Ammonium Perchlorate Propellants Research Articles

High-performance ammonium perchlorate propellants enabled by ferrocene-functionalized carbon nanotube catalysts

Ferrocene-based burning rate catalysts (BRCs) are essential for controlling the combustion of ammonium perchlorate (AP)-based composite solid propellants. However, their efficacy is often limited by migration during storage, leading to performance degradation. This work reports a novel class of covalently grafted ferrocene-functionalized multi-walled carbon nanotubes (CNT-Fc-n, n = 1, 2, 3) exhibiting enhanced catalytic activity and anti-migration properties. Structural characterization confirmed successful functionalization, while electrochemical analysis revealed facilitated electron transfer during AP decomposition due to π-π conjugation within the CNT-Fc-n structure. Consequently, CNT-Fc-n catalysts significantly reduced the AP decomposition activation energy, with CNT-Fc-3 (highest ferrocene loading) demonstrating the most pronounced catalytic effect. Specifically, CNT-Fc-3 lowered the AP decomposition temperature by 103 °C and 39 °C compared to pure AP and Catocene-catalyzed AP, respectively. Kinetic analysis revealed a 28-fold increase in the rate constant for CNT-Fc-3 catalyzed AP decomposition compared to pure AP. Moreover, the unique architecture of CNT-Fc-3 significantly reduced migration during a 50 °C simulation. This work presents a promising strategy for developing high-performance, migration-resistant BRCs for next-generation solid propellants.

Prediction of Burning Characteristics of Dihydroxyglyoxime Composite Propellant

An optimized engine start procedure is critical to the successful operation of a liquid rocket engine in launch vehicles. A solid propellant gas generator is widely adopted for the turbine starter during engine startup, and ammonium nitrate and ammonium perchlorate propellants are conventionally used for this purpose. However, these propellants have shortcomings such as high flame temperature, corrosive combustion residues, and low ignitability. In this study, a dihydroxyglyoxime (DHG)-based propellant was applied to turbine starters. The burning rate, characteristic velocity, and combustion temperature of the DHG propellant were evaluated using motor tests. The DHG-based propellant burned 3–11% slower in motor firing tests than that in strand burner tests, and an inversely proportional relationship was observed between the strand burn rate and the burning rate factor (ratio between motor burning rate measurement and strand burner prediction). The temperature sensitivity of the burning rate factor was found to be 0.23–0.24%/°C, and the pressure sensitivity of the characteristic velocity was 0.48–0.50%/MPa. These burning characteristics of the DHG-based propellant from static evaluations provide the evolution of the chamber pressure and the mass flow rate versus the time of the motor using internal ballistic analysis.

Burning characteristics of ammonium nitrate propellant containing fine ammonium perchlorate – influence of porosity of ammonium perchlorate**

AbstractFine porous ammonium perchlorate (PAP) has small holes in its crust, and the voids in the particles are connected to the outside. The porosity of PAP results in fine bubble contamination in a propellant because the voids in PAP cannot be completely charged with a binder. Fine bubble contamination can improve the burning rate characteristics of an ammonium perchlorate (AP) propellant. The influence of the porosity of PAP on the burning characteristics of an ammonium nitrate (AN)/AP propellant and the effect of Fe2O3 as a catalyst on them were investigated in this study. The void fraction of the propellant increased with increasing mass ratio between AP and all oxidizers (ξ) and ranged from 1.3 % to 3.2 %. The porosity of PAP increased the burning rate of AN/AP propellants. This effect increased with decreasing pressure and was independent of ξ. However, porosity had minimal influence on the burning rate of AN/AP propellants with Fe2O3. The effect of the catalyst on the increase in the burning rate due to the porosity of PAP was influenced by pressure and ξ. The effect on the AN/AP propellant was greatest when ξ was in the 0.5–0.6 range.

