Double-base Propellants Research Articles

Thermophysical and Chemical Processes of Burning of Double-Base Solid Propellants under External Irradiation

A piece-wise linear function for the dependence of the burning rate on the radiant flux and its break point are important burning characteristics of double base propellants under external irradiation. The Fourier equation can be used to analyze the burning characteristics, but some early models resulted in discontinuous characteristic parameters at the break point. In this paper, a new model, where the loss of external irradiation energy was considered above the surface of condensed phase, would be used to resolve the contradiction. The burning characteristics of 1040, 1041, N-5 and N propellants were analyzed.

Studies on diaminoglyoxime (DAG): Thermolysis and evaluation as ballistic modifier in double base propellant

This paper reports thermolysis of diaminoglyoxime (DAG) and its evaluation as a ballistic modifier in double base propellant formulations. Differential scanning calorimetry (DSC) and simultaneous thermal analysis (DTA–thermogravimetric (TG)) revealed that DAG decomposes in two stages. Kinetics of initial stage of thermal decomposition of DAG evaluated from TG data gave activation energy ( E a) of 153 kJ mol −1. The high-temperature Fourier transform Infrared (FTIR) spectra of DAG suggested preferential cleavage of N O and C NH 2 during decomposition. Mass spectral data also suggest possibility of similar process. The hyphenated TG–FTIR data also revealed the evolution of gases containing species, such as CN, NH, OH and oxides of nitrogen during thermal decomposition. Evaluation of DAG as a ballistic modifier in RDX incorporated double base propellant formulations indicated that it brings down the pressure index to 0.17 compared to 0.79 for a control composition in the pressure range 6.9–8.8 MPa when used in combination with basic lead salycilate (BLS). The study suggests that combination of DAG and BLS need to be optimized to achieve more remarkable effects than BLS alone. It was observed that DAG does not have adverse effect on vulnerability and chemical stability of the propellant formulation.

High-performance thin-layer chromatographic analysis of the organic components of composite modified double-base propellants

Qualitative and quantitative analysis of the organic components of composite modified double-base (CMDB) propellants have been performed by HPTLC. The method enabled analysis of a five-component mixture in less than 10 min. The relative distribution of the components of the mixture was determined by means of a UV absorbance detector capable of monitoring at several different wavelengths and of providing UV spectra which could be used to assess peak purity. Detection limits were at nanogram levels.

Plasma Ignition and Combustion of JA2 Propellant

Experiments were performed to investigate the effects of various parameters on plasma-driven ignition and combustion of a double-base propellant under closed-chamber conditions. The parameters varied include input electrical energy, nozzle length and inner diameter, nozzle exit to propellant distance, as well as propellant sample thickness. Chamber pressure was measured to determine the ignition delay and to deduce the regression rate. High-speed images of the plasma jets and combustion event were also recorded. At low plasma energies, rapid, plasma-driven burning occurred, but self-sustained burning was not achieved. With moderate plasma energies, combustion of the propellant exhibited a two-stage burning behavior: one stage of plasma-driven rapid burning that occurred during the plasma pulse and a second stage of slower self-sustained burning that occurred with a clear delay after the first stage. When plasma energy was increased further, the two-stage behavior became less distinct and eventually disappeared, leaving only one stage of burning. Nozzle length and diameter affected the ignition and combustion characteristics as a result of energy losses from the plasma as it flows through the nozzle. The propellant burning behavior is also affected by both nozzle-sample distance and sample thickness. High-speed images revealed vigorous motion of gases in the closed chamber, which was induced by the plasma jet. Also, the images showed what appeared to be JA2 fragments; this observation was confirmed by recovery of fragmented propellant after some of the tests.

Thermal decomposition behavior and non‐isothermal decomposition reaction of copper(II) salt of 4‐hydroxy‐3,5‐dinitropyridine oxide and its application in solid rocket propellant

AbstractThe thermal decomposition behavior and kinetic parameters of the exothermic decomposition reactions of the title compound in a temperature‐programmed mode have been investigated by means of DSC, TG‐DTG and lower rate Thermolysis/FTIR. The possible reaction mechanism was proposed. The critical temperature of thermal explosion was calculated. The influence of the title compound on the combustion characteristic of composite modified double base propellant containing RDX has been explored with the strand burner. The results show that the kinetic model function in differential form, apparent activation energy Ea and pre‐exponential factor A of the major exothermic decomposition reaction are 1‐a,207.98 kJ*mol−1 and 1015.64 s−1, respectively. The critical temperature of thermal explosion of the compound is 312.87 C. The kinetic equation of the major exothermic decomposition process of the title compound at 0.1 MPa could be expressed as: dα/dT=1016.42 (1–α)e‐2.502×104/T As an auxiliary catalyst, the title compound can help the main catalyst lead salt of 4‐hydroxy‐3,5dinitropyridine oxide to enhance the burning rate and reduce the pressure exponent of RDX‐CMDB propellant.

