Abstract: Modular streamtraced Busemann inlets were studied in detail for Mach 7.8 flight at 20 km altitude conditions.Numerical simulations were performed to study the effect of truncation angle and contraction ratio on the performance parameters of inlets,which were created by correcting the inviscid streamlines for turbulent boundary layer displacement obtained from finite difference calculations.To assess these inlets and calculate engine performance,they were coupled to an ideal combustor and nozzle.Mass-weighted average performance parameters of inlet/exit obtained by simulations were used as combustor entry flow conditions.The fuel used in the calculation is octane.The results show that mass capture ratio varies from 0.89 to 0.97 with truncation angles of 2°～10°.Larger truncation angle leads to higher mass capture ratio,pressure ratio and engine specific impulse.