.36 (−6.72) 2.11 (−3.21) 2.39 (−0.83) 2.12 (6.00) 2.16 (6.93) 2.38 (11.21) 2.59 (−1.52) 2.55 (7.59) 2.60 (5.26) 2.53 (6.30) 2.76 (3.76) 2.65 (0.76) 2.70 (0) 2.70 (−0.37) 2.65 (−1.12) 2.68 (0.75) 2.60 (1.17) 2.78 (−0.36) 2.83 (0) 2.79 (0) 2.84 (0.35) 2.73 (0) 2.85 (−2.73) 2.75 (1.10) 2.77 (0.36) 1.84 1.86 1.835 1.72 1.84 1.841 1.885 1.76 1.790 1.805 1.82 −3.14 1.50 4.07g 0.08 2.28 −20.84 −25.20h −30.99i 2.63j 2.89q 2.92w 2.80q 2.75z 2.90 2.90w 2.377 2.64πΌ 2.65π½ 2.60s 8.840 8.82a 8.800 8.42 8.80 8.880π 7.691π 8.28 8.320 7.720 2.88 (−0.35) 2.85 (−2.40) 2.84 (1.43) 2.67 (−2.91) 2.86 (−1.38) 2.87 (−1.03) 2.34 (−1.56) 2.55 (−3.41) 2.55 (−3.77) 2.54 (−2.31) 2.99 (3.46) 2.99 (2.40) 2.95 (5.36) 2.76 (0.36) 3.00 (3.45) 2.98 (2.76) 2.76 (16.11) 2.87 (8.71) 2.91 (9.81) 2.62 (0.77) 2.92 (1.04) 2.90 (−0.68) 2.91 (3.93) 2.84 (3.27) 2.91 (0.34) 2.93 (1.03) 2.52 (6.02) 2.77 (4.92) 2.77 (4.53) 2.57 (−1.15) 2.86 (−1.04) 2.82 (−3.42) 2.84 (1.43) 2.70 (−1.82) 2.85 (−1.72) 2.86 (−1.38) 2.51 (5.60) 2.68 (1.52) 2.64 (−0.38) 2.56 (−1.54) 2.92 (1.04) 2.86 (−2.05) 2.89 (3.21) 2.72 (−1.09) 2.90 (0) 2.91 (0.34) 2.46 (3.49) 2.69 (1.89) 2.64 (−0.38) 2.53 (−2.69) 1.854 −23.08i 2.49s 8.141 2.47 (−0.80) 2.86 (14.86) 2.68 (7.63) 2.63 (5.62) 2.61 (4.82) 1.635 −15.09i 2.39r 7.040 2.36 (−1.26) 2.53 (5.86) 2.41 (0.84) 2.48 (3.77) 2.45 (2.51) 1.660 −8.90i 2.45r 7.410 2.47 (0.82) 2.56 (4.49) 2.52 (2.86) 2.54 (3.67) 2.53 (3.27) 1.810 1.825 1.803 i −7.75 −10.83i −1.59k πΎ 2.76 2.73πΎ 2.47πΏ 8.600 8.480 7.934 2.71 (−1.81) 2.64 (−3.30) 2.42 (−2.02) 2.88 (4.35) 2.86 (4.76) 2.69 (8.91) 2.86 (3.62) 2.81 (2.93) 2.64 (6.88) 2.73 (−1.09) 2.70 (−1.10) 2.57 (4.05) 2.75 (−0.36) 2.71 (−0.73) 2.55 (3.24) 1.780 1.750 1.700 1.752 1.481 10.12l 15.20l −4.05m 3.77n −35.30° 2.85π 2.77π 2.47π 2.31n 2.13π 8.63 8.28 7.202 7.71 6.580 2.84 (−0.35) 2.78 (0.36) 2.45 (−0.81) 2.21 (−4.33) 2.04 (−4.23) 0.05 1.67 2.82 (−1.05) 2.68 (−3.25) 2.46 (−0.40) 2.68 (16.02) 2.40 (12.68) 0.18 5.45 2.88 (1.05) 2.78 (0.36) 2.44 (−1.21) 2.59 (12.12) 2.31 (8.45) 0.11 3.27 2.79 (−2.11) 2.72 (−1.81) 2.43 (−1.62) 2.48 (7.36) 2.26 (6.10) 0.10 3.00 2.83 (−0.70) 2.75 (−0.72) 2.38 (−3.64) 2.43 (5.19) 2.19 (2.82) 0.08 2.31 2πΈG (km/s) (Eq.(10)) a Heats of formation (HOF) and Gurney velocities, unless otherwise stated, were taken from [35]. b [37]. c [38]. d [39]. e [40]. f HOF of wax was taken from [41]. g HOF of HTPB was taken from [42]. h HOF of FOX-7 and Hytemp were taken from [37] and [43], respectively. i HOF of FOX-7, NTO and DNAN were taken from [37]. j HOF of CL-14 was taken from [44].k HOF of NTO and DAAF were taken from [37] and [39], respectively. l HOF of wax and 3,4-Dinitropyrazole (DNP) were taken from [41] and [45] respectively.m HOF of PYX was taken from [46].n HOF of ANTA was taken