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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Aeroelastic stability and control of an oblique wing

Dynamic model tests were staged to compare the aeroelastic stability of a free-flying oblique-winged aircraft and the known divergent instability characterizing swept-forward wing configurations, to test the effect of wing elasticity on aileron control and trim. The aircraft fuselage was clamped in some tests and left free to roll in others. Two rigid wing panels were hinged near the wing center with elastic restraining springs. It is found that the aeroelastic divergence affecting swept-forward wings does not occur with an oblique wing, whose aeroelastic instability sets in at a dynamic pressure exceeding that for static divergence of swept-forward wings, and appears in the form of undamped oscillations. Oblique wing stability is sensitive to the moment of inertia of the fuselage in roll. Roll control and lateral trim are attainable with conventional ailerons, even at speeds at which divergence of a clamped forward wing shows up.

Jones, R. T.↗
NASA NTRS1976

An Analytical Study for Subsonic Oblique Wing Transport Concept

The oblique wing concept has been investigated for subsonic transport application for a cruise Mach number of 0.95. Three different mission applications were considered and the concept analyzed against the selected mission requirements. Configuration studies determined the best area of applicability to be a commercial passenger transport mission. The critical parameter for the oblique wing concept was found to be aspect ratio which was limited to a value of 6.0 due to aeroelastic divergence. Comparison of the concept final configuration was made with fixed winged configurations designed to cruise at Mach 0.85 and 0.95. The crossover Mach number for the oblique wing concept was found to be Mach 0.91 for takeoff gross weight and direct operating cost. Benefits include reduced takeoff distance, installed thrust and mission block fuel and improved community noise characteristics. The variable geometry feature enables the final configuration to increase range by 10% at Mach 0.712 and to increase endurance by as much as 44%.

Bradley, E. S.↗
NASA NTRS1978

Aerodynamic derivatives for an oblique wing aircraft estimated from flight data by using a maximum likelihood technique

There are several practical problems in using current techniques with five degree of freedom equations to estimate the stability and control derivatives of oblique wing aircraft from flight data. A technique was developed to estimate these derivatives by separating the analysis of the longitudinal and lateral directional motion without neglecting cross coupling effects. Although previously applied to symmetrical aircraft, the technique was not expected to be adequate for oblique wing vehicles. The application of the technique to flight data from a remotely piloted oblique wing aircraft is described. The aircraft instrumentation and data processing were reviewed, with particular emphasis on the digital filtering of the data. A complete set of flight determined stability and control derivative estimates is presented and compared with predictions. The results demonstrated that the relatively simple approach developed was adequate to obtain high quality estimates of the aerodynamic derivatives of such aircraft.

Maine, R. E.↗
NASA NTRS1978

Interpolation and extrapolation of creep rupture data by the minimum commitment method. II - Oblique translation

An outline is presented of a new procedure, termed the oblique translation method, which emerged in the development of the focal point convergence method. Approaches for implementing the oblique translation method are discussed. It is shown that the new method is essentially a minimum commitment method when manually-graphically implemented, in the sense that the form of the functions involved are not forced into particular analytical forms. The individual constants and functions are independently determined. The minimum commitment concept is extended to the analysis of creep rupture data wherein each isothermal is to be generated by an oblique translation of the 'master curve' when plotted. Attention is given to a manual-graphical analysis, the preassessment of data, and an analysis by computer code.

Manson, S. S.↗
NASA NTRS1978

Measurements in a large angle oblique jet impingement flow

The flow field associated with the oblique impingement of an axisymmetric jet was investigated in the externally blown flap configuration for the STOL aircraft. The passive and active spreading characteristics of the shallow angle (a greater than or = approximately to 15 degrees) oblique impingement flow, the role of the initially azimuthal vorticity field, and the stagnation point region were studied, and compared to the large ( a = 45 degres) oblique jet impingement flow. A description of the characteristics of the large angle impingement flow is presented: A flow field near the plate as showing two distinct patterns, one near the location of the maximum surface pressure, and another about the geometric intersection of the jet axis with the plate; and turbulence in the region above the plate which is greater than the one accounted for by the convection of turbulence energy by the mean motion.

Foss, J. F.↗
NASA NTRS1979

Past obliquity oscillations of Mars - The role of the Tharsis uplift

The paper deals with possible ancient variations of the obliquity of Mars. Consideration of data on internal differentiation, Tharsis uplift and crustal phenomena, mantle convection, and eigenfrequencies and mean motion suggest that (1) differentiation with core formation decreased the primeval spin precession constant (alpha) by 4-5%, driving it through resonance with the j = 2 orbital term; (2) a combination of geophysical processes caused alpha to drift back and forth through resonance with the j = 2 orbital term during part of Mars' history; (3) this situation was turned off by the Tharsis uplift, which drove alpha away from j = 2 resonance and possibly through the j = 26 resonance. The consequences of such events for the planet's obliquity are analyzed. Various types of motions are calculated, demonstrating the sensitivity of the obliquity to passage through resonance with such minor orbital terms.

