This scientific article examines the process of designing a gas dynamic tube used for testing liquid rocket engines on firing stands with simulated vacuum conditions. The gas dynamic tube is an integral component of the extensive testing stand system as it facilitates the creation of a rarefied environment during the operation of the rocket engine. This is achieved through the creation of self-ejection, which, in turn, ensures uninterrupted gas flow through the nozzle. The article presents the results of testing the gas dynamic tube under real conditions, highlighting its effectiveness and reliability in operation. Additionally, a mathematical model for calculating the gas dynamic tube, implemented in the ANSYS software environment, is utilized, which corroborates the experimental data obtained. The process of designing and testing the gas dynamic tube reflects the importance of a meticulous scientific approach to the creation and optimization of components in large systems, such as testing stands for rocket engines. The research results pave the way for further advancement of technologies in this field and provide a foundation for further scientific exploration.