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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1935

The Effect of Lateral Inclination of the Thrust Axis and of Sweepback of the Leading Edge of the Wing on Propulsive and Net Efficiencies of a Wing-Nacelle-Propeller Combination

This report describes and gives the results of tests made to determine the effect of lateral inclination of the propeller thrust axis to the direction of flight. A wing-nacelle-propeller combination with the nacelle axis located successively parallel to and at 15 degrees to the perpendicular to the leading edge of a wing was tested with the combination at several angles of yaw. Tests of the wing alone at the same angles of yaw were also made. The data are presented in the usual graphic form. An increase in propulsive efficiency with increase in angle of the thrust axis was found. The change in net efficiency, found by charging the whole nacelle drag to the power unit, was negligible, however, within the range of the tests.

Wood, Donald H.↗
NASA NTRS1994

Numerical Simulation of Cylindrical, Self-field MPD Thrusters with Multiple Propellants

A two-dimensional, two-temperature, single fluid MHD code was used to predict the performance of cylindrical, self-field magnetoplasmadynamic (MPD) thrusters operated with argon, lithium, and hydrogen propellants. A thruster stability equation was determined relating maximum stable J(sup 2)/m values to cylindrical thruster geometry and propellant species. The maximum value of J(sup 2)/m was found to scale as the inverse of the propellant molecular weight to the 0.57 power, in rough agreement with limited experimental data which scales as the inverse square root of the propellant molecular weight. A general equation which relates total thrust to electromagnetic thrust, propellant molecular weight, and J(sup 2)/m was determined using reported thrust values for argon and hydrogen and calculated thrust values for lithium. In addition to argon, lithium, and hydrogen, the equation accurately predicted thrust for ammonia at sufficiently high J(sup 2)/m values. A simple algorithm is suggested to aid in the preliminary design of cylindrical, self-field MPD thrusters. A brief example is presented to illustrate the use of the algorithm in the design of a low power MPD thruster.

Lapointe, Michael R.↗
NASA NTRS1923

Reduction in efficiency of propellers due to slipstream

In the slipstream behind a propeller there is a considerable amount of kinetic energy which has been imparted to it by the engine without producing any corresponding propeller thrust. The increased absorption of power reduces the propeller efficiency. Attention has been previously directed to this question by Bendemann and Madelung and other writers. Their contribution serves to verify a simple method of calculating the reduction in the propeller efficiency due to the slip stream. That method of calculation is given here. Explanations and examples are given for as single propeller and for two propellers mounted in tandem.

Munk, Max M↗
NASA NTRS1991

A method for the construction of a lunar transfer trajectory using ballistic capture

The weak stability boundary (WSB) method for the design and optimization of lunar transfer trajectories is described. Considerable savings of propellant are shown over classical methods of orbit transfer such as the Hohmann transfer method. The savings in Delta V required of the spacecraft ranges from 100 to 200 m/s, which translates into a 5-10 percent reduction in spacecraft propellant for a science payload. Another advantage of the WSB method involves the utilization of low thrust propellant systems. Since the transfer trajectory is nearly completely ballistic, thrusting propulsive maneuvers may be performed over a long time duration.

Miller, James K.↗
NASA NTRS1973

Constrained low-thrust guidance.

Constrained low thrust guidance algorithms for three axis and spin-stabilized, constant power, solar electric propelled spacecraft on fixed time rendezvous missions are developed. A 'bang-bang' type of minimum-propellant thrust program is used. Control constraints arise from the specification that the thrust vector must remain fixed relative to the solar panels. The guidance law is derived from deterministic linear perturbation theory and is controllable to first order on trajectories containing at least two thrust arcs. The number and timing of guidance updates and the effectiveness of the guidance law in compensating for state and control estimation biases and uncertainties are discussed. Numerical comparisons between the optimal control and the restricted control case are presented on a Encke comet rendezvous.

Ungs, M. J.↗
NASA NTRS2014

Implementation Options for the PROPEL Electrodynamic Tether Demonstration Mission

The PROPEL flight mission concept will demonstrate the safe use of an electrodynamic tether for generating thrust. PROPEL is being designed to be a versatile electrodynamic-tether system for multiple end users and to be flexible with respect to platform. As such, several implementation options are being explored, including a comprehensive mission design for PROPEL with a mission duration of six months; a space demonstration mission concept design with configuration of a pair of tethered satellites, one of which is the Japanese H-II Transfer Vehicle; and an ESPA-based system. We report here on these possible implementation options for PROPEL. electrodynamic tether; PROPEL demonstration mission; propellantless propulsion

Bilen, Sven G.↗
NASA NTRS1989

Performance of a 100 kW class applied field MPD thruster

Performance of a 100 kW, applied field magnetoplasmadynamic (MPD) thruster was evaluated and sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. Thermal efficiencies as high as 60 percent, thrust efficiencies up to 21 percent, and specific impulses of up to 1150 s were attained with argon propellant. Thrust levels up to 2.5 N were directly measured with an inverted pendulum thrust stand at discharge input powers up to 57 kW. It was observed that thrust increased monotonically with the product of arc current and magnet current.

Mantenieks, Maris A.↗
NASA NTRS1989

Performance of a 100 kW class applied field MPD thruster

The performance of a 100 kW class, applied field MPD thruster was evaluated and sensitivities of discharge characteristics to arc current, mass flow rate, and applied magnetic field were investigated. Thermal efficiencies as high as 60 percent , thrust efficiencies up to 21 percent, and specific impulses of up to 1150 s were attained with argon propellant. Thrust levels up to 2.5 N were directly measured with an inverted pendulum thrust stand at discharge input powers up to 57 kW. It was observed that thrust increased monotonically with the product of arc current and magnet current.

