MINIMUM-MASS DESIGN OF SANDWICH AEROBRAKES FOR A LUNAR TRANSFER VEHICLE

A structural mass optimization study of a sandwich aerobrake for a lun ar transfer vehicle was conducted. The proposed spherical aerobrake ha d a base diameter of 15.2 m and radius of 13.6 m, A hot thermal protec tion system (TPS) and cold structure were used in the design. Honeycom b sandwich aerobrake structures made up of four different materials-al uminum alloy, titanium alloy, graphite-epoxy, and graphite-polyimide-w ere considered. Cases of aerodynamic load, equivalent uniform pressure , and aerodynamic plus thermal load were analyzed. Both linear stress and buckling analyses were conducted for a range of skin and core thic knesses. A graphical optimization procedure was used to determine the skin and core thicknesses of a minimum-mass aerobrake. The design crit eria used were material strength, global buckling, and TPS tile deform ation. Among them, the TPS deformation criterion was the most critical . The graphite-epoxy aerobrake was the lightest among the four materia ls studied. Its total mass is about 12.3 of of the LTV mass, for suppo rts at 75% span. Equivalent uniform loading produced smaller deformati ons, stresses, and buckling loads than did the more realistic aerodyna mic loading for the same aerobrake configuration. Thermally induced st resses countered the aerodynamically induced stresses and hence had a beneficial effect on the deformation and buckling of the aerobrake.