Ward, W. R.↗
NASA NTRS1980

AD-1 oblique wing aircraft program

The oblique wing concept for super- and subsonic transport was assessed by analysis and wind tunnel radio control model and remotely piloted vehicle testing. A one-sixth scale wind tunnel model and a low speed manned oblique wing research airplane (AD-1) were developed. Model wind tunnel test data on dynamic structural response characteristics were used in a simulator to develop the control system. The airplane is of simple design with fiber glass skin, weight of approximately 2100 lbs and speeds of up to 175 knots at altitudes up to 15,000 ft. Flight testing will investigate handling and flying qualities, oblique wing flight control characteristics, aeroelastic wing design and will compare actual with predicted aerodynamic characteristics. Nineteen flights were made at 12,000 to 13,000 feet with speeds of 100-160 knots. Flutter clearance as a function of wing sweep angle is now under investigation.

Andrews, W. H.↗
NASA NTRS1983

The scaling of oblique plasma double layers

Strong oblique plasma double layers are investigated using three methods, i.e., electrostatic particle-in-cell simulations, numerical solutions to the Poisson-Vlasov equations, and analytical approximations to the Poisson-Vlasov equations. The solutions to the Poisson-Vlasov equations and numerical simulations show that strong oblique double layers scale in terms of Debye lengths. For very large potential jumps, theory and numerical solutions indicate that all effects of the magnetic field vanish and the oblique double layers follow the same scaling relation as the field-aligned double layers.

Borovsky, J. E.↗
NASA NTRS1984

The oblique impact hypothesis and relative probabilities of lunar and Martian meteorites

The suggestion by Nyquist (1983) that shergottites and possibly other SNC (shergottites, nakhlites, and Chassigny) meteorites were launched from the Martian surface by the oblique impact of large meteoroids is further evaluated in the context of the subsequent discovery of a lunar meteorite. It is demonstrated that within calculational uncertainties and the current poorly known fall statistics of lunar and probable Martian meteorites, the oblique impact hypothesis provides a satisfactory explanation of the relative abundances of lunar, Martian, and other meteorites. It is noted that these results support the oblique-impact-on-Mars origin of SNC meteorites and satisfactorily explain the occurrence of a lunar meteorite.

Nyquist, L. E.↗
NASA NTRS1984

The production of ion conics by oblique double layers

Magnetized test ions are subjected to acceleration through a numerically simulated oblique double layer in order to determine whether they emerge with velocity vectors aligned with or oblique to the ambient magnetic field. A criterion for oblique alignment, depending on the double-layer parameters and on the external magnetization, is obtained. When it is applied to observed and theoretical auroral double layers, this criterion predicts that accelerated heavy ions will be substantially less magnetic field aligned than will accelerated hydrogen ions, thus suggesting auroral double layers as a source of high-energy ion conics. Test particle simulations are also used to investigate the perpendicular heating of ions at low altitudes by the electric fields associated with moving auroral arcs. The rapid motion of small-scale structures in the arcs is suggested as a source of low-energy conical ion distributions, and the slow drifts of the entire arc forms are inferred to heat ionospheric ions.

Borovsky, J. E.↗
NASA NTRS1987

Oblique impact: Projectile richochet, concomitant ejecta and momentum transfer

Experimental studies of oblique impact indicate that projectile richochet occurs for trajectory angles less than 30 deg and that the richocheted projectile, accompanied by some target material, are ejected at velocities that are a large fraction of the impact velocity. Because the probability of occurrence of oblique impact less than 30 deg on a planetary body is about one out of every four impact events, oblique impacts would seem to be a potential mechanism to provide a source of meteorites from even the largest atmosphere-free planetary bodies. Because the amount of richocheted target material cannot be determined from previous results, additional experiments in the Ames Vertical Gun laboratory were undertaken toward that purpose using pendulums; one to measure momentum of the richocheted projectile and concomitant target ejecta, and a second to measure the momentum transferred from projectile to target. These experiments are briefly discussed.

Gault, Donald E.↗
NASA NTRS1987

Model-following output feedback controller for oblique-wing aircraft

A variable-skew oblique-wing offers a substantial aerodynamic performance advantage for aircraft missions that require both high efficiency in subsonic flight and supersonic dash or cruise. The most obvious characteristics of the oblique-wing concept is the asymmetry of the wing-skew angle that causes a significant aerodynamic and inertial cross coupling between the aircraft longitudinal and lateral-directional axes. This paper presents a technique for synthesizing a decoupling controller while providing the desired stability augmentation. The use of output feedback in control law synthesis without the requirement of state estimation is presented. An explicit model-following control system with output feedback is developed. The effectiveness of the control laws developed in achieving the desired decoupling is illustrated for a given flight condition for an oblique-wing aircraft.

