SEARCH · Engineering Papers

Results for “effect measure”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 505 records · Page 28

All sources NASA NTRS DOE OSTI

NASA NTRS1972

Solid propulsion advanced concepts

The feasibility and application of a solid propulsion powered spacecraft concept to implement high energy missions independent of multiplanetary swingby opportunities are assessed and recommendations offered for future work. An upper stage, solid propulsion launch vehicle augmentation system was selected as the baseline configuration in view of the established program goals of low cost and high reliability. Spacecraft and propulsion system data that characterize mission performance capabilities were generated to serve as the basis for subsequent tradeoff studies. A cost effectiveness model was used for the preliminary feasibility assessment to provide a meaningful comparative effectiveness measure of the various candidate designs. The results substantiated the feasibility of the powered spacecraft concept when used in conjunction with several intermediate-sized launch vehicles as well as the existence of energy margins by which to exploit the attainment of extended mission capabilities. Additionally, in growth option applications, the employment of advanced propulsion systems and alternate spacecraft approaches appear promising.

Nakamura, Y.↗

NASA NTRS1972

Discrete sonic jets used as boundary-layer trips at Mach numbers of 6 and 8.5

The effect of discrete three-dimensional sonic jets used to promote transition on a sharp-leading-edge flat plate at Mach numbers of 6 and 8.5 and unit Reynolds numbers as high as 2.5 x 100,000 per cm in the Langley 20-inch hypersonic tunnels is discussed. An examination of the downstream flow-field distortions associated with the discrete jets for the Mach 8.5 flow was also conducted. Jet trips are found to produce lengths of turbulent flow comparable to those obtained for spherical-roughness-element trips while significantly reducing the downstream flow distortions. A Reynolds number based upon secondary jet penetration into a supersonic main flow is used to correlate jet-trip effectiveness just as a Reynolds number based upon roughness height is used to correlate spherical-trip effectiveness. Measured heat-transfer data are in agreement with the predictions.

Stone, D. R.↗

NASA NTRS1971

Radiolysis of water in sealed aluminum capsules - Its prediction and inhibition.

This report presents the results of an investigation into methods of inhibiting the radiolysis of water in sealed aluminum capsules in the Plum Brook Reactor of NASA. Experimental design techniques are employed to identify the measured effects of eight variables and their interactions which control water decomposition and the resultant pressure buildup. Multiple regression analyses are used to develop predictive models for the pressure rise observed in an inpile capsule system. Predictive equations are derived for pressure rise due to the radiolysis of water with air as a cover gas or with helium cover gas containing air as an impurity or mixtures of hydrogen, oxygen, and nitrogen as impurities. Radiation induced reaction products of nitrogen and oxygen are identified as the key to radiolysis behavior. The prevention of radiolysis depends on the exclusion of air or mixtures of nitrogen and oxygen from the system. Pure inert gases, helium, neon, and argon prove to be satisfactory radiolysis inhibitors. This is demonstrated for helium by inpile tests lasting up to 14 days (one reactor cycle) in the Plum Brook Reactor.

Sheibley, D. W.↗

NASA NTRS1972

Experimental investigation of two-phase heat transfer in a porous matrix.

One-dimensional two-phase flow transpiration cooling through porous metal is studied experimentally. The experimental data is compared with a previous one-dimensional analysis. Good agreement with calculated temperature distribution is obtained as long as the basic assumptions of the analytical model are satisfied. Deviations from the basic assumptions are caused by nonhomogeneous and oscillating flow conditions. Preliminary derivation of nondimensional parameters which characterize the stable and unstable flow conditions is given. Superheated liquid droplets observed sputtering from the heated surface indicated incomplete evaporation at heat fluxes well in access of the latent energy transport. A parameter is developed to account for the nonequilibrium thermodynamic effects. Measured and calculated pressure drops show contradicting trends which are attributed to capillary forces.

Von Reth, R.↗

NASA NTRS1972

Intracavity CdTe modulators for CO2 lasers.

The use of cadmium telluride as an electrooptic material for intracavity modulation of CO2 lasers is described. Included are the predicted and measured effects of CdTe intracavity modulators on laser performance. Coupling and frequency modulation are discussed and experimental results compared with theoretically predicted performance for both techniques. Limitations on the frequency response of the two types of modulation are determined.

