Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “cents”

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.

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

At least 739 records · Page 41
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Vibration characteristics of unidirectional filamentary composite material panels.

An experimental and analytical study of the vibration characteristics of a series of boron/epoxy composite panels with all layers having the same filament orientation has been conducted. Nodal patterns and natural frequencies are found to be highly dependent on the filament angle. Frequencies change by as much as 90 per cent with a 30-deg change in the filament angle. Measured damping coefficients are only moderately higher than those of comparative aluminum panels. There is no strong correlation between the filament angle and the amount of damping. In general, calculations based on a finite element mathematical model are in good agreement with the experimental data.

Clary, R. R.↗
NASA NTRS1972

A note on the calculation of photon loss in an image-tube scanner.

It is found that in the case of 500 image elements and system gains above 3000 only a few per cent of input photons will be lost. Photon loss is not excessive for even lower gains. Aperture variations within a fairly wide range have little effect on the loss. However, losses increase if dead time at the end of a sweep is permitted. A system with continuous sweep at the fastest possible rates is recommended for optimal results.

Mcnall, J. F.↗
NASA NTRS1972

Effects of bedrest and centrifugation of humans on serum thyroid function tests.

Changes in plasma volume and protein concentration have been reported when normal subjects are bedrested or centrifuged. Since thyroid hormones are transported by specific plasma proteins, each of these procedures could be expected to change plasma levels of these hormones. In this study centrifugation of normal healthy human subjects produced an increased concentration of total protein and albumin. When these same subjects were bedrested for six days, no change in total protein, albumin or thyroxine binding globulin were found although there was an eight per cent decrease in plasma volume. Centrifugation and, to a lesser extent, bedrest produced changes in serum T-4 levels and the T-3 test results. The direction of these changes (decreased % T-3 values and increased T-4 levels) indicate that these two situations produce an increased plasma concentration of thyroxine binding sites.

Leach, C. S.↗
NASA NTRS1972

Resonance scattering of the first positive system of N2 in the dayglow.

Rocket measurements of the differential photoelectron flux and the volume emission rate of the N2(0, 0) second positive band are used to calculate the daytime concentration of metastable A(super 3)Sigma(sub u)+ molecules, and consequently the resonance scattering contribution to the N2 first positive emission in the dayglow. The dominant source of N2 first positive emission is found to be photoelectron impact, with resonance scattering contributing only 10-20 per cent the total emission.

Feldman, P. D.↗
NASA NTRS1972

Effect of temperature on the tensile and creep characteristics of PRD49 fiber/epoxy composites.

Tensile and creep data of PRD49-I and -II fiber/epoxy-resin composites are presented. Tensile data were obtained from 20 to 477 K. Tensile strengths and moduli were determined at selected temperatures. Creep data up to 1000 hours are presented for fiber composites at 279, 422, and 450 K at stress levels of approximately 50 and 80 per cent of the ultimate tensile strength at 297 K. Details are presented of tensile specimens and test procedures used in the investigation.

Hanson, M. P.↗
NASA NTRS1972

Measurement of the neutral composition of the lower thermosphere above Fort Churchill by rocket-borne mass spectrometer.

Measurement of the neutral atmospheric composition above Fort Churchill, Canada (59 N, 94 W), by mass spectrometers in two rocket flights at 0835 CST on Feb. 4 and 6, 1969. A quantitative measure for the extent of agreement with static diffusive equilibrium is introduced, and substantial agreement with profiles predicted when static diffusive equilibrium was assumed is found for all constituents including helium. A sensitive search for atomic nitrogen yielded upper limits of a few per cent for one flight and of 0.2% for the other.

Hickman, D. R.↗
NASA NTRS1972

Monte Carlo treatment of Lyman-alpha radiation in a plane-parallel atmosphere.

A Monte Carlo technique involving Stokes vectors is used to obtain the state of polarization and intensity of solar Lyman-alpha photons as they diffuse through a plane-parallel homogeneous model of earth's hydrogen envelope. Fine structure of Lyman-alpha and Doppler redistribution of frequencies are taken into account. Comparison of the results with Heath's observed upper limit for polarization of 1.5 per cent implies an optical thickness tau greater than 7 and intensities of 8-10 kilorayleighs for a solar Lyman-alpha flux of 5.8 ergs per sq cm per sec.

Modali, S. B.↗
NASA NTRS1971

Photometric radii of Io and Europa.

