David Adamczak

HIFiRE-1 Boundary Layer Transition Experiment Design

*† ‡ § ** The HIFiRE (Hypersonic International Flight Research and Experimentation) project will develop and demonstrate fundamental hypersonic technologies deemed critical to the realization of next generation aerospace weapon systems. Flight one focuses primarily on integration of instrumentation on the test vehicle, with application to future flights. Boundary layer transition has been chosen as one aerodynamic parameter to measure in order to assess instrumentation performance. Analysis has been performed to place requirements on the payload. Results show that the temperature of the aeroshell is relatively benign, easing temperature requirements on transducers. Reynolds number on the vehicle is relatively low, making it marginal for smooth-body boundary layer transition. Roughness must be placed on the vehicle to ensure transition and to obtain rough-wall data. I. Introduction The HIFiRE (Hypersonic International Flight Research and Experimentation) project will develop and demonstrate fundamental hypersonic technologies deemed critical to the realization of next generation aerospace weapon systems. The research effort will consist of a series of focused tasks to resolve hypersonic phenomena through validation of computational analysis; comparison with performance predictions, enhancement of design data bases; and development of correlations with ground test. Each research effort will culminate with a flight experiment to be launched to representative flight conditions (Reynolds number and Mach) employing low cost sounding rockets. The primary objective of flight one is to determine the feasibility of applying high-bandwidth instrumentation to aerothermal flight measurements for short duration hypersonic flights at Mach numbers up to eight. The experiment will determine the suitability and survivability of multiple instrumentation types in this environment. The experiment will be incorporated into the nose cone of a Terrier-Orion launch vehicle. This paper will refer to the nose cone as the “payload.” The measurement of three aerothermal phenomena will serve to assess the performance of the instrumentation. These sub-experiments are, in order of priority, boundary layer transition (BLT), turbulent separated shock boundary layer interaction (SBLI), and optical measurement of mass capture (OMC) in a duct. Measurement of these phenomena will serve as secondary objectives of the experiment. This paper describes analysis related to the BLT experiment to determine requirements for flight one. Boundary layer transition has an important impact on hypersonic vehicle aerodynamics and aerothermodynamics. It is an inherently challenging problem due to its nonlinear nature and sensitivity to initial and boundary conditions. Ground test of boundary layer transition is generally unsatisfactory due to the high noise levels of ground facilities compared to flight. Computation is challenging since it requires resolution of instabilities of relatively high wavenumber and frequency over large spatial domains. Flight provides the best environment for measuring transition. Instrumentation for the flight environment however, is challenging. The highest level of validation for transition prediction requires high bandwidth instrumentation. The current tests will explore the use of high-bandwidth instrumentation for flight measurement of transition. Careful measurement and computation of boundary conditions will provide added value in interpreting the data. Data from numerous past flight tests of supersonic and hypersonic transition exist. Schneider 1 offers a detailed review of transition flight tests. Vehicles were frequently thin-skin models. Backface thermocouples monitored transition, and heat transfer rates were inferred by lumped-capacitance heating models. Transition criteria based on

Stability Analysis for HIFiRE Experiments

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.

HIFiRE-5 Flight Vehicle Design

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratories (AFRL) and Australian Defence Science and Technology Organization (DSTO). HIFiRE flight 5 is devoted to measuring transition on a three-dimensional body. This paper summarizes payload configuration, trajectory, vehicle stability limits and roughness tolerances. Results show that the proposed configuration is suitable for testing transition on a three-dimensional body. Transition is predicted to occur within the test window, and a design has been developed that will allow the vehicle to be manufactured within prescribed roughness tolerances

Aerothermodynamic Characteristics of Boundary Layer Transition and Trip Effectiveness of the HIFiRE Flight 5 Vehicle

An experimental wind tunnel test was conducted in the NASA Langley Research Center’s 20-Inch Mach 6 Tunnel in support of the Hypersonic International Flight Research Experimentation Program. The information in this report is focused on the Flight 5 configuration, one in a series of flight experiments. This report documents experimental measurements made over a range of Reynolds numbers and angles of attack on several scaled ceramic heat transfer models of the Flight 5 vehicle. 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.

HIFiRE-1 Preliminary Aerothermodynamic Measurements

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratory (AFRL) and Australian 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. HIFiRE1 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.

