Propellant Properties

It is important to distinguish between the characteristics and properties of the liquid propellants (the fuel and oxidizer liquids in their unreacted condition) and those of the hot gas mixture, which result from the reaction in the combustion chamber. The chemical nature of the liquid propellants determines the properties and characteristics of both of these types. Unfortunately, none of the practical, known propellants have all the desirable properties, and the selection of the propellant combination is a compromise of various factors, such as those listed below.

Economic Factors

Availability in large quantity and a low cost are very important considerations in the selection of a propellant. In military applications, consideration has to be given to logistics of production, supply, and other possible military uses. The production process should be simple, requiring only ordinary chemical equipment and available raw materials. It is usually more expensive to use a toxic or cryogenic propellant than a storable, non-toxic one, because it requires additional steps in the operation, more safety provisions, additional design features, longer check-out procedures, and often more trained personnel.

Performance of Propellants

The performance can be compared on the basis of the specific impulse, the effective exhaust velocity, the characteristic velocity, the specific propellant consumption, the ideal exhaust velocity, or other engine parameters. They have been explained in Chapter 3, 5 and 6. The specific impulse and exhaust velocity are functions of pressure ratio, specific heat ratio, combustion temperature, mixture ratio, and molecular mass. Values of performance parameters for various propellant combinations can be calculated with a high degree of accuracy and several are listed in Table 5-5. Very often the performance is expressed in terms of flight performance parameters for a given rocket application, as explained in Chapter 4. Here the average density, the

50 100 150 200 250 300 350

50 100 150 200 250 300 350

Temperature, *F

FIGURE 7-1. Specific gravities of several liquid propellants as a function of temperature.

Temperature, *F

FIGURE 7-1. Specific gravities of several liquid propellants as a function of temperature.

TABLE 7-1. Some Physical Properties of Several Common Liquid Propellants

Was this article helpful?

0 0
Project Management Made Easy

Project Management Made Easy

What you need to know about… Project Management Made Easy! Project management consists of more than just a large building project and can encompass small projects as well. No matter what the size of your project, you need to have some sort of project management. How you manage your project has everything to do with its outcome.

Get My Free Ebook


Post a comment