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At least 127 records · Page 7

Summary of shuttle data processing and aerodynamic performance comparisons for the first 11 flights

NASA Space Shuttle aerodynamic and aerothermodynamic research is but one part of the most comprehensive end-to-end flight test program ever undertaken considering: the extensive pre-flight experimental data base development; the multitude of spacecraft and remote measurements taken during entry flight; the complexity of the Orbiter aerodynamic configuration; the variety of flight conditions available across the entire speed regime; and the efforts devoted to flight data reduction throughout the aerospace community. Shuttle entry flights provide a wealth of research quality data, in essence a veritable flying wind tunnel, for use by researchers to verify and improve the operational capability of the Orbiter and provide data for evaluations of experimental facilities as well as computational methods. This final report merely summarizes the major activities conducted by the AMA, Inc. under NASA Contract NAS1-16087 as part of that interesting research. Investigators desiring more detailed information can refer to the glossary of AMA publications attached herein as Appendix A. Section I provides background discussion of software and methodology development to enable Best Estimate Trajectory (BET) generation. Actual products generated are summarized in Section II as tables which completely describe the post-flight products available from the first three-year Shuttle flight history. Summary results are presented in Section III, with longitudinal performance comparisons included as Appendices for each of the flights.

Findlay, J. T.↗

Comparison of aerodynamic performance of several STOL concepts

Wind tunnel tests to determine the aerodynamic characteristics of basically similar short takeoff aircraft were conducted. The investigations were designed to provide data for a systematic direct comparison of five of the concepts considered. The configurations of the five models are illustrated and described. The aerodynamic data are presented in the form of graphs. It was concluded that the most complex systems require the least amount of net thrust.

Hoad, D. R.↗

An interaction solution algorithm for viscous aerodynamic performance prediction

A weak-interaction solution algorithm is established for aerodynamic flow field prediction about an isolated airfoil. It requires numerical solution of differential equations governing potential flow, viscous and turbulent boundary layer flow, and the turbulent wake flow downstream of a trailing edge. The algorithm accounts for computed viscous displacement effects on the potential flow. These in turn alter the viscous flow through imposed pressure gradients. Closure for turbulence is accomplished using a second order model. Numerical evaluations assess factors affecting solution accuracy, convergence and stability for the combined potential, boundary layer, and parabolic Navier-Stokes equation systems as solved using a finite element algorithm.

Baker, A. J.↗

Aerodynamic Performance and Turbulence Measurements in a Turbine Vane Cascade

Turbine vane aerodynamics were measured in a three vane linear cascade. Surface pressures and blade row losses were obtained over a range of Reynolds and Mach number for three levels of turbulence. Comparisons are made with predictions using a quasi-3D Navier-Stokes analysis. Turbulence intensity measurement were made upstream and downstream of the vane. The purpose of the downstream measurements was to determine how the turbulence was affected by the strong contraction through 75 deg turning.

Boyle, Robert J.↗

Unstructured Grid Euler Method Assessment for Longitudinal and Lateral/Directional Aerodynamic Performance Analysis of the HSR Technology Concept Airplane at Supersonic Cruise Speed

Unstructured grid Euler computations, performed at supersonic cruise speed, are presented for a High Speed Civil Transport (HSCT) configuration, designated as the Technology Concept Airplane (TCA) within the High Speed Research (HSR) Program. The numerical results are obtained for the complete TCA cruise configuration which includes the wing, fuselage, empennage, diverters, and flow through nacelles at M (sub infinity) = 2.4 for a range of angles-of-attack and sideslip. Although all the present computations are performed for the complete TCA configuration, appropriate assumptions derived from the fundamental supersonic aerodynamic principles have been made to extract aerodynamic predictions to complement the experimental data obtained from a 1.675%-scaled truncated (aft fuselage/empennage components removed) TCA model. The validity of the computational results, derived from the latter assumptions, are thoroughly addressed and discussed in detail. The computed surface and off-surface flow characteristics are analyzed and the pressure coefficient contours on the wing lower surface are shown to correlate reasonably well with the available pressure sensitive paint results, particularly, for the complex flow structures around the nacelles. The predicted longitudinal and lateral/directional performance characteristics for the truncated TCA configuration are shown to correlate very well with the corresponding wind-tunnel data across the examined range of angles-of-attack and sideslip. The complementary computational results for the longitudinal and lateral/directional performance characteristics for the complete TCA configuration are also presented along with the aerodynamic effects due to empennage components. Results are also presented to assess the computational method performance, solution sensitivity to grid refinement, and solution convergence characteristics.

