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This paper reports the boundary-layer transition characteristics of airbreathing hypersonic configurations and their impact on design environments. It discusses the evolution of the National Aerospace Plane configuration from an axisymmetric baseline to a wedgelike configuration where the transition mechanism is dominated by "natural" transition. The natural transition is characteristic of the "quiet" environment in free flight of smooth slender vehicles. This type of transition mechanism gradually evolves spatially in different modes that can be computed analytically and verified experimentally. The paper discusses the effect of leading-edge bluntness, surface wall temperature, and adverse pressure gradient in compression ramp on transition. The effect of freestream Mach number, Reynolds number, and angle of attack are also studied over the range of peak aerodynamic heating conditions of the National Aerospace Plane environment. The transition behavior was investigated using e N -type calculations based on a linear stability code known as the e Malik code.static pressure coefficient for the local condition c p = specific heat of air at constant pressure, Btu=lb m ; R c v = specific heat of air at constant volume, Btu=lb m ; R H aw = adiabatic wall enthalpy, Btu=lb m H t = total enthalpy, Btu=lb m H w = wall enthalpy, Btu=lb m h i = heat transfer coefficient for the local condition, Btu=ft 2 s; R L = length, inches or feet M = Mach number M e = boundary-edge Mach number Pr = Prandtl number p e = pressure at the boundary-layer edge, psia or psfa p i = pressure for the local condition, psia or psfa p t , p t1 = total or settling pressure, psia or psfa p t2 = pitot pressure in test section, psia or psfa p 1 , p = freestream static pressure, psia or psfa _ q w = heat transfer rate based on wall temperature, Btu=ft 2 s q 1 = freestream dynamic pressure, psi or psf R = radius, ft R g = gas constant per unit mass Re = Reynolds number Re = momentum thickness Reynolds number r = recovery factor St = Stanton number St 1 = freestream Stanton number T aw = adiabatic wall temperature, R T o = total temperature, R T t = total temperature, R T w = model wall temperature, R T 1 = freestream static temperature, R v 1 , v = freestream velocity, ft=s x=L = longitudinal position as a fraction of the reference length = angle of attack, degrees = angle of sideslip, degrees = ratio of specific heats, c p =c v = boundary-layer momentum thickness 1 = freestream dynamic viscosity, slugs=ft s e = dynamic viscosity at the boundary-layer edge, slugs=ft s w = dynamic viscosity at the wall, slugs=ft s = kinematic viscosity, slugs=ft s 1 = freestream density, slugs=ft 3 e = density at the boundary-layer edge, slugs=ft 3 w = density at the wall, slugs=ft 3 Subscripts aw = adiabatic wall condition e = boundary-layer edge condition effective = composite boundary-layer transition value used for vehicle design rn = nosetip/leading-edge (bluntness) t = total condition threshold = baseline boundary-layer transition value from simple correlation w = wa...

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The objective of this effort is to modify an existing engineering code to provide fast prediction capabilities to assess the aerothermodynamic performance characteristics of advanced high speed configurations throughout a flight trajectory. The prediction techniques are to be engineering methods suitable for preliminary design analysis and configuration tradeoff studies. The code expands the core capability of the current Viscous Effects on Complex Configuration (VECC) which was originally developed for the Air Force by Boeing's team in St. Louis. The final aerothermodynamic trajectory analysis tool kit, named Hypersonic Engineering Aerothermodynamic Trajectory Tool Kit (HEAT-TK), incorporate modern geometry handling capabilities, a modern GUI, updated engineering aerodynamic heating analysis methods, modern data handling (including material thermal properties) and integration methods, three degree-of-freedom trajectory analysis, aeroheating/thermal analysis along trajectories, and a two-dimensional/three-dimensional analysis output display capability with real-time viewing manipulation. All coding are performed with a modular, open-architecture philosophy.