Influence of Hydroxyl-Terminated Polybutadiene Variants on the Wettability of Ammonium Perchlorate

Increased adhesion is important for many material science and manufacturing processes, including solid propellants. Improved adhesion affects mechanical properties and minimizes unwanted flame spread in rocket motors. This study investigated the surface energy interactions between ammonium perchlorate (AP) and hydroxyl-terminated polybutadiene (HTPB) polymers. Analytical techniques were used to determine the energy of the three-phase system. The pendant drop method was employed to determine the surface tension of the commercial polymers, with results showing no variation besides PolyBD R45. Static contact angle measurements show that molecular weight, OH-group content, and viscous properties affect the wettability of commercial variants of HTPB with polytetrafluoroethylene (PTFE) and AP solid substrates. Results show commercial variants of HTPB forming contact angles on AP ranging from 27.0 to . The contact angle of HTPB on PTFE ranged from 86.0 to . The wettability of AP varied greatly with which crystal face formed the liquid–solid interface. Nanoindentation of the and crystal faces provided a first-order AP surface free energy measurement. The crystal face was found to have higher energy than the crystal face, indicating better adhesion. Limitations of the measurement and implications for AP propellant performance are discussed.

Slow-Burn Ammonium Perchlorate Propellants with Oxamide: Burn Rate Model, Testing, and Applications

Low-thrust long-burn-time solid rocket motors may be useful as propulsion for small, fast, uncrewed aerial vehicles. These motors require a slow-burning propellant that can operate at unusually low chamber pressures (0.3–2 MPa). Slow-burn propellants were developed using ammonium perchlorate oxidizer and the burn rate suppressant oxamide. By varying the amount of oxamide (from 0 to 20%), burn rates from 4 to (at 1 MPa) were achieved. The adjustable burn rate allows a set of similar propellants to serve many aircraft and mission concepts. This work presents burn rate measurements (from both a strand burner and a research motor), minimum burn pressure measurements, and combustion chemical equilibrium simulations. A novel model of oxamide’s effect on burn rate is also presented, and it fits well to the experimental data. Finally, these propellant data and models are applied to select the propellant and chamber pressure for an example low-thrust solid rocket motor.

B/Metal composites’ thermochemical properties and their effect on the performance of an ammonium perchlorate propellant

ABSTRACT Mainly the purpose of this research is to increase the oxidation efficiency of boron powder as well as to accelerate the decomposition of AP by carrying out the trials of several metals with boron-based and AP-based propellants. B/Mg, B/Al, B/Ni, B/Fe and B/Mo composites are prepared by employing ball milling method. The thermal analysis of doped boron powder with Fe and Mo shows the better activity and reaction performance. Then, the solid propellant (SP) is kneaded within proposed proportions of B/Metal composites, HTPB and AP. The B/Metal composites have improved the combustion performance of SP in air, notably in closed bomb and these had an obvious accelerating effect on the thermal decomposition of SP, especially B/Fe. The burning rates of SP/B/Fe in air and closed bomb are 60.4 and 139% faster than that of SP, respectively. Furthermore, B/Fe changed the decomposition process of AP and dropped in the peak temperature due to Fe-promoting effect. The multiple oxidation states enable Fe to be an attractive candidate as a dopant in propellants, which exhibits superior activity in the oxidation of B and decomposition of AP.

Estimation of burning characteristics of AP/HTPB composite solid propellant using a sandwich model

The present study suggests a technique to estimate the burn rate of non-aluminized propellant compositions. A random packing algorithm is used to generate a three-dimensional propellant pack consisting of spherical Ammonium perchlorate (AP) particles and Hydroxyl-terminated poly butadiene (HTPB) binder. Intercept lengths of AP and HTPB were obtained by slicing the propellant pack and lines drawn on the sliced planes. The average intercept lengths were recorded and then used as thickness of AP and binder sandwich propellants. A discussion on the choice of parameters is made for both AP monopropellant flame and the diffusion flame. Comparison of burn rates of computational results is done with experimental studies reported in literature. A reasonable match has been obtained in these comparisons. Further, temperature sensitivity, which is an important factor, has been estimated and the values are closer to those reported from experimental studies than the values reported by earlier studies.