from [47]. o HOF of HTPB, BDNPA/F and MDI were taken from [42, 48], and [46], respectively.p Average value from [49]. q [50]. r [51]. s [52]. t [53]. u [28]. v [54]. w [55]. x [14]. y [56]. z [57]. πΌ [58]. π½ [59]. πΎ [60]. πΏ [61]. π [45]. π [62]. π [63]. π Unless otherwise stated, the experimental detonation velocity was taken from the same reference as the Gurney velocity. π The detonation velocities were calculated using the BKW thermochemical code with the RDX parameter set [41]. π The detonation velocity was calculated using the BKW thermochemical code with the TNT parameter set [41]. 285 D. Frem FirePhysChem 3 (2023) 281–291 Fig. 2. Chemical structures of explosives for which the Gurney velocity has been determined experimentally [65]. 3.1.1. Licht’s Gurney velocity data H.H. Licht has compiled an extensive body of data on experimental Gurney velocities performed at the French-German Research Institute of Saint-Louis (ISL) for pure and mixed CHNO-based explosives [65]. Cylindrical charges (16 mm diameter × 145 mm long) with metal conο¬nement were employed to simultaneously obtain the detonation velocity and Gurney velocity at various loading densities. For insensitive explosives like TATB or cast TNT larger charges (25 mm diameter × 250 mm long) were used. Fig. 2 depicts the chemical structures for some of the investigated pure explosives including nitroaromatics, cyclic and acyclic nitramines, nitrate esters as well as hydrogen- and nitrogen-rich compounds like ANQ and TAGN. Equations used previously were once again used to evaluate the Gurney velocity of the compositions shown in Table 5 with one exception, Eq. (10) was excluded because it was found to be the least accurate among all the tested models. It was found from the results in Table 5 that 90% of the estimated Gurney velocities using Eq. (2) lie within ±4% of the experimental values compared to 60%, 67% and 63% for Eqs. (11)–(13), respectively, proving once more the superior performance of the new model in pre286 D. Frem FirePhysChem 3 (2023) 281–291 Table 5 Comparison of experimental and predicted Gurney velocities using Eq.(2) and Eqs.(11)-(13). Percent deviations are shown in parentheses. Compositions HMX PETN RDX TeNHHPm NMP TNAD Tetryl Bis-MNDPy TMNTz 2-MNDPy TNT PETN TATB NTO DADPyOx ADPyOx AMP DINA NITRA HMX/TNT (70/30) RDX/TNT (60/40) HMX/ETN (65/35) ETN/HMX (80/20) RDX/HTPB (85/15) PETN/rubber (89/11) TATB/TNT (60/40) DINA-Dynamite (90/10) NC/DINA (60/40) NTO/HNE/wax (76/19/5) √ 2πΈG (km/s) (Eq.(2)) √ √ 2πΈG (km/s) (Eq.(12)) √ 2πΈG (km/s) (Eq.