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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1956

Theoretical calculations of the pressure, forces, and moments at supersonic speeds due to various lateral motions acting on thin isolated vertical tails

Velocity potentials, pressure, distributions, and stability derivatives are derived by use of supersonic linearized theory for families of thin isolated vertical tails performing steady rolling, steady yawing, and constant-lateral-acceleration motions. Vertical-tail families (half-delta and rectangular plan forms) are considered for a broad Mach number range. Also considered are the vertical tail with arbitrary sweepback and taper ratio at Mach numbers for which both the leading edge and trailing edge of the tail are supersonic and the triangular vertical tail with a subsonic leading edge and a supersonic trailing edge. Expressions for potentials, pressures, and stability derivatives are tabulated.

Margolis, Kenneth↗
NASA NTRS1985

Flutter clearance of the Schweizer 1-36 deep-stall sailplane

A Schweizer 1-36 sailplane was modified for a controlled, deep-stall flight program. This modification allowed the horizontal stabilizer to pivot as much as 70 deg leading edge down. Ground vibration and flutter testing were accomplished on the sailplane with the horizontal stabilizer in the normal flight and deep-stall flight positions. Test results indicated satisfactory damping levels and trends for the structural modes of the sailplane. The modified sailplane was demonstrated to be free of aeroelastic instabilities to 83 KEAS with the horizontal stabilizer in the normal flight position and to 39 KEAS with the horizontal stabilizer in the deep-stall flight position. This flight envelope was adequate for the controlled, deep-stall flight experiments.

Kehoe, M. W.↗
NASA NTRS2018

LUVOIR Primary Mirror Segment Alignment Control With Joint Laser Metrology and Segment Edge Sensing

An approach is developed for the alignment and stability maintenance of the LUVOIR segmented primary mirror using a segment state estimation and wavefront control method based on a hybrid segment motion sensing architecture of laser truss metrology and segment edge sensors. Our current computer model was generated for LUVOIR Architecture Option A with a 15-meter aperture, 120segment primary mirror. The methodology and simulation results will be presented and analyzed. JPL has a long history of technology development in laser metrology and edge sensors, including work in SIM [7], Keck and TMT [8], CCAT [3] and LUVOIR [1]. We will discuss our current efforts of LUVOIR laser metrology and edge-sensor models development, showing sensitivities of sensor measurements to various mirror eigenmodes, removing global modes and strengthening weak modes by performing joint (hybrid) laser-metrology and edge sensing. We will define and derive an important performance metric called wavefront error multiplier (WEM), and show that WEM provides a simple link between sensor errors and the closed-loop (controlled) system wavefront error. We will show WEM values for several hybrid sensor configuration options studied. We will discuss an algorithm for mirror shape control and maintenance through segment state and wavefront estimations using joint edge-metrology sensing. We will compare simulated performance of mirror state estimation, wavefront estimation and wavefront control based on joint edge-metrology sensing among several sensor configurations, and show the impact of sensor error distributions on the segmented mirror alignment performance. Mirror shape control performance will be also be evaluated in terms of imaging contrast between inner working angles (IWA) and outer working angles (OWA) of a LUVOIR coronagraph. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. LUVOIR is a mission concept under study for the next astronomy Decadal Survey—the information presented in this paper is pre-decisional and is provided for planning and discussion purposes only.

Shelton, Chris↗
NASA NTRS1948

An Investigation of the McDonnell XP-85 Airplane in the Ames 40- by 80-foot Wind Tunnel. Force and Moment Tests

Wind-tunnel tests of the McDonnell XP-85 airplane were conducted to determine its longitudinal, lateral, and directional stability and the characteristics of the aileron, the ruddervator, the leading-edge droop nose flap, and the stall control vanes. The directional stability of the airplane with numerous skyhook modifications and with a ventral fin was also investigated. The results of the tests showed that the effectiveness of the droop nose flaps and the stall control vanes was negligible with regard to either the maximum lift or longitudinal stability of the airplane. Contrary to any previous small-scale results, extension of the skyhook caused a 75-percent reduction in the directional stability of the airplane for both low and high values of lift coefficient. The simplest solution to the problem short of a major redesign of the skyhook appears to be the adoption of a ventral fin.

