Showing papers on "Ammonium perchlorate published in 1981"

Experimental and theoretical study of the effects of pressure and crossflow velocity on composite propellant burning rate

Abstract: A model for prediction of burning rates of composite (ammonium perchlorate oxidizer) propellants has been developed. In addition, an experimental device for measuring effects of crossflow on burning rate has been used to characterize eight propellants with systematicall, varied formulation parameters. Model predictions of no-crossflow burning rate-pressure behavior agree very well with data, while agreement between erosive burning predictions and data is generally good. The dominant factor influencing composite propellant burning rate sensitivity to crossflow is the base (no-crossflow) burning rate (lower base rate leading to increased sensitivity) with other factors having at most second order effects outside their influence on base rate. Three formulations with widely variant compositional and ingredient particle size parameters, but nearly identical base burning characteristics, exhibited very similar crossflow behavior.

Combustion characteristics of advanced nitramine-based propellants

Abstract: The combustion of HMX (cyclotetramethylene tetranitramine) based propellants was studied in a window bomb with high speed motion picture photography. The HMX concentration was varied from 20 to 60% by weight with the remaining material being an active binder composed of nitrocellulose and nitroglycerin. A new technique using a powerful He−Ne Laser was developed to measure burning rate characteristics over the pressure range from 10 to 350 atm (150 to 5000 psi). The temperature sensitivity coefficient σp is determined in the interval from −40°C to +80°C. The present experiments included high speed cinephoto-micrography of the combustion zone and scanning electron microscope study of the extinguished surface which helped to clarify the combustion mechanism. The data show the influence of HMX mass loading and particle size on the burning rate characteristics. Because of the diffusion flame, the addition of small concentrations of ammonium perchlorate (AP) is effective in increasing the burning rate and decreasing the pressure exponent. On the other hand, AP markedly increases the temperature sensitivity coefficient. The cinemicrography study of the combustion of nitramine propellants shows that previous speculations regarding the ejection of HMX particles from the burning surface are erroneous. The glowing agglomerates which appear on the surface are emitted by the double base matrix. The HMX particle size has no influence on the agglomerate dimensions which are considerably more important in the case of nitramine propellants prepared by the casting process. A 5 minute movie consisting of selected film clips from the experiments will be shown. It provides great detail on the processes occuring at the burning surface of nitramine propellants.

A pocket model for aluminum agglomeration in composite propellants

Abstract: This paper presents a model for the purpose of estimating the fraction of aluminum powder that will form agglomerates at the surface of deflagrating composite propellants. The basic idea is that the fraction agglomerated depends upon the amount of aluminum that melts within effective binder pocket volumes framed by oxidizer particles. The effective pocket depends upon the ability of ammonium perchlorate modals to encapsulate the aluminum and provide a local temperature sufficient to ignite the aluminum. Model results are discussed in the light of data showing effects of propellant formulation variables and pressure.

Composite solid propellant containing FeOOH as burning rate modifier

Abstract: The burning rate of a composite solid propellant comprising ammonium perchlorate and a fuel binder such as polysulfide, polyurethane or polybutadiene can remarkably be increased by the addition of a small amount of FeOOH. Considering the mechanical properties of the propellant, the maximum amount of FeOOH is preferably limited to 7 Wt % of the toatal of the fuel binder and ammonium perchlorate. It is possible to jointly use FeOOH and Fe2 O3 on condition that the weight ratio of FeOOH to Fe2 O3 is at least 10:90 and that the total weight of FeOOH and Fe2 O3 is in the range from 0.9 to 7% of the total weight of the fuel binder and ammonium perchlorate.

Effect of gamma/neutron irradiation and permanganate additives on thermal decomposition of ammonium perchlorate

Abstract: When mixed with 2% by weight of either KMnO4, Ba(MnO4)2 or NH4MnO4, an enhanced thermal decomposition of cubic ammonium perchlorate, AP, was observed over the temperature range 255–300‡. A still more pronounced effect was observed when AP was subjected to a radiation dose of 10 Mrad. The activation energy involved over the acceleratory stage was found to be 46 kJ mol−1 for the irradiated AP, as against the normal value of 85 kJ mol−1. The value remained unaltered in the case of the first two additives, while in the presence of NH4MnO4 it decreased to 55 kJ mol−1. Neutron bombardment did not change the decomposition characteristics of AP; the38Cl activity produced following the (n, γ) reaction showed highly damaged centres with the activity distribution ratio 0∶8.5∶20∶71.5 for ClO 4 − ∶ ClO 3 − ∶ (ClO− + ClO 2 − ) ∶ Cl−. Heating above 220‡ created further disorder through complete reduction of the recoil oxyanions.