Rotational hydrogen thermometry by hybrid fs/ps coherent anti-Stokes Raman scattering in the plume of a burning metalized propellant

We employed a hybrid femtosecond/picosecond coherent anti-Stokes Raman scattering (fs/ps CARS) instrument to probe rotational temperatures of molecular hydrogen in the multiphase reaction zone of an aluminized ammonium perchlorate (AP) propellant flame. Significant concentrations of hydrogen, present in the plume due to the decomposition of the propellant binder material and subsequent reactions with AP oxidizers, allowed for single-shot thermometry at the laser repetition rate of 1 kHz. A time-asymmetric picosecond probe pulse time-gated the impulsively generated Raman coherence at a delay of 2.66 ps from the pump and Stokes pulses, before any appreciable coherence dephasing occurred in the atmospheric pressure flames and mitigating uncertainties in the Raman transition frequencies and dephasing processes. Measurements in near-adiabatic H2-air flames at equivalence ratios of $$\phi$$ = 1–1.8 demonstrated measurement accuracy to near 5% of equilibrium predictions with a precision approaching 3% for high signal-to-noise ratio spectra. Introduction of a time-delayed probe pulse provided Raman-resonant spectra from the plumes of burning propellants with ample signal above broadband background emission, which were fit to libraries of synthetic spectra to infer the gas rotational temperature 0–15 mm from the burning surface. The mean fitted temperature of 2494 K from three propellant burns compares favorably to other measurements of gas and particle temperatures in similar propellant studies.

Theoretical Performance Evaluation of a Marine Solid Propellant Water-Breathing Ramjet Propulsor

This work analyzes and presents theoretical performance of a marine water-breathing ramjet propulsor. A conceptual scheme of the motor is shown, the equation of thrust is presented, and the dependence on cruise velocity and depth are discussed. Different propellant compositions, representing a wide variety of formulations suitable for propelling a water-breathing ramjet, are investigated. The theoretical results reveal that the specific impulse of a water-breathing ramjet can increase by as much as 30% compared to a standard rocket, when using a conventional hydroxyl terminated polybutadiene (HTPB)-ammonium perchlorate (AP) propellant, which does not react chemically with the water. When employing a water-reactive propellant containing metal particles such as magnesium or aluminum, the specific impulse may be more than doubled. The thrust coefficient of the propulsor was computed at different cruise velocities and depths and was found to be greater than the predictable drag even at significant depth.

Preparation of B/Nitrocellulose/Fe particles and their effect on the performance of an ammonium perchlorate propellant

The application of boron in fuel-rich solid propellant is limited by its long combustion time, ignition delay and low combustion efficiency. To overcome these problems, B/Nitrocellulose (NC)/Fe particles were fabricated by electrospraying. The reactivity and combustion behavior of B/NC/Fe particles were characterized by TG/DSC, oxygen bomb calorimeter and laser ignition. Compared with pure boron, lower oxidation temperature was observed in the thermal analysis of prepared particles. Meanwhile, the prepared particles released more heat and ignite more readily during the combustion. Furthermore, B/NC/Fe particles were added into Hydroxyl-terminated polybutadiene (HTPB)/Ammonium perchlorate (AP) propellants as additives to test their combustion performance. The burning rate of propellants in air and closed bomb were both improved by 8.20% and 117%, respectively. Overall, B/NC/Fe particles not only show the superior reaction performance, but also contribute to the tunable burning rate of propellants.

Influence of MnO2 and Fe2O3 on the Burning Characteristics of AN/AP‐Based Composite Propellants

AbstractThe partial substitution of ammonium perchlorate (AP) for ammonium nitrate (AN) improves the burning characteristics of AN‐based propellants, because the advantages of AP propellants compensate for the drawbacks of AN propellants and vice versa. The burning characteristics of AN/AP‐based propellants supplemented with MnO2 and Fe2O3 were measured, and the effects of these catalysts on the burning characteristics of the propellants were investigated using the collected data. The ignitability and the burning rate of the AN/AP propellant was improved by the addition of MnO2. The addition of the MnO2/Fe2O3 bicatalyst improved the ignitability of the propellants compared to adding only MnO2, but the improvement was identical to that obtained using Fe2O3. The burning rate increased in the order MnO2<Fe2O3<bicatalyst. Furthermore, the effect of these catalysts on the burning characteristics was found to depend on the size of the AP particles and the type of binder.