Ghaffari, Farhad↗

Aerodynamic Performance of the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) Technology Demonstration Mission

The Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) mission successfully demonstrated the deployment and entry performance of a 6 m diameter Hypersonic Inflatable Decelerator on November 10, 2022. This was the largest blunt body flown to date and demonstrated this inflatable aeroshell technology at scale and conditions relevant to Earth and Mars Entry, Descent, and Landing applications. LOFTID built upon the prior successes of the suborbital IRVE and IRVE-3 missions, leveraging and expanding on the flight experience from these and other planetary and Earth sample return missions. Both the re-entry vehicle and ejectable data module were successfully recovered from the Pacific Ocean, with LOFTID satisfying requirements for decelerator performance and stable flight from orbital entry conditions through parachute deployment and splashdown. This work discusses the pre-flight aerodynamics database and reconstructed flight performance of the LOFTID re-entry vehicle.

LOFTID↗

Aerodynamic Performance of the Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) Technology Demonstration Mission

The Low-Earth Orbit Flight Test of an Inflatable Decelerator (LOFTID) mission successfully demonstrated the deployment and entry performance of a 6 m diameter Hypersonic Inflatable Decelerator on November 10, 2022. This was the largest blunt body flown to date and demonstrated this inflatable aeroshell technology at scale and conditions relevant to Earth and Mars Entry, Descent, and Landing applications. LOFTID built upon the prior successes of the suborbital IRVE and IRVE-3 missions, leveraging and expanding on the flight experience from these and other planetary and Earth sample return missions. Both the re-entry vehicle and ejectable data module were successfully recovered from the Pacific Ocean, with LOFTID satisfying requirements for decelerator performance and stable flight from orbital entry conditions through parachute deployment and splashdown. This work discusses the pre-flight aerodynamics database and reconstructed flight performance of the LOFTID re-entry vehicle.

LOFTID↗

Aerodynamic performance of a full-scale lifting ejector system in a STOVL fighter aircraft

The aerodynamic characteristics of an advanced lifting ejector system incorporated into a full-scale, powered, fighter aircraft model were measured at statically and at transition airspeeds in the 40- by 80- and 80- by 120-Foot Wind Tunnels at NASA-Ames. The ejector system was installed in an ejector-lift/vectored thrust STOVL (Short Take-Off Vertical Landing) fighter aircraft configuration. Ejector thrust augmentation ratios approaching 1.6 were demonstrated during static testing. Changes in the internal aerodynamics and exit flow conditions of the ejector ducts are presented for a variety of wind-off and forward-flight test conditions. Wind-on test results indicate a small decrease in ejector performance and increase in exit flow nonuniformity with forward speed. Simulated ejector start-up at high speed, nose-up attitudes caused only small effects on overall vehicle forces and moments despite the fact that the ejector inlet flow was found to induce large regions of negative pressure on the upper surface of the wing apex adjacent to the inlets.

Smith, Brian E.↗

Effect of leading-edge vortex flaps on aerodynamic performance of delta wings

The effect of leading-edge vortex flaps on the aerodynamic characteristics of highly swept-back wings is analytically investigated, using the free vortex sheet method. The method, based on a three-dimensional inviscid flow model, is an advanced panel type employing quadratic doublet distributions to represent the wing surface, rolled-up vortex sheet and wake and is capable of computing forces, moments and surface pressures.

Reddy, C. S.↗

Aerodynamic performance of a drag reduction device on a full-scale tractor/trailer

The effectiveness of an aerodynamic boattail on a tractor/trailer road vehicle was measured in the NASA Ames Research Center 80- by 120-Foot Wind Tunnel. Results are examined for the tractor/trailer with and without the drag reduction device. Pressure measurements and flow visualization show that the aerodynamic boattail traps a vortex or eddy in the corner formed between the device and the rear corner of the trailer. This recirculating flow turns the flow inward as it separates from the edges of the base of the trailer. This modified flow behavior increases the pressure acting over the base area of the truck, thereby reducing the net aerodynamic drag of the vehicle. Drag measurements and pressure distributions in the region of the boattail device are presented for selected configurations. The optimum configuration reduces the overall drag of the tractor/trailer combination by about 10 percent at a zero yaw angle. Unsteady pressure measurements do not indicate strong vortex shedding, although the addition of the boattail plates increases high frequency content of the fluctuating pressure.

Lanser, Wendy R.↗

Aerodynamic performance of an annular flat plate airfoil cascade with nonuniform inlet velocity

The demand for increased gas turbine engine efficiency with minimum weight is leading to more complex blading designs, in which viscous and three-dimensional effects are significant. As a result, design procedures based on first principle, experimentally verified, three-dimensional aerodynamic analyses are required. This paper describes a series of experiments performed in a large-scale, subsonic, annular cascade facility specifically designed to provide three-dimensional aerodynamic data suitable for code verification. In particular, the effect of inlet velocity profile on the overall three-dimensional performance of a classical flat plate airfoil cascade is investigated over a range of incidence angles including those resulting in airfoil surface flow separation. All of the data are analyzed and correlated with appropriate nonseparated flow predictions.

