Propellants physical state

Structural analysis of the solid rocket case-grain system using experimentally determined propellant response properties may permit a complete description of the combined stresses and resultant deformations, but a statement expressing the ability of the propellant to withstand these stresses is also required. Such a statement, which relates the physical state at which failure occurs to some material parameters, is called a failure criterion. The criterion for failure permits a prediction of safety margins expected under motor operation and handling and defines the loading regimes where abnormal operations will occur with intolerable frequency. 

There are several types of propellant which may be broadly classified on the basis of their application and their physical state. Based on their applications, propellants may be classified as gun propellants or rocket and missile propellants and this classification is shown in Figure 4.1. 

Another way to classify propellants is in terms of their physical state (Figure 4.2). Yet another way to classify propellants is based on their nature, that is, whether propellants are homogeneous or heterogeneous (Figure 4.3). 

SB DB NB Composite CMDB Fuel-rich Figure 4.2 Classification of propellants based on their physical state. 

The linear burning rate of a propellant is the velocity with which a chemical reaction progresses as a result of thermal conduction and radiation (at right angles to the current surface of the propellant). It depends on the chemical composition, the pressure, temperature and physical state of the propellant (porosity particle size distribution of the components compression). The gas (fume) cloud that is formed flows in a direction opposite to the direction of burning. 

Propellants also called propergols are intimate chemical mixtures of a fuel and an oxidizer. This particular type of energetic material acts both as the energy source and the propelling agent, hence, they are extensively used as rocket propellants. Propellants are classified according to their physical state as ... 

Carbon dioxide is a colorless, odorless gas. When cooled at atmospheric pressure, it solidifies to form dry ice. This solid sublimes at atmospheric pressure and a temperature of —78°C. AU three physical states of CO2 are useful more than half the solid CO2 produced annually is used as a refrigerant, liquid CO2 is used as an aerosol propellant, and gaseous CO2 is used primarily to carbonate beverages. 

In conclusion of this rept, Gibson, et al state that deflagration to detonation transition seems to be related to the physical characteristics of an explosive or propellant bed Gibson et al (Refs 12a 12b) also conducted at the BurMines a research which was broader than transition from combustion and deflagration to detonation. The prime objective of the reseat ch was to evaluate mechanisms involved in the initiation and growth of detonation in systems that ate capable of rapid exothermal decomposition. 

Compared with the almost limitless number of chemical compounds that exist or can be formed, the number of chemical propellants in common use is relatively few. This situation arises from criteria including costs, source availability, toxicity, resistance to shock, and other requirements imposed by the vehicle application and the propulsion system design. Another practical reason is that extensive overlap of physical, chemical, and economic properties are displayed by many of the theoretically possible propellants. During the 1960s, the universities, industry, and government in the United States pursued extensive research programs for synthesizing new chemical compounds viewed as candidate propellants,... 

Curing. A propellant mix is similar to any other formulation in that many chemical reactions must occur to reach the final desired "inert" state with the appropriate physical properties. 

Tn the United States, use of CFC propellants, designated as Propellants 11, 12, and 114, is strictly limited to specialized medicinal aerosol products such as metered-dose inhalers. The physical properties and chemical names of these propellents are given in Table 2. 

Studies on the physical properties, sublimation, decomposition, ignition, and self-deflagration of nitramine propellants conducted prior to 1984 are summarized by Boggs [44] and Fifer [45], and the state of understanding of steady-state combustion of nitramine propellants up to 1990 is given by Alexander et al. [46]. A summary of the latest development is covered in a volume edited by Yang et al. [47]. 

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