Combustion and Flame 182 (2017) 114–121 Contents lists available at ScienceDirect Combustion and Flame journal homepage: www.elsevier.com/locate/combustfame An effective method to embed catalyst on AP and its effect on the burn rates of aluminized composite solid propellants Gaurav Marothiya ∗ , Chaitanya Vijay, K. Ishitha, P.A. Ramakrishna Department of Aerospace Engineering, Indian Institute of Technology Madras, Chennai 600036, India a r t i c l e i n f o Article history: Received 29 August 2016 Revised 18 October 2016 Accepted 7 April 2017 Keywords: Ammonium perchlorate Catalyst embedded AP Burn rate Composite propellant Iron oxide a b s t r a c t This study makes an attempt to demonstrate the feasibility of a technique to embed the catalyst on am- monium 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 compos- ite 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 pro- pellant. The end of mix viscosity of the propellant prepared with nano IO was observed to be highest (4.27 × 10 3 Poise) when it is mechanically mixed in the propellant. The viscosity of the propellant was observed to improve to 3.79 × 10 3 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. Published by Elsevier Inc. All rights reserved. 1. Introduction In most of space application where solid rockets are being used, the composition of solid propellant is an aluminized composition with ∼86% of solid loading. This is due to the fact that addition of the aluminum enhances the specific impulse of the solid propellant [1]. However, addition of aluminum reduces the burn rate of solid propellant [1]. To counter this problem, various techniques like en- hancing the reactivity of aluminum [2], reducing the particle size of AP [3], mechanical addition of catalyst (iron oxide (IO), copper chromate (CC)) in the composition [4–7], have been suggested by the many researchers around the world. Literature [8,9] has also dealt with reducing the particle size of catalysts (nano catalysts). Chakravarthy et al. [8] have added nano sized IO in the AP-binder matrix. They observed that the nano cat- alysts act on the interface of the binder and AP and enhance the burn rates of the AP-binder matrix. Although this is effective in enhancing the burn rates, it leads to an increased viscosity of the propellant. They have also conducted experiments with the reduc- tion in the size of AP while keeping the catalyst content and par- ticle size of catalyst same. They have reported an increase in burn rates with the reduction in the size of AP, which they say is due to the increase in the number density of AP-binder interface. Lu et al. ∗ Corresponding author. E-mail address: gaurav.marothiya29@gmail.com (G. Marothiya). [9] demonstrated that the nano sized IO enhances the regression rates of propellant with 2% catalyst content, however the enhance- ment observed was not so significant over micron sized catalyst. Following the above literature and technique used for embed- ding the catalyst on AP surface as discussed by Ishitha and Ra- makrishna [10], nano and micron sized catalyst were embedded on the AP surface using the aforementioned technique. Aluminized composite solid propellants were prepared with the catalyst em- bedded AP. The burn rates of these propellants were compared with the solid propellant burn rates when a micron/nano sized cat- alyst is just added (mechanically mixed) at the time of mixing the propellant. To explain these results, a computational model similar to the one developed by Ramakrishna [11] of randomly packed AP, Al and catalyst particles was also created. 2. Experiments 2.1. Preparation of propellants The ingredients used for preparing the solid propellant in this study, in addition to those described in the Ref. [2], are tabulated in Table 1. Ingredients were weighed using an electronic weighing machine with a least count of 10 mg. All the solid ingredients were stored in an oven at 333 K for 24 h to remove the moisture from them before using them to make the propellant. The procedure fol- lowed to make the propellant is the same as that followed in Ref. http://dx.doi.org/10.1016/j.combustflame.2017.04.010 0010-2180/© 2017 The Combustion Institute. Published by Elsevier Inc. All rights reserved.