(13)) 8.773 8.142 8.489 8.368 8.054 7.775 7.573 7.651q 7.228 7.372q 6.913 5.516 7.539 7.959 7.328 6.963 7.876 7.713 7.350 8.319 2.90 (−2.03) 2.90 (−0.68) 2.86 (−0.35) 2.92 (3.55) 2.84 (4.80) 2.63 (−1.13) 2.68 (1.52) 2.63 (0.77) 2.45 (−2.00) 2.53 (1.61) 2.39 (0) 2.32 (−1.28) 2.40 (2.56) 2.41 (3.88) 2.36 (2.61) 2.28 (3.64) 2.67 (2.69) 2.74 (−5.19) 2.24 (−1.75) 2.79 (0) 2.91 (−1.69) 2.74 (−6.16) 2.86 (−0.35) 2.80 (−0.71) 2.70 (−0.37) 2.66 (0) 2.56 (−3.03) 2.62 (0.38) 2.52 (0.80) 2.54 (2.01) 2.38 (−0.42) 2.11 (−10.21) 2.48 (5.98) 2.64 (13.79) 2.44 (6.09) 2.36 (7.27) 2.68 (3.08) 2.65 (−8.30) 2.55 (11.84) 2.76 (−1.08) 2.87 (−3.04) 2.81 (−3.77) 2.82 (−1.74) 2.84 (0.71) 2.79 (2.95) 2.66 (0) 2.61 (−1.14) 2.60 (−0.38) 2.53 (1.20) 2.52 (1.20) 2.41 (0.84) 2.27 (−3.40) 2.57 (9.83) 2.60 (12.07) 2.54 (10.43) 2.44 (10.91) 2.68 (3.08) 2.71 (−6.23) 2.47 (8.33) 2.77 (−0.72) 2.93 (−1.01) 2.87 (−1.71) 2.88 (0.35) 2.90 (2.84) 2.83 (4.43) 2.68 (0.75) 2.61 (−1.14) 2.60 (−0.38) 2.53 (1.20) 2.50 (0.40) 2.36 (−1.26) 2.29 (−2.55) 2.54 (8.55) 2.57 (10.78) 2.50 (8.70) 2.39 (8.64) 2.71 (4.23) 2.76 (−4.50) 2.45 (7.46) 2.80 (0.36) 2.75 7.965 2.71 (−1.45) 2.68 (−2.55) 2.69 (−2.18) 2.71 (−1.45) −8.89l 2.89 8.645q 2.90 (0.35) 2.88 (−0.35) 2.88 (−0.35) 2.95 (2.08) 1.75 −28.11l 2.93 8.160 2.89 (−1.37) 2.74 (−6.48) 2.88 (−1.71) 2.96 (1.02) 1.57 3.55m 2.56 7.897 2.50 (−2.34) 2.73 (6.64) 2.55 (−0.39) 2.56 (0) 1.2 −37.77m 2.38 6.431 2.35 (−1.26) 2.37 (−0.42) 2.35 (−1.26) 2.35 (−1.26) 1.79 −11.38 2.42 7.303 2.42 (0) 2.43 (0.41) 2.53 (4.55) 2.49 (2.89) 1.61 −34.09n 2.85 7.665 2.71 (−4.91) 2.63 (−7.72) 2.69 (−5.61) 2.73 (−4.21) 1.55 −51.76 n 2.49 7.227 2.54 (2.01) 2.51 (0.80) 2.56 (2.81) 2.57 (3.21) 1.64 −14.63° 2.27 7.523 2.20 (−3.08) 2.57 (13.22) 2.57 (13.22) 2.56 (12.78) 1.63 −11.23p 2.32 6.986 2.25 (−3.02) 2.39 (3.02) 2.65 (14.22) 2.68 (15.52) 0.07 2.06 0.14 4.17 0.14 4.28 0.13 3.85 π (g/cm3 ) Δπ»f0 (kcal/mol)a 1.81 1.72 1.73 1.76 1.75 1.64 1.71 1.63 1.53 1.60 1.60 0.98 1.86 1.81 1.80 1.69 1.67 1.62 1.56 1.81 √ 2πΈG (km/s) (Exp.)b π· (km/s) 17.93 −128.7 14.71 2.00c −31.55d 17.5e 4.67 36.45f 65.75f 22.44f −16.0 −128.7 −36.85 −24.07 g −31.60h −45.50i 65.73d −73.33j 22.44k 2.13 2.96 2.92 2.87 2.82 2.71 2.66 2.64 2.61 2.50 2.49 2.39 2.35 2.34 2.32 2.30 2.20 2.60 2.89 2.28 2.79 1.74 1.16 1.79 b DINGU/HNE/wax (63/32/5) RMSE (km/s) MAPE (%) 2πΈG (km/s) (Eq.(11)) a Heats of formation (HOF), unless otherwise stated, were taken from [35]. b Experimental Gurney and detonation velocities were taken from [65] unless otherwise stated. c [66]. d [67]. e [68]. f [69]. g [37]. h [70]. i [71]. j [46]. k [72]. l HOF of ETN was taken from [73]. m HOF of HTPB (or rubber) was taken from [42]. n HOF of DINA was taken from [46] while HOF of NC and dynamite (both considered as Nitrocellulose with 12% nitrogen content) was taken from [35]. o HOF of NTO and HNE were taken from [37] while HOF of wax was taken from [41]. p HOF of DINGU, HNE and wax were taken