Interaction of Capillary Plasma with Double-Base and Composite Propellants

Experiments were conducted to characterize the electrothermal capillary plasma and its interaction with a double-base propellant, JA2, and two nitramine composite propellants, M43 and XM39, in closed-chamber and open-air conditions. Pressure-time histories were recorded during ignition and burning of the propellants in the closed chamber. Experimental results indicate significant differences in ignition and combustion of the propellants. The composite propellants exhibited a two-stage burning behavior: one stage of rapid burning driven by the plasma and a second stage of slower self-sustained burning, which occurred with a clear delay after the first stage. During the burning that is driven by the plasma, the burn rate was largely independent of propellant type. Optical microscopic images of recovered propellant samples showed clear physical changes in surface and possibly in subsurface structure, an indication of in-depth melting, vaporization, and possibly chemical reactions. Plasma-induced mass losses for the three propellants were obtained from open-air testing and compared to the values calculated based on the pressure data from closed-chamber tests.

Effect of Some Catalysts on Combustion of Double-Base Propellants

The effect of PbO2, SnO2, TiO2, and Bi on the combustion of propellants of various compositions is investigated. It is established that SnO2, TiO2, and Bi have a significant effect on the burning rate of propellants without carbon black and additional plastifiers. A marked catalytic effect of PbO2 is manifested only when its content is higher than 5%. It is shown that the addition of SnO2 and PbO2 to propellants leads to formation of a carbon black matrix on the burning surface, on which catalyst particles build up. With the addition of carbon black to propellants, the catalytic action of TiO2 and Bi is enhanced only slightly, and the effect of SnO2 at moderate pressures is markedly reduced due to a considerable increase in the degree of reduction of the active form of (SnO2) catalyst up to its inactive forms (SnO and β‐Sn).

Studies on azotetrazolate based high nitrogen content high energy material spotential additives for rocket propellants

This paper reports the synthesis, characterisation and thermolysis studies of a series of azotetrazolate salts, viz., ammonium/guanidinium/triaminoguanidinium [azotetrazolate]. TG-DTA and DSC results of these compounds exhibited their thermal stability up to 180°C. DSC indicated the highest heat release (2804 J g−1) for guanidinium azotetrazolate salt during exothermic decomposition. FTIR of the decomposition products of azotetrazolate salts showed bands at 3264 and 2358 cm−1 which may be attributed to gaseous species such as NH3 and HCN or NH2CN. The sensitivity data suggests low vulnerability of ammonium and guanidinium salts. In cyclic voltammetric studies all the salts showed similar response in reduction reactions. Triamino guanidinium azotetrazolate (TAGAZ) was incorporated into solid propellant formulations in order to establish the compatibility of this class of compounds. DSC results revealed that it does not have adverse effect on thermal stability of double base matrix. The burning rate data obtained indicated that TAGAZ acts as an efficient energetic additive in composite modified double base (CMDB) propellant formulations in high-pressure region.

A Study on Gun Propellants Based on Butyl-NENA

Researchers have sought to improve performance of gun propellants by incorporating various additives in the propellant matrix. Energetic plasticizers were primarily introduced in the formulation to improve the energy content of the propellant with the possible fallout in the form of improvement in the mechanical property. Butyl-NENA is widely reported to play the dual role of better energetics with an improved mechanical property. In the present paper butyl-NENA has been introduced in typical single, double, and triple base propellant formulations. Introduction of butyl-NENA in a single base propellant has resulted in significant improvement in energetics, while in double base and triple base propellants, it has contributed to enhancing insensitivity and improving mechanical properties.

Properties of Gas‐Generating Mixtures Related to Different Fuel and Oxidizer Compositions

AbstractThis work focuses on solid energetic materials designed to produce high‐pressure gas for pressurizing or inflating devices. In small gas generators sodium azide is often used. Unfortunately, this chemical exhibits drawbacks concerning toxicity and yield of gas. Other classical gas‐generating agents are double base propellants. However, they deliver toxic and reactive gases and their combustion temperatures are high. In previous work a series of alternative gas‐generating compositions have been proposed, fuelled with double base propellants, azodicarbonamide, nitroguanidine or guanidine nitrate and oxidized with potassium nitrate or potassium perchlorate. They were theoretically and experimentally evaluated on a series of combustion properties, such as ignition delay, burning rate, vivacity, specific energy, etc. The purpose of this paper is to experimentally examine the gas production of the previously proposed compositions. The yield of gas is determined through static pressure measurements after a closed vessel test, while the composition of the combustion gases is investigated through gas analysis. The addition of an oxidizer causes a significant drop in the yield of gas, but avoids the formation of hazardous gases, such as H2 and CO, in most of the studied cases. The only exception is the mixture of a double base propellant with potassium nitrate: potassium nitrate does not fully react with the double base propellant and therefore the formation of CO and H2 is not prevented.

