Propellants homogeneous

These propellants are also called colloidal or double-base (DB) propellants and have nitrocellulose (NC) and nitroglycerine (NG) as their principal ingredients. Some ingredients may also be added in small proportions to serve as stabilizer, non-explosive plasticizer, coolant, lubricant, opacifier and burning-rate modifier or other additives to impart desirable properties to the propellants. These propellants are processed into desired shapes by two methods, that is, extrusion and casting. They find wide applications in anti-tank missiles. 

Homogeneous or colloidal propellants consist of single, double and triple-base propellants whose salient features are  

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Lengelle, G., Bizot, A., Duterque, J., and Trubert, J. F., Steady-State Burning of Homogeneous Propellants, Fundamentals of Solid-Propellant Combustion (Eds. Kuo, K. K., and Summerfield, M.), Progress in Astronautics and Aeronautics, Vol. 90, Chapter 7, AlAA, New York (1984). 

Spalding (89) has developed a theory for the burning behavior of homogeneous propellants. Although his theory obviously is not applicable... 

Casting of proplnts techniques may be subdivided into A)Manuf of cast homogeneous proplnts B)Manuf of proplnts by slurry casting and C)Manuf of cast composite proplnts A)tAanuf of Cast Homogeneous Propellants. This includes, solvent, solventless- or ball-proplnrs as srarting materials. The method consists of the following operations ... 

In rocket technology the name for liquid and homogeneous propellants, which require no other reaction partner for the formation of gaseous reaction products. Gas formation can be due to catalytic decomposition (on concentrated H202 or anhydrous hydrazine) or to an intramolecular reaction, e.g., by decomposition of propylnitrate generating N2, CO, C02, NO, etc., -> Liquid Propellants. 

There are numerous possibilities for using equation (29) in conjunction with interface or gas-phase conditions to determine both m and T-. For example, the condensed product of equation (14) conceivably might experience the rate process of equation (1) as soon as Y = 1, so that equations (6) and (29) become two independent expressions for m and 7]. Alternatively and somewhat less unlikely, surface equilibrium may occur so that equation (12) determines T- in equation (29) in this case, a gas-phase analysis is generally needed to find Pi, j. It appears that in most real homogeneous propellants, the products of the exothermic condensed-phase reactions are mainly gaseous, so that considerations of dispersion or possibly of gas-phase reactions are most relevant for determining in equation (29), and equations (6), (11), or (12) are not directly useful. 

There are plateau propellants that exhibit an intermediate range of pressure over which m is practically independent of p and mesa propellants for which m(p) achieves a maximum at a particular value of p then a minimum at a higher value. These effects may be produced in conventional double-base propellants by suitable addition of burning-rate catalysts (typically certain metal-organic salts) to the propellant formulation. It has been shown experimentally that these catalysts usually operate by modifying the interaction between the condensed-phase and dispersed-phase reaction zones [57], [58]. Thus dispersion phenomena are of importance to the deflagration of homogeneous propellants in a number of ways. 

Fig. 1 Problem schematic for burning homogeneous propellant showing condensed phase (surface) reaction zone, gas phase reaction zone and corresponding steady-state temperature profiles. Propellant is fed from left at surface regression rate r. Simplified kinetics description has propellant (A) decomposing in condensed phase to intermediate species (B) via zero-order, high activation energy, irreversible single-step reaction, and (B) reacting to (C) in gas phase via second-order (overall), irreversible single-step reaction.

The basic characteristic of engine efficiency is the impulse produced by the fuel combustion. The impulse depends on the chamber and nozzle geometry. As in the experiments, in calculations the impulses produced by detonation of a homogeneous propellant-air mixture and by injecting the propellant in air under identical conditions were compared. The impulse is calculated by the thrust at the closed and open tube ends. Time histories of the specific impulse are illustrated in Fig. 7.10. The results of calculations are listed in Table 7.1. 

Homogeneous propellants are either simple base or double base. A simple base propellant consists of a single compound, usually nitrocellulose, which has both an oxidation capacity and a reduction capacity. Double base propellants usually consist of nitrocellulose and nitroglycerine, to which a plasticizer is added. Homogeneous propellants do not usually have specific impulses greater than about 210 seconds under normal conditions. Their main asset is that they do not produce traceable fumes and are, therefore, commonly used in tactical weapons. 

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