1. The reason that the M2-F2 vehicle and the slender shapes of references 46 and 47 (that is, those having aspectratios lessthan 1.O)haverelatively high lift-curve slopes may be related to well-developed forebody vortices caused by crossflow asreported by Allen and Perkinsz9 and Hoemer.30-31Because the model data of references 46 and 47 were untrimmed, their lift-curve slopes would be expected to be optimistic. The halfcones, having relatively sharp lateral edges, would be expected to produce vortex lift. However, the elliptical cone with the most slender planform (lowest aspect ratio) also has a relatively high slope compared to theory. Thus, the conjecture regarding well-developed vortices (resulting from body crossflow) providing an extra component of lift is afforded credence even if sharp lateral edgesareabsent.
2. Regarding compressibility effects, table 2 shows that the lift-curve slope data obtained from the vehicles represent a range of subsonic Mach numbers. Compressibility effects may be at least approximately accounted for by applyinfthe often-used Prandtl-Glauert factor, (1 -1w2) .5. Both Gothert" and Hoerne?' believe that for the lower aspect ratios, the exponent n in (1 -&)" should be less than 0.5. Nevertheless, compressibility effects are approximated hereby useof the more common exponent of 0.5. Figure 2(b) shows the lift-curve slopes from figure 2(a) for the seven vehicles, based on the more representative reference area,adjusted for compressibility effects. The purpose hereis toshow that, for the vehicles having data at two Mach numbers (the M2-F2, X-24B, and the X-15 vehicles, and the-~Shuttle prototype), accounting for compressibility effects places the affected data somewhat in alignment with the relationships of equations (1) and (2).