Hunton, Lynn W.↗
NASA NTRS1979

Investigation of aerodynamic characteristics of subsonic wings

An analytical strake design procedure is investigated. A numerical solution to the governing strake design equation is used to generate a series of strakes which are tested in a water tunnel to study their vortex breakdown characteristics. The strakes are scaled for use on a half-scale model of the NASA-LaRC general research fuselage with a 44 degrees trapezoidal wing. An analytical solution to the governing design equation is obtained. The strake design procedure relates the potential-flow leading-edge suction and pressure distributions to vortex stability. Several suction distributions are studied and those which are more triangular and peak near the tip generate strakes that reach higher angles of attack before vortex breakdown occurs at the wing trailing edge. For the same suction distribution, a conical rather than three dimensional pressure specification results in a better strake shape as judged from its vortex breakdown characteristics.

Dejarnette, F. R.↗
NASA NTRS1995

Low-speed wind-tunnel investigation of the stability and control characteristics of a series of flying wings with sweep angles of 70 deg

A wind-tunnel investigation was conducted in the Langley 12-Foot Low-Speed Tunnel to study the low-speed stability and control characteristics of a series of four flying wings over an extended range of angle of attack (-8 deg to 48 deg). Because of the current emphasis on reducing the radar cross section (RCS) of new military aircraft, the planform of each wing was composed of lines swept at a relatively high angle of 70 deg, and all the trailing edges and control surface hinge lines were aligned with one of the two leading edges. Three arrow planforms with different aspect ratios and one diamond planform were tested. The models incorporated leading-edge flaps for improved longitudinal characteristics and lateral stability and had three sets of trailing-edge flaps that were deflected differentially for roll control, symmetrically for pitch control, and in a split fashion for yaw control. Three top body widths and two sizes of twin vertical tails were also tested on each model. A large aerodynamic database was compiled that could be used to evaluate some of the trade-offs involved in the design of a configuration with a reduced RCS and good flight dynamic characteristics.

Ross, Holly M.↗
NASA NTRS1987

Subsonic longitudinal and lateral-directional characteristics of a forward-swept-wing fighter configuration at angles of attack up to 47 deg

Subsonic lateral-direction and longitudinal characteristics of a forward-swept-wing fighter configuration were examined in wind-tunnel tests at Mach numbers of 0.2 and 0.5 for angles of attack from -7 to 47 deg. and over a sidelslip range of +/- 15 deg. The effects of a canard, strakes, vertical tail, and leading- and trailing-edge flaps are examined. The canard and strakes both reduce asymmetric moments and side forces at zero sideslip for angles of attack up to about 30 deg. The canard has a small influence on lateral-directional stability; however, strakes produce a substantial reduction in lateral stability for angles of attack greater than about 20 deg. The vertical tail improves directional stability for angles of attack up to 30 deg. Deflection of the leading-edge flap to 20 deg. at high angles of attack on the strake and canard configurations degrades lateral and directional stability. Deflection of the trailing-edge flap to 20 deg. on the canard configuration generally increases lateral and directional stability at high angles of attack. Leading- and trailing-edge flaps on the wing-body and canard configurations are effective for increased lift only for angles of attack up to about 40 deg. The leading-edge flap remains effective on the strake configuration over the entire angle-of-attack range tested.

Mann, Michael J.↗
NASA NTRS1949

Stability derivatives at supersonic speeds of thin rectangular wings with diagonals ahead of tip Mach lines

The investigation includes steady and accelerated vertical and longitudinal motions and steady rolling, yawing, sideslipping, and pitching for Mach numbers and aspect ratios greater than those for which the Mach line from the leading edge of the tip section intersects the trailing edge of the opposite tip section. The stability derivatives are derived with respect to principal body axes and then transformed to a system of stability axes. Theoretical results are obtained, by means of the linearized theory, for the surface-velocity-potential functions, surface-pressure distributions, and stability derivatives for various motions at supersonic speeds of thin flat rectangular wings without dihedral. In the case of yawing, a treatment for the infinitely long wing which takes account of the spanwise variation in the stream Mach number is extended to the finite wing, and a plausible, although not rigorous, solution is obtained for the wing tip effects.

