Method of autonomous determination of the rocket’s reference attitude during pre-launch processing

To solve the navigation tasks (determination of the apparent accelerations and angular velocities and calculation of rocket orientation angles) in the rocket engineering, the data from the sensing elements (angular velocity sensors and accelerometers) is used. Accuracy of reference attitude determination of the rocket in the steady mode (at lift-off) has great influence on accuracy of the received navigation data during the flight. Gimballess inertial navigation system, built on the basis of inertial MEMS-sensors of Industry class (three angular velocity sensors and three accelerometers), is taken as the navigation device. In the classical version, the integration of data from angular velocity sensors and from accelerometers is the basis of gimballess inertial navigation system operation. It results in accumulation of errors when solving the navigation task (in particular due to the integration of data from angular velocity sensors). Taking it into consideration, the alternative method of rocket's reference attitude determination during the pre-launch processing is offered. This method does not use mathematical operations of integration and is autonomous. Initial data, received from the gimballess inertial navigation system, is used as the output data. This data is used to determine the rocket's reference attitude (orientation of object-centered coordinates in the geographical reference system) in the steady mode. Orientation angles are determined without the integration of data picked up from the angular velocity sensors. The comparative analysis to define the processing efficiency of the navigation device initial data was held during the determination of the rocket's orientation angles in the steady mode, using the proposed method and Runge-Kutta method. The received results showed that accuracy of the reference attitude determination with the proposed method is higher. Thus, the proposed method will help reduce the errors in determination of the rocket's reference attitude in the steady mode that in the future will improve the accuracy in determination of navigational parameters during the rocket's flight.