Simultaneous two-color photoelectric photometry of Io and Europa performed during their eclipse by Jupiter on the night of April 5/6, 1971, is reported and discussed. The results are compared with satellite radii obtained using other observational techniques. It is concluded that the eclipse technique can be used to infer satellite radii accurate to plus or minus 10 per cent. In principle the eclipse technique can also be applied to the satellites of Saturn, Uranus, and Neptune for early objective determinations of their radii.

Price, M. J.↗
NASA NTRS1972

Plane elastostatic analysis of V-notched plates.

Solutions are given for several plane elastostatic problems of plates having a V-notch on one edge, and subjected to a variety of boundary conditions. The effect of the magnitude of the V-notch angle and specimen geometry on stress intensity factors KI and KII are obtained for unloaded notch surfaces. There is less than one per cent difference in opening model stress intensity factor in going from a zero degree notch angle to a 30 degree notch angle. Notch opening displacements at the plate edge were measured experimentally, and the results obtained were in excellent agreement with the computed results.

Gross, B.↗
NASA NTRS1972

Stopping rate of negative cosmic-ray muons near sea level.

A relatively simple method for measuring with high sensitivity the rate of stopped negative muons is described. A process in which Ar-37 is obtained from K-39 in connection with the stopping of a negative muon was used in the experiments. The Ar-37 activity can be measured in small proportional counters with extremely low backgrounds. It is possible to remove Ar-37 from potassium acetate powder at room temperature with almost 100 per cent efficiency merely by trapping the gas from the storage container with a charcoal trap at the liquid nitrogen temperature.

Spannagel, G.↗
NASA NTRS1972

Thermal protection optimization for the space shuttle.

This paper discusses optimal entry trajectories for the space shuttle that minimize the weight of an entry thermal protection system. The analysis was made using mathematical models of two types of thermal protection systems that were under consideration for the space shuttle: a metallic thermal protection system, and a reusable surface insulation thermal protection system. Optimal entries were generated using maximum orbiter nose temperature as a parameter. Thermal protection system weights were computed for both fixed and variable angles of attack using three-dimensional entry trajectories. Results indicated that variable angle-of-attack entries require less thermal protection system weight than entries at a constant angle of attack (35 deg) for both systems considered. Results also showed that 95 to 99 per cent of the thermal protection system weight requirement resulted from flight regimes in which the flow was still laminar.

Garcia, F., Jr.↗
NASA NTRS1973

Preliminary study of supersonic-transport configurations with low values of sonic boom

A parametric study of low-boom supersonic transport airplanes with conventional configurations was made to identify the features of specific configurations that promise relatively low sonic boom overpressures (less than 47.9 N/sq m). The range of values considered was gross weight from 28,300 to 170,000 kg; cruise Mach numbers of 2 to 3.2; and wing loadings of 1436, 2870, and 4309 N/sq m. Fuselage length was varied from 49.1 to 102.4 m and fuselage diameter from 2.75 to 3.98 m. A nominal Mach 2 configuration weighing 56,700 kg and having a wing loading of 2870 N/sq m was selected; and its gross geometric, aerodynamic, and structural features were estimated. At a cruise altitude of 18,300 m, lift-drag ratio was estimated to be 7.35, while sonic boom overpressure was 41.7 N/sq m. Takeoff thrust loading using four afterburning turbojet engines at maximum dry thrust was 0.32. Payload for a 4440-km range was 16.7 percent of gross weight, giving a direct operating cost of 0.82 cent per seat statute mile.

Dugan, J. F., Jr.↗
NASA NTRS1973

Preliminary study of an integral fan lift/cruise engine for a 100 passenger VTOL transport

A simplified mission analysis was performed to determine an optimum engine cycle for a 100-passenger VTOL transport with a range of 500 statute miles. The aircraft had a total of eight integral fan lift engines, three of which serve as cruise engines. Fan pressure ratio was varied from 1.2 to 1.3, overall pressure ratio from 7 to 13, and turbine inlet temperature from 2460 to 2860 R. Bypass ratio was selected to meet a 500-foot altitude flyover noise goal of 95 PNdB. Airplane gross weight and direct operating cost (DOC) were calculated. The lowest DOC of 1.82 cents per seat-mile was achieved with a fan pressure ratio of 1.3, overall pressure ratio of 12, and turbine inlet temperature of 2860 R.

