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  • 1
    Publication Date: 2011-08-19
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 25; 19-23
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  • 2
    Publication Date: 2011-08-19
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 24; 198-204
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  • 3
    Publication Date: 2019-06-28
    Description: A computer code named DOWN was created to implement a flat wake theory for the calculation of rotor inflow and wake velocities. A brief description of the code methodology and instructions for its use are given. The code will be available from NASA's Computer Software Management and Information Center (COSMIC).
    Keywords: AERODYNAMICS
    Type: NASA-TM-104139 , NAS 1.15:104139 , AVSCOM-TR-91-B-016 , AD-B161021L
    Format: application/pdf
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  • 4
    Publication Date: 2019-06-28
    Description: A wind-tunnel investigation was conducted to determine 2-D aerodynamic characteristics of nine polygon-shaped models applicable to helicopter fuselages. The models varied from 1/2 to 1/5 scale and were nominally triangular, diamond, and rectangular in shape. Side force and normal force were obtained at increments of angle of flow incidence from -45 to 90 degrees. The data were compared with results from a baseline UH-60 tail-boom cross-section model. The results indicate that the overall shapes of the plots of normal force and side force were similar to the characteristic shape of the baseline data; however, there were important differences in magnitude. At a flow incidence of 0 degrees, larger values of normal force for the polygon models indicate an increase in fuselage down load of 1 to 2.5 percent of main-rotor thrust compared with the baseline value. Also, potential was indicated among some of the configurations to produce high fuselage side forces and yawing moments compared with the baseline model.
    Keywords: AERODYNAMICS
    Type: NASA-TP-3233 , L-16951 , NAS 1.60:3233 , AVSCOM-TR-92-B-002 , AD-A254938
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  • 5
    Publication Date: 2019-06-28
    Description: The landing footprint of a conceptual high-lift transatmospheric vehicle is defined for aeromaneuvering entry from a typical low-earth orbit. The flight strategy for trajectory construction to maximize the landing area by extending downrange and crossrange as far as possible is developed in four phases by optimal programming of the vehicle's roll angle. Trajectories that reach any given landing site were calculated with the corresponding heating rates at three critical vehicle locations (stagnation point, wing leading edge, and body centerline). An optimization methodology was developed that demonstrates the trades between crossrange, peak heating and total heat loads as a function of three key flight parameters (altitude, flight-path angle, and vehicle roll angle). The maximum extent of the landing footprint was found to be 29,690 km downrange and 6560 km crossrange. Large variations in the ballistic coefficient had negligible effect on the extent of the footprint but could significantly affect heating. However, the footprint's longitude was displaced downstream or upstream with increasing or decreasing ballistic coefficient, respectively.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: AIAA PAPER 88-0300
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  • 6
    Publication Date: 2019-06-28
    Description: The theory for predicting helicopter inflow-wake velocities called flat wake theory was correlated with several sets of experimental data. The theory was developed by V. E. Baskin of the USSR, and a computer code known as DOWN was developed at Princeton University to implement the theory. The theory treats the wake geometry as rigid without interaction between induced velocities and wake structure. The wake structure is assumed to be a flat sheet of vorticity composed of trailing elements whose strength depends on the azimuthal and radial distributions of circulation on a rotor blade. The code predicts the three orthogonal components of flow velocity in the field surrounding the rotor. The predictions can be utilized in rotor performance and helicopter real-time flight-path simulation. The predictive capability of the coded version of flat wake theory provides vertical inflow patterns similar to experimental patterns.
    Keywords: AERODYNAMICS
    Type: NASA-TM-4334 , L-16953 , NAS 1.15:4334 , AVSCOM-TR-92-B-004 , AD-A250192
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  • 7
    Publication Date: 2019-06-28
    Description: The low-earth orbit rendezvous capability of a conceptual transatmospheric vehicle is analyzed for two endo-/exo-atmospheric ascent missions. Both cases involve coasting aerodynamic maneuvers starting from the burn-out conditions corresponding to air-breathing propulsion systems that achieve orbital velocity within the atmosphere. The powered phase of the ascent trajectories approximate constant dynamic pressure, fuel-efficient flightpaths typically flown by supersonic aircraft. The aeromaneuvering coast phases of the ascent include both coplanar (to determine altitude capability without plane-inclination changes) and aeroturning to LEO rendezvous at 400 km altitude (to assess plane-change capability). The coast-phase ascent maneuvers are correlated with G-load requirements and aerothermodynamic heating characteristics at two critical locations on the vehicle surface (i.e., the nose stagnation point and the body centerline). The results are correlated and recommendations are made concerning thermal protection and structural requirements.
    Keywords: LAUNCH VEHICLES AND SPACE VEHICLES
    Type: AIAA PAPER 87-0513
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