A series of experiments was conducted for studying scramjet nozzles under Mach 8 flight conditions using a high temperature gas flow produced by combustion of monomethyl-hydrazine (MMH) and nitrogen tetroxide (NTO). The stagnation temperature was designed to be 3170K, and the stagnation pressure to be 1MPa. Scramjet nozzles with expansion ratios of 3 (EN₃) and 5 (EN₅) were examined. Delivered specific impulse (I_sp) was found to be 17.3s (EN₃) and 26.1s (EN₅). Performances of nozzles were predicted using numerical codes, and energy release loss, kinetic loss and two-dimensional loss were identified. The two-dimensional loss was predicted to be 16.5% in the EN₃ nozzle and to decrease to 7.0% in the EN₅ nozzle. The kinetic loss due to chemical freezing was found to be about 4%. A friction loss evaluated from thrusts suggested laminar flow in the scramjet nozzle with the MMH/NTO experiments. Measured heat flux on nozzles also supported the laminar boundary layer. Experiments using a cold gas flow with the nozzles were also conducted to compare with the hot flow.