Silicone bridged iron metallocene butadiene composite solid propellant binder: aspects of thermal decomposition kinetics, pyrolysis and propellant burning rate

ABSTRACTPropellant binders are essential components of composite solid propellants (CSP’s) used in launch vehicles and missiles. Binders act as a fuel and contribute directly to the combustion in conjunction with oxidizer particles and metallic fuel apart from imparting structural integrity to the solid propellant grain .The performance of CSP’s are directly related to the burn rate of the propellant. The burn rates of the ammonium perchlorate (AP) propellants are generally moderated using various types of transition metal oxide (TMO) catalysts. However, TMO’s are associated with inherently large dispersions in propellant burn rates and compromise on energetics. One of the most suitable methods for achieving lower dispersion in burn rate is using binders wherein a burn rate catalyst is grafted to the polymer matrix. In the present paper, the thermal decomposition of ferrocene bound hydroxyl terminated polybutadiene (FC-Si-HTPB) grafted to butadiene backbone via hydrosilylation was investigated The thermal degradation mechanism, stability and its effectiveness as burn rate catalyst are the most important aspects for use in CSP’s. The mechanism of decomposition of the neat resin and in combination with AP has been elucidated using pyrolysis gas chromatography–mass spectrometric technique (GC-MS). FC-Si-HTPB exhibits single stage decomposition in the temperature range of 263–491°C. The decomposition of FC-Si-HTPB with AP oxidizer follows a two stage mechanism in the 195–490°C.The char residue was characterized using FTIR, Raman spectroscopy and FE-SEM analysis, which enables to vindicate the mechanism of reaction. The activation energy for the decomposition of HTPB is 283.6 kJ/mol, FC-Si-HTPB is 251.5 kJ/mol and for Fc-Si-HTPB-AP system is 67.1 kJ/mol. The major pyrolysis products of neat FC-Si-HTPB are ferrocenyl derivatives, silylated ferrocenyl derivatives and precursors emanating from polybutadiene backbone. The propellants based on the new binder exhibited an increase in burn rate with iron content and higher fine content. A comparison of propellant burn rate with conventional micron sized ferric oxide exhibited an improvement of 34%.Based on the thermal analysis studies, the thermal endurance of the system was computed to be FC-HTPB> HTPB> FC-HTPB-AP.

Influence of iron oxide on thermal decomposition behavior and burning characteristics of ammonium nitrate/ammonium perchlorate-based composite propellants

The thermal decomposition behavior and burning characteristics of ammonium nitrate(AN)/ammonium perchlorate(AP) propellants supplemented with Fe2O3 were investigated. Based on these data, the performance differences between the propellants with Fe2O3 and those without Fe2O3 were investigated to reveal the influence of Fe2O3 on the thermal decomposition behavior and burning characteristics of AN/AP-based composite propellants. TG-DTA showed the peak temperature and temperature range of thermal decomposition due to AN decomposition to be independent of the presence of Fe2O3. The peak and the offset temperature of thermal decomposition due to AP decomposition decreased owing to the addition of Fe2O3, while the onset temperature did not vary. The burning rate of the AN/AP propellant was increased by the addition of Fe2O3; the effect of Fe2O3 on increasing the burning rate was influenced by the type of oxidizer, AP content in the oxidizer (ξ), and AP size. Furthermore, Fe2O3 allowed the suppression of the remarkable heterogeneity of the combustion wave of the AN/AP propellant without Fe2O3. The ignitability of the AN/AP propellant was improved by the addition of Fe2O3, except for the propellant with a ξ of 0.4. The cause of depressed ignitability by the addition of Fe2O3 for the propellant with a ξ of 0.4 is discussed based on thermogravimetry-differential thermal analysis, the visual observations of the unignited propellant surfaces, and the decomposition phenomena of the propellants using a high-temperature observation equipment. A large quantity of AN remained on the surface of the unignited propellant at 0.5 MPa. The cause of the depressed ignitability is that AN, AP, and HTPB do not simultaneously decompose and as a result AN remains on the burning surface. Thus, the burning surface of AN did not regress simultaneously with the burning surface of the AP-filled region, the matrix of AP, and HTPB.

