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At least 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Flight test results of an active flutter suppression system installed on a remotely piloted research vehicle

Flight flutter test results of the first aeroelastic research wing of NASA's Drones for Aerodynamic and Structural Testing (DAST) program are presented. The implementation of the flutter suppression system and the flight test operation are described. The conduct of the flutter testing and the near-real time damping estimation algorithm are also described in detail. Flight data was obtained at Mach numbers up to 0.91 and was of high quality. Response to fast frequency sweep excitation provided reliable damping estimates and the open-loop flutter boundary was well defined. Evidence of angle-of-attack effects upon damping at high transonic Mach numbers is also presented. While the flutter suppression system provided augmented damping at speeds below the flutter boundary, an error in the implementation of the system gain caused the system to be less stable than predicted and the vehicle encountered system-on flutter on the third flight.

Edwards, J. W.↗
NASA NTRS1981

Full-scale study of the cooling system aerodynamics of an operating piston engine installed in a light aircraft wing panel

Measurements of the drag and of the nacelle internal pressures on a wing and nacelle that housed a horizontally opposed piston engine were made in the 40- by 80-Foot Wind Tunnel at Ames Research Center. These tests are follow-ons to earlier tests made with the same wing and nacelle but in which the engine was replaced with an electric motor and an adjustable orifice plate. In the initial tests the orifice plate was used to control the rate of cooling-air flow through the nacelle and thereby to simulate a range of gasoline engine types. Good agreement was found between the results of those tests and of the test reported here. Also, the upper and lower plenum pressure and cooling-air flow rate were found to be related by conventional equations used to represent the flow through orifices. Tests were run with three cooling air inlet sizes over a free-stream velocity range from 50 to 150 knots, an angle of attack range from 0 deg to 10 deg, and a cowl-flap deflection range from 0 deg to 30 deg. The data were analyzed by computing a flow coefficient similar to that used in the analysis of orifices. It was found that all of the flow coefficient values fell within a band that varied linearly with inlet area. The linear mean line through this band provides an estimate of the relationship between cooling-air flow rate and upper plenum pressure over a wide range of test conditions.

Corsiglia, V. R.↗
NASA NTRS1981

The design, fabrication and installation of cable routing mockups in support of Spacelab 2

From flight and mockup drawings of Spacelab 2 (SL 2) experiments and hardware, shop ready mockup drawings were produced. Floor panels were the first items considered for fabrication. Cold plate and orthogrid mockups were designed and fabricated. Experiment and other hardware mockups were fabricated of aluminum or plywood, depending on size and configuration. Eighty-three cable routing bracket mockups were fabricated of aluminum and delivered for painting.

Source record↗
NASA NTRS1982

Effects of installation of F101 DFE exhaust nozzles on the afterbody-nozzle characteristics of the F-14 airplane

A wind-tunnel investigation was conducted to determine the effects of F101 DFE (derivative fighter engine) nozzle axial positioning on the afterbody-nozzle longitudinal aerodynamic characteristics of the F-14 airplane. The model was tested in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0.7 to 1.25 and angles of attack from about -2 to 6 degrees. Compressed air was used to simulate nozzle exhaust flow at jet total-pressure ratios from 1 (jet off) to about 8. The results of the investigation show that for subsonic Mach numbers the intermediate cruise nozzle position of the three positions tested resulted in the lowest drag.

Reubush, D. E.↗
NASA NTRS1982

Aeropropulsive characteristics of Mach numbers up to 2.2 of axisymmetric and nonaxisymmetric nozzles installed on an F-18 model

An investigation to determine the aeropropulsive characteristics of nonaxisymmetric nozzles on an F-18 jet effects model was conducted in the Langley 16-foot transonic tunnel and the AEDC 16-foot supersonic wind tunnel. The performance of a two dimensional convergent-divergent nozzle, a single expansion ramp nozzle, and a wedge nozzle was compared with that of the baseline axisymmetric nozzle. Test data were obtained at static conditions and at Mach numbers from 0.60 to 2.20 at an angle of attack of 0 deg. Nozzle pressure ratio was varied from jet-off to about 20.