Combustion and Thermal Studies on Al/Ti/Ni/Zr Composite Modified Double-Base Systems

Slurry-cast metallized ammonium perchlorate (AP)-composite modified double-base (CMDB) propellants incorporating Ni, Ti, and Zr were studied. Aluminized formulations were investigated as reference. Selected ballistic modifiers, namely, copper chromite (Cu-chromite)/ferric oxide (Fe 2 O 3 )/ferric acetyl acetonate (FeAA)/basic lead salicylate (BLS)+Cu 2 O+carbon black (C-black) combinations were also evaluated for their effectiveness. An acoustic emission technique was applied to determine the burning rates in the pressure range of 1-10.8 MPa, and thermal data were generated by applying differential thermal analysis, thermogravimetry, and differential scanning calorimetry techniques. The control formulation based on 30% AP dispersed in a 70% double base matrix, gave stable combustion in the entire pressure range studied. Inclusion of metals (2.5-17.5% at the expense of AP) resulted in a decrease in the burning rates with the increase in metal content. Ni-based formulations exhibited burning rates superior to aluminized formulations particularly with high metal content. The overall best burning-rate results were obtained with Zr, followed by Ti. Among ballistic modifiers, Cu-chromite was found to be the most effective, followed by the BLS + Cu 2 O + C-black combination. An interesting composition with super-burning-rate characteristics (10-60 mm/s in the 1-10.8 MPa pressure range) emerged during the research. Thermal studies show the heat sink effect of metals. However, Ni, Ti, and Zr appear to produce compensating heat feedback to a greater extent than Al. Cu-chromite appears to be highly effective in facilitating both condensed- and gas-phase combustion reactions.

Combustion-Front Non-One-Dimensionality in Single- and Double-Base Propellants

Parameters of transverse waves propagating over the surface of specimens pressed from colloxylin and double-base propellants A and N are studied. By means of microvideofilming and thermocouple measurements, it is shown that the burning sites on the specimen surface are formed by a set of transverse waves. Under atmospheric pressure, the transverse-wave front has the form of a step 0.5–1.1 mm high and decreases with increasing pressure or initial temperature of the specimen. The front propagates with variable velocities in the horizontal and vertical directions. The mean velocity of the transverse wave is three to eight times higher than the normal burning rate of the specimen as a whole (with a wide spread of local values) and increases with increasing pressure. Behind the front, combustion can be interrupted till the arrival of the next transverse wave. As in the SHS process, the reason for the emergence of the transverse waves is combustion-wave spatial instability.

Approach to the Catalytic Mechanism of Fullerene in Propellants

Through burning rate experiments and thermal analysis, the influence of adding three forms of carbon--carbon black, C 60 , and fullerene soot--separately in double-based propellants is studied. It is shown that C 60 and fullerene soot enhance the burning rate of double-based propellants and broaden the plateau region. By the AM1 method calculation, an attractive force between C 60 and NO is proved, which suggests a catalytic effect of fullerene on NO reduction, in contrast with a repellent force between graphite structure and NO. From analysis of the molecular structure of fullerene and its bonding ability, the catalytic mechanism of Pb x C 60 active sites is posed to explain why C 60 and fullerene soot have better catalytic effects than carbon black in a Pb-Cu-carbon black catalytic system in double-based propellants.

Mechanical analysis on rocket propellants

The mechanical properties of solid rocket propellants are very important for good functioning of rocket motors. During use and storage the mechanical properties of rocket propellants are changing, due to chemical and mechanical influences such as thermal reactions, oxidation reactions or vibrations. These influences can result in malfunctioning, leading to an unwanted explosion of the rocket motor. Most of modern rocket propellants consist of a polymer matrix (i.e. HTPB) filled with a crystalline material (i.e. AP, AN). However, the more conventional double base propellants consist of a solid gel matrix with additives, such as stabilizers. Both materials show a mechanical behaviour, quite similar to that of general polymers. To describe the material behaviour of both propellants a linear visco-elastic theory is often used to describe the mechanical behaviour for small deformations. Because the time-temperature dependency is also valid for these materials a mastercurve can be constituted. With this mastercurve the response properties (stiffness) under extreme conditions can be determined. At TNO-PML a mastercurve of a double base propellant was constituted using dynamical mechanical analysis (DMA) and compared with a mastercurve reduced from conventional (static) stress relaxation tests. The mechanical properties of this double base propellant determined by DMA were compared with conventional (quasi-static) tensile test results.