Buffum, D.↗

Computations of Aerodynamic Performance Databases Using Output-Based Refinement

Objectives: Handle complex geometry problems; Control discretization errors via solution-adaptive mesh refinement; Focus on aerodynamic databases of parametric and optimization studies: 1. Accuracy: satisfy prescribed error bounds 2. Robustness and speed: may require over 105 mesh generations 3. Automation: avoid user supervision Obtain "expert meshes" independent of user skill; and Run every case adaptively in production settings.

Nemec, Marian↗

Aerodynamic Performance of Supersonic Parachutes Behind Slender Bodies

NASA's ASPIRE (Advanced Supersonic Parachute Inflation Research Experiments) project was launched to investigate the supersonic deployment, inflation and aerodynamics of full-scale disk-gap-band (DGB) parachutes. Three flight tests (October 2017, March 2018 and July 2018) deployed and examined parachutes meant for the upcoming "Mars 2020" mission. Mars-relevant conditions were achieved by performing the tests at high altitudes over Earth on a sounding rocket platform, with the parachute deploying behind a slender body (roughly 1/6-th the diameter of the capsule that will use this parachute for descent at Mars). All three tests were successful and delivered valuable data and imagery on parachute deployment and performance. CFD simulations were used in designing the flight test, interpreting the flight data, and extrapolating the results obtained during the flight test to predict parachute behavior at Mars behind a blunt capsule. This presentation will provide a brief overview of the test program and flight test data, with emphasis on differences in parachute performance due to the leading body geometry.

Muppidi, Suman↗

Aerodynamic Performance Predictions of Single and Twin Jet Afterbodies

The multiblock three-dimensional Navier-Stokes method PAB3D was utilized by the Component Integration Branch (formerly Propulsion Aerodynamics Branch) at the NASA-Langley Research Center in an international study sponsored by AGARD Working Group #17 for the assessment of the state-of-the-art of propulsion-airframe integration testing techniques and CFD prediction technologies. Three test geometries from ONERA involving fundamental flow physics and four geometries from NASA-LaRC involving realistic flow interactions of wing, body, tail, and jet plumes were chosen by the Working Group. An overview of results on four (1 ONERA and 3 LaRC) of the seven test cases is presented. External static pressures, integrated pressure drag and total drag were calculated for the Langley test cases and jet plume velocity profiles and turbulent viscous stresses were calculated for the ONERA test case. Only selected data from these calculations are presented in this paper. The complete data sets calculated by the participants will be presented in an AGARD summary report. Predicted surface static pressures compared favorably with experimental data for the Langley geometries. Predicted afterbody drag compared well with experiment. Predicted nozzle drag was typically low due to over-compression of the flow near the trailing edge. Total drag was typically high. Predicted jet plume quantities on the ONERA case compared generally well with data.

Carlson, John R.↗

Dynamic Analysis of Reynolds Number Effects on Trailing Edge Transonic Vortex Shedding and Its Impact on Turbine Blade Aerodynamic Performance

Time-resolved, high-speed self-aligned focusing schlieren images were acquired in the NASA Glenn Research Center Transonic Turbine Blade Cascade facility to help understand the aerodynamic behavior of high-pressure, thick trailing edge turbine blades. The trailing edge thickness of 9% of axial chord tested represents simulated ceramic matrix composite fabrication constraints, which was verified previously to possess a high-loss flow regime at high inlet turbulence conditions over a narrow range of Reynolds numbers and at a fixed design exit Mach number of 0.74. Our high-speed images, which were acquired at 10 distinct Reynolds numbers, show a significant increase in energy from flow oscillations due to transonic vortex shedding at Reynolds numbers corresponding to the high loss conditions. For those conditions, strong acoustic waves turn into shock waves. Spectral Proper Orthogonal Decomposition of the high-speed images shows acoustic waves from trailing edge vortex shedding at all conditions, with increased spectral energy at the high-loss conditions and slightly increasing frequency (about 6%) as a function of Reynolds number. Analysis of potential feedback timing is performed using velocity fields from a previous LES simulation, considering different feedback mechanisms. Most noteworthy is the acoustic/shock-boundary layer interaction mechanism on the suction surface at the blade geometric throat, which likely plays an important role in realistic curved blade passages.

Trailing Edge↗