Capone, F. J.↗
NASA NTRS1982

Some NTF laser velocimeter installation and operation considerations

Two velocimeter techniques were considered as potential candidates for achieving the flow field angularity measurements. The first was the fringe laser Doppler velocimeter, (LDV). A great deal of experience was obtained with this approach at Langley and the literature is rich with papers describing many experimental applications and system performance details. That is, many velocity flow field measurements were conducted with the LDV but not with high resolution precise angularity measurements. The second candidate considered was the two-spot laser transit anemometer, (LTA). This approach was not as extensively used as the LDV technique, but literature does contain experimental applications and system performance details. Again, a lack of high resolution, high precision angularity measurements is noted for the LTA. The results of the study suggested that the LDV and LTA tests and other efforts did not reveal any fundamental problems that would suggest that laser velocimetry is not a viable diagnostic technique for the National Transonic Facility. However, there are a number of engineering problems that need to be solved.

Hunter, W. W., Jr.↗
NASA NTRS1982

A study of aerodynamic heating distributions on a tip-fin controller installed on a Space Shuttle Orbiter model

The aerodynamic heating of a tip-fin controller mounted on a Space Shuttle Orbiter model was studied experimentally in the Calspan Advanced Technology Center 96 inch Hypersonic Shock Tunnel. A 0.0175 scale model was tested at Mach numbers from 10 to 17.5 at angles of attack typical of a shuttle entry. The study was conducted in two phases. In phase 1 testing a thermographic phosphor technique was used to qualitatively determine the areas of high heat-transfer rates. Based on the results of this phase, the model was instrumented with 40 thin-film resistance thermometers to obtain quantitative measurements of the aerodynamic heating. The results of the phase 2 testing indicate that the highest heating rates, which occur on the leading edge of the tip-fin controller, are very sensitive to angle of attack for alpha or = 30 deg. The shock wave from the leading edge of the orbiter wing impinges on the leading edge of the tip-fin controller resulting in peak values of h/h(Ref) in the range from 1.5 to 2.0. Away from the leading edge, the heat-transfer rates never exceed h/h(Ref) = 0.25 when the control surface, is not deflected. With the control surface deflected 20 deg, the heat-transfer rates had a maximum value of h/h(Ref) = 0.3. The heating rates are quite nonuniform over the outboard surface and are sensitive to angle of attack.

Wittliff, C. E.↗
NASA NTRS1982

Flow analysis of nozzle installations with strong airplane flow interactions

A numerical procedure has been developed to calculate the flow fields resulting from the viscous-inviscid interactions that occur when a strong jet exhaust and aircraft flow field coupling exists. The approach used in the current procedure is to divide the interaction region into zones which are either predominantly viscous or inviscid. The flow in the inviscid zone, which surrounds most of the aircraft, is calculated using an existing linearized potential flow code. The viscous flow zone, which encompasses the jet plume, is modeled using a parabolized Navier-Stokes code. The key feature of the present procedure is the coupling of the zonal solutions such that sufficient information is transferred between the zones to preserve the effects of the interactions. The zonal boundaries overlap with the boundary conditions being the information link between zones. An iteraction scheme iterates the coupled analysis until convergence has been obtained. The procedure has been successfully used for several test cases for which the computed results are presented.

Roberts, D. W.↗
NASA NTRS1983

Preliminary design of an Earth-based debris detection system using current technology and existing installations

A simple instrument based on present-epoch technology for optical detection of orbital debris is described. The limits of detectability at various altitudes and under different operating conditions for this system are assessed. The kinds of information which can be deduced from this data are examined. Optimal systems for debris detection are discussed. Alternatives and possible improvements from new technologies are also considered.

Morgan, T. H.↗
NASA NTRS1983

A new system for observing solar oscillations at the Mount Wilson Observatory. I - System design and installation

An observation system designed to obtain daily measurements of solar photospheric and subphotospheric rotational velocities, from the frequency splitting of nonradial solar p-mode oscillations of degree greater than 150, is nearing completion of the Mount Wilson Observatory. The system will combine a 244 x 248 pixel CID camera with a high speed floating point array processor, a 32-bit minicomputer, and a large capacity disk storage system. These components will be integrated into the spectrograph of the 60-foot solar tower telescope at Mount Wilson.

Rhodes, E. J., Jr.↗
NASA NTRS1984

Installation noise measurements of model SR and CR propellers

Noise measurements on a 0.1 scale SR-2 propeller in a single and counter rotation mode, in a pusher and tractor configuration, and operating at non-zero angles of attack are summarized. A measurement scheme which permitted 143 measurements of each of these configurations in the Langley 4- by 7-meter low speed tunnel is also described.

