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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

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NASA NTRS1974

The influence of polarization on millimeter wave propagation through rain

The influence of polarization on millimeter wave propagation through rain is investigated. The experimental equipment consisted of a 1.43 km line-of-sight path with 4-foot diameter dual-polarized parabolic reflector antennas at each end. Linearly polarized 17.65 GHz signals were transmitted with the electric field vectors at plus 45 degrees and minus 45 degrees from the vertical. These polarizations were initially chosen to maximize the measured depolarization at any given rainfall rate. Later it was discovered that the cross polarization levels measured with plus or minus 45 degree linearly polarized signals are theoretically the least sensitive to variations in drop canting angle and this choice of polarization reduces the scatter in the data.

Bostian, C. W.↗

NASA NTRS1974

Develop minimum thrustor control laws and select orbits for a geodesy drag-free satellite

The original motivation for studying control laws for pulse plasma systems was based on the improved life characteristics possible with pulse plasma jets. These pulse plasma units are relatively massive compared with cold gas thrustors. As a result, therefore, significant mass savings can be achieved by minimizing the the number of thrustors. The control laws, therefore, were developed for thrust available from two thrustors only. In a spinning satellite, these thrustors are sufficient to completely control the vehicle as long as the spin rate is sufficiently high for a given level of external disturbance. The thrustors are canted so that a component of each is along the plus and minus spin axis. The other component of each thrustor acts in the radial direction. It is sufficient to analyze the behavior in the plane of spin assuming a single thrustor.

Breakwell, J. V.↗

NASA NTRS1973

Solid motor aft closure insulation erosion

The erosion rate of aft closure insulation in a number of large solid propellant motors was empirically analyzed by correlating the average ablation rate with a number of variables that had previously been demonstrated to affect heat flux. The main correlating parameter was a heat flux based on the simplified Bartz heat transfer coefficient corrected for two-dimensional effects. A multiplying group contained terms related to port-to-throat ratio, local wall angle, grain geometry and nozzle cant angle. The resulting equation gave a good correlation and is a useful design tool.

Stampfl, E.↗

NASA NTRS1976

Device for installing rocket engines

A device for installing rocket engines is reported that is supported at a cant relative to vertical by an axially extensible, tiltable pedestal. A lifting platform supports the rocket engine at its thrust chamber exit, including a mount having a concentric base characterized by a concave bearing surface, a plurality of uniformly spaced legs extended radially from the base, and an annular receiver coaxially aligned with the base and affixed to the distal ends of said legs for receiving the thrust chamber exit. The lifting platform rests on a seat concentrically related to the pedestal and affixed to an extended end portion thereof having a convex bearing surface mated in sliding engagement with the concave bearing surface of the annular base for accommodating a rocking motion of the platform.

George, T. R., Jr.↗

NASA NTRS1977

Theoretical Parametric Study of the Relative Advantages of Winglets and Wing-Tip Extensions

This study provides sweeping confirmation, for a wide range of wings, of the recommendations of Whitcomb in NASA TN D-8560. For identical increases in bending moment, a winglet provides a greater gain in induced efficiency than tip extension. Winglet toe angle allows design trades between efficiency and root moment. A winglet shows the greatest benefit when the wing loads are heavy near the tip. Washout diminishes the benefit of either tip modification, and the gain in induced efficiency becomes a function of lift coefficient; thus, heavy wing loadings obtain the greatest benefit from a winglet, and low-speed performance is enhanced even more than cruise performance. Both induced efficiency and bending moment increase with winglet length and outward cant. The benefit of a winglet relative to a tip extension is greatest for a nearly vertical winglet. Root bending moment is proportional to the minimum weight of bending material required in the wing; thus, it is a valid index of the impact of tip modifications on a new wing design.

Aerodynamics↗

NASA NTRS1977

Theoretical parametric study of the relative advantages of winglets and wing-tip extensions

It was found that for identical increases in bending moment, a winglet provides a greater gain in induced efficiency than a tip extension. Winglet toe-in angle allows design trades between efficiency and root moment. A winglet showed the greatest benefit when the wing loads were heavy near the tip. Washout diminished the benefit of either tip modification, and the gain in induced efficiency became a function of lift coefficient; heavy wing loadings obtained the greatest benefit from a winglet, and low speed performance was enhanced even more than cruise performance. Both induced efficiency and bending moment increased with winglet length and outward cant. The benefit of a winglet relative to a tip extension was greatest for a nearly vertical winglet. Root bending moment was proportional to the minimum weight of bending material required in the wing; it is a valid index of the impact of tip modifications on a new wing design.

