This paper reports the development of a nonaluminized composite solid-propellant formulation with high burning rates. To achieve high burning rates, potassium (described in the literature as an impurity) has been doped into ammonium perchlorate. It is seen that beyond a potassium content of 0.19% the increase in the burning rates of a composite propellant is not significant.Ahigh-burn-rate pressure index at high pressures and the dual slope has been observed with the potassium doped ammonium perchlorate in a composite solid propellant even with the use of only fine sized ammonium perchlorate particles. These features have been explained through surface scanning electron microscope pictures of quenched propellant samples. © 2014 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Periyapatna A. Ramakrishna

Department of Aerospace Engineering

Kumar Ishitha

Composite propellants

Scanning electron microscopy

Solid propellants

AMMONIUM PERCHLORATES

Burning rate

Composite solid propellant

DUAL SLOPE

High pressure

PRESSURE INDEX

potassium

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Propulsion and Power

In this work, iron containing hydroxyl terminated polybutadiene (Fe-HTPB) based binder cum burn rate catalyst has been developed without altering the crucial physical properties of HTPB. Ferrocene, the source of Fe in the Fe-HTPB, has been grafted at the terminal carbons of HTPB to ensure no alternation in microstructure of HTPB which in turn helped in retaining physical properties of pristine HTPB. The structure and the presence of ferrocene as the end cap groups of the Fe-HTPB were confirmed by solid-state NMR and MALDI-TOF-MS analysis. Control over the viscosity and Fe content of the Fe-HTPB was achieved by varying the grafting reaction recipes and conditions. The Fe content, as measured by inductively coupled plasma - atomic emission spectroscopy (ICP-AES) in the Fe-HTPB varied from 0.06% to 0.165% (by weight) and found to be responsible for increasing viscosity of Fe-HTPB from 5857 mPa S to 11,890 mPa S. Non aluminized composite solid propellants (CSPs) with 86% (wt%) ammonium perchlorate loading were prepared using Fe-HTPB as a binder for studying the burn rate efficiency. Burn rates of CSPs made from Fe-HTPB binders were found to be enhanced by ∼125% compared to CSPs of pristine HTPB. At 40 bar pressure, the burn rate of CSPs made from Fe-HTPB and pristine HTPB binders are 20.56 and 9.07 mm/s burn rate, respectively. In addition, all the CSPs made from Fe-HTPB were found to be very stable as their pressure index is less than 0.5. © 2019 Elsevier Ltd

Polymer

Ferrocene grafted hydroxyl terminated polybutadiene: A binder for propellant with improved burn rate

This paper presents a comparison of actual solid propellants with a computationally generated propellant pack, which is intended for use in combustion modelling studies. X-ray computed tomography (XCT) was used to obtain a 3D reconstruction of an actual propellant sample. Random distribution of spherical particles of ammonium perchlorate (AP) has been used to model a composite solid propellant (random pack). The simulated random pack and 3D reconstructed propellant are compared based on three parameters capturing volume, area and length metrics, viz., density, exposed AP area and AP/binder intercept lengths. The density match is within 1.5 % between the actual propellant and the simulated propellant pack. The exposed AP surface area lies in the range 53–63 % for the 80–86 % solid loaded non-aluminized propellants considered in the study. The histogram of the intercept lengths matched reasonably as well capturing the variation in particle size and solid loading of the propellant. However, the comparison between simulated and XCT reconstructed packs was found to be limited by the resolution of the XCT reconstruction of actual propellant samples. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Propellants, Explosives, Pyrotechnics

Use of X-Ray Computed Tomography for Validation of Random Packs of Composite Solid Propellants

Iron oxide and copper chromite have been used as burn-rate modifiers of composite solid propellants. In recent times, studies have been reported on potassium-doped ammonium perchlorate and on dry activated charcoal. These have shown an increase in composite solid propellant burning rates. The studies on composite solid propellants using dry activated charcoal have also shown a reduction in the burn-rate pressure index for a composite solid propellant. With this knowledge, experiments are conducted to develop compositions that result in both high burning rates and low burn-rate pressure index of the propellant.In additiontothese, the study also reports propellants with dual burnrate pressure index. The change in the burn-rate pressure index is from 0.2 to 0.65 in one of the propellants. These could be very useful in that the same grain can act as boost and sustain grain depending on the combustion chamber pressure. With the addition of different burn-rate modifiers, the pressure at which the change in burn-rate pressure index is observed shifts. This could be a very useful tool for propellant designers. It was observed that, with the use of activated charcoal along with potassium-doped ammonium perchlorate, the burn-rate pressure index was brought down from around 0.65 to 0.38, whereas the burn rates were still higher (60%) than the base propellant. Copyright © 2015 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Burning rate studies: Potassium-doped ammonium perchlorate with other burn-rate modifiers