Civinskas, K. C.↗
NASA NTRS1972

Investigation of the fracture mechanics of boride composites

Significant results were obtained in fabrication studies of the role of metallic additives of Zr, Ti, Ni, Fe and Cr on the densification of ZrB2. All elemental additions lower the processing temperatures required to effect full densification of ZrB2. Each addition effects enhanced densification by a clearly distinguishable and different mechanism and the resulting fabricated materials are different. A significant improvement in strength and fracture toughness was obtained for the ZrB2/Ti composition. Mechanical characterization studies for the ZrB2/SiC/C composites and the new ZrB2/Metal materials produced data relevant to the effect of impacting load on measured impact energies, a specimen configuration for which controlled fracture could occur in a suitably hard testing apparatus, and fracture strength data. Controlled fracture--indicative of measurable fracture toughness--was obtained for the ZrB2-SiC-C composite, and a ZrB2/Ti composite fabricated from ZrB2 with an addition of 30 weight per cent Ti. The increased strength and toughness of the ZrB2/Ti composite is consistent with the presence of a significantly large amount of a fine grained acicular phase formed by reaction of Ti with ZrB2 during processing.

Clougherty, E. V.↗
NASA NTRS1973

Application of ERTS-1 imagery in the fields of geology, agriculture, forestry, and hydrology to selected test sites in Iran

The preliminary study of the ERTS-1 imagery coverage of Iran, commenced on October 26, 1972. All of the images were carefully examined, and a photomosaic covering approximately ninety-five per cent of the country was prepared. A number of images of selected areas were studied in detail. In the field of geology, a number of large scale faults were identified, which do not figure on geological maps. Furthermore, a preliminary study was carried out on the recent sediments, their possible sources, and origin. A limited number of geological work maps were prepared as well. In the fields of agriculture and forestry, studies based on color composite prints of certain areas were undertaken, with a purpose of identifying potential arable areas. Investigations in the field of water resources resulted in the discovery of a number of small lakes, and streams. Furthermore, fluctuations of the water level in some lakes were observed.

Ebtehadj, K.↗
NASA NTRS1973

Carbon dioxide adsorbent study

A study was initiated on the feasibility of using the alkali metal carbonate - bi-carbonate solid-gas reaction to remove carbon dioxide from the atmosphere of an EVA life support system. The program successfully demonstrates that carbon dioxide concentrations could be maintained below 0.1 mole per cent using this chemistry. Further a practical method for distributing the carbonates in a coherent sheet form capable of repeated regeneration (50 cycles) at modest temperatures (423 K), without loss in activity was also demonstrated. Sufficiently high reaction rates were shown to be possible with the carbonate - bi-carbonate system such that EVA hardware could be readily designed. Experimental and design data were presented on the basis of which two practical units were designed. In addition to conventional thermally regenerative systems very compact units using ambient temperature cyclic vacuum regeneration may also be feasible. For a one man - 8 hour EVA unit regenerated thermally at the base ship a system volume of 14 liters is estimated.

Onischak, M.↗
NASA NTRS1972

Circular polarimetry of fifteen interesting objects.

The results of a search are presented for circular polarization of visible light in 15 objects, including two eclipsing binaries, six magnetic Ap stars, three planetary nebulae, Hubble's Nebula, M87, Sirius, and the Orion A region. On the whole, the results were null, down to typical upper limits for q of 0.01 per cent. A complete description of the used photoelastic polarimeter is given, with special attention to the incidental linear-circular conversion.

Kemp, J. C.↗
NASA NTRS1972

Durability tests of a five-centimeter diameter ion thruster system.

A modified Hughes SIT-5 system is being tested for durability at the Lewis Research Center. As of Oct. 1, 1972, the thruster subsystem has logged over 8000 hours of operation. The initial 2023 hours were run with a translating screen thrust vector grid. The thruster is currently operating with an electrostatic type vector grid. Profiles and maps taken at widely separated intervals show that performance and operating characteristics have remained essentially constant. Overall efficiency is about 32 per cent and power to thrust ratio is 170 watts per millipound at a specific impulse of 2500 seconds. Telescopic examination of the vector grid shows some sputtering erosion due to charge exchange and direct impingement ions. An independent test of the propellant storage and cathode-isolator-vaporizer subsystem has demonstrated good reliability under simulated thruster operating conditions.

Nakanishi, S.↗