Nozzle start flow investigation in the conditions of high-altitude test

Rocket engines for future-technology vehicles development requires special ground-based test facilities to simulate the conditions at high altitude. The unsteady flow phenomena in the nozzle during starting process can cause the dangerous loads on the nozzles. The real propulsion engines high-altitude tests in the vacuum chamber are very expensive due to the huge vacuum chamber should be used. Usually ejector pumps are used for the initial rarefaction creation. The investigations of real propulsions in the test facilities with ejector are not so expensive but they can cause external loads on the nozzle wall at the nozzle start. Both of these techniques do not allow the flow pattern in the diffuser observing. Because the modern nozzles usually are thin any pressure excess around the nozzle may cause nozzle damage. In the present paper, a method of experimental and numerical analyses of disturbances at the start of a rocket engine is proposed.