Heyson, H. H.↗

NASA NTRS1978

Space Shuttle Plume Simulation Effect on Aerodynamics

Technology for simulating plumes in wind tunnel tests was not adequate to provide the required confidence in test data where plume induced aerodynamic effects might be significant. A broad research program was undertaken to correct the deficiency. Four tasks within the program are reported. Three of these tasks involve conducting experiments, related to three different aspects of the plume simulation problem: (1) base pressures; (2) lateral jet pressures; and (3) plume parameters. The fourth task involves collecting all of the base pressure test data generated during the program. Base pressures were measured on a classic cone ogive cylinder body as affected by the coaxial, high temperature exhaust plumes of a variety of solid propellant rockets. Valid data were obtained at supersonic freestream conditions but not at transonic. Pressure data related to lateral (separation) jets at M infinity = 4.5, for multiple clustered nozzles canted to the freestream and operating at high dynamic pressure ratios. All program goals were met although the model hardware was found to be large relative to the wind tunnel size so that operation was limited for some nozzle configurations.

Hair, L. M.↗

NASA NTRS1979

Aerodynamic interactions from reaction controls for lateral control of the M2-F2 lifting-body entry configuration at transonic and supersonic and supersonic Mach numbers

Tests were conducted in the Ames 6 by 6 foot wind tunnel to determine the interaction of reaction jets for roll control on the M2-F2 lifting-body entry vehicle. Moment interactions are presented for a Mach number range of 0.6 to 1.7, a Reynolds number range of 1.2 x 10 to the 6th power to 1.6 x 10 to the 6th power (based on model reference length), an angle-of-attack range of -9 deg to 20 deg, and an angle-of-sideslip range of -6 deg to 6 deg at an angle of attack of 6 deg. The reaction jets produce roll control with small adverse yawing moment, which can be offset by horizontal thrust component of canted jets.

Bailey, R. O.↗

NASA NTRS1980

Wind tunnel investigation of the Titan Forward Skirt compartment vent from a free-stream Mach number of 0.80 to 1.96

A test was conducted to determine the flow characteristics of the Titan forward skirt compartment vent over a free stream Mach number range of 0.80 to 1.96. The vent was mounted in a flat plate and the plate was flush mounted to the tunnel side wall with coinciding center lines. Air was discharged from a duct, located on the tunnel side wall behind the plate, through a canted aft 30 deg honeycomb vent into the free stream. Data for the analysis of the Titan forward skirt compartment venting during ascent through the atmosphere are provided. Full scale simulated flight hardware, such as the honeycomb vent, duct corrugations and field joint ring were used. Boundary layer thicknesses were used to vary boundary height. The highest vent discharge coefficient for any given Mach number and vent pressure ratio generally occurred at the maximum displacement thickness. With no vent flow the static pressure in the vent region was generally less than the free stream static pressure. With vent flow, the static pressures upstream of the vent increased, and those downstream of the vent decreased.

Johns, A. L.↗

NASA NTRS1980

Effect of winglets on performance and handling qualities of general aviation aircraft

Recent flight and wind tunnel evaluations of winglets mounted on general aviation airplanes have shown improvements in cruise fuel efficiency, and climbing and turning performance. Some of these analyses have also uncovered various effects of winglets on airplane handling qualities. Retrofitting an airplane with winglets can result in reduced cross wind take-off and landing capabilities. Also, winglets can have a detrimental effect on the lateral directional response characteristics of aircraft which have a moderate to high level of adverse yaw due to aileron. Introduction of an aileron-rudder-interconnect, and reduction of the effective dihedral by canting-in of the winglets, or addition of a lower winglet can eliminate these flying quality problems.

Van Dam, C. P.↗

NASA NTRS1980

Experiments on multiple vortices in a side dump gas generator ramjet

The role of multiple vortices in the flame stabilization process of a 4 inlet side dump ramjet was determined. Very rich propane air mixtures were injected at the head to simulate a gas generator ramjet. Swirl was introduced by canting the inlets at the dump station. The inlet angle, swirl angle, and the distance of the head from the dump station were varied over a wide range to determine the importance of the vortices located at the dump stations and at the head. It is shown that with proper design, the vortex at the head can be made to perform as a pilot burner allowing a great deal of versatility of operation and it appears to provide all the criteria of pollution free operation.

Choudhury, P. R.↗

NASA NTRS1981

Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA Ames 40 by 80 foot wind tunnel: Acoustic data report

Moore, M. T.↗

NASA NTRS1981

Investigation of powered nacelles on a high aspect ratio NASA supercritical wing, phase 2

A modified wing with the long core separate flow nacelle and several E(3) nacelles was utilized. The effects of nacelle and pylon cant angles and nacelle longitudinal and vertical location were investigated over a Mach number range from 0.70 to 0.83. The results at the cruise condition 0.82 Mach number and 0.55 lift coefficient are presented.