Modeling of burning rate equation of ammonium perchlorate particles over Cu–Cr–O nanocomposites

The present study is aimed at introducing the application of design of experiment (DOE) with artificial neural networks (ANN) in couple over Cu–Cr–O nanocomposites, which can be used as catalysts in the combustion of ammonium perchlorate (AP), as well as a method of data collection/fitting for the experiments. To this end, a practical scheme has been proposed to select the characterization parameters of Cu–Cr–O nanocomposites as the catalytic combustion of AP propellant. Moreover, a calculation model has been established to identify the primary combustion characteristics based on backpropagation neural networks. The model was subsequently validated and then used to predict the primary combustion characteristics of the aforementioned propellant. In addition, due to the complex nature of the system, neural networks were employed as an efficient and accurate tool to model the behavior of the system. Response surface methodology (RSM) and ANN methods were also constructed based upon the DOE’s points and were then utilized to generate extra simulated data. The data sets, including the original experimental data and the simulation results yielded by the ANN and RSM methods were subsequently used to fit the combustion rate expression for AP. A comparison of the results of kinetic modeling with the simulated data sets from ANN and RSM models was then made, which indicated that both methods could satisfactorily fit the experimental data presented in the literature. The results also revealed that the error of burning rate calculation is less than ±5 % and the variations of the calculation results were consistent with those of the experimental results.

Humidity induced burning rate degradation of an iron oxide catalyzed ammonium perchlorate/HTPB composite propellant

Burn rate degradation of ammonium perchlorate based solid propellants can occur when moisture diffuses in and out of the material while exposed to fluctuating ambient humidity conditions. For high burn rate propellants with significant mass fractions of ammonium perchlorate particles less than 10μm, small changes in particle diameter can significantly alter the total oxidizer surface area resulting in propellant burning rate reductions. Ammonium perchlorate propellant samples are aged at various relative humidity and constant temperature. The samples are subsequently dried to equal moisture content and examined by SEM and optical microscopy. The propellant samples are combusted in a closed combustion bomb to measure the burning rate of the aged samples. The results show a clear correlation of the burning rate degradation and the level of humidity exposure. Evidence indicates that the degradation is a result of ammonium perchlorate crystal size growth and surface morphology changes reducing the available surface area. The changes are shown to be correlated with the moisture content of the aging environment.

Synthesis, characterization and catalytic behavior of Cu nanoparticles on the thermal decomposition of AP, HMX, NTO and composite solid propellants, Part 83

The synthesis of Cu nanoparticles by reducing CuSO4 with hydrazine in ethylene glycol under microwave irradiation, has been described. These nanoparticles have been characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED) pattern and X-ray diffraction (XRD) which shows an average particle diameter of 20.3nm. The catalytic activity, of Cu nanoparticles on thermal decomposition of ammonium perchlorate (AP), composite solid propellants (CSPs) using thermogravimetry (TG), differential scanning calorimetry (DSC) have been measured. Results indicate that nanoscale Cu particle lowers the energy of activation for thermal decomposition of AP and CSPs. Activation energy for ignition has also been found to be lowered in case of AP, CSPs, HMX and NTO. The burning rate of CSPs has been found to be enhanced. Isothermal TG data was used to evaluate kinetic parameters by model fitting as well as isoconversional methods and values of activation energy were found to be lowered with Cu nanoparticles.