This paper is concerned with a new and novel approach to modeling composite propellant burn rate behavior. It is founded on the fact that composite propellant combustion is largely boxed between the premixed limits – of pure AP and fine AP-binder (HTPB, here) whose burn behaviors are taken as known. The current strategy accounts for particle size distribution using the burn time averaging approach. The diffusional effects are accounted for through a calibrated heterogeneous quasi-one-dimensional model (HeQu1-D for short) that allows for the flame temperature dependence on the local AP size-binder thickness geometry. Fine AP-binder homogenization is adopted as in recent models with refinement on the particle size as a function of pressure. The specialty of the present approach is that it invokes local extinction for fuel rich conditions for specific particle sizes when the heat balance causes the surface temperature to drop below the low pressure deflagration limit of AP; this feature allows for the prediction of extinction of propellant combustion. Combining these ideas into a MATLAB® calculation framework that uses a single dataset on properties of AP and binder consistent with burn rate vs. pressure of pure AP and fine AP-binder system allows for making the predictions of propellants with multiple particle sizes and different fractions. Comparisons of burn rate data over nearly thirty compositions from different sources appear excellent to good. It is found that it is important to treat the full particle size distribution to achieve better predictions. Low burn rate index (∼0.25) observed with addition of SrCO3 is captured by extending the model to include the effect of binder melt; the gas phase effect is accounted for by calibration against catalytic effect on the fine AP-binder propellant. An interesting deduction from the model is that the temperature sensitivity of propellants should not exceed that of AP. The robustness of the current model and speed of determining the burn rate behavior allow for the possibility of determining the particle size distribution required to meet the burn rate specifications of a specific propellant for practical applications before actually embarking on making the propellant. © 2016 The Combustion Institute

Combustion and Flame

A novel approach to composite propellant combustion modeling with a new Heterogeneous Quasi One-dimensional (HeQu1-D) framework

This paper is concerned with a new and novel approach to modeling composite propellant burn rate behavior. It is founded on the fact that composite propellant combustion is largely boxed between the premixed limits – of pure AP and fine AP-binder (HTPB, here) whose burn behaviors are taken as known. The current strategy accounts for particle size distribution using the burn time averaging approach. The diffusional effects are accounted for through a calibrated heterogeneous quasi-one-dimensional model (HeQu1-D for short) that allows for the flame temperature dependence on the local AP size-binder thickness geometry. Fine AP-binder homogenization is adopted as in recent models with refinement on the particle size as a function of pressure. The specialty of the present approach is that it invokes local extinction for fuel rich conditions for specific particle sizes when the heat balance causes the surface temperature to drop below the low pressure deflagration limit of AP; this feature allows for the prediction of extinction of propellant combustion. Combining these ideas into a MATLAB®calculation framework that uses a single dataset on properties of AP and binder consistent with burn rate vs. pressure of pure AP and fine AP-binder system allows for making the predictions of propellants with multiple particle sizes and different fractions. Comparisons of burn rate data over nearly thirty compositions from different sources appear excellent to good. It is found that it is important to treat the full particle size distribution to achieve better predictions. Low burn rate index (∼0.25) observed with addition of SrCO3is captured by extending the model to include the effect of binder melt; the gas phase effect is accounted for by calibration against catalytic effect on the fine AP-binder propellant. An interesting deduction from the model is that the temperature sensitivity of propellants should not exceed that of AP. The robustness of the current model and speed of determining the burn rate behavior allow for the possibility of determining the particle size distribution required to meet the burn rate specifications of a specific propellant for practical applications before actually embarking on making the propellant. © 2016 The Combustion Institute

The objective of this paper is to understand the observed changes in behavior of ammonium perchlorate deflagration characteristics reported in literature, when it is doped with potassium. Successive recrystallization is employed to dope potassium into ammonium perchlorate. This paper, through various recrystallization techniques, conclusively puts an end to doubts regarding the actual process of acquisition of potassium by ammonium perchlorate. It is concluded that the increase in the potassium content in ammonium perchlorate is due to the filter used during recrystallization process. From the experiments conducted to obtain the deflagration rates of ammonium perchlorate, it is observed that potassium doped ammonium perchlorate has higher burning rates and also a higher low-pressure deflagration limit. As potassium doped is within the ammonium perchlorate crystal, thermal conductivity and specific heat values for ammoniumperchlorate with various percentages of potassium are obtained. These values are incorporated into the computational studies on ammonium perchlorate. The computational studies performed in this paper are not intended to reproduce the experimental results but to illustrate the various features of the potassium doped ammonium perchlorate deflagration. With these computational studies, the observed burning rate increase and low-pressure deflagration limit increase of ammonium perchlorate with doped potassium are explained. Copyright © 2013 by the authors. Published by the American Institute of Aeronautics and Astronautics, Inc.

Enhancing composite solid propellant burning rates with potassium doped ammonium perchlorate-Part i

This paper examines the effect of mixer size on the density of the propellant and it also explores the role of the propellant density with regards to burning rate and burn rate pressure index. Propellant samples were prepared in the four different size (15, 70, 200 and 1000 g) mixers with identical input of ingredients to examine the effect of mixer size on density and burning rate of the composite solid propellant. It was noticed that density and burning rate of the propellant changes significantly with change in the mixer size from 15 g to 1000 g. This is because for the smaller mixers the surface area to volume ratio is large and the actual percentage of aluminum and ammonium perchlorate (especially coarse) that goes into the propellant reduces. High burning rate with decrease in mixer size is also accompanied with increase in burn rate pressure index. The composition analysis was also carried out and it is noticed that the actual percentage of the ingredients is different from the intended percentage of the ingredients and percentage change is more when the mixer size decreases. © 2013 IAA.

