Rocket Propellant Formulations Research Articles

Application of Lee–Tarver Model for Energetic Materials Safety Assessment Utilized in Aerospace Applications

Energetic materials, essential for rocket propulsion, play a crucial role in aerospace systems. These materials lack sufficient safety assessments and pose significant risks to life and infrastructure. The slow progress in this field is hindered by prohibitively high experimental costs and the inherently destructive nature of these experiments. This study aimed to evaluate modeling-based safety assessments, primarily utilizing the Lee–Tarver model. It specifically addressed the threat posed by shaped charges during transportation. Experimental analyses employed 50 mm JH-2 shaped charges, targeting RDX-based JH-2 formulation, since RDX is widely used in various rocket motor propellant formulations. TNT was also used to enhance the validation of the Lee–Tarver model findings. Various logistical configurations were explored, testing steel container walls ranging from 10 mm thickness to reinforced walls of 50 mm, 60 mm, and 65 mm steel. Comparative analysis with experiments reinforced the accuracy of the Lee–Tarver model’s numerical predictions. Both simulations and experiments affirmed that a 65 mm steel protection suffices for the safe transportation of RDX-based JH-2 formulations and TNT within a 10 mm storage box in logistical setups. Furthermore, this study emphasizes the Lee–Tarver model’s reliability for most energetic materials safety assessments, while acknowledging certain limitations.

Titanium a novel catalyst and high energy dense material: an opportunity for composite propellants with enhanced performance

ABSTRACT Whereas aluminum with combustion enthalpy of 32 KJ/g is the universal reactive metal particles, its passive protective oxide layer could encounter its efficient combustion. While titanium can offer low combustion enthalpy (20 KJ/g), it does not expose passive oxide layer. The impact of both reactive particles on ammonium perchlorate (AP) decomposition enthalpy was investigated via DSC. Aluminum and titanium particles secured an increase in AP decomposition enthalpy by 46.9%, and 80.7% respectively. This significant impact of titanium particles was ascribed to full exploitation of metal energy content. The impact of titanium particles on AP decomposition kinetics was assessed via Kissinger, KAS, and FWO models using TGA. Whereas virgin AP demonstrated average apparent activation energy of 155 KJ/mol, Ti/AP demonstrated average apparent activation energy of 141.2 KJ/mol. Solid rocket propellant formulations based on 17 wt % metal (Al or Ti) were developed via mixing and vacuum casting. Ballistic performance was investigated using small-scale ballistic evaluation rocket motor. Ti-based formulation offered an increase in propellant burning rate, average operating pressure, average thrust by 18.2%, 26.5%, and 19.7% respectively. It was concluded that titanium particles have a dual effect as efficient high energy dense material and as a catalyst.

Thermal decomposition and kinetic modeling of HNTO/AN-based composite solid propellant in the presence of GO-based nanocatalyst

The present study has been conducted to investigate the characteristics of composite solid propellant (CSP) based on hydrazinium 3-nitro-1,2,4-triazol-5-one and ammonium nitrate (HNTO/AN) cocrystal as an oxidizer and hydroxyl-terminated polybutadiene (HTPB) as a binder, supplemented with or without nanocatalyst (triaminoguanidine-transition iron, containing graphene oxide). NASA Lewis Code, Chemical Equilibrium with Application (CEA), has been used to select the optimal formulation through the evaluation of the theoretical performance. Compared to the AP/HTPB baseline formulation, the developed one presents promising properties since it may deliver an interesting specific impulse value (231 s−1). On the other hand, based on the DSC data, the kinetic triplet of the studied samples was determined using four model-free integral methods, namely, it-KAS, it-FWO, VYA, and TAS. It was observed that the decomposition peak temperature (Tp) and the activation energy (Ea) decreased obviously after the addition of the nanocatalyst. This study will certainly motivate further researches in the field of energetic cocrystals and graphene-based materials expected to be used in solid rocket propellant formulations.