from [74, 37] and [41], respectively.q The detonation velocities were calculated using the BKW thermochemical code with the RDX parameter set [41]. dicting the Gurney velocities of diο¬erent classes of explosives at any loading density. Slightly larger deviations (around 5%) were observed for NMP, DINA and DINA-Dynamite. Also, mention should be made that NMP and DINA are the only studied compounds bearing a nitramine and a nitrate ester functionality. On the other hand, however, Eq. (2) correctly reproduces (deviations < 4%) the experimentally observed √ ( 2πΈG ) for insensitive nitrobenzene and nitroheterocyclic derivatives like TATB, NTO and DADPyOx, which was not the case for the other equations. Recall that all equations, except Eq. (2), had a trend to overestimate the Gurney velocity of most insensitive compositions compared with the measured value. Moreover, Eqs. (11)–(13) have almost double the MAPE and RMSE values, indicating a lower predictive power and accuracy level than the best performing model Eq. (2). observed Gurney velocities, and therefore the value of the adjustable parameter (λ) had to be changed from 0.5 to 0.25 which results in model estimates that are in close agreement with the empirical data. Fig. 3 shows the chemical structure of compounds used in the formulation of the explosives listed in Table 6, which, except for hydrazinium nitrate (HN), fall into Type IV or V explosives. Further, it is noticed in Fig. 3 that these compounds are particularly hydrogen- and nitrogenrich energetic materials and that many of these feature the guanidine moiety substituted with nitro- or amino functionalities like NQ, ANQ and TAGN. One interesting observation that emerges from the analysis of the results provided in Table 6 is that Eq. (11) fails to correctly estimate the Gurney velocity of explosives compositions listed in the ο¬rst ο¬ve entries of the table which was not surprising since, as mentioned earlier, these compositions are distinguished by high contents of hydrogen, a fact that contributes to their high detonation velocity despite the low to moderate loading densities as seen, for example, in the case of TAGN and ANQ (1.47 g/cm3 and 1.66 g/cm3 , respectively). The observed high detona- 3.2. Explosive compositions with π = 0.25 For a small group of pure and mixtures of explosives, it was found that the use of Eq. (2) with π = 0.5 consistently underestimate the 287 D. Frem FirePhysChem 3 (2023) 281–291 Fig. 3. Chemical structures for hydrogen- and nitrogen-rich neutral and ionic high explosives. Table 6 Comparison of experimental and predicted Gurney velocities for explosives compositions with λ = 0.25. Percent deviations are shown in parentheses. Compositions TAGN ANQ X-0535 TKX-50/paraο¬n (97/3) AFX-902 NQ/TNT (50/50) NQ/TNT (35/65) NQ/HMX/Estane (45.3/50.2/4.5) HMX/HN/TAGN (45/40/15) HMX/HN (70/30) HN/HMX (65/35) RDX/HN (55/45) PETN/HN (45/55) RMSE (km/s) MAPE (%) √ 2πΈG (km/s) (Eq.