Interactions between the rotors and wing of a rotary wing aircraft in hover have a significant detrimental effect on its payload performance. The reduction of payload results from the wake of lifting rotors impinging on the wing, which is at 90 deg angle of attack in hover. This vertical drag, often referred as download, can be as large as 15 percent of the total rotor thrust in hover. The rotor wake is a three-dimensional, unsteady flow with concentrated tip vortices. With the rotor tip...
Topics: NASA Technical Reports Server (NTRS), AIRFOILS, COMPUTATIONAL GRIDS, DRAG, HOVERCRAFT GROUND EFFECT...
A two dimensional model for the chordwise flow near the wing tip of the tilt rotor in hover is presented. The airfoil is represented by vortex panels and the rotor is modeled by doublet panels. The rotor slipstream and the airfoil wake are simulated by free point vortices. Calculations on a 20 percent thick elliptical airfoil under a uniform rotor inflow are performed. Variations on rotor size, spacing between the rotor and the airfoil, ground effect, and the influence upper surface blowing in...
Topics: NASA Technical Reports Server (NTRS), AIRFOIL PROFILES, GROUND EFFECT (AERODYNAMICS), HOVERCRAFT...
A reusable space flight launch system is configured to eliminate complex descent and landing systems from the space flight hardware and move them to maneuverable ground based systems. Precision landing of the reusable space flight hardware is enabled using a simple, light weight aerodynamic device on board the flight hardware such as a parachute, and one or more translating ground based vehicles such as a hovercraft that include active speed, orientation and directional control. The ground...
Topics: NASA Technical Reports Server (NTRS), SPACECRAFT RECOVERY, RECOVERABLE LAUNCH VEHICLES, HOVERCRAFT...
Flow characteristics of impinging jets emanating from rectangular exit area converging nozzles of exit area aspect ratio four, six, and eight were investigated. Azimuthal distributions of wall jet radial momentum flux in the ground plane were strongly directional and sensitive to rectangular nozzle exit area aspect ratio, jet impingement angle, and height above ground, H/D. Effects of jet exit velocity profile nonuniformities were also investigated. Data from the single nozzle rectangular jet...
Topics: NASA Technical Reports Server (NTRS), AERODYNAMIC CONFIGURATIONS, ELEVATION ANGLE, FLOW...
The results of a forty-minute exposure of the HM.2 Hoverferry are presented. Quantitative evaluations were made from aft seats on the starboard side for a sea state considered calm and visually estimated at one-half to one foot. Since this type of craft is sensitive to sea state, the conclusions are based on ideal conditions. Some drawings are included.
Topics: NASA Technical Reports Server (NTRS), AIRCRAFT DESIGN, AIRCRAFT PERFORMANCE, HOVERCRAFT GROUND...
