Rotary Wing Decelerators for Miniature Atmospheric Entry Probes

Abstract

Rotary wing decelerators were investigated as part of a miniature entry probe feasibility study. Previous technology demonstrations have shown that traditional low speed aerodynamic deceleration systems for this size class of probe can be relatively massive and risky. Rotary wing decelerators offer many potential advantages for miniature entry probes. The objectives of this project were to investigate the potential advantages of the rotary wing decelerator technology, assess aerodynamic modeling tools, and quantify performance of duel wing decelerator concepts using wind tunnel experimentation. Test models included a variety of two wing rotors with diameters of 152 mm or less in low speed air flows less than 20 m/s. The models with the lowest aspect ratio, 0.7 and 1.1, and highest solidity, 0.39 and 0.56, were observed to have the largest average thrust coefficients, 1.13 and 1.32 respectively. The tip speed ratio and the blade pitch were also identified as important parameters related to the magnitude of the Thrust Coefficient. Blade Element Momentum theory demonstrated the ability to predict average rotor thrust within 30% when compared with experimental observation for the majority of the cases considered. Nomenclature Ab - Area of the blades Ar - Area of the rotor disk CT - Thrust Coefficient c - Chord length D - Rotor diameter N - Number of rotor blades R - Radius of the rotor disk Reb - Reynolds number based on blade geometry Ret - Reynolds number based on rotor geometry s - Span length T – Thrust force U - Free stream flow velocity - Angle of attack - Tip speed ratio (or TSR) - Angular velocity of the rotor (in radians per second) - Fluid density σ - Solidity γ - Kinematic viscosity