Method for generating rocket motor data profiles for firings at various temperatures
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorJohn M. King
Life of this patent
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Abstract
A method for generating predictions of rocket motor ballistic performance at specific firing temperatures and for generating data profiles for analysis. The method requires generally available specifications for the rocket motor to be tested and test data from one or more test firings at a known temperature. The method is implemented in software form and generates pressure and thrust versus time data at a selected temperature. The method generates a burnback profile with a correct final web that integrates to the correct final propellant weight as well as a throat area profile and thrust coefficient profile, for the test firing temperature and for the temperature to be predicted.
Claims15
A method for developing rocket motor ballistics performance at an output temperature, comprising:
- receiving input data comprising data from an actual test firing using an input temperature and rocket motor specifications;
- selecting a coefficient of throat erosion by iteratively solving an expression for rate of throat erosion as a function of said input data until a throat dimension matches a user input value;
- calculating an array of throat dimension by time increment with the selected coefficient of throat erosion;
- selecting a reference burn rate by iteratively solving an expression for total web burned as a function of said input data until total linear web burned matches the user input value for web thickness;
- calculating an array of linear web burned values at the input temperature with the selected reference burn rate;
- selecting a characteristic velocity by iteratively solving an expression for total propellant weight burned as a function of said input data until a total propellant weight burned matches a user input value;
- calculating an array of burn surface values at the input temperature with the selected characteristic velocity;
- and
- developing data profiles at an output temperature selected by the user.
A computer program embedded on a computer-readable medium with method steps of predicting rocket motor ballistics performance at a user selected output temperature, comprising:
- receiving input of data from at least one test firing, and rocket motor specifications including firing temperature, initial throat dimension, final throat dimension, propellant weight, propellant density data, web thickness, pressure exponent data, and pressure versus time;
- processing the pressure data in an iterative operation, varying a coefficient in an expression for the rate of throat erosion, as a function of pressure, to solve for a final throat dimension and selecting the coefficient of throat erosion which produces a final throat dimension matching the user input value;
- calculating an array of incremental values of throat dimension with the selected coefficient of throat erosion;
- processing the pressure and pressure exponent data in an iterative operation, varying a reference burn rate, in an expression for linear web burned as a function of pressure, reference pressure, reference burn rate and the pressure exponent, to solve for the total linear web burned and selecting the reference burn rate which produces a total linear web burned matching the user input value for web thickness;
- calculating an array of incremental values of burn rate at the input temperature and linear web burned at the input temperature, with the selected reference burn rate;
- processing the pressure and throat dimension data in an iterative operation, varying a characteristic velocity in an expression for propellant weight burned as a function of pressure, characteristic velocity, and throat dimension to solve for total propellant weight burned and selecting the characteristic velocity which produces the user input value for propellant weight;
- calculating an array of incremental values of burn surface at the input temperature, with the selected characteristic velocity;
- processing the arrays of values at the input temperature, for incremental throat dimension, linear web burned, and burn surface using equations expressing temperature dependence of the linear web burned and burn surface said equation expressing temperature dependence of burn surface including a burn surface modifier, and repeatedly solving equations for incremental values at the output temperature selected by the user, in an iterative operation varying the burn surface modifier, in an equation for total propellant weight burned and selecting the burn surface modifier which generates a propellant weight burned matching the user input value of propellant weight;
- calculating an array of incremental values of linear web burned and an array of incremental values of burn surface, using the selected burn surface modifier, both at the user selected output temperature;
- combining the burn surface values with the linear web burned values to form a burnback profile of the rocket motor, for the output temperature selected by the user.
A method for predicting rocket motor ballistic performance at a user-selected output temperature, comprising:
- developing rocket motor data profiles at an input temperature, said data profiles including an array of incremental thrust coefficient values at the input temperature;
- and
- developing predicted rocket motor ballistic performance for the user-selected output temperature based on the rocket motor data profiles, said predicted rocket motor data profiles including an incremental array of thrust values as a function of thrust coefficient, pressure and throat dimension;
- wherein said rocket motor ballistic performance is predicted absent an actual propellant grain geometry.
A method for predicting rocket motor ballistic performance at a user-selected output temperature, comprising:
- inputting an actual throat diameter of a rocket motor;
- inputting a value for web burned;
- measuring pressure data at a test firing of said rocket motor;
- using said measured pressure data in a predetermined throat diameter equation and varying coefficients therein until a calculated final throat diameter matches said actual throat diameter;
- using the measured pressure data in a predetermined web burned equation and varying a reference burn rate therein until a calculated web burned matches said user input value for web burned;
- and
- using the measured pressure data, calculated web burned, and calculated throat diameter to derive a burnback profile.
Dependencies are inferred from the claim text.