Alag, Gurbux Singh↗
NASA NTRS1988

Further investigations of oblique hypervelocity impact phenomena

The results of a continuing investigation of the phenomena associated with the oblique hypervelocity impact of spherical projectiles onto multi-sheet aluminum structures are described. A series of equations that quantitatively describes these phenomena is obtained through a regression of experimental data. These equations characterize observed ricoshet and penetration damage phenomena in a multi-sheet structure as functions of the geometric parameters of the structure and the diameter, obliquity, and velocity of the impacting projectile. Crater damage observed on the ricochet witness plates is used to determine the sizes and speeds of the ricochet debris particles that caused the damage. It is shown that, in general, the most damaging ricochet debris particle is approximately 0.25 cm (0.10 in) in diameter and travels at the speed of approximately 2.1 km/sec (6,890 ft/sec). The equations necessary for the design of shielding panels that will protect external systems from such ricochet debris damage are also developed. The dimensions of these shielding panels are shown to be strongly dependent on their inclination and on their circumferential distribution around the spacecraft. It is concluded that obliquity effects of high-speed impacts must be considered in the design of any structure exposed to the meteoroid and space debris environment.

Schonberg, William P.↗
NASA NTRS1989

The conceptual design of a Mach 2 Oblique Flying Wing supersonic transport

This paper is based on a performance and economics study of a Mach two oblique flying wing transport aircraft that is to replace the B747B. In order to fairly compare our configuration with the B747B an equal structural technology level is assumed. It will be shown that the oblique flying wing configuration will equal or outperform the B747 in speed, economy and comfort while a modern stability and control system will balance the aircraft and smooth out gusts. The aircraft is designed to comply with the FAR25 airworthiness requirements and FAR36 stage 3 noise regulations. Geometry, aerodynamics, stability and control parameters of the oblique flying wing transport are discussed.

Vandervelden, Alexander J. M.↗
NASA NTRS1989

On the obliquity and tidal heating of Triton

Although tidal heating is generally associated with spin-locked satellites on eccentric orbits, a satellite with a large obliquity can undergo substantial heating due to obliquity tides, even on a circular orbit. The near-100-deg obliquity of the Neptune moon, Triton, could generate significant tidal heating and eventually lead to a damping of its orbital inclination to 180 deg. Ground-based observations of Triton have tentatively found a synchronous rotational state that is consistent with despinning times of about 10,000 years, indicating that Triton is almost certainly rotating synchronously.

Jankowski, David G.↗
NASA NTRS1989

A two-stage earth-to-orbit transport with translating oblique wings for booster recovery

A two-stage earth-to-orbit transport is disclosed which includes an orbiter vehicle and a pair of boosters, each having a deployable oblique wing located along a longitudinal axis of the booster. The wing is deployed in an oblique disposition in supersonic and hypersonic speeds, and disposed at 90 degree for subsonic speeds encountered during entry. The oblique wing is driven axially and rotated by means of a turret mounted on rails.

Macconochie, Ian O.↗
NASA NTRS1990

Output model-following control synthesis for an oblique-wing aircraft

Recent interest in oblique-wing aircraft has focused on the potential aerodynamic performance advantage of a variable-skew oblique wing over a conventional or symmetric sweep wing. Unfortunately, the resulting asymmetric configuration has significant aerodynamic and inertial cross-coupling between the aircraft longitudinal and lateral-directional axes. Presented here is a decoupling control law synthesis technique that integrates stability augmentation, decoupling, and the direct incorporation of desired handling qualities into an output feedback controller. The proposed design technique uses linear quadratic regulator concepts in the framework of explicit model following. The output feedback strategy used is a suboptimal projection from the state space to the output space. Dynamics are then introduced into the controller to improve steady-state performance and increase system robustness. Closed-loop performance is shown by application of the control laws to the linearized equations of motion and nonlinear simulation of an oblique-wing aircraft.

Pahle, Joseph W.↗
NASA NTRS1990

Supersonic flameholding by attached oblique shock waves

The object of this investigation was to explore various regimes of shock-induced combustion that may occur as a result of supersonic flow of a reactive gas mixture past a simple compression ramp or wedge. Attention was confined to combinations of wedge angles, fuel-air mixture ratios and freestream velocities that permit the resulting oblique shock or oblique detonation wave to remain attached. Computational fluid dynamic (CFD) simulations, both inviscid and viscous, were performed and analyzed in order to investigate two modes of compression ramp flameholding; namely, complete oblique detonation wave (ODW) and shock-induced combustion. In addition, the possibility of flame persistence or hysteresis was explored. It was preliminarily concluded that inclusion of viscous effects may be essential to accurately predict the occurrence of the various flameholding modes.

Fort, James A.↗