Effectiveness of Two Flap Controls on a Mercury Type Capsule at a Mach Number of 15 in the Ames Hypersonic Helium Tunnel

The trim effectiveness of two types of control flaps was measured at a Mach number of 15 and a Reynolds number of 1.8 million (based on maximum diameter). The two flaps were; (1) a flat surface perpendicular to the model axis at the juncture between the spherical segment front face and the conical afterbody, and (2) a "conical' flap which was an extension, in the forward direction, of the conical afterbody. The ratios of flap area to model frontal area were 0.049 and 0.047 for the flat and conical flaps, respectively. The measured shock-wave shapes for the basic capsule at angles of attack are compared to predicted shapes. A brief description of the wind tunnel and the nozzle flow characteristics at M = 15 also is presented. Results indicate that for approximately equal ratios of flap area to frontal area the conical flap had the greater trim effectiveness. Force and moment coefficients for the basic capsule and for the capsule with the flat flap were adequately predicted by theory. Force and moment coefficients measured in helium at a Mach number of 15 agreed well with those measured in air at Mach numbers of 3.3 and 5.5. The largest difference was in drag coefficient which in helium was approximately 7 percent lower than in air. Measured shock-wave shapes agreed with estimated shapes in the nose region at angles of attack from O° to -15°.