HIFiRE-1: Payload Design, Manufacture, Ground Test, and Lessons Learned

HIFiRE (Hypersonic International Flight Research Experimentation) is a joint flight test program supported by the US Air Force Research Laboratory (AFRL) and the Australian Defence Science and Technology Organisation (DSTO). One of the main program goals is to gather basic research data on aspects of hypers onic flight not easily accessible to ground testing. Flight one focuses primarily on integration of instrumentation on the test vehicle, with application to boundary layer transition and shock interaction experiments. The HIFiRE 1 payload consists of a blunted 7° half angle cone and a cylinder/33° flare configuration. The payload will be boosted to Mach 8 utilizing a two stage Terrier-Orion sounding rocket. The payload was designed and manufactured to achieve the desired boundary layer transition and shock boundary layer interaction properties and collect the required data. Extensive analysis and ground testing was conducted to ensure the payload will survive the expected flight environment. The HIFiRE 1 launch campaign is scheduled for March 2010. A number of valuable lessons learned during the development of HIFiRE 1 are included in this paper. I. Introduction HIFiRE is a cooperative flight test program between the United States and Australia. The goal of this program is to advance technologies associated with hypersonic flight. Special emphas is is placed on exploring phenomena not readily accessible to ground tests. Fli ght one will focus on instrumentation an d telemetry systems to be used for flights occurring later in the program. The primary objec tive of HIFiRE 1 is to determine the feasibility of applying high-bandwidth instrumentation to aero-thermal flight measurements for short duration hypersonic flights at Mach numbers up to eight. The experiment will determine the suitability and survivability of multiple instrumentation types in this environment. The experiments will be incorporated into the nose cone of a Terrier-Orion launch vehicle 1 . This paper will refer to the nose cone as the “payload.” The measurement of three aero-thermal phenomena will serve to assess the performance of the instrumentation. The corresponding sub-experiments are, in order of priori ty, boundary layer transition (BLT), turbulent separated shock boundary layer interaction (SBLI), and optical measurement of mass capture (OMC). This paper describes the design, manufacture, integration and ground testing of the payload. It also includes valuable lessons that were learned during this process. The scientific motivations for the primary and secondary experiments on HIFiRE 1 have been discussed in a number of published papers 2,3,4,5,6,7,8,9 and will not be repeated here. Design parameters critical to the BLT experiment have been derived from past correlations, computational analyses and ground testing. The most critical paramete rs affecting the BLT experiment are surface roughness and step/gap sizes at and between payload sections. The most restrictive values were 0.08mm for an allowable discrete roughness and 0.001mm root mean square (rms) roughness at the nosetip (relaxing to 0.008mm rms aft of the nosetip). More recent results 3,10 indicated that larger values would have been acceptable, however the more restrictive roughness limits were employed for the payload design to provide a generous factor of safety for the experiment. A discrete roughness trip was installed on one side of the payload with the aim of extracting

Transition Analysis for the HIFiRE-1 Flight Experiment

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 incidence. This paper reports the initial findings from the ongoing computational analysis pertaining to 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 first mode instabilities were 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 PSE N-factor of approximately 14.

HIFiRE-1 Flight Trajectory Estimation and Initial Experimental Results

The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratories (AFRL) and Australian Defence Science and Technology Organization (DSTO). HIFiRE flight 1 consists of several hypersonic flight experiments to examine: transition on a conical body, shock boundary layer interaction on a conical flare, and an optical mass capture experiment. This abstract summarizes the flight 1 vehicle, the launch in March 2010, the flight trajectory flown and some initial results for the experiments.

HIFiRE-1 Data Analysis: Boundary Layer Transition Experiment During Reentry

Analyses of data collected during reentry of the HIFiRE-1 flight for the boundary layer transition experiment are reported. The data collected was complicated by the dynamic motion of the flight vehicle at large angles-of-attack, and by missing data, which resulted in an unevenly spaced time domain. The unevenly spaced time data increased the complexity of spectral analysis. Normalized root-mean-square (RMS) surface pressures were computed, and correlated well with periodic surface pressure fluctuations, boundary layer separation, and the boundary layer transition front. The periodic surface pressure fluctuations were first discernable underneath a laminar boundary layer on the leeside surface, at Re = 1.9x10 6 , and persisted until the boundary layer transitioned to turbulent, at Re = 5.1x10 6 . At Re values of 1.9x10 6 and 5.1x10 6 , the extent of the fluctuations in the azimuthal direction ranged between 15and 75-degrees, respectively. Corresponding wavelengths, computed using the Lomb-Scargle periodogram, ranged between 4.0 and 9.5 mm. The wavelengths of the periodic surface pressure fluctuations decreased as the vehicle descended and Re increased.

HIFiRE-1 Background and Lessons Learned

*† The Hypersonic International Flight Research Experimentation (HIFiRE) program is a hypersonic flight test program executed by the Air Force Research Laboratories (AFRL) and Australian Defence Science and Technology Organization (DSTO). HIFiRE flight one flew in March 2010. Principle goals of this flight were to measure boundary layer transition (BLT) and shock boundary layer interaction (SBLI) in hypersonic flight. This paper reports background preparation and analysis for HIFiRE-1, and lessons that may be derived from this flight and applied to future hypersonic flight tests, particularly boundary layer transition tests. The boundary layer transition experiment was complicated and compromised to some extent by secondary experiments incorporated into HIFiRE. The high bandwidth instrumentation tested on HIFiRE-1 survived and performed well. The measurement of second-mode instabilities in flight using piezo pressure gauges appears feasible.