Combustion and Thermal Decomposition of Ammonium Perchlorate–Aluminium Composite Pellets: Mechanism for Aluminium Participation

Abstract: Thermal behaviour of ammonium perchlorate-aluminium composites is studied using differential thermal analysis, thermogravimetry and differential scanning calorimetry. Electrical resistivity studies throw light on the mechanism of ammonium perchlorate decomposition at different aluminium contents. The differences observed in burning behaviour by earlier authors is explained in terms of porosity and thermal conductivity of the composite.

Silane ballistic modifier containing propellant

Abstract: A silicon compound as a burning rate catalyst for a solid propellant comption is disclosed along with the solid propellant composition for which the silicon compound is an effective catalyst. The silicon compound is selected from a class of silicon compounds characterized by having one or more silicon bonds selected from silicon to hydrogen bonds, silicon to nitrogen bonds, and silicon to carbon bonds. Representative silicon compounds of the described class of compounds include p-bis(dimethylsilyl) benzene, tris(dimethylsilyl) amine, triethylsilane, hexamethyldisilane, bis(dimethylamino) dimethylsilane, bis(dimethylamino) methylsilane, octylsilane, hexamethylcyclotrisilazane, and dimethyldiicyanatosilane. The burning rate of the solid propellant composition varies as a function of the silicon content in the propellant composition which is additionally comprised of hydroxyl terminated polybutadiene binder, an optional bonding agent which is the reaction product formed from equimolar quantities of 12-hydroxystearic acid and tris [1-(2-methylaziridinyl)]phosphine oxide, an optional quick cure catalyst of triphenyl bismuthine, an oxidizer of 1 micrometer ultrafine ammonium perchlorate and 90 micrometers ammonium perchlorate, aluminum metal powder fuel, and a curing agent of isophorone diisocyanate.

Some Observations on Sublimation and Decomposition of Ammonium Perchlorate

Abstract: Ammoniumperchlorate (AP) was aged at 100°C and 150°C. Depending on the aging time, AP shows different decomposition characteristics. By a special experimental arrangement sublimation and thermal decomposition could be separated.

Combustion and Thermal Decomposition of a Binary Oxidiser System: Ammonium Perchlorate-Potassium Perchlorate

Abstract: Combustion behaviour of ammonium perchlorate-potassium perchlorate pellets is studied using Crawford strand burners. At low concentrations of potassium perchlorate (up to 30 percent potassium perchlorate) the burning rate of ammonium perchlorate-potassium perchlorate condensed mixtures increases with potassium perchlorate content. Above 40 percent potassium perchlorate content, combustion sustenance becomes difficult. Decomposition products of ammonium perchlorate sensitize the melting and subsequent decomposition of potassium perchlorate. The results are explained in terms of the melt layer thickness, flame temperature and the resultant surface temperature, and heat wave penetration into the solid. The study suggests the importance of melt layer on the burning surface in the deflagration behaviour of ammonium perchlorate-potassium perchlorate condensed mixtures

Burning Rate Evaluation of Composite Solid Propellants. A simplified approach

Abstract: One of the principal parameters associated with a solid propellant is its linear burning rate. Many attempts have been made in the past to determine theoretically the burning rates of solid propellants by the use of appropriate combustion models. The object of the present paper is to propose a simplified theory of burning rate suitable for composite solid propellants. While the paper follows basically the scheme suggested for this purpose by Beckstead, Derr and Price using multiple flamelets, certain simplifying assumptions have been introduced with a view to make the model easier to operate. An attempt is also made in the paper to extend it to the case of aluminized solid propellants as well on the basis of a specific hypothesis regarding the role of aluminium. The relevant transcendental equations of combustion were solved on a digital computer. The burning rates and related characteristics were evaluated by this technique for two specific ammonium perchlorate-based solid propellants, one aluminized and the other non-aluminized, and the results obtained agree reasonably with the reported experimental trends.

High temperature propellant development

Abstract: It is reported that the neccessary technology has been developed and demonstrated for the manufacture of heat-sterilizable solid propellants which meet specific ballistic goals. It is shown that: (1) phosphate doping of ammonium perchlorate significantly enhances the thermal stability of the substance; (2) grinding the ammonium perchlorate to reduce particle size further increases thermal stability; and (3) unsaturated polymers such as the polybutadienes can be successfully used in a heat-sterilizable propellant system. Among the topics considered by the study are oxidizers, dopants, binders, and the thermal cycling of 70 lb and 600 lb propellant grains.