Experimental and Numerical Research on the Diversion Effect of a Conic Flame Deflector for a Lunar Module Ascent Stage

The diversion effect of a conic flame deflector for a lunar module ascent stage is investigated experimentally and numerically. Eighteen tests were performed in a vacuum chamber mounted with a liquid helium cryogenic pump using a scaled engine and models. The experimental results indicate that the conic flame deflector can guide the exhaust gas away from the ascent stage model more effectively than a plate; meanwhile, the conic flame deflector can create a reverse torque, which helps to correct the deflection of the ascent stage model. Finally, the experimental results show that the reverse torque changes with the distance and angle between the ascent stage model and the conic flame deflector model. Numerical simulations have been done with the computational fluid dynamics and direct simulation Monte Carlo (CFD/DSMC) method, and the numerical results are in good agreement with the experimental results. The numerical results reveal that the reason for the above phenomena is shock waves. An expansion wave starting from the nozzle lip and a compression wave starting from the cone surface control the amount and speed of the exhaust gas by changing the magnitude and direction of flow velocity and then influence the aerodynamic pressure on the ascent stage model.