(2)) √ √ 2πΈG (km/s) (Eq.(12)) √ 2πΈG (km/s) (Eq.(13)) 8.048 8.522 8.453l 8.810h 2.44 (−1.21) 2.51 (−1.57) 2.60 (4.00) 2.69 (1.51) 2.83 (14.57) 2.90 (13.73) 2.82 (12.80) 2.96 (11.70) 2.58 (4.45) 2.66 (4.31) 2.59 (3.60) 2.74 (3.40) 2.61 (5.67) 2.68 (5.10) 2.57 (2.80) 2.76 (4.15) 2.36i 2.45j 8.344i 7.300j 2.26 (−4.24) 2.51 (2.45) 2.80 (18.64) 2.48 (1.22) 2.52 (6.78) 2.52 (2.86) 2.49 (5.51) 2.50 (2.04) −12.02 2.45j 7.050j 2.56 (4.49) 2.40 (−2.04) 2.50 (2.04) 2.47 (0.82) 1.757 −10.86 2.67k 8.561l 2.74 (2.62) 2.87 (7.49) 2.71 (1.50) 2.73 (2.25) 1.73 −23.16f 2.88 9.008 2.91 (1.04) 3.03 (5.21) 2.85 (−1.04) 2.92 (1.39) 1.78 −14.40f 2.95 9.000 3.04 (3.05) 3.00 (1.69) 2.88 (−2.37) 2.95 (0) 1.71 −38.27f 2.88 9.023 2.87 (−0.35) 3.05 (5.90) 2.87 (−0.35) 2.94 (2.08) 1.68 −24.32 f 2.85 8.675 2.93 (2.81) 2.94 (3.16) 2.83 (−0.70) 2.90 (1.75) 1.65 −52.51f 2.71 8.277 2.91 (7.38) 2.82 (4.06) 2.82 (4.06) 2.90 (7.01) 0.09 2.82 0.24 7.86 0.08 2.88 0.10 3.12 π (g/cm3 ) Δπ»f0 (kcal/mol)a 1.47 1.66 1.787 1.750 √ 2πΈG (km/s) (Exp.)b π· (km/s) −11.50c 5.27c 21.34d 19.90e 2.47 2.55 2.50 g 2.65h 1.742 1.665 −29.09 −14.15 1.658 b 2πΈG (km/s) (Eq.(11)) a Heats of formation (HOF), unless otherwise stated, were taken from [35]. b Experimental Gurney and detonation velocities were taken from [65] unless otherwise stated. c [37]. d HOF of LAX-112 was taken from [75]. e HOF of TKX-50 and paraο¬n (wax) were taken from [76] and [41], respectively. f HOF of TAGN and hydrazinium nitrate (HN) were taken from [37]. g [77]. h [76]. i [28]. j [50]. k [78]. l The detonation velocities were calculated using the BKW thermochemical code with the RDX parameter set [41]. tion velocity for the hydrogen-rich systems may be attributed to their high Chapman-Jouguet (CJ) particle density or the number of moles of gas per gram of explosive [41], however, such an increase in detonation velocity does not necessarily translate into high Gurney velocity which is most likely due to their low heats of detonation. In fact, the calculated heat of detonation for TAGN and ANQ is around 25% lower than that of the conventional explosive TNT (πTNT = 4.329 kJ/g). On the other hand, predictions made by Eq. (2) and Eqs. (12) and (13) that take into account the heat of detonation are in close agreement with experimen- tal data, displaying comparable accuracy in terms of MAPE and RMSE values. 