Effect of Mixed Isocyanate Curing Agents on the Performance of In Situ‐Prepared HTPE Binder Applied in Propellant

AbstractA novel hydroxyl‐terminated block copolymer (HTPE) binder was prepared through an in situ preparation method to replace the traditional HTPE binder. The preparation method is less costly and bypasses the preparation of the HTPE prepolymer intermediate, thus avoiding the complicated prepolymer synthesis process. Uniaxial tensile testing, low‐field nuclear magnetic resonance, and infrared spectroscopy were used to investigate the mechanical properties, curing networks, and hydrogen bonding (H‐bonds) of the binder. The crosslink density (Ve) decreased with an increase in the ratio of −NCO in the IPDI to the total −NCO in the IPDI and N100 (χ). The proportion of H‐bonds formed by the imino groups increased with the IPDI content and reached 86.53 % at a χ value of 90 %, indicating a positive correlation between the H‐bonds and σm. Additionally, to study the pot life of the in situ‐prepared HTPE binder, the rheological properties of the curing reactions were studied. When the χ value was in the range of 50 %–90 %, the pot life of the binder met the composite propellant requirements for military applications. The thermal decomposition behaviors of the in situ‐prepared HTPE binder and the traditional HTPE binder were investigated by the coupling analysis of thermogravimetry‐Fourier transform infrared spectroscopy (TG‐FTIR), and the novel in situ‐prepared HTPE binder exhibited good thermal stability and superior energetic performance. Compared with the traditional HTPE‐based propellant, the mechanical properties of the in situ‐prepared‐HTPE‐based propellants were greatly improved. With these data, the in situ‐prepared HTPE binder has great potential for application in rocket propellant formulations.

Catalytic action of carbon nanotubes on ammonium perchlorate thermal behavior

This work focuses on the catalytic activity of ammonium perchlorate (AP) through the encapsulation technique using the single-walled carbon nanotubes (SWCNTs) and the multi-walled Carbon Nanotubes (MWCNTs). Encapsulation process took place utilizing a revised approach of the fast-crash solvent–antisolvent method. Particle shape and size were characterized using EDX and SEM, while the thermal behavior of AP/SWCNTs and AP/MWCNTs composite particles was evaluated using DSC together with TGA. The TGA data were applied for quantifying the AP activation energy using the Kissinger method and was confirmed through the Kissinger–Akahira–Sunose (KAS) method. The obtained encapsulated AP showed a significant reduction in the decomposition temperature and a major increase in the overall heat release of AP. Also, kinetics study data showed that encapsulated AP possessed lower activation energy in comparison to that of the pure AP. These results established that carbon nanotubes (CNTs) could be a promising innovative catalyst that has a straightforward impact on the ammonium perchlorate thermal activity, thus affects the thermal behavior and performance of the rocket propellant formulations.

Design of new energetic materials based on derivatives of 1,3,5-trinitrobenzenes: A theoretical and computational prediction of detonation properties, blast impulse and combustion parameters

This paper reports the design of some of the new ionic based high energy materials derived from the anion of picric acid (2,4,6-trinitrobenzene-1-ol), styphnic acid (2,4,6-trinitrobenzene-1,3-diol) and 2,4,6-trinitrophloroglucinol (2,4,6-trinitrobenzene-1,3,5-triol) and cation derived from the key synthon molecules such as 5-trifluoromethyl-1H-tetrazole, 5-dinitromethyl-1H-tetrazole and 5-azido-1H–tetrazole-1-carbonitrile. The detonation properties of these newly proposed compounds are predicted by using software such as EXPLO-5, EXTEC and LOTUSES and Keshvarz method. Moreover, other explosive parameters such as density, gurney velocity, and oxygen balance and decomposition products of the newly designed molecules have also been predicted and reported for the first time in this manuscript. The predicted detonation parameters of some of the newly designed compounds exhibit higher velocity of detonation (VOD) and detonation pressure in comparison to other well-known benchmark explosives such as 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitro-1,3,5-triazinane (RDX). Further, the peak over pressure (POP) and the blast impulse parameters of the newly designed compounds are predicted by using Shock physics explicit eulerian dynamics (SPEED) software, and the same is reported for the first time in this work. The work also reports the theoretical prediction of impact and electrostatic spark sensitivity parameters for the newly designed molecules. The ballistic performance parameters of the newly designed ionic energetic materials are also predicted by incorporating them into model composite rocket propellant formulations. The predicted ballistic parameters indicate that the proposed materials may find an application in the propellant formulation as an energetic additive.

