325. Weight Analysis of an Uncooled Rocket Engine Nozzle
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Paper
Abstract
This paper was presented at the Twenty-first Annual National Conference of the Society of Aeronautical Weight Engineers at Seattle, Washington, May 14-17, 1962. The objective of this paper is to develop methods of analysis that will be useful in estimating the weight of un-cooled rocket engine nozzles. This is the type of nozzle used on most current solid-propellant rocket engines.
A combination of analytical and empirical methods is used in developing the weight estimating methods in this paper. First, basic physical relationships determine the form of the equations and curves. Then, provisions are made to bring the results into agreement with empirical weight data by inserting a constant in the final weight equation. A value based on empirical weight data for several nozzles is given for each of these constants. Although these empirical constants should have essentially the same values for all nozzle configurations, it is recommended that they be re-evaluated when weight information is available on nozzle designs similar to the type being analyzed.
For purposes of analysis, the nozzle is divided into four major components: 1) exit cone structure, 2) throat structure, 3) exit cone insulation, and 4) throat insulation. Each of these components is represented by a simple geometric form such as a cone or cylinder.
The weight of the structural material in the exit cone and throat is correlated with that portion of the thrust force supported by the exit cone. After a family of curves that enables the weight engineer to calculate this force is plotted, weight equations are developed for both the throat and exit cone structural weight.
The exit cone insulation and throat insulation exist in a thermal environment that can be described by the local convective heat transfer coefficient and gas temperature. Methods are presented for calculating each of these parameters. Graphical and analytical methods derived from transient heating theory are then developed for estimating the thickness of the insulation. A graphical method is also developed for determining the volume of the exit cone insulation.