Effect of carbon nanotube on the thermal decomposition characteristics of selected propellant binders and oxidisers

The effect of carbon nanotube (CNT) on the thermal decomposition behaviour of polymeric binders viz., hydroxyl terminated polybutadiene (HTPB) and glycidyl azide polymer (GAP) as well as oxidisers namely ammonium perchlorate (AP) and phase stabilised ammonium nitrate (PSAN) was investigated using simultaneous TG–DSC. The results indicate that addition of CNT to AP, lowered the thermal decomposition of AP but CNT addition to HTPB, increased the thermal stability of HTPB. The thermal decomposition characteristics of PSAN and GAP were not influenced by CNT. Ignition delay studies were carried out in a tube furnace using HTPB–AP propellant systems. CNT reduced the ignition delay of a propellant based on HTPB with AP oxidiser. The observed phenomena were explained based on the likely reaction of CNT with the compounds formed at high reaction temperatures.

Model for Melt-Layer Front in Ammonium Perchlorate Propellant Combustion

In solid rocket-propellant combustion, the dynamic phase change from condensed to gas occurs across the melt layer. During the surface burning, liquid and gas phases are mixed in the intermediate zone between the propellant and the flame to form microscale bubbles. The known thickness of the entire melt layer is approximately 1 μm at 10 5 Pa and 0.1 μm at approximately 10 7 Pa for ammonium-perchlorate/hydroxy-terminated polybutadiene propellant. In this paper, a model of the melt-layer front between the condensed and gaseous phases and the dynamic motion of the melt-layer front derived from the classical phase-field theory is presented. The model results show that the melt-layer front grows and propagates uniformly according to exp(―1/T s ), with T, being the propellant surface temperature.

Preparation, characterization and catalytic behavior of CdFe 2O 4 and Cd nanocrystals on AP, HTPB and composite solid propellants, Part: 79

CdFe 2O 4 and Cd nanocrystals were synthesized by wet chemical and hydrazine reduction methods, respectively. These nanocrystals were characterized by XRD and TEM. Their catalytic activity was investigated on the thermal decomposition of ammonium perchlorate (AP), hydroxyl terminated polybutadiene (HTPB) and composite solid propellants (CSPs) using TG and TG-DSC. Burning rate of CSPs was considerably enhanced by these nanocrystals. Rapid thermolysis of the CSPs and AP has also been studied using ignition delay measurements.

Flame structure in aluminized wide-distribution AP composite propellants

Flame structure in wide-distribution ammonium-perchlorate (AP), hydroxyl-terminated-polybutadiene (HTPB) binder, aluminum (Al) composite propellants is studied using 2-D laminates with oxygenated binder. Very fine (2-μm) AP (FAP) is used to produce fuel-rich, matrix propellant (oxygenated binder) with a FAP/binder ratio of 75/25. Coarse AP (CAP) is simulated by pressed AP lamina. A flame-structure regime map for the CAP/oxy-fuel matrix interaction flame is generated as a function of oxy-fuel matrix thickness and pressure using high-speed video imaging analysis. The flame structure is found to be similar to that previously described using UV and IR imaging for non-aluminized laminates with split (diffusion) flame structure at high pressures ( P) and low fuel thicknesses ( L) and merged (partially premixed) flame structure for low P and L. The CAP/matrix flame regime boundary is shown to be correlated by Peclet number, indicating the relevance of conserved-scalar (Shvab–Zeldovich) theory with simple, global AP/hydrocarbon chemistry to describe the CAP/matrix diffusion-flame stoichiometry. Other findings include a slight stabilizing effect of Al on the 1-D premixed combustion of the marginally stable fuel-rich matrix. Also, when burning in 2-D laminates assisted slightly by the CAP/matrix interaction flame, the 75/25 matrix is found to burn flat (perpendicular to regression direction) even in the split-flame regime, in contrast to lower FAP/binder ratio matrices, which protrude into the gas-phase. Findings such as these are essential for developing a fundamental understanding of and truly predictive simulation capability for combustion of wide-distribution AP propellants, including plateau, mesa and bi-plateau propellants.