The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratory (AFRL) andAustralian Defence Science and Technology Organisation (DSTO). HIFiRE flight one flew in March 2010. Principle goals of this flight were to measure hypersonic boundary-layer transition and shock boundary layer interactions in flight. The flight successfully gathered pressure, temperature and heat transfer measurements during ascent and reentry. HIFiRE-1 has provided transition measurements suitable for calibrating N-factor prediction methods for flight, and has produced some insight into the structure of the transition front on a cone at angle of attack. Pressure and heat transfer measurements in the shock-boundary-layer interaction were obtained. Preliminary analysis of the shock boundary layer interaction shows intermittent pressure fluctuations qualitatively similar to those measured in wind tunnel experiments. A large amount of data was obtained on the flight, and significant data reduction efforts continue. Nomenclature Symbolsamplitude at lower neutral bound, dimensionless C h = heat transfer coefficient (Stanton number), , dimensionless C p = specific heat, J/kg K f = frequency, Hz h = altitude, m H = specific enthalpy, J/kg k = thermal conductivity, W/mK L = reference length from stagnation point to flare / cylinder corner, 1.6013 m full scale M = freestream (upstream of vehicle shock) Mach number N = ln[A(f)/A 1 (f)], dimensionless p = pressure, kPa = fluctuating pressure (instantaneous departure from local mean), kPa p = pressure zero-shift at t=60 seconds, kPa = heat transfer rate, W/m 2 Re = freestream unit Reynolds number per meter,  ∞ U ∞ / ∞ s = streamwise surface arc length from stagnation point, m t = time after liftoff, seconds T = temperature, K U = magnitude of the velocity vector, m/s v = velocity component normal to missile x-axis, m/s x = distance from stagnation point along vehicle centerline, m y = vertical (pitch-plane) coordinate, or depth below model wetted surface m 2  = thermal diffusivity, k/C p , m 2 /s  = wind-fixed angular coordinate around vehicle circumference, =0 on windward stagnation line, degrees (Figure 11)  = body-fixed angular coordinate around vehicle circumference,  = 0 on primary instrumentation ray, degrees (Figure 11)  = density, kg/m 3  = viscosity, N s / m 2 Subscripts 0 = stagnation conditions 1 = lower neutral bound m = measured in flight e = evaluated at boundary-layer edge tr = transition location w = evaluated at model wall x = evaluated at distance x from stagnation point ∞ = freestream conditions, upstream of model bow shockAcronyms AFRL Air Force Research Laboratory AoA angle of attack AOSG Aerospace Operational Support Group, Royal Australian Air Force ARC Ames Research Center AVD Air Vehicles Division BC boundary condition BEA best estimated atmosphere BET best estimated trajectory BLT boundary-layer transition

The HIFiRE-1 flight experiment provided a valuable database pertaining to boundary layer transition over a 7-degree half-angle, circular cone model from supersonic to hypersonic Mach numbers, and a range of Reynolds numbers and angles of attack. This paper reports selected findings from the ongoing computational analysis of the measured in-flight transition behavior. Transition during the ascent phase at nearly zero degree angle of attack is dominated by second mode instabilities except in the vicinity of the cone meridian where a roughness element was placed midway along the length of the cone. The growth of first mode instabilities is found to be weak at all trajectory points analyzed from the ascent phase. For times less than approximately 18.5 seconds into the flight, the peak amplification ratio for second mode disturbances is sufficiently small because of the lower Mach numbers at earlier times, so that the transition behavior inferred from the measurements is attributed to an unknown physical mechanism, potentially related to step discontinuities in surface height near the locations of a change in the surface material. Based on the time histories of temperature and/or heat flux at transducer locations within the aft portion of the cone, the onset of transition correlated with a linear N-factor, based on parabolized stability equations, of approximately 13.5. Due to the large angles of attack during the re-entry phase, crossflow instability may play a significant role in transition. Computations also indicate the presence of pronounced crossflow separation over a significant portion of the trajectory segment that is relevant to transition analysis. The transition behavior during this re-entry segment of HIFiRE-1 flight shares some common features with the predicted transition front along the elliptic cone shaped HIFiRE-5 flight article, which was designed to provide hypersonic transition data for a fully 3D geometric configuration. To compare and contrast the crossflow dominated transition over the HIFiRE-1 and HIFiRE-5 configurations, this paper also analyzes boundary layer instabilities over a subscale model of the HIFiRE-5 flight configuration that was tested in the Mach 6 quiet tunnel facility at Purdue University. Nomenclature

The heat transfer rate was measured using global phosphor thermography and the resulting images and heat transfer rate distributions were used to infer the state of the boundary layer on the windside, leeside and side surfaces. Boundary layer trips were used to force the boundary layer turbulent, and a study was conducted to determine the effectiveness of the trips with various heights. The experimental data highlighted in this test report were used determine the allowable roughness height for both the windside and side surfaces of the vehicle as well as provide for future tunnel-to-tunnel comparisons.

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