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Correction Factors for Solid Propellant Rocket Performance Prediction Code

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Our customer is involved in design and realization of solid propellant rocket motors for all kind of mission critical missiles. One of the steps in conceptualization of rocket motor is determination of propellant composition that gives desired performance indicators i.e. specific impulse (Isp) and characteristic velocity (C*). Customer has been utilizing an open source chemical equilibrium code (NASA CEC / CEA2) for estimating propellant performance. Though nominally successful, there have existed significant differences in absolute performance values when compared against experimental data. Customer sought to improve the prediction accuracy of the legacy code by incorporating certain correction factors.

Having realized that equilibrium code is based on assumption of ideal conversion of energy from chemical to thermal to mechanical, Zeus Numerix identified three types of correction factors that correspond to inefficiencies in a practical rocket motor. These were namely (i) effect of ambient pressure (ii) combustion efficiency factor, and (iii) nozzle efficiency factor. The factors were statistically benchmarked with experimental trial data and were implemented in the Fortran based code.

Illustration
Solid rocket motor propulsion schematic

Customer was delivered with an improved version of solid propellant performance code. It was made possible for user to supply the efficiency factors through a graphical user interface. The code helped reduce the differences between theoretical and experimental performance parameters.

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