Bis(3-nitro-1-(trinitromethyl)-1H-1,2,4-triazol-5-yl)methanone: An Applicable and Very Dense Green Oxidizer.

Ammonium perchlorate (AP) is most often used as a practical solid rocket propellant because of its excellent performance. However, AP has many shortcomings, including instability, high negative enthalpy of formation, and claimed health and environmental issues resulting from its combustion products. The pursuit of highly dense, high-performance, and environmentally friendly oxidizers as solid propellants has long attracted scientists around the world. In this work, bis(3-nitro-1-(trinitromethyl)-1H-1,2,4-triazol-5-yl)methanone (3) was obtained from bis(3-nitro-1H-1,2,4-triazol-5-yl)methane (1) with chloroacetone followed by nitration. The structure of 3 was confirmed by elemental analysis and single-crystal X-ray diffraction. By introducing the carbonyl moiety, the density of 3 was increased to 1.945 g/cm3 and the decomposition temperature increased to 164 °C. Compound 3 is a green energetic oxidizer that has a positive oxygen balance (+8.7%), a high specific impulse (218 s), and an acceptable sensitivity (9 J, 240 N), making it a practical replacement for AP in solid rocket propellant formulations.

1,3-Bis(3,4,5-trifluoro-2,6-dinitrophenyl)urea (ZXC-19): a multifluorine substituted propellant with superior detonation performance

Fluorine-containing explosives have potential applications in rocket propellant and explosive formulations because they produce a large number of products with a smaller molecular weight and high detonation performance when they are detonated.

TGA, DSC and DFT Studies of TKX‐50, ABTOX and Their Key Precursors

AbstractTKX‐50 (Dihydroxylammonium 5,5’‐bistetrazolate‐1,1’‐dioxide) and ABTOX (Diammonium salt of 5,5’‐bistetrazole‐1,1′‐diolate) being simple and cheap to prepare from commonly available chemicals, are emerging as promising energetic materials along with the advantages like required thermal insensitivity, low toxicity and safe handling. In order to synthesize such powerful materials with utmost care, it is essential to know about the precursors and reaction intermediates involved. Therefore, the detailed thermal analyses of various precursors such as glyoxime (I), dichloroglyoxime (II), diazidoglyoxime (III) and bistetrazoledihydroxide (IV) and final products viz., TKX‐50 (V) and ABTOX (VI) were carried out using differential scanning calorimetric and thermal gravimetric analysis experiments. The relative trend of band gap values calculated from the difference of HOMO and LUMO is well correlated with the decomposition temperatures (Tmax) values at a heating rate of 10 °C min−1 indicating the relative thermal stability of I–VI. The impact and friction sensitivity of ABTOX and TKX‐50 indicated that these compounds are safer than the currently known powerful explosives such as CL‐20. The calculated density impulse of TKX‐50 in rocket propellant formulations was found to be 499 g m−2 s−1 which is similar as that of HMX (494 g m−2 s−1). The theoretical performance prediction of TKX‐50 as the potential ingredient in gun propellant formulations indicated that the TKX‐50 could yield higher force constant (1471 J K−1) in comparison to currently known explosive such as RDX (1412 J K−1).

Recent advances in new oxidizers for solid rocket propulsion

Recent progress in the synthesis and modification of green oxidizers and their application in solid rocket propellant formulations during these last few decades are reviewed.