4. Conclusions The new model Eq. (2) has demonstrated a decent prediction accuracy in Gurney velocity determination, compared with the results obtained by Eqs. (10)–(13). With the adjustable parameter (π) set to 0.5, Eq. (2) successfully predicted the Gurney velocity of most of the in288 D. Frem FirePhysChem 3 (2023) 281–291 vestigated explosives including sensitive and insensitive explosives. For explosives belonging to Type IV and V and for hydrazinium nitratecontaining compositions a value of 0.25 for (π) was necessary for Eq. (2) to achieve satisfactory performance compared to the other methods considered. An important implication that emerges from this study is that models based on detonation velocity like Eq. (11) display poor prediction ability when applied to insensitive and hydrogen-rich explosives, in that they tend to overestimate their Gurney velocities which indicate that chemical explosives designed to have high detonation velocity may not necessarily exhibit high Gurney velocity. πΉmix = Substituting the value of (πmix ), (πΉmix ), (π) and (π) into Eq. (2) gives: √√ √ 3 2πΈG = 14.74 (1.742)(2.373) − 0.25 √ 2πΈG = 2.26 kmβs Example 2: Cyclotol 77/23 is made of 77wt% RDX and 23wt% TNT. Both RDX and TNT are Type III explosives. The values of (π) and (πΉ ) for TNT and RDX are calculated as follow: ( ) 1.772(5) + 52(6) − 10(7) − 16 πTNT = = 1.035 kcal/g 4.330 kJβg 227 The author declares that there is no conο¬ict of interest concerning this paper. Appendix πΉTNT = I. Pure compounds 46(7) + 36.75(5) + 190(3) + 277(6) = 12.06 227 πRDX = Example 1: For pentaerythritol tetranitrate (PETN, C5 H8 N4 O12 , Type II explosive, λ = 0.5) the heat of detonation and the parameter psi are calculated from the equations in Table 3: πΉ= (0.95 × 15.52) = 14.74 π=1 Declaration of Competing Interest π = π ∑ πΉRDX = ( ) 1.772(6) + 52(6) − 10(3) + 14.71 = 1.384 kcalβg 5.791 kJβg 222 46(3) + 36.75(6) + 190(6) + 277(6) = 14.24 222 (πmix ) and (πΉmix ) for cyclotol 77/23 are calculated using Eqs. (4a) and (4b): ( ) 2.365(8) + 52(12) − 10(5) − 128.7 = 1.469 kcalβg 6.147 kJβg 316 46(5) + 9.95(8) + 190(4) + 277(12) = 13.90 316 πmix = π ∑ (0.23 × 4.330) + (0.77 × 5.791) = 5.455 kJβg π=1 Substituting the value of (π), (πΉ ), (π) and (π) into Eq. (2) gives: √√ √ 3 2πΈG = 13.90 (1.76)(6.147) − 0.5 πΉmix = √ Substituting the value of (Qmix ), (πΉmix ), (π) and (π) into Eq. (2) gives: √√ √ 3 2πΈG = 13.74 (1.754)(5.455) − 0.5 Example 2: Pressed 2,4-dinitroanisole (DNAN, C7 H6 N2 O5 , Type III explosive, λ = 0.5) ( ) 1.772(6) + 52(5) − 10(7) − 44.61 π = = 0.788 kcalβg 3.297 kJβg 198 √ 46(7) + 36.75(6) + 190(2) + 277(5) = 11.65 198 2πΈG = 2.08 kmβs II. Mixture of explosives Example 1 For AFX-902 (95/5 NQ/Viton A) the heat of detonation and the parameter psi are calculated for NQ (CH4 N4 O2 , Type V explosive, λ = 0.25) only since Viton A is an inert binder: π = ( ) 57.8(2) − 31.4(1) − 22.11 = 0.597 kcalβg 2.498 kJβg 104 πΉ = 