Ammonium perchlorate is the most widely employed oxidizer for composite solid propellants. When exposed to atmosphere, it absorbs moisture and agglomerates. It is usually vacuum dried in order to avoid this agglomeration. When ammonium perchlorate that has been exposed to atmosphere for a certain period of time, is used in making a composite solid propellant, the burning rate is different because of the change in particle size distribution due to its agglomeration. This change in burning rate will change the thrust-time profile from that of what it is designed for. As one goes to a finer ammonium perchlorate particle size this problem becomes more evident. Experimental studies aimed at reducing the agglomeration of ammonium perchlorate by coating it with activated charcoal. Ammonium perchlorate coated with 1 % activated charcoal showed almost no agglomeration, even when the particle size of ammonium perchlorate is approx. 1 μm. The burning rates also remained unchanged when ammonium perchlorate coated with 1 % activated charcoal was employed in propellant composition, after it has been exposed to the atmosphere for a period of 1 h. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Periyapatna A. Ramakrishna

Department of Aerospace Engineering

Kumar Ishitha

Activated carbon

Agglomeration

Composite propellants

particle size

Particle size analysis

Propellants

Solid propellants

AMMONIUM PERCHLORATES

Burning rate

Composite solid propellant

Exposed to

Inorganic compounds

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

Propellants, Explosives, Pyrotechnics

This studymakes an attempt to demonstrate a technique to embed the catalyst on ammoniumperchlorate surface. In the present study, various techniques like differential scanning calorimeter, thermogravimetric analysis, scanning electron microscope, and x-ray computed tomography scan analysis as well as others were used to establish the effectiveness of this technique.Micron-sized iron oxide was used in this study for embedding the catalyst on ammonium perchlorate. Burn rates of pellets containing different fractions of iron oxide from various sources were measured to establish an optimumfraction for highest burn rate of ammoniumperchlorate pellets achievable with iron oxide. These burn ratesweremeasured using aCrawford bomb, and a fraction of1%iron oxide (Sigma-Aldrich)was highestamong them for pellets. The burn rate of the ammoniumperchlorate pellet with 1%iron oxide at 70 bar pressure recordedwas 13.33 mm/s. This fraction of iron oxide was also used to study the effect of embedding the catalyst on ammonium perchlorate surface when used in nonaluminized composite solid propellants. It is observed that catalyst-embedded ammonium perchlorate yields a higher burn rate as compared to the mechanically mixed catalyst. ©2017 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Journal of Propulsion and Power

Effects on burn rates of pellets and propellants with catalyst-embedded AP

This study makes an attempt to demonstrate the feasibility of a technique to embed the catalyst on ammonium perchlorate (AP) surface, in aluminized composite solid propellants. Micron sized iron oxide (IO) and nano sized IO were used in this study and its effect on the viscosity and burn rates of composite solid propellants were recorded. Burn rates of propellants prepared with this catalyst embedded AP were measured using a Crawford bomb and observed to be increasing using this technique due to the proximity of the catalyst with AP. The increase in burn rate obtained with micron sized and nano sized catalyst embedded on AP were 27.4% and 7.3%, respectively over those mechanically mixed in the propellant. The end of mix viscosity of the propellant prepared with nano IO was observed to be highest (4.27 × 103 Poise) when it is mechanically mixed in the propellant. The viscosity of the propellant was observed to improve to 3.79 × 103 Poise with the use of the technique of embedding the nano catalyst on AP as the total number of particles reduced. These explanations were the result of a computational model of randomly packed particles of AP, aluminum and catalyst generated for a propellant with 1% catalyst. © 2017 The Combustion Institute

Combustion and Flame

An effective method to embed catalyst on AP and its effect on the burn rates of aluminized 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 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

International Journal of Advances in Engineering Sciences and Applied Mathematics

Activated charcoal: as burn rate modifier and its mechanism of action in non-metalized composite solid propellants

Burning Characteristics and Thermochemical Behavior of AP/HTPB Composite Propellant Using Coarse and Fine AP Particles

Explosives. Third, revised and extended edition.Rudolf Meyer. VCH-Verlagsgesellschaft, Weinheim, FRG, 1987,452 pages, 21 figures and 107 tables. Price: DM 120,-/US $82.50

Reducing Agglomeration of Ammonium Perchlorate Using Activated Charcoal

Journal	Data powered by TypesetPropellants, Explosives, Pyrotechnics
Publisher	Data powered by TypesetWiley-VCH Verlag
ISSN	07213115
Open Access	No