Block, P. J. W.↗
NASA NTRS1985

Preliminary design of an Earth-based debris detection system using current technology and existing installations

Assessment of debris hazard requires the determination of debris down to mm sizes for near-Earth orbits and near-stationary points. It is necessary to obtain reasonable orbits for a statistically significant sample of the debris population. Several ground-based techniques for detection are available. Radar detection was used to obtain information of existing debris population. Another technique is optical detection. The possibilities and application of optical detection with state-of-the-art instrumentation is studied.

Morgan, T. H.↗
NASA NTRS1985

Method for the prediction of the installation aerodynamics of a propfan at subsonic speeds

A subsonic flow panel code has been modified to handle the effects of a propeller wake. The effects of the propeller were modelled by a system of ring vortices of constant strength. Principles based on the blade element theory, the vortex theory and the momentum theory were used to evaluate the axial velocity increase, the swirl velocity and the pressure increase across the propeller. Theoretical calculations are compared to experimental results at Mach numbers up to 0.70 over a range of angles of attack. The discrepancies between the theory and the experimental results are analyzed. Suggestions for improvements to enhance the accuracy of the theoretical prediction are indicated.

Chandrasekaran, B.↗
NASA NTRS1985

Wind tunnel acoustic study of a propeller installed behind an airplane empennage: Data report

The open test section of the NASA-Ames 7- by 10- ft wind tunnel was used for an acoustic test of a propeller mounted behind an airplane empennage. The empennage was attached to a model fuselage and the propeller with its electric motor drive was mounted separately so that the relative positions of empennage and propeller could be varied. A single vertical fin, and a V-tail with, and without, a dorsal fin configurations were used the model propeller had four blades (SR-1). Data were recorded at several locations for two tunnel flow speeds (45.7) and 62.5 m/s) and propeller speeds in the range 4000 to 8200 rpm. Data reduction was performed in narrowband and one-third octave band spectra, with emphasis on harmonics of the passage frequency blade. The influence of flow speed, propeller rpm, empennage configuration, axial and vertical separation between propeller axis and empennage centerline, and empennage angle of incidence on propeller harmonic levels and acoustic field directivity are studied.

Wilby, J. F.↗
NASA NTRS1985

The capability of the existing network of installations for detecting the antineutrino burst from collapsing stars

As the neutrino fluxes can bring information from the internal layers of the collapsing star, the problem of the neutrino burst detection is of importance for both the direct registering of the collapse itself and the investigation of its dynamics. The main characteristics of the neutrino fluxes have been obtained by simulations. The total neutrino flux energy is estimated as 2.5 x 10 to the 53 to 1.4 x 10 to the 54 erg, the energy of NU sub E flux being 10 to the 53 erg. Predictions on neutrino energy spectra are quite different. Two models of the collapse will be used: the model by Bowers and Wilson, hereafter BW, and the model by Nadyozhin and Otroschenko (NO). The NU sub e spectrum in the BW-model reaches the maximum at E max sub NU = 8 MeV. Average energy of NU sub E E sub nu approx. = 10 MeV. The NO-model gives E max sub Nu = 10.5 MeV and E sub nu = 12.6 MeV. The NU sub E-burst duration is DELTA tau sub NU = 20s for the NO-model. As the black hole formation is the result of the star collapse in the BW-model, DELTA tau sub nu is taken to be 5s.

Khalchukov, F. F.↗
NASA NTRS1986

Method for the prediction of the installation aerodynamics of a propfan at subsonic speeds: User manual

This document is the user's guide for the method developed earlier for predicting the slipstream wing interaction at subsonic speeds. The analysis involves a subsonic panel code (HESS code) modified to handle the propeller onset flow. The propfan slipstream effects are superimposed on the normal flow boundary condition and are applied over the surface washed by the slipstream. The effects of the propeller slipstream are to increase the axial induced velocity, tangential velocity, and a total pressure rise in the wake of the propeller. Principles based on blade performance theory, momentum theory, and vortex theory were used to evaluate the slipstream effects. The code can be applied to any arbitrary three dimensional geometry, expressed in the form of HESS input format. The code can handle a propeller alone configuration or a propeller/nacelle/airframe configuration, operating up to high subcritical Mach numbers over a range of angles of attack. Inclusion of a viscous modelling is briefly outlined. Wind tunnel results/theory comparisons are included as examples for the application of the code to a generic supercritical wing/overwing Nacelle with a powered propfan. A sample input/output listing is provided.

Chandrasekaran, B.↗