354(1) + 107(4) + 190(4) + 36(2) = 15.52 104 (πmix ) and (πΉmix ) are calculated for the energetic component (NQ) using Eqs. (4a) and (4b): πmix = π ∑ 2πΈG = 2.79 kmβs List of chemical and atomic compositions of explosive compounds/formulations ADPyOx: 4-Amino-3,5-dinitropyridine-N-oxide (C5 H4 N4 O5 ) AFX-521: 95/5 PYX/Kel-F 800 (C2.697 H1.095 N1.683 O2.448 F0.133 Cl0.036 ) AFX-902: 95/5 NQ/Viton A (C1.047 H3.747 N3.654 O1.827 F0.174 ) AMP: Azidomethyl-trinitrohexahydropyrimidine (C5 H8 N8 O6 ) AmPicCC: 80/12/6.5/1.5 Explosive D/HTPB/BDNPA-F/MDI (C3.043 H3.554 N1.402 O2.519 ) ANQ: 1-Amino-3-nitroguanidine (CH5 N5 O2 ) CL-14/Viton A (97/3): C2.354 H1.572 N2.273 O2.273 F0.104 Composition A-3: 91/9 RDX/wax (C1.87 H3.74 N2.46 O2.46 ) Composition-B: 63/36/1 RDX/TNT/wax (C2.03 H2.64 N2.18 O2.67 ) Composition C-3: 77/4/10/5/1/3 RDX/TNT/Dinitrotoluene/ Mononitrotoluene/ Nitrocellulose/Tetryl (C1.90 H2.83 N2.34 O2.60 ) Composition C-4: 91/5.3/2.1/1.6 RDX/Di(2-ethylhexyl) sebacate/Polyisobutylene/Motor oil (C1.82 H3.54 N2.46 O2.51 ) Cyclotol 75/25: RDX/TNT (C1.78 H2.58 N2.36 O2.69 ) Cyclotol 77/23: RDX/TNT (C1.750 H2.588 N2.385 O2.689 ) DAAF: 3,3′-Diamino-4,4′-Azoxyfurazan (C4 H4 N8 O3 ) DADPyOx: 2,6-Diamino-3,5-dinitropyridine-N-oxide (C5 H5 N5 O5 ) DINA: Dioxyethylnitramine dinitrate (C4 H8 N4 O8 ) DINA-Dynamite (90/10): C1.728 H3.294 N1.586 O3.361 DINGU/HNE/wax (63/32/5): C1.657 H1.800 N2.269 O2.909 DNAN: 2,4-Dinitroanisole (C7 H6 N2 O5 ) DNAN/RDX/NTO (40/20/40): C2.300 H2.368 N2.175 O2.474 ETN/HMX (80/20): C1.330 H2.130 N1.600 O3.719 FOX-7: 1,1-Diamino-2,2-dinitroethylene (C2 H4 N4 O4 ) Substituting the value of (π), (πΉ ), (π) and (π) into Eq. (2) gives: √√ √ 3 2πΈG = 11.65 (1.52)(3.297) − 0.5 √ (0.23 × 12.06) + (0.77 × 14.24) = 13.74 π=1 2πΈG = 2.93 kmβs πΉ= π ∑ (0.95 × 2.498) = 2.373 kJβg π=1 289 D. Frem FirePhysChem 3 (2023) 281–291 (FOX-7)vit: 94/6 FOX-7/Viton A (C1.431 H2.653 N2.541 O2.541 F0.208 ) HMX: 1,3,5,7-Tetranitro-1,3,5,7-tetraazacyclooctane (C4 H8 N8 O8 ) HMX/ETN (65/35): C1.342 H2.452 N2.220 O3.147 HMX/HN (70/30): C0.946 H3.471 N2.839 O2.839 HMX/HN/TAGN (45/40/15): C0.698 H4.130 N3.108 O2.749 HMX/TNT (70/30): C1.871 H2.553 N2.288 O2.685 HMX/wax (96/4): C1.583 H3.166 N2.595 O2.595 HN: Hydrazinium nitrate (H5 N3 O3 ) HN/HMX (65/35): C0.473 H4.367 N2.999 O2.999 HNS: 2,2′,4,4′,6,6′-Hexanitrostilbene (C14 H6 N6 O12 ) KH 30: 66.5/30/3.5 HMX/NTO/Viton A (C1.454 H2.324 N2.720 O2.490 F0.122 ) KH 50: 47.5/50/2.5 HMX/NTO/Viton A (C1.478 H2.100 N2.822 O2.438 F0.087 ) LAX-112: 3,6-Diamino-s-tetrazine-1,4-dioxide (C2 H4 N6 O2 ) LX-09: 93/4.6/2.4 HMX/DNPA/FEFO (C1.43 H2.74 N2.59 O2.72 F0.02 ) LX-10: 95/5 HMX/Viton A (C1.41 H2.66 N2.57 O2.57 F0.16 ) LX-14: 95.5/4.5 HMX/Estane 5702-F1 (C1.52 H2.92 N2.59 O2.66 ) 