Annotation: The measurement errors upon conducting flight tests for launch vehicles are evaluated by considering the interferences and uncertainties in the measurement system procedure. Formal use of this approach can lead to unpredictable consequences. More reliable evaluation of errors upon conducted measurements can be achieved if the measurement process is regarded as a procedure of successive activities for designing, manufacturing, and testing the measurement system and the rocket including measurements and their processing during the after-flight analysis of the received data. The sampling rates of the main controlled parameters are three to ten times higher than the frequency range of their changing. Therefore, it is possible to determine the characteristics of the random error components directly on the basis of registered data. The unrevealed systematic components create the basic uncertainty in the evaluation of the examined parameter’s total measurement error. To evaluate the precision and measurement accuracy of a particular launch, the article suggests specifying the preliminary data on measurement error components determined during prelaunch processing and launch. Basic structures of algorithms for evaluation of precision and measurement accuracy for certain mathematical models that form the measured parameters were considered along with the practical case when static correlation existed among the measured parameters.

Annotation: One of the main design parameters of the automatic equipment in the launch vehicle’s pneumohydraulic systems is the flow friction characteristic, which represents the proportionality factor between the automatic equipment pressure differential and velocity head. The flow friction characteristic of the completely open automatic device should have very small value with required dimensions and mass. With decrease of the pressure losses, the required upstream pressure of the propulsion system is ensured with smaller pressurization of the tanks. It results in the decrease of the required pressurization gas volume, which boosts reduction of the performance of the launch vehicle as a whole. This paper describes the method of reduction of the flow friction characteristic of the dividing valve, optimizing the geometric shape of the flow passage. The problem of minimization of the valve’s flow friction characteristic is considered with the specified mass and design dimensions restrictions. The initial design of the valve was developed, taking into account the specified requirements, literature references and parameters of the analogue units. With the goal of optimization various options of valve design were considered, different from the initial design in configuration of the inlet and discharge nozzles, notably various angle sizes, forming the stream profile, and lengths of the direct-flow sections. Four options of the valve design were calculated using numerical methods of ANSYS CFX software. Navier – Stokes equations and k-ω SST turbulence model were used. Based on the calculations results the optimal design was selected. Initial design of the valve was compared with the optimal one. The flow friction characteristic of the optimal valve design decreased by 26 % in comparison with initial design with insignificant change of mass and dimensions. The design of the developed dividing valve can be involved in the design of the new launch vehicles.