SUMMARY

The laminar boundary layer on a cooled 20 cone was investigated at Mach numbers of 1.5 and 2.0 to determine the variation of the position of transition with surface temperature for both constant surface temperatures and surface temperatures that increased toward the rear of the cone. Small circumferential grooves at the tip were necessary to cause transition near the center of the cone at the condition of zero heat transfer. The results obtained at all test conditions indicate that removing heat from the bound-ary layer delays transition from laminar to turbulent flow. The theory of laminar—boundary—layer stability developed by Lees in NACA TN 1360, 19^7> is in qualitative agreement with this result. At the test conditions of the present investigation, the increase in the extent of the laminar bound-ary layer was found to be a linear function of the rate of heat transfer