Harmon, Sidney M↗
NASA NTRS1972

Leading-edge force features of the aerodynamic finite element method.

Description of a practical procedure for computing the wing leading-edge thrust distribution by the finite element method. When incorporated into a wing-body aerodynamic computer program, the technique is capable of predicting (at subsonic and supersonic speeds) the leading-edge thrust distribution (and therefore, the lateral-directional stability derivatives due to roll) and the nonlinear aerodynamic characteristics of low aspect-ratio wings with leading edge separation due to the application of suction technology.

Lan, C.-T.↗
NASA NTRS1979

Exploratory study of the effects of wing-leading-edge modifications on the stall/spin behavior of a light general aviation airplane

Configurations with full-span and segmented leading-edge flaps and full-span and segmented leading-edge droop were tested. Studies were conducted with wind-tunnel models, with an outdoor radio-controlled model, and with a full-scale airplane. Results show that wing-leading-edge modifications can produce large effects on stall/spin characteristics, particularly on spin resistance. One outboard wing-leading-edge modification tested significantly improved lateral stability at stall, spin resistance, and developed spin characteristics.

Source record↗
NASA NTRS1984

Process and apparatus for growing a crystal ribbon

A process and apparatus is disclosed for growing a crystal ribbon of a substance of theoretically infinite length from a melt of the substance. A pair of fixedly positioned edge defining members are partially submerged into the melt so as to break the surface of the melt at a predetermined distance from one another. The edge defining members are wettable by the melt and the predetermined distance substantially corresponds to the width of the crystal ribbon to be grown. The crystal ribbon is grown by contacting the surface of the melt with a seed ribbon between the edge defining members whereby a meniscus of the melt is established on the seed ribbon. The meniscus is stabilized by the meniscus of the melt on the edge defining members. Pulling the seed crystal ribbon away from the melt results in continuous growth of the crystal ribbon.

Thornhill, J. W.↗
NASA NTRS1987

Wind-tunnel investigation of a general aviation airplane equipped with a high aspect-ratio, natural laminar-flow wing

A wind tunnel investigation has been conducted to evaluate the aerodynamic performance, stability, and control characteristics of a full-scale general aviation aircraft equipped with an advanced natural laminar flow wing. Force and moment data were measured over wide angle-of-attack and sideslip ranges and at Reynolds numbers from 1.4 million to 2.4 million based on the mean aerodynamic chord. Additional measurements determined the condition of the wing boundary layer and the wing stalling characteristics. The results showed that large regions of natural laminar flow existed on the wing which would significantly enhance the cruise performance of the configuration. Artificially tripping the boundary layer did not significantly affect the lift, stability, and control characteristics. Leading-edge modifications were effective in improving the stall resistance of the configuration, and resulted in only minor penalties in calculated cruise performance.

Murri, Daniel G.↗
NASA NTRS1957

Ground Effects on the Longitudinal Characteristics of Two Models with Wings Having Low Aspect Ratio and Pointed Tips

Wind-tunnel tests were conducted to determine the ground effects on a tailless model with a wing of aspect ratio 2 and infinite taper, and on a tailed model with a triangular wing of aspect ratio 3, with flaps. Control-surface hinge moments were measured on the tailless model. The results are compared with the predictions of the theory of Tani, et al.

CONTROLS, FLAP-TYPE - COMPLETE WINGS↗
NASA NTRS2000

An Evaluation Technique for an F/A-18 Aircraft Loads Model Using F/A-18 Systems Research Aircraft Flight Data

A limited evaluation of the F/A-18 baseline loads model was performed on the Systems Research Aircraft at NASA Dryden Flight Research Center (Edwards, California). Boeing developed the F/A-18 loads model using a linear aeroelastic analysis in conjunction with a flight simulator to determine loads at discrete locations on the aircraft. This experiment was designed so that analysis of doublets could be used to establish aircraft aerodynamic and loads response at 20 flight conditions. Instrumentation on the right outboard leading edge flap, left aileron, and left stabilator measured the hinge moment so that comparisons could be made between in-flight-measured hinge moments and loads model-predicted values at these locations. Comparisons showed that the difference between the loads model-predicted and in-flight-measured hinge moments was up to 130 percent of the flight limit load. A stepwise regression technique was used to determine new loads derivatives. These derivatives were placed in the loads model, which reduced the error to within 10 percent of the flight limit load. This paper discusses the flight test methodology, a process for determining loads coefficients, and the direct comparisons of predicted and measured hinge moments and loads coefficients.

