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Results for “Aerodynamic Stability”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 505 records · Page 28
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Sunspots and the physics of magnetic flux tubes. I - The general nature of the sunspot. II - Aerodynamic drag

Analysis of the dynamical stability of a large flux tube suggests that the field of a sunspot must divide into many separate tubes within the first 1000 km below the surface. Buoyancy of the Wilson depression at the visible surface and probably also a downdraft beneath the sunspot hold the separate tubes in a loose cluster. Convective generation of Alfven waves, which are emitted preferentially downward, cools the tubes. Aerodynamic drag on a slender flux tube stretched vertically across a convective cell is also studied. Since the drag is approximately proportional to the local kinetic energy density, the density stratification weights the drag in favor of the upper layers. Horizontal motions concentrated in the bottom of the convective cell may reverse this density effect. A downdraft of about two km/sec through the flux tubes beneath the sunspot is hypothesized.

Parker, E. N.↗
NASA NTRS1971

A method for determining the response of space shuttle to atmospheric turbulence. Volume 2: Computer program description and usage instructions

A description is given of a computer program which calculates the response of an elastic aerospace vehicle to random and discrete turbulence. The program uses vibration modes as generalized coordinates. Inputs to the program include modal information, generalized aerodynamic forces, flight data, stability augmentation system description, and description of the disturbing function. Program outputs include tabulations of the ratio of root-mean-square response to root-mean-square turbulence and response upward zero crossings per second, and SC4020 plots of transfer functions, response power spectral densities, and Nyquist stability traces.

Huntington, R.↗
NASA NTRS1972

Reduction of wave drag by antisymmetric arrangement of wings and bodies.

The wave interference effects for bodies or wings in a mirror-symmetric arrangement, and in an antisymmetric arrangement are discussed. It is shown that while in the case of a mirror-symmetric arrangement large adverse interference effects can be observed, antisymmetric arrangements provide comparatively much smaller wave drags. The single continuous wing panels also adapt themselves more readily to varying angles of obliquity, and hence, to varying flight speeds. A detailed review is presented of the previous work on the aerodynamic properties and flight stability of oblique elliptic wing combinations. A possible mode of application of these combinations to transport aircraft operating at moderate supersonic speeds is suggested.

Jones, R. T.↗
NASA NTRS1973

Non-linear flap-lag dynamics of hingeless helicopter blades in hover and in forward flight.

The aeroelastic instability of the coupled nonlinear flap-lag motion of a torsionally rigid helicopter blade is treated by using the perturbation method in multiple time scales. The nonlinearities present in the equations are those arising from the inclusion of moderately large deflections in the inertia and aerodynamic loading terms. The stability boundaries, amplitudes of nonlinear response, and conditions for existence of limit cycles are obtained analytically. Thus the different roles played by the forcing, parametric excitation, and nonlinear coupling in affecting the solution can be easily identified. Numerical results illustrating the behavior of the blade are presented.

Friedmann, P.↗
NASA NTRS1977

Stability of an elastic airplane

FLEXSTAB computer program is used to evaluate trim state, static, and dynamic stability characteristics, inertial and aerodynamic loading, and elastic deformations of aircraft configurations at subsonic and supersonic speeds.

Erickson, L. L.↗
NASA NTRS1977

Performance and safety aspects of the XV-15 tilt rotor research aircraft

Aircraft performance is presented illustrating the flexibility and capability of the XV-15 to conduct its planned proof-of-concept flight research in the areas of dynamics, stability and control, and aerodynamics. Additionally, the aircraft will demonstrate mission-type performance typical of future operational aircraft. The aircraft design is described and discussed with emphasis on the safety and fail-operate features of the aircraft and its systems. Two or more levels of redundancy are provided in the dc and ac electrical systems, hydraulics, conversion, flaps, landing gear extension, SCAS, and force-feel. RPM is maintained by a hydro-electrical blade pitch governor that consists of a primary and standby governor with a cockpit wheel control for manual backup. The two engines are interconnected for operation on a single engine. In the event of total loss of power, the aircraft can enter autorotation starting from the airplane as well as the helicopter mode of flight.

Wernicke, K. G.↗
NASA NTRS1988

Aeroelastic Computations For Wings With Loaded Tips

External fuel tanks or missiles degrade stability because of unsteady aerodynamics. Transonic aeroelasticity of wings with tip stores simulated with improved version of ATRAN3S computer code, previously used to study behavior of clean wings only. Output of code agrees well with wind-tunnel data.