Kiefer, J. E.↗

NASA NTRS1973

Supersonic Experiments on Dynamic Cross-Derivatives Due to Pitching and Yawing of Aircraft-Like Vehicles

A wind tunnel apparatus has been developed and constructed for the determination of moment cross-derivatives due to pitching and yawing on models at moderate angles of attack and sideslip. The apparatus can also be used to determine the direct moment derivatives in pitch and yaw. Experimental results were obtained at Mach 2 on a cone-wing-fin configuration at angles of attack and sideslip up to 15. Although at small values of these angles the cross-derivatives were always negligibly small, measureable effects were sometimes observed, at all angles of attack included in this investigation (i.e. up to 15 deg), when the angle of sideslip was 10 deg or 15 deg.

Orlik-Ruckemann, K. J.↗

NASA NTRS1972

Measurements of the growth of the ice budget in a persisting contrail.

An experiment was conducted with the NCAR Sabreliner to measure the ice water content (IWC) and the total ice budget within its contrail. Particle size distributions were measured with an optical-array particle size spectrometer. The experiment was performed in a region of the atmosphere void of natural ice crystals (cirrus) but estimated to be above ice saturation and favorable to ice crystal growth. The IWC measured was found to be in excess of 0.1 g/cu m near the contrail axis with average values of a few hundredths of a gram throughout the contrail. The measured water mass within the contrail was found to be four orders of magnitude greater than that computed as a combustion product. Average crystal sizes of nearly 0.5 mm allow for a transfer of moisture at generation level to much lower levels before reevaporation. Because of the magnitude of the measured effect and its believed frequent occurrence, the overall effect of subtropopause jet traffic is likely to lower the water abundance at the most traveled levels.

Knollenberg, R. G.↗

NASA NTRS1973

Knudsen effects in a Scott effect experiment.

A thermal torque sometimes observed in Scott effect measurements has been studied experimentally and an explanation for the thermal torque proposed. The magnitude of the thermal torque can be comparable to the Scott torque depending on geometrical and thermal anisotropies. The thermal torque is predicted to decrease with application of an axial magnetic field.

Wells, C. W.↗

NASA NTRS1975

Study of materials for space processing

Materials were selected for device applications and their commercial use. Experimental arrangements were also made for electrical characterization of single crystals using electrical resistivity and Hall effect measurements. The experimental set-up was tested with some standard samples.

Lal, R. B.↗

NASA NTRS1975

Investigation of scrubbing and impingement noise

Tests were conducted in an acoustic wind tunnel to determine surface pressure spectra and far field noise caused by turbulence impinging on an airfoil and turbulence convected past a sharp trailing edge. Measured effects of flow velocity and turbulence intensity were compared with predictions from several theories. Also, tests were conducted in an anechoic chamber to determine surface pressure spectra and far field noise caused by a deflected airfoil scrubbed by a subsonic jet. This installation simulated both an under-the-wing and an upper-surface-blowing externally blown flap, depending on the deflection angle. Surface and far field spectra, and cross correlation coherence and delay time, were utilized to infer the major noise-producing mechanisms.

Fink, M. R.↗

NASA NTRS1975

A noise study of the A-6 airplane and techniques for reducing its aural detection distance

A study was undertaken to determine the noise reduction potential of the A-6 airplane in order to reduce its aural detection distance. Static and flyby noise measurements were taken to document the basic airplane signature. The low-frequency noise which is generally most critical for aural detection was found to be broad-band in nature from this airplane, and its source is the turbojet engine exhaust. High-frequency compressor noise, which is characteristic of turbojet powerplants, and which is prominent at close range for this airplane, has no measurable effect on aural detection distance. The use of fluted-engine exhaust nozzles to change the far-field noise spectra is suggested as a possible means for reducing the aural detection distances. Detection distances associated with eight-lobe and four-lobe nozzles are estimated for a 1,000-foot altitude and grassy terrain to decrease from 4 miles to about 3 miles, and from 3 miles to about 2 miles for a 300-foot altitude and grassy terrain.

Hilton, D. A.↗

NASA NTRS1975

Langley Research Center entry aerothermodynamic technology development in support of Pioneer Venus multiprobe mission studies

A program of entry aerothermodynamics has been conducted to support the Pioneer Venus multiprobe mission. Aspects of the study include radiative property data, radiative blockage effectiveness measurements, heating calculations, aerodynamic and convective heating studies, and radio communications blackout models. Some of the historical background for the investigation is reviewed, and recommendations are made concerning the use of the developed technology in probe design and the continuation of certain elements of the program.