High pressure structural, elastic and vibrational properties of green energetic oxidizer ammonium dinitramide

Ammonium DiNitramide (ADN) is one of the most promising green energetic oxidizers for future rocket propellant formulations. In the present work, we report a detailed theoretical study on structural, elastic, and vibrational properties of the emerging oxidizer under hydrostatic compression using various dispersion correction methods to capture weak intermolecular (van der Waals and hydrogen bonding) interactions. The calculated ground state lattice parameters, axial compressibilities, and equation of state are in good accord with the available experimental results. Strength of intermolecular interactions has been correlated using the calculated compressibility curves and elastic moduli. Apart from this, we also observe discontinuities in the structural parameters and elastic constants as a function of pressure. Pictorial representation and quantification of intermolecular interactions are described by the 3D Hirshfeld surfaces and 2D finger print maps. In addition, the computed infra-red (IR) spectra at ambient pressure reveal that ADN is found to have more hygroscopic nature over Ammonium Perchlorate (AP) due to the presence of strong hydrogen bonding. Pressure dependent IR spectra show blue- and red-shift of bending and stretching frequencies which leads to weakening and strengthening of the hydrogen bonding below and above 5 GPa, respectively. The abrupt changes in the calculated structural, mechanical, and IR spectra suggest that ADN might undergo a first order structural transformation to a high pressure phase around 5-6 GPa. From the predicted detonation properties, ADN is found to have high and low performance characteristics (DCJ = 8.09 km/s and PCJ = 25.54 GPa) when compared with ammonium based energetic oxidizers (DCJ = 6.50 km/s and PCJ = 17.64 GPa for AP, DCJ = 7.28 km/s and PCJ = 18.71 GPa for ammonium nitrate) and well-known secondary explosives for which DCJ = ∼8-10 km/s and PCJ = ∼30-50 GPa, respectively.

Thermal and mechanical properties of two kinds of hydroxyl-terminated polyether prepolymers and the corresponding polyurethane elastomers

In order to analyze the differences in performance between two kinds of hydroxyl-terminated polyether (HTPE) binders, the curing reaction kinetics of the prepolymers and polyfunctional isocyanate (N-100) molecules and the thermal properties of the prepolymers and the corresponding polyurethane (PU) elastomers were studied by non-isothermal differential scanning calorimetry. The mechanical properties of PU elastomers were also studied by uniaxial tensile tests. With these data, the binder type could be chosen more appropriately for its application in rocket propellant formulations. The results showed that the reactivity of hydroxyl-terminated block copolyether (TPEG) with an isocyanate group is higher than that of hydroxyl-terminated random copolyether (PET). The chain flexibility of TPEG was less than that of PET, but the stereoregularity and crystallization ability of the former were superior. Compared to the prepolymers, the chain flexibility of the corresponding PU elastomers was reduced, and the crystallization ability became weaker such that their onset of crystallization was delayed. After the prepolymers were reacted with N-100, the thermal properties of PU elastomers remained consistent with their respective prepolymers. In summary, it was concluded that the mechanical properties of TPEG/N-100 PU elastomer films were found to be superior to the PET/N-100 films.

A New Method for Determining the Vapor Pressure of Nitroglycerine Above Solid Rocket Propellants

AbstractMeasuring the vapor pressure of compounds such as nitroglycerine (NG) which have a low volatility has not been a straightforward task in the past. There are a wide range of values in the literature for the vapor pressure of NG and furthermore, there is little information regarding the vapor pressure of this compound above solid rocket propellant formulations. We have devised a new method for determining the vapor pressure of NG both above the pure material and solids containing this nitrate ester. The values obtained for pure liquid NG are in good agreement with some previously published values. It was also found that the vapor pressure of this compound is slightly lowered when it is incorporated into solid rocket propellant formulations.

