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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1949

Wind-Tunnel Tests of a 0.16-Scale Model of the Douglas MX-656 Airplane at High Subsonic Speeds: Stability and Control Characteristics - 1

Wind tunnel tests of the 0.16-scale Douglas MX-656 model were made at low and high subsonic Mach numbers to investigate the static longitudinal- and lateral stability characteristics. The tests shows that undesirable changes in longitudinal stability at the stall were apparently caused by an altered downwash pattern at the tail. The jettisonable nose fins were highly destabilizing. Compressibility effects for the test Mach numbers were not detrimental to the longitudinal- or lateral-stability characteristics.

Hamilton, William T.↗
NASA NTRS2015

Arrival Metering Precision Study

This paper describes the background, method and results of the Arrival Metering Precision Study (AMPS) conducted in the Airspace Operations Laboratory at NASA Ames Research Center in May 2014. The simulation study measured delivery accuracy, flight efficiency, controller workload, and acceptability of time-based metering operations to a meter fix at the terminal area boundary for different resolution levels of metering delay times displayed to the air traffic controllers and different levels of airspeed information made available to the Time-Based Flow Management (TBFM) system computing the delay. The results show that the resolution of the delay countdown timer (DCT) on the controllers display has a significant impact on the delivery accuracy at the meter fix. Using the 10 seconds rounded and 1 minute rounded DCT resolutions resulted in more accurate delivery than 1 minute truncated and were preferred by the controllers. Using the speeds the controllers entered into the fourth line of the data tag to update the delay computation in TBFM in high and low altitude sectors increased air traffic control efficiency and reduced fuel burn for arriving aircraft during time based metering.

human/systems↗
NASA NTRS1991

Closed-loop motor control using high-speed fiber optics

A closed-loop control system for controlling the operation of one or more servo motors or other controllable devices is described. The system employs a fiber optics link immune to electromagnetic interference, for transmission of control signals from a controller or controllers at a remote station to the power electronics located in proximity to the motors or other devices at the local station. At the remote station the electrical control signals are time-multiplexed, converted to a formatted serial bit stream, and converted to light signals for transmission over a single fiber of the fiber optics link. At the local station, the received optical signals are reconstructed as electrical control signals for the controlled motors or other devices. At the local station, an encoder sensor linked to the driven device generates encoded feedback signals which provide information as to a condition of the controlled device. The encoded signals are placed in a formatted serial bit stream, multiplexed, and transmitted as optical signals over a second fiber of the fiber optic link which closes the control loop of the closed-loop motor controller. The encoded optical signals received at the remote station are demultiplexed, reconstructed and coupled to the controller(s) as electrical feedback signals.

Dawson, Reginald↗
NASA NTRS2010

Development and Application of Plasma Actuators for Active Control of High-Speed and High Reynolds Number Flows

Active flow control is often used to manipulate flow instabilities to achieve a desired goal (e.g. prevent separation, enhance mixing, reduce noise, etc.). Instability frequencies normally scale with flow velocity scale and inversely with flow length scale (U/l). In a laboratory setting for such flow experiments, U is high, but l is low, resulting in high instability frequency. In addition, high momentum and high background noise & turbulence in the flow necessitate high amplitude actuation. Developing a high amplitude and high frequency actuator is a major challenge. Ironically, these requirements ease up in application (but other issues arise).

Sammy, Mo↗
NASA NTRS1986

Wall temperature control of low-speed body drag

The use of thermal means to control drag under turbulent boundary layer conditions is examined. Numerical calculations are presented for both skin friction and (unseparated) pressure drag for turbulent boundary-layer flows over a fuselage-like body with wall heat transfer. In addition, thermal control of separation on a bluff body is investigated. It is shown that a total drag reduction of up to 20 percent can be achieved for wall heating with a wall-to-total-freestream temperature ratio of 2. For streamlined slender bodies, partial wall heating of the forebody can produce almost the same order of total drag reduction as the full body heating case. For bluff bodies, the separation delay from partial wall cooling of the afterbody is approximately the same as for the fully cooled body.