2-MNDPy: 2-Methylnitramino-3,5-dinitropyridine (C6 H5 N5 O6 ) Bis-MNDPy: 2,6-Bis(methylnitramino)−3,5-dinitropyridine (C7 H7 N7 O8 ) NC/DINA (60/40): C2.032 H3.094 N1.181 O3.499 NITRA: 3-Nitramino-1,2,4-triazole (C2 H3 N5 O2 ) NM: Nitromethane (CH3 NO2 ) NMP: 5-Nitroxymethyl-1,3,5-trinitro-hexahydropyrimidine (C5 H8 N6 O9 ) NQ: Nitroguanidine (CH4 N4 O2 ) NQ/HMX/Estane (45.3/50.2/4.5): C1.345 H3.437 N3.108 O2.307 NQ/TNT (35/65): C2.341 H2.778 N2.205 O2.391 NQ/TNT (50/50): C2.023 H3.024 N2.584 O2.283 NTO: 3-Nitro-1,2,4-triazol-5-one (C2 H2 N4 O3 ) NTO/DAAF/Kel-F 800 (67/30/3): (C1.654 H1.611 N3.193 O1.970 F0.080 Cl0.022 ) NTO/FOX-7/Kel-F 800 (67/30/3): C1.494 H1.856 N2.872 O2.357 F0.08 Cl0.022 NTO/HNE/wax (76/19/5): C1.653 H1.884 N2.718 O2.514 Octol 75/25: HMX/TNT (C1.78 H2.58 N2.36 O2.69 ) Octol 78/22: HMX/TNT (C1.732 H2.593 N2.399 O2.690 ) PAX-60-MD: 62/37/1 HMX/DNP/wax (C1.612 H2.287 N2.612 O2.612 ) PAX-63-MD: 20/79/1 HMX/DNP/wax (C1.842 H1.683 N2.541 O2.541 ) PBX-91C: 90/10 HMX/HTPB (C1.924 H3.497 N2.439 O2.455 ) PBX-9501: 95/2.5/2.5 HMX/Estane/BDNPA-F (C1.47 H2.86 N2.60 O2.69 ) PBX-9502: 95/5 TATB/Kel-F 800 (C2.304 H2.232 N2.208 O2.208 F0.133 Cl0.036 ) PBX-9404: 94/3/3 HMX/NC/CEF (C1.40 H2.75 N2.57 O2.69 Cl0.03 P0.01 ) PETN: Pentaerythritol tetranitrate (C5 H8 N4 O12 ) PETN/HN (45/55): C0.712 H4.034 N2.306 O3.446 PETN/rubber (89/11): C2.186 H3.425 N1.134 O3.404 PETN/Viton (95/5): C1.637 H2.499 N1.203 O3.608 F0.174 QRX080: 95/5 FOX-7/Hytemp C1.557 H3.036 N2.568 O2.646 RDX: 1,3,5-Trinitro-1,3,5-triazacyclohexane (C3 H6 N6 O6 ) RDX/HN (55/45): C0.743 H3.855 N2.908 O2.908 RDX/HTPB (85/15): C2.210 H3.895 N2.307 O2.331 RDX/TNT (50/50): C2.218 H2.453 N2.012 O2.673 RDX/TNT (60/40): C2.044 H2.503 N2.150 O2.679 RDX/wax (94/6): C1.70 H3.39 N2.54 O2.54 RDX/wax (95/5): C1.641 H3.282 N2.568 O2.568 RX-45-AA: 95/5 ANTA/Kel-F 800 (C1.570 H2.233 N3.682 O1.473 F0.133 Cl0.036 ) SK TNBI: Bis(semicarbazidium) 4,4′,5,5′-tetranitro-2,2′-biimidazol1-ide (C8 H12 N14 O10 ) TAGN: Triaminoguanidine nitrate (CH9 N7 O3 ) TATB: 1,3,5-Triamino-2,4,6-trinitrobenzene (C6 H6 N6 O6 ) TATB/TNT (60/40): C2.628 H2.275 N1.923 O2.452 TeNHHPm: 1,1,3,5-Tetranitrohexahydropyrimidine (C4 H6 N6 O8 ) Tetryl: 2,4,6-Trinitrophenyl-N-methylnitramine (C7 H5 N5 O8 ) TKX-50: Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (C2 H8 N10 O4 ) TKX-50/paraο¬n (97/3): C1.036 H3.717 N4.110 O1.644 TMNTz: 2,4,6-Tris(methylnitramino)−1,3,5-triazine (C6 H9 N9 O6 ) TNAD: 1,4,5,8-Tetranitro-1,4,5,8-tetraazadecalin (C6 H10 N8 O8 ) TNT: 2,4,6-Trinitrotoluene (C7 H5 N3 O6 ) TNT/RDX/NTO (40/20/40): C2.119 H2.037 N2.300 O2.521 X-0535: 95/5 LAX-112/Oxy-461 (C1.438 H2.746 N3.958 O1.319 F0.071 Cl0.06 ) References [1] T.M. 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