Acta Astronautica

Dependence of density and burning rate of composite solid propellant on mixer size

Through careful experimentation, this paper establishes that moisture trapped inside the pores of activated charcoal was the reason for the burn-rate enhancement of composite solid propellant observed in literature. This paper demonstrates that, even with the presence of moisture in activated charcoal, the propellants can not only be cured to be free from blow holes and voids but also have good mechanical properties. Experiments were also carried out to examine the possible mechanism for high burn rates and burn-rate pressure index observed in composite propellants when moisture was present in activated charcoal. Scanning-electron-microscope images show that moisture in activated charcoal reduces the binder melt flow. It is noticed that formation of the bubbly layer is more when moisture is present in the binder. This bubbly layer might be exploding near the surface of the propellant and taking away the binder melt layer. This could be the cause for the observed increase in the burn rate and burn-rate pressure index of aluminized composite propellants.

Investigations on activated charcoal, a burn-rate enhancer in composite solid propellant

This paper reports the discovery of activated charcoal as an effective burn rate enhancer of aluminized composite solid propellant. Experiments were carried out using a strand burner at pressures ranging from 10 to 70. bar with varying fractions of activated charcoal. The results show that with the addition of activated charcoal in an aluminized composite propellant higher burn rates (in excess of 25. mm/s at 70. bar) were obtained. This paper also explores the possibility of further enhancing the burn rates of aluminized composite propellant by using iron oxide along with activated charcoal. Burn rates recorded with iron oxide and activated charcoal both present in the propellant were in excess of 50. mm/s at 70. bar. It was noticed that these high burn rates were accompanied by a higher (0.65) pressure index of combustion. A series of experiments were designed to understand the burn rate enhancement with activated charcoal in aluminized composite propellant. TGA and DSC tests were carried out on AP pellets with and without activated charcoal to detect any condensed phase activity of activated charcoal. These tests did not show any significant difference between the AP pellets with and without activated charcoal. The AP pellets with and without activated charcoal were also burnt in a strand burner to understand if any gas phase reaction was being catalyzed by activated charcoal. AC does not enhance any gas phase activity while addition of AC in AP increased the LPDL of AP and reduced the burn rate. Lastly, sandwich propellant with activated charcoal at the interface was prepared to determine if interface reactions were being affected with the addition of activated charcoal. It has been observed that with the addition of activated charcoal at the AP-binder interface the burn rates are higher than those recorded without activated charcoal at the AP-binder interface. © 2009 The Combustion Institute.

Activated charcoal - A novel burn rate enhancer of aluminized composite propellants

Nano-aluminium particles of ∼50 nm size, produced at this laboratory, are added to composite solid propellants based on ammonium perchlorate and hydroxyl-terminated poly-butadiene binder that exhibit plateau burning rate trends and those including burning rate catalysts. The nano-aluminized propellant burning rates are compared with corresponding micro-aluminized and non-aluminized ones in the 1-12 MPa pressure range. The mid-pressure extinction of the matrixes containing the fine-sized ammonium perchlorate particles in the propellant along with the binder is investigated in all the cases to understand the mechanism of plateau-burning. Further, the variations in aluminium content, the aluminium size (within nano- and micro-ranges), bimodal combination of nano- and micro-aluminium are considered. Ferric oxide and titanium dioxide are the burning rate catalysts considered. Large scale accumulation of aluminium is observed not only in micro-aluminized matrixes, but also in nano-aluminized ones as clusters of 1-5 μm size. Since aluminium is added at the expense of the coarse ammonium perchlorate particles to preserve the total-solids loading in the present formulations, addition of micro-aluminium decreases the burning rate; whereas, nano-aluminized propellants exhibit ∼80-100% increase in the burning rate under most conditions. The near-complete combustion of nano-aluminium close to the burning surface of the propellant provides heat feedback that controls the burning rate. Mid-pressure extinctions of matrixes and plateau burning rates of propellants are washed out when nano-aluminium is progressively added beyond 50% in bimodal aluminium blends, but low pressure-exponents are observed in the nano-aluminized propellant burning rates at elevated pressures. Adjusting the plasticizer content in the binder alters the pressure range of plateau burning rates in non-aluminized propellants. Catalysts increase the burning rate by ∼50-100% in non-aluminized and micro-aluminized propellants, but in nano-aluminized propellants, the μm-sized catalyst does not affect the burning rate significantly; whereas, the nanometre size catalysts increases the burning rate merely by ∼5-15%. © 2009 The Combustion Institute.

Journal	Data powered by TypesetJournal of Propulsion and Power
Publisher	Data powered by TypesetAmerican Institute of Aeronautics and Astronautics Inc.
ISSN	07484658
Impact Factor	1.868
Open Access	No
Citation Style	unsrt
Sherpa RoMEO Archiving Policy	Green