Effect of crystallization parameters and presence of surfactant on ammonium perchlorate crystal characteristics

ABSTRACTAmmonium perchlorate is an exceptional oxidizer in composite solid rocket propellant formulations. Crystallization is the most critical step in the manufacture of ammonium perchlorate, which determines the size, shape, morphological characteristics, crystal strength, grinding characteristics, and thermal characteristics of the crystals. Attempts are made in the present study to establish the effect of crystallization parameters such as cooling patterns, agitator rpm, retention of crystals in the mother liquor, and presence of surfactant, on the morphological, thermal, and physical characteristics of ammonium perchlorate crystals. Based on the trials conducted in a 5-L capacity laboratory glass crystallizer, it is found that spherical, transparent, and smooth-surface crystals are obtained by crystallization having a slow cooling pattern and an agitator rpm of 600. Irregular-shaped crystals are obtained under fast cooling pattern and/or lower agitator rpm. It is also seen from XRD patterns that ammonium perchlorate crystals made in the present study do not have any amorphous phase on the surface. Porous nature of the crystals made in the presence of surfactant was verified by scanning electron microscopy images, bulk density, transparency of crystals, and change in the low temperature decomposition pattern in Differential Scanning Calorimeter (DSC) curves.

Aging of ADN Rocket Propellant Formulations with Desmophen®‐Based Elastomer Binder

AbstractDesmophen® binder‐based rocket propellant formulations containing ammonium dinitramide (ADN) and different fuel filler types (Al, HMX) were manufactured and investigated. Desmophen® D2220 is a polyesterpolyol. Polyesters are seen as a binder possibility, because of the relatively low temperature of the glass transition region compared to polyether‐based prepolymers such as GAP. The analogous formulations with AP instead of ADN were also included for comparison. The aging was followed by SEM, DSC, and DMA measurements. The accelerated aging program was developed on the principle of thermal equivalent load and the generalized van’t Hoff rule with a scaling factor equal to F=2.9. The aging was performed in air (RH<10 %) at temperature values between 65 and 85 °C and aging times adjusted to a thermal equivalent load of 15 years at 25 °C. DMA measurements of the aged ADN/Desmophen®‐based propellants identified changes in the loss factor curve. In contrast to HTPB‐Al‐AP rocket propellant formulations, the loss factor curve of the ADN formulations with Desmophen®‐based elastomer binder shows only one main apparent peak. The loss factor curves were modeled with exponentially modified Gaussian functions, which have revealed the presence of a second hidden peak. It was found that the aging could be characterized by the time‐temperature dependence of the areas of the hidden peak. The area increased with aging, which is explained by scissioning of the polymer in the shell around the ADN particles. By this process the strength is reduced, which was recognized by the decrease in storage shear modulus.

Effect of inert plasticizers on mechanical, thermal, and sensitivity properties of polyurethane‐based plastic bonded explosives

ABSTRACTMechanical, thermal, and sensitivity properties of plastic bonded explosives (PBX) depend on the type of ingredients in their formulation. Aim of the work is to develop aluminized cast PBX formulations and process conditions by using alternative inert plasticizers to have similar or better properties than PBXN‐109 without compromising sensitivity properties. Although very small portion of total production of plasticizers is used for solid rocket propellant and explosive formulations, they play very significant role in that area. Both inert and energetic plasticizers have involved propellant and explosive formulations to improve process parameters, mechanical properties, and even insensitivity properties of them. Isodecyl pelargonate and dioctyl adipate are the most preferred inert plasticizers in polyurethane based thermoset propellant and explosive formulations. In addition to them, diisononyl adipate and diisononyl phthalate were used and screened as inert plasticizer candidates for aluminized cast PBX formulations. Mechanical, thermal, and sensitivity properties of PBX formulations were studied and compared in detail. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40907.