Flechner, S. G.↗

NASA NTRS1971

Preliminary wind-tunnel investigation of the effects of engine nacelles on a transport configuration with high lift drag ratios to a Mach number of 1.00

Wind tunnel tests to determine the effect of engine nacelles added to a low wing fuselage vertical tail configuration utilizing the NASA supercritical airfoil and a refined area ruled fuselage are discussed. The engine arrangement consisted of two aft fuselage, side mounted flow through nacelles and a solid body of revolution mounted above the fuselage in a manner similar to the Boeing 727. A preliminary analysis of the wind tunnel data shows that favorable interference drag can be obtained with the proper longitudinal locations of the nacelles, by canting the nacelle inlets, and by cusping the rearward region of the nacelle.

Flechner, S. G.↗

NASA NTRS1981

Foldable beam

A foldable beam possessing superior qualities of light weight, compactness for transportation, quick deployment with minimum use of force, and high strength is described. These qualities are achieved through the use of a series of longitudinally rigid segments, hinged along one side and threaded by one or two cables along the opposite side. Tightening the cables holds the beam extended. Loosening the cables permits the segments to fold away from the threaded side. In one embodiment the segments are connected by canted hinges with the result that the beam may be folded in a helix-like configuration around a cylinder. In another embodiment the segments themselves may be hinged to fold flat laterally as the beam is folded, resulting in a configuration that may be helixed around a shorter cylinder.

Hedgepeth, J. M.↗

NASA NTRS1981

Effects of wingtip modifications on handling qualities of agricultural aircraft

The effect of wingtip modifications on the stability and control characteristics of an agricultural airplane has been studied by means of a nonplanar quasi-vortex-lattice method. The method is used to compute the changes in steady state and perturbed state lateral-directional stability and control derivatives produced by wingtip mounted winglets, vortex diffuser vanes, and tip extensions. The study shows that the combination of the excessive positive dihedral effect produced by the winglets and adverse yaw due to aileron deflection can have a detrimental effect on the roll control characteristics of the airplane. Introduction of an aileron-rudder-interconnect, and reduction of the effective dihedral by canting-in of the winglets, or addition of a lower winglet can eliminate the roll control problems.

Van Dam, C. P.↗

NASA NTRS1980

Forward velocity effects on fan noise and the suppression characteristics of advanced inlets as measured in the NASA-Ames 40 by 80 foot wind tunnel

Forward velocity effects on the forward radiated fan noise and on the suppression characteristics of three advanced inlets relative to a baseline cylindrical inlet were measured in the NASA Ames Research Center 40 x 80 foot Wind Tunnel. A modified JT15D turbofan engine in a quiet nacelle was the source of fan noise; the advanced inlets were a Conventional Takeoff/Landing (CTOL) hybrid inlet, a Short Takeoff/Landing (STOL) hybrid inlet, and a treated deflector inlet. Also measured were the static to flight effects on the fan noise of canting the baseline inlet 4 deg downward to simulate typical wing mounted turbofan engines. The CTOL hybrid inlet suppressed the high tip speed fan noise as much as 18 PNdB on a 61 m (200 ft) sideline scaled to a CF6 size engine while the STOL hybrid inlet suppressed the low tip speed fan noise as much as 13 PNdB on a 61 m (200 ft) sideline scaled to a OCSEE size engine. The deflector inlet suppressed the high tip speed fan noise as much as 13 PNdB at 61 m (200 ft) overhead scaled to a CF6 size engine. No significant changes in fan noise suppression for the CTOL and STOL hybrid inlets occurred for forward velocity changes above 21 m/s (68 ft/s) or for angle of attack changes up to 15 deg. However, changes in both forward velocity and angle of attack changed the deflector inlet noise unpredictably due to the asymmetry of the inlet flow field into the fan.

Moore, M. T.↗

NASA NTRS1982

The Development of a Handbook for Astrobee F Performance and Stability Analysis

An astrobee F performance and stability analysis is presented, for use by the NASA Sounding Rocket Division. The performance analysis provides information regarding altitude, mach number, dynamic pressure, and velocity as functions of time since launch. It is found that payload weight has the greatest effect on performance, and performance prediction accuracy was calculated to remain within 1%. In addition, to assure sufficient flight stability, a predicted rigid-body static margin of at least 8% of the total vehicle length is required. Finally, fin cant angle predictions are given in order to achieve a 2.5 cycle per second burnout roll rate, based on obtaining 75% of the steady roll rate. It is noted that this method can be used by flight performance engineers to create a similar handbook for any sounding rocket series.

Wolf, R. S.↗