Joseph Ferry
Missouri University of Science and Technology
Marshall Space Flight Center
Mentor: Joe Leahy
Abstract
The analysis team within the Liquid Engine & Main Propulsion Systems Branch (ER21) at NASA-MSFC required a computer tool, which could quickly and accurately find the properties of gases produced by chemical combustion of two liquids. Chemical equilibrium routines such as CEA were accurate, but took considerable time to run from within another program. Property table lookup schemes ran quickly but did not have high enough fidelity in some cases.

The approach and results presented in this paper yielded a tool, which could run quickly and give answers with a very high degree of accuracy. Microsoft Excel was used to create regression equations with two independent variables: chamber pressure and oxidizer/fuel mixing ratio. Equations were found for four different combustion properties: combustion temperature, exhaust gas specific heat, exhaust gas molecular weight, and the exhaust gas ratio of specific heats (?).

Equations were found for each property of each propellant combination. To ensure a high level of accuracy, each property used between 10 and 75 equations. Each of these equations was valid for a certain range of mixing ratios and chamber pressures. This approach allowed the tool to return values that in most cases were within 0.5% error of the values generated by the chemical equilibrium programs.

In its final form, the tool provided this information for eight different propellant combinations over a wide range of mixing ratios and chamber pressures. These propellant combinations include Liquid Oxygen (LOX)/Liquid Hydrogen (LH2), LOX/RP-1 (Kerosene), LOX/Methane, LOX/Alcohol (C2H5OH), LOX/Hydrazine, Nitrogen Tetroxide (NTO)/Hydrazine, NTO/Aerozine-50, and NTO/Monomethyl Hydrazine (MMH).
NOTE: This work was sponsored by the Exploration Systems Mission Directorate (ESMD) Space Grant Internship Program.