Olney, Candida D.↗
NASA NTRS2019

Active Flow Control on Vertical Tail Models

Active flow control (AFC) subscale experiments were conducted at the Lucas Wind Tunnel of the California Institute of Technology. Tests were performed on a generic vertical tail model at low speeds. Fluidic oscillators were used at the trailing edge of the main element (vertical stabilizer) to redirect the flow over the rudder and delay or prevent flow separation. Side force increases in excess of 50% were achieved with a 2% momentum coefficient (C(sub μ)) input. The results indicated that a collective C(sub μ) of about 1% could increase the side force by 30–50%. This result is achieved by reducing the spanwise flow on the swept back wings that contributes to early flow separation near their tips. These experiments provided the technical backdrop to test the full-scale Boeing 757 vertical tail model equipped with a fluidic oscillator system at the National Full-scale Aerodynamics Complex 40-by 80-foot Wind Tunnel, NASA Ames Research Center. The C(sub μ) is shown to be an important parameter for scaling a fluidic oscillator AFC system from subscale to full-scale wind tunnel tests. The results of these tests provided the required rationale to use a fluidic oscillator AFC configuration for a follow-on flight test on the Boeing 757 ecoDemonstrator.

Andino, Marlyn Y.↗
NASA NTRS1981

Advanced technology lightweight fuel cell program

The potential of the alkaline electrolyte fuel cell as the power source in a multi hundred kilowatt orbital energy storage system was studied. The total system weight of an electrolysis cell energy storage system was determined. The tests demonstrated: (1) the performance stability of a platinum on carbon anode catalyst configuration after 5000 hours of testing has no loss in performance; (2) capability of the alkaline fuel cell to operate to a cyclical load profile; (3) suitability of a lightweight graphite electrolyte reservoir plate for use in the alkaline fuel cell; (4) long life potential of a hybrid polysulfone cell edge frame construction; and (5) long term stability of a fiber reinforced potassium titanate matrix structure. The power section tested operates with passive water removal eliminating the requirement for a dynamic hydrogen pump water separator thereby allowing a powerplant design with reduced weight, lower parasite power, and a potential for high reliability and extended endurance. It is concluded that two perovskites are unsuitable for use as a catalyst or as a catalyst support at the cathode of an alkaline fuel cell.

Martin, R. E.↗
NASA NTRS1961

Transonic Investigation of Aerodynamic Characteristics of a Swept-Wing Fighter-Airplane Model with Leading-Edge Droop in Combination with Outboard Chord-Extensions and Notches

An investigation of the effects of several wing leading-edge modifications on the aerodynamic characteristics of a 45 degree swept-wing fighter-airplane model has been conducted in the Langley 16-foot transonic tunnel at low and high lifting conditions at Mach numbers from 0.85 to 1.03. The investigation included the determination of the effect on longitudinal stability and performance characteristics of wing leading-edge and chord-extension droops of 60 and 20 degrees chord-extension overhangs of 0.075c and 0.15c (where c inboard end of the 0.075c chord-extension to depths of 0.075c and 0.l25c, and indention of the model fuselage to conform partially to the supersonic area rule for a Mach number of 1.20. Lift, drag, and pitching-moment data were obtained for configurations with the tail on and off. Comparisons of data obtained from the present model with data from a configuration with leading-edge slats are included. Generally, the model wing modifications provided only slight improvements of the airplane longitudinal stability characteristics, but did substantially reduce the airplane drag coefficients at moderate and high lifting conditions.

Whitcomb, Charles F.↗