16. Oscillation Processes in Rig at the Moment of SRM Transfer to Main Operation Mode

Annotation: This paper describes the configuration of the rig, designed to fasten the solid-propellant rocket engine (hereunder referred to engine) during their testing, with engine thrust measurements by force transducers. It is determined that rig is the important link in the measurement chain, which directly impacts the thrust measurements, values of which will be used for calculation of the most important engine characteristics (for example, total burn). It was observed that when engine starts the basic mode of operation the thrust-measuring system of the rig is impacted by the dynamic loading caused by the engine thrust, which results in the occurrence of the oscillating processes in the rig, therefore it is important to know the behavior of these oscillating processes to estimate their impact on the thrust measurement during the design of the rigs and their thrustmeasuring systems. It is shown that if there is no procedure in the design practice to define the mode of oscillations in the rig it is rational to do it analyzing experimental thrust – time curves when different engines start the basic mode of operation. Number of experimental thrust (displacement of the engine/rig moving part) – time curves are provided for analysis when four different engines with different ballistic characteristic and capabilities start the basic mode of operation. Oscillating processes in the rig distort the physical behavior of the thrust, which requires additional analysis of the data following the tests, but since the oscillations subside rapidly, they will not significantly affect the calculation of the total burn. It is also observed that frequency of oscillations of the moving part of the rig, registered by the motion sensor, coincides with oscillation frequency, registered by the force transducer, moreover stable behavior of the oscillating processes, registered by the force transducer of the same engines, when they started the basic mode of operation, indicate the stable behavior of those engines and stable performance of the rig.