Lin, J. C.↗
NASA NTRS2004

Tiperon

A control surface for an air vehicle (e.g., an aircraft, rocket, or missile) is useful for flight control at both subsonic and supersonic speeds. The control surface defines the outboardmost tip of a flight structure (e.g., a wing, tail or other stabilizer) of the air vehicle. Hence, the control surface is referred to as a `tiperon`. The tiperon has an approximately L-shaped configuration, and can be rotated relative to a fixed portion of the flight structure about a control axis. The respective surface areas of the tiperon sections forward and aft of the control axis are proportioned to place the subsonic center of pressure aft of the control axis to enhance aircraft control, and preferably also forward of the centroid of tiperon surface area. Also, the control surface sections forward and aft of the control axis are preferably mass-balanced, or at least nearly so, to enhance aircraft control at supersonic speeds. Either of the tiperon sections forward and aft of the control axis can be tapered to reduce the dependence of the moment exerted by air flow about the control axis, upon the tiperon's angle-of-attack. The tiperon also has enough surface area to control the air vehicle, even at low airspeeds. The invention is also directed to air vehicles incorporating one or more such control surfaces.

Lewis, Carl E.↗
NASA NTRS2005

Aeroelastic Sizing for High-Speed Research (HSR) Longitudinal Control Alternatives Project (LCAP)

The Longitudinal Control Alternatives Project (LCAP) compared three high-speed civil transport configurations to determine potential advantages of the three associated longitudinal control concepts. The three aircraft configurations included a conventional configuration with a layout having a horizontal aft tail, a configuration with a forward canard in addition to a horizontal aft tail, and a configuration with only a forward canard. The three configurations were aeroelastically sized and were compared on the basis of operational empty weight (OEW) and longitudinal control characteristics. The sized structure consisted of composite honeycomb sandwich panels on both the wing and the fuselage. Design variables were the core depth of the sandwich and the thicknesses of the composite material which made up the face sheets of the sandwich. Each configuration was sized for minimum structural weight under linear and nonlinear aeroelastic loads subject to strain, buckling, ply-mixture, and subsonic and supersonic flutter constraints. This report describes the methods that were used and the results that were generated for the aeroelastic sizing of the three configurations.

Walsh, Joanne L.↗
NASA NTRS1973

System design of the Pioneer Venus spacecraft. Volume 9: Attitude control/mechanisms subsystems studies

The Pioneer Venus mission study was conducted for a probe spacecraft and an orbiter spacecraft to be launched by either a Thor/Delta or an Atlas/Centaur launch vehicle. Both spacecraft are spin stabilized. The spin speed is controlled by ground commands to as low as 5 rpm for science instrument scanning on the orbiter and as high as 71 rpm for small probes released from the probe bus. A major objective in the design of the attitude control and mechanism subsystem (ACMS) was to provide, in the interest of costs, maximum commonality of the elements between the probe bus and orbiter spacecraft configurations. This design study was made considering the use of either launch vehicle. The basic functional requirements of the ACMS are derived from spin axis pointing and spin speed control requirements implicit in the acquisition, cruise, encounter and orbital phases of the Pioneer Venus missions.

Neil, A. L.↗
NASA NTRS1959

Low-Speed Static Stability and Control Characteristics of a Model of a Right Triangular Pyramid Reentry Configuration

An investigation of the low-speed static stability and control characteristics of a model of a right triangular pyramid reentry configuration has been made in the Langley free-flight tunnel. The investigation showed that the model had generally satisfactory longitudinal and lateral static stability characteristics. The maximum lift-drag ratio was increased from about 3 to 5 by boattailing the base of the model.

Paulson, John W.↗
NASA NTRS1954

Longitudinal Stability and Control Characteristics at Transonic Speeds of a 1/30-Scale Model of the Republic XF-103 Airplane

The longitudinal stability and control characteristics of a 1/30-scale model of the Republic XF-103 airplane were investigated in the Langley 8-foot transonic tunnel. The effect of speed brakes located at the end of the fuselage was also investigated. The main part of the investigation was made with internal flow in the model, but some data were obtained with no internal flow. The longitudinal stability and control at transonic-speeds appeared satisfactory. The transonic drag rise was small. The speed brakes had no adverse effects on longitudinal stability.

Luoma, Arvo A.↗
NASA NTRS1992

Control of low-speed turbulent separated flow using jet vortex generators

A parametric study has been performed with jet vortex generators to determine their effectiveness in controlling flow separation associated with low-speed turbulent flow over a two-dimensional rearward-facing ramp. Results indicate that flow-separation control can be accomplished, with the level of control achieved being a function of jet speed, jet orientation (with respect to the free-stream direction, and jet location (distance from the separation region in the free-stream direction). Compared to slot blowing, jet vortex generators can provide an equivalent level of flow control over a larger spanwise region (for constant jet flow area and speed).

Selby, G. V.↗