Correlation of Attitude Effects on Slender Vehicle Transition

Abstract

The effects of boundary-layer transition on the motion of a slender re-entry body are large. In order to predict how transition can cause these large effects on slender vehicle stability and trim characteristics, one has to know how the vehicle attitude influences the transition geometry. Contrary to general expectations, a correlation study has shown that the percentage change from the a = 0 transition geometry can be defined simply as a function of the relative vehicle attitude (oc/0 c ). The windward side forward transition movement on a blunted cone is guided by entropy impingement (and associated entropy swallowing effects) in a manner that can be predicted using transition measurements at a = 0 in combination with embedded Newtonian theory. The leeward side forward transition movement is completely dictated by boundary layer crossflow effects and can be defined using slender cone data obtained in different ground facilities.= axial body coordinate from sharp cone apex x 0 = start of conic frustum on blunted cone a = angle of attack A = difference 9 C = cone half-angle v = kinematic viscosity p = air density X = hypersonic similarity parameter (see Fig. 4) Subscripts AW = adiabatic wall B, N = base and nose, respectively EW = entropy wake impingement = inviscid flow = entropy swallowing = transition = wall condition i SW TR W 0 oo = freestream conditions IntroductionT HE effect of boundary-layer transition on high-performance re-entry bodies has been studied by the missile industry for a long time. The early concern was with the increased aft body ablation when transition moves forward of the base, 1 as it could be shown experimentally 2 and theoretically 3 that the associated increased ablation rates adversely affect the vehicle damping and can lead to dynamic instability. Later it was shown both experimentally 4 and theoretically 5 that in addition to the above effect of symmetric transition, the effect of asymmetric transition on vehicle dynamics is possibly even stronger.During recent times a great volume of experimental results has become available for the combined effects of crossflow and Presented as Part I of AIAA Paper 73-126 at the AIAA llth