Mantenieks, M. A.↗
NASA NTRS1941

The Selection of Propellers for High Thrust at Low Airspeed

Problem of improving thrust at low speeds is primarily one of reducing angle of attack of operation of sections to improve L/D or reducing blade helix angle. An analysis, based on recent propeller data, is presented for determining improvements in thrust or efficiency which could be obtained by increased number of blades, increased blade width, increased diameter, dual rotation, and two-speed gearing. All methods were found very effective, particularly two-speed gearing.

PROPELLERS - CURTISS↗
NASA NTRS2006

Channel-wing System for Thrust Deflection and Force/Moment Generation

An aircraft comprising a Channel Wing having blown c h - ne1 circulation control wings (CCW) for various functions. The blown channel CCW includes a channel that has a rounded or near-round trailing edge. The channel further has a trailing-edge slot that is adjacent to the rounded trailing edge of the channel. The trailing-edge slot has an inlet connected to a source of pressurized air and is capable of tangentially discharging pressurized air over the rounded trailing edge. The aircraft further has a propeller that is located in the channel and ahead of the rounded trailing edge of the channel. The propeller provides a propeller thrust exhaust stream across the channel wing to propel the aircraft through the air and to provide high lift. The pressurized air being discharged over the rounded trailing edge provides a high lift that is obtained independent of an aircraft angle of attack, thus preventing the asymmetry. separated flow, and stall experienced by the CC wing at the high angle of attack it required for high lift generation. The aircraft can further include blown outboard circulation control wings (CCW) that are synergistically connected to the blown channel CCWs. The blown outboard CCWs provide additional high lift, control thrust/drag interchange, and can provide all three aerodynamic moments when differential blowing is applied front-to-rear or left-to-right. Both the blown channel CCW and the outboard CCW also have leading-edge blowing slots to prevent flow separation or to provide aerodynamic moments for control.

Englar, Robert J.↗
NASA NTRS1989

Time-dependent boundary-layer response in a propeller slipstream

The time-dependent behavior of a wing boundary layer immersed in a propeller slipstream has been studied experimentally in wind-tunnel tests and in flight. Hot-wire anemometer measurements were made through the boundary layer for time-dependent, ensemble-average velocity and turbulence-intensity profiles at various chord locations. The boundary layer has a coherent, time-dependent cycle of transitional behavior, varying from a laminar to a turbulent-transitional state. Local drag coefficients determined from the velocity profiles for the freewheeling propeller case in flight show that the time-dependent drag in the propeller slipstream varies from the undisturbed laminar value to a value less than that predicted for fully turbulent flow. Local drag coefficients determined from the thrusting propeller case in the wind tunnel indicate that the effects of the slipstream are to enhance the stability of the boundary layer and to reduce the drag coefficient in the laminar portion of the cycle below its undisturbed laminar value.

Howard, Richard M.↗
NASA NTRS1941

Flight Tests of the Wilford XOZ-1 Sea Gyroplane

During August 1939 a series of flight tests was made at Langley Field on the Wilford sea gyroplane, designated by the Navy as the XOZ-1. These tests were intended to permit rough evaluation of the stability and control characteristics of the machine, with particular reference to possible improvements in rigging which might be made in future machines with fixed wing and nonarticulated feathering control rotor, and to provide data on the bending and feathering motions of the rotor blades. The tests made in 1939 proved inadequate, chiefly because the machine as flown did not have sufficient propeller thrust to give it an appreciable speed range in steady flight. Further tests were therefore made in August 1940 after overhauling the engine and substituting a metal propeller for the wooded one first used. The range of speeds covered in steady flight was markedly extended. Steady-flight runs only were made in this series, since it was felt that takeoffs and landings had been covered sufficiently in the previous tests.

Gustafson, Frederic B.↗
NASA NTRS1925

Determination of the lift and drag characteristics of an airplane in flight

Flight tests to determine lift and drag characteristics are discussed. A review is given of the fundamental principles on which the tests are based and on the forces acting on an airplane in the various conditions of steady flight. Glide with and without propeller thrust and the relation between angle of attack and the indicated airspeed for different conditions of steady flight are discussed. The glide test procedure and the problem of the propeller are discussed.

Green, Maurice W↗
NASA NTRS2001

Spinning Rocket Simulator Turntable Design

Contained herein is the research and data acquired from the Turntable Design portion of the Spinning Rocket Simulator (SRS) project. The SRS Project studies and eliminates the effect of coning on thrust-propelled spacecraft. This design and construction of the turntable adds a structural support for the SRS model and two degrees of freedom. The two degrees of freedom, radial and circumferential, will help develop a simulated thrust force perpendicular to the plane of the spacecraft model while undergoing an unstable coning motion. The Turntable consists of a ten-foot linear track mounted to a sprocket and press-fit to a thrust bearing. A two-inch high column grounded by a Triangular Baseplate supports this bearing and houses the slip rings and pressurized, air-line swivel. The thrust bearing allows the entire system to rotate under the moment applied through the chain-driven sprocket producing a circumferential degree of freedom. The radial degree of freedom is given to the model through the helically threaded linear track. This track allows the Model Support and Counter Balance to simultaneously reposition according to the coning motion of the Model. Two design factors that hinder the linear track are bending and twist due to torsion. A Standard Aluminum "C" channel significantly reduces these two deflections. Safety considerations dictate the design of all the components involved in this project.

Miles, Robert W.↗