Olstad, W. B.↗

NASA NTRS1976

The use of LANDSAT-1 imagery in mapping and managing soil and range resources in the Sand Hills region of Nebraska

The author has identified the following significant results. Evaluation of ERTS-1 imagery for the Sand Hills region of Nebraska has shown that the data can be used to effectively measure several parameters of inventory needs. (1) Vegetative biomass can be estimated with a high degree of confidence using computer compatable tape data. (2) Soils can be mapped to the subgroup level with high altitude aircraft color infrared photography and to the association level with multitemporal ERTS-1 imagery. (3) Water quality in Sand Hills lakes can be estimated utilizing computer compatable tape data. (4) Center pivot irrigation can be inventoried from satellite data and can be monitored regarding site selection and relative success of establishment from high altitude aircraft color infrared photography. (5) ERTS-1 data is of exceptional value in wide-area inventory of natural resource data in the Sand Hills region of Nebraska.

Seevers, P. M.↗

NASA NTRS1976

A design approach and selected wind tunnel results at high subsonic speeds for wing-tip mounted winglets

Winglets, which are small, nearly vertical, winglike surfaces, substantially reduce drag coefficients at lifting conditions. The primary winglet surfaces are rearward above the wing tips; secondary surfaces are forward below the wing tips. This report presents a discussion of the considerations involved in the design of the winglets; measured effects of these surfaces on the aerodynamic forces, moments, and loads for a representative first generation, narrow body jet transport wing; and a comparison of these effects with those for a wing tip extension which results in approximately the same increase in bending moment at the wing-fuselage juncture as did the addition of the winglets.

Whitcomb, R. T.↗

NASA NTRS1976

Skin friction reduction by slot injection at Mach 0.8

Surface skin friction, boundary layer profiles and turbulent intensity due to axially symmetric tangential slot injection into a transonic boundary layer were measured. Effects of slot height, multiple slot injection, and injection mass flow rate on the surface skin friction downstream of the the slot have been investigated. Surface skin friction was a function of the injection mass flow rate for x/s 40. Large normal pressure gradient and relatively large turbulent intensity were found near the slot with small injection mass flow rate; the region the high turbulent intensity moved downstream with increasing injection mass flow rate. The results with two slot injections indicated that the distance between slots should be less than 30 slot heights in order to achieve some benefits from the first slot. Of significant importance in the present investigation is that the skin friction reduction obtained at transonic speed is of the same order as obtained in the hypersonic regime. Additional work is required in order to formulate a correlation between the turbulent intensity and the injection mass flow rate that may be used in future analysis.

Zakkay, V.↗

NASA NTRS1975

A general non-parametric classifier applied to discriminating surface water from terrain shadows

A general non-parametric classifier is described in the context of discriminating surface water from terrain shadows. In addition to using non-parametric statistics, this classifier permits the use of a cost matrix to assign different penalties to various types of misclassifications. The approach also differs from conventional classifiers in that it applies the maximum-likelihood criterion to overall class probabilities as opposed to the standard practice of choosing the most likely individual subclass. The classifier performance is evaluated using two different effectiveness measures for a specific set of ERTS data.

Eppler, W. G.↗

NASA NTRS1978

Low-cost ultrasonic lamb-wave transducer

Transducer propagates Lamb wave through thin aluminum sheet material. Model includes two elements that measure effects of damping and loading which, in turn, are indirectly equated to bond integrity. Transducer has been used to evaluate bond integrity of aluminum facing adhesively bonded to aluminum facing. Because of versatility, it is now possible to inspect many objects of different configurations that could not be reached with earlier transducers.

Kammerer, C. C.↗

NASA NTRS1977

Mossbauer spectroscopy of iron in the Luna 20 regolith

Results of the Mossbauer effect measurements on Fe-57 in the average sample of the Luna 20 regolith, and their comparison with similar measurements of the Luna 16 samples are presented. Room temperature measurements of the nonmagnetic as well as magnetic components of the spectra were performed. By careful least-squares analysis, six quadrupole doublets in the inner parts of spectra were resolved. According to their splittings, they were interpreted as four types of iron in silicates (olivine, two inequivalent pyroxene sites, and a glassy fraction) and two types of nonmagnetic iron-titanium oxides (ilmenite and a spinel). Velocity-window measurements, were used to determine the average nickel content of (2.01 plus or minus 0.84) wt. %. These results are discussed in terms of distribution of iron among different phases. In comparison with the Luna 16 sample, the Luna 20 sample contains more olivine and less ilmenite as well as metal with a slightly higher nickel content.

Zemcik, T.↗