NOZZLE EROSION CHARACTERIZATION IN A NON-METALLIZED SOLID-PROPELLANT ROCKET MOTOR SIMULATOR

An understanding of the nozzle throat erosion processes and developing methods for mitigation of erosion rate can allow higher operating pressure of rocket motors. To evaluate the individual effects of oxidizing species on the chemical erosion rates of rocket nozzles (e.g., G-90 graphite material), a solid-propellant rocket motor simulator (RMS) was designed and tested. The RMS simulates the mass fractions of the oxidizing product species (like H2O, OH, CO2) and product composition temperature generated from a non-metallized composite propellant, called Propellant S, at the throat region. Test firings of the RMS have been conducted at various chamber pressures up to 6.9 MPa (1,000 psia). This instrumented RMS test setup incorporates the use of a real-time X-ray radiography system for measurement of the instantaneous contour of the rocket nozzle throat region. The instantaneous erosion rates of the G-90 nozzle throat were deduced from the recorded X-ray images. Holding oxidizing species concentrations and gas temperature constant, nozzle erosion rates measured from the RMS were correlated to operating pressure. The correlation shows the strong effect of increased heat transfer rates at higher pressures on increased nozzle erosion rates. To avoid nozzle throat erosion, an optional nozzle boundary-layer control system (NBLCS) was utilized in the RMS and was found to work efficiently for preventing nozzle erosion of G-90 graphite material.