Improvement of mechanical properties of double base propellants for buster motors

Acetone vapors influence on the double base propellant mechanical properties and the burning rate is shown and analyzed. Mechanical investigations were done with uniaxial tensile and impact tests. Burning rate investigations were carried out in the manometric bomb and rocket motors. The obtained results of the investigations show a significant acetone vapors influence on mechanical properties without a significant influence on the burning rate.

Tailoring of unsaturated polyesters for inhibition of double-base and composite modified double-base rocket propellants†

Unsaturated polyesters have proved their potential for inhibition of double-base (DB) and composite modified double-base (CMDB) rocket propellants but usually suffer from slightly higher nitroglycerine (NG) absorption andlower flame retardant characteristics. This requires tailoring of their properties through different techniques. This review summarizes different techniques for this purpose and presents the data generated. The present status of these tailored/modified systems is also discussed in detail followed by future scope of research in this field.

Catalytic activity of lead and copper oxides in the reaction of double base propellant burning

The investigation includes experimental and phenomenological studies of the catalytic activity of lead and copper oxides, (with a constant ratio of basic lead-stearate, calcium carbonate and carbon - black) in the process of burning of double base propellants of different energies. The catalytic activity ratio is used as a measure of catalytic activity, and it represents the ratio of the burning rate of double base propellants with a catalyst referent model to the burning rate of double base propellants without a ballistic catalyst referent model.

Contribution to the analysis of burning of double base propellants

The investigation included studies of catalytic activities of ballistic modificators and the process of burning of double base propellants. Burning of solid rocket propellants in one of the most complex types of burning. As it is known, any kind of burning is presented by chemical reactions and therefore chemical kinetics should play the basic role in the theory of burning. But, in rocket motors, burning is often complex and its character is change enable. The laws of chemical kinetics, therefore yield before the laws of thermal conduction and gas-dynamics.

ETC closed-vessel experiments with alkali-doped propellants

Experiments with the objective to stimulate combustion of solid propellant through addition of electric energy are reported. In this paper, the idea of stimulating combustion by conducting an electric current through the flame is tested. The current leads to resistive heating of the flame, which adds to the reaction heat, and thus amplifies the heat feedback to the unburnt propellant. The electric conductivity of the flame must be sufficiently high in order to reduce random delay and to increase controllability of the electric discharge. The propellant composition has to be modified to meet this requirement. Thermochemical calculations give the equilibrium state and composition, which are used to estimate the flame conductivity. Calculations are carried out for several propellant compositions: some being considered for preparation, while others are intended solely for comparison. The calculation results indicate that, given a high flame temperature, a substantial increase in conductivity can be obtained by doping the propellants with alkali compounds. A double-base propellant doped with potassium nitrate has been used in the experiments so far. The experiments are performed in a closed vessel where a propellant slab is pinched between two copper plates connected to a pulsed power supply. Results presented include current and voltage recordings, yielding the added electric energy, and pressure measurements from which the burn rate can be determined.

Properties of a Gas-Generating Composition Related to the Particle Size of the Oxidizer

In general gas generators are defined as devices which produce force or power in the form of gas. In the present work we will focus on cold gas generators actuated by pyrotechnics. These gas generators are often applied for pressurizing or inflating systems in which high temperatures are not acceptable. Typical applications are: airbags, seat-belt tensioners, fire extinguishers. Depending on the application, gas-generating materials have to fulfil a series of requirements, such as good performance reproducibility, easy and reliable ignition, low explosion temperature, high yield of gas, low yield of condensed products, specific gas composition, and adequate burning rate and vivacity. In previous work a whole range of possibly suitable single compounds, such as sodium azide, double base propellant, azodicarbonamide, guanidine derivatives and azole derivatives were studied. These compounds – whether or not stoichiometrically mixed with an oxidizer (e.g. KNO3, KClO4 or NH4NO3) – were theoretically and experimentally examined in order to evaluate their combustion properties. The objective of this work is to experimentally investigate the influence of the particle size of an oxidizer on the combustion behavior of a gas-generating pyrotechnic mixture. As an example a series of nitroguanidine (NQ) / potassium nitrate (KNO3)-mixtures with well-defined KNO3-particle size fractions are selected. Raman spectroscopy is used to examine the constituent distribution within the bulk and thus the mixing efficiency. Closed vessel tests are used to experimentally compare ignition delay, burning rate, dynamic vivacity, and yield of gas. The composition of the combustion gases is examined through gas analysis. The experiments show that a decrease of the particle size of the KNO3-particles has a positive influence on the mixing efficiency and on the investigated combustion properties of a NQ/KNO3-composition. The combustion process of this mixture becomes better controllable when a small KNO3-particle size fraction is selected, but its combustion behavior is comparable to that of a NQ/KNO3-mixture containing a broad KNO3-particle size distribution.