Goorjian, Peter M.↗
NASA NTRS1989

Airframe/propulsion integration characteristics at transonic speeds

The aerodynamic characteristics for both single and twin-engine high-performance aircraft are significantly affected by shock induced flow interactions as well as other local flow interference effects which usually occur at transonic speeds. These adverse interactions can not only cause high drag, but also cause unusual aerodynamic loadings and/or severe stability and control problems. Many programs are under way to not only develop method for reducing the adverse effects, but also to develop an understanding of the basic flow conditions which are the primary contributors. It is anticipated that these programs will result in technologies which can reduce the aircraft cruise drag through improved integration as well as increase aircraft maneuverability through the application of thrust vectoring. Some of the primary integration problems for twin-engine aircraft at transonic speeds are identified, and several methods are demonstrated for reducing or eliminating the undersirable characteristics, while enhancing configuration effectiveness.

Henderson, William P.↗
NASA NTRS1989

Propulsion integration for military aircraft

The transonic aerodynamic characteristics for high-performance aircraft are significantly affected by shock-induced flow interactions as well as other local flow interference effects which usually occur at transonic speeds. These adverse interactions can not only cause high drag, but can cause unusual aerodynamic loadings and/or severe stability and control problems. Many new programs are underway to develop methods for reducing the adverse effects, as well as to develop an understanding of the basic flow conditions which are the primary contributors. It is anticipated that these new programs will result in technologies which can reduce the aircraft cruise drag through improved integration as well as increased aircraft maneuverability throughh the application of thrust vectoring. This paper will identify some of the primary propulsion integration problems for high performance aircraft at transonic speeds, and demonstrate several methods for reducing or eliminating the undesirable characteristics, while enhancing configuration effectiveness.

Henderson, William P.↗
NASA NTRS1993

Titan III Feasibility for HL-20 Prototype Missions

A set of studies was performed to investigate the feasibility of using the Titan III launch vehicle to launch an unmanned prototype HL-20 personnel launch system and, potentially, operational HL-20 missions. The launch of an HL-20 spacecraft on a Titan III poses a unique set of concerns, primarily because the lifting body vehicle is carried on top of the Titan vehicle without a fairing. The Titan III/HL-20 feasibility study addressed the primary vehicle issues of performance, aerodynamics, loads, control and stability, launch availability, and vehicle configuration for the launch of an unmanned HL-20 prototype vehicle. Titan launch operations, launch site systems, and facilities were assessed to determine HL-20 operations compatibility. Additional studies determined the potential launch opportunity and window capabilities of the Titan III for the operational HL-20 mission and the existing Titan III's reliability. The feasibility study determined that the Titan III system, with minor changes, is compatible with the HL-20 vehicle and mission. It could provide nearly daily launch windows for a rendezvous with Space Station Freedom. Titan III reliability, when combined with the HL-20 launch escape system, provides a sufficiently high probability of crew survival to support its consideration as the primary vehicle for HL-20 operational missions.

Benson, Scott W.↗
NASA NTRS1992

Design of a refueling tanker delivering liquid hydrogen

A refueling tanker that could deliver 155,000 lb of liquid hydrogen to a hypersonic tanker in 15 min was designed. A flying boom system was chosen to fit strict delivery criteria. Tank design and material specification were also addressed. To assure the flow required, it was important to cancel the pressure drop phenomenon. Geometry, aerodynamics, weight considerations, propulsion, stability, and performance for the tanker were also considered. Finally, the cost of developing three prototypes was estimated.

Lourme, Daniel↗
NASA NTRS2002

Ground and Flight Evaluation of a Small-Scale Inflatable-Winged Aircraft

A small-scale, instrumented research aircraft was flown to investigate the night characteristics of innersole wings. Ground tests measured the static structural characteristics of the wing at different inflation pressures, and these results compared favorably with analytical predictions. A research-quality instrumentation system was assembled, largely from commercial off-the-shelf components, and installed in the aircraft. Initial flight operations were conducted with a conventional rigid wing having the same dimensions as the inflatable wing. Subsequent flights were conducted with the inflatable wing. Research maneuvers were executed to identify the trim, aerodynamic performance, and longitudinal stability and control characteristics of the vehicle in its different wing configurations. For the angle-of-attack range spanned in this flight program, measured flight data demonstrated that the rigid wing was an effective simulator of the lift-generating capability of the inflatable wing. In-flight inflation of the wing was demonstrated in three flight operations, and measured flight data illustrated the dynamic characteristics during wing inflation and transition to controlled lifting flight. Wing inflation was rapid and the vehicle dynamics during inflation and transition were benign. The resulting angles of attack and of sideslip ere small, and the dynamic response was limited to roll and heave motions.

Murray, James E.↗