An Innovative Approach for Generation of Aluminium Nanoparticles Using Micro Electrical Discharge Machining

Nanoparticles exhibit enhanced size dependant properties when compared to ultrafine or larger particles of the same material. Aluminium nanoparticles are used as ingredients in solid rocket propellant formulations and explosives. Aluminium nanoparticles are produced by various physical and chemical methods viz. wire explosion, laser ablation, combustion flame and aerosol synthesis, but micro-electrical discharge machining (micro-EDM) system has not yet explored to generate nanoparticles. This article presents the development of an innovative approach using the micro-EDM process to generate aluminium nanoparticles. Micro-EDM was performed with various operating parameters such as the voltage, current, pulse duration and duty cycle. In this proposed process, both cathode and anode made of aluminium, are melted and vaporized in DI water, used as a dielectric liquid. Meanwhile, the ultrasonic vibration is applied to remove the vaporized metal particles rapidly from the melting zone. The generated nanoparticles in the base fluid are characterized using transmission electron microscopy (TEM), energy dispersive analysis by X-rays (EDAX), selected electron diffraction pattern (SAED), optical absorption spectroscopy and dynamic light scattering technique (DLS) studies. The presence of FCC crystalline aluminium particles were verified by EDAX, SAED and absorption spectroscopy. The TEM results reveal that the particle sizes lies in the range of 50-130nm with average primary particle size of ∼ 90nm and the DLS analysis of particle size indicates that it follows normal distribution.

Characterization of ADN/GAP‐Based and ADN/Desmophen®‐Based Propellant Formulations and Comparison with AP Analogues

AbstractSeveral ADN‐based rocket propellant formulations containing different pre‐polymers (GAP diol/triol, Desmophen® 2200), curing agents (BPS, Desmodur® N100, Desmodur® N3400), plasticizers (BDNPA‐F, TMETN), and filler types (Al, HMX) have been manufactured. Propellant formulations were characterized by tensile tests, SEM analyses and DMA measurements. The study has focused on characterizations of the propellants in terms of evaluation of the strength and strain capability, investigation of the presence/absence of dewetting phenomena, compatibility issues and evaluation of the glass transition temperature. Ammonium perchlorate‐based propellant formulations have also been manufactured and analyzed in order to make comparisons. Aging was investigated using mass loss measurements.

Aging of HTPB/Al/AP Rocket Propellant Formulations Investigated by DMA Measurements

AbstractThree HTPB‐based rocket propellant formulations containing ammonium perchlorate and aluminum particles, with different aluminum content and particle size, have been manufactured. The study has focused on the change of mechanical properties with aging time by using dynamic mechanical analysis (DMA). Therefore, propellant formulations underwent an accelerated aging program, in air (RH<10 %), between 60 °C and 90 °C with aging time adjusted to a thermal equivalent load of 15 to 20 years at 25 °C. DMA investigations revealed distinct changes in the shape of the loss factor curve. These curves were modeled with three exponentially modified Gaussian (EMG) functions in order to get the molecular interpretation of the involved aging phenomena by separating the binder fractions with different mobility. Aging of propellant formulations can be followed by considering only two parameters: the areas of the second and third loss factor transition peaks (A2, A3), and the corresponding maximum temperature values of the assigned Gauss peaks (Tc2, Tc3).

Mechanical Properties of Smokeless Composite Rocket Propellants Based on Prilled Ammonium Dinitramide

AbstractAmmonium dinitramide (ADN) is a high performance solid oxidizer of interest for use in high impulse and smokeless composite rocket propellant formulations. While rocket propellants based on ADN may be both efficient, clean burning, and environmentally benign, ADN suffers from several notable disadvantages such as pronounced hygroscopicity, significant impact and friction sensitivity, moderate thermal instability, and numerous compatibility issues. Prilled ADN is now a commercially available and convenient product that addresses some of these disadvantages by lowering the specific surface area and thereby improving handling, processing, and stability. In this work, we report the preparation, friction and impact sensitivity and mechanical properties of several smokeless propellant formulations based on prilled ADN and isocyanate cured and plasticized glycidyl azide polymer (GAP) or polycaprolactone‐polyether. We found such propellants to have very poor mechanical properties in unmodified form and to display somewhat unreliable curing. However, by incorporation of octogen (HMX) and a neutral polymeric bonding agent (NPBA), the mechanical properties of such smokeless formulations were significantly improved. Impact and friction sensitivities of these propellants compare satisfactorily with conventional propellants based on ammonium perchlorate (AP) and inert binder systems.