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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 955 records · Page 53
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Comparative study of flare control laws

The development of a digital, three dimensional, automatic control law designed to achieve an optimal transition of a B-737 aircraft between glide slope conditions and the desired final touchdown condition is presented. The digital control law is a time invariant, state estimate feedback law, and the design is capable of using the microwave landing system. Major emphasis is placed on the reduction of aircraft noise in communities surroundings airports, the reduction of fuel consumption, the reduction of the effects of adverse weather conditions on aircraft operations, and the efficient use of airspace in congested terminal areas. Attention is also given to the development of the capability to perform automatic flares from steep glide slopes to precise touchdown locations.

Nadkarni, A. A.↗
NASA NTRS1981

Comparative analyses of space-to-space central power stations

The technological and economical impact of a large central power station in Earth orbit on the performance and cost of future spacecraft and their orbital transfer systems are examined. It is shown that beaming power to remote users cannot be cost effective if the central power station uses the same power generation system that is readily available for provision of onboard power and microwave transmission and reception of power through space for use in space is not cost competitive with onboard power or propulsion systems. Laser and receivers are required to make central power stations feasible. Remote power transmission for propulsion of orbital transfer vehicles promises major cost benefits. Direct nuclear pumped or solar pumped laser power station concepts are attractive with laser thermal and laser electric propulsion systems. These power stations are also competitive, on a mass and cost basis, with a photovoltaic power station.

Holloway, P. F.↗
NASA NTRS1981

Comparative cost assessment of planetary missions

A study to explore the cost differences resulting from implementing a series of representative solar system exploration missions in either ballistic or low-thrust flight modes is presented. Cost comparisons of missions using a solar electric propulsion delivery systems with ballistic equivalent mission designs were made. The mission set, cost elements, and delivery modes are detailed. Objectives for each of the six mission sets including two asteroid missions, a comet mission, a Mercury mission, and two outer planet missions are given.

Source record↗
NASA NTRS1982

Comparative analysis of the conceptual design studies of potential early commercial MHD power plants (CSPEC)

A conceptual design study of the MHD/steam plant that incorporates the use of oxygen enriched air preheated in a metallic heat exchanger as the combustor oxidant showed that this plant is the most attractive for early commercial applications. The variation of performance and cost was investigated as a function of plant size. The contractors' results for the overall efficiencies are in reasonable agreement considering the slight differences in their plant designs. NASA LeRC is reviewing cost and performance results for consistency with those of previous studies, including studies of conventional steam plants. LeRC in house efforts show that there are still many tradeoffs to be considered for these oxygen enriched plants and considerable variations can be made in channel length and level of oxygen enrichment with little change in overall plant efficiency.

Sovie, R. J.↗
NASA NTRS1980

Cloud top structure of a tornadic thunderstorm from 3 min interval stereo satellite images compared with radar and other observations

Cloud heights from 3 min interval GOES EAST/GOES WEST stereo pairs are shown to provide an important new tool for studying severe convective storms with potential for the detection of severe local storms. It is possible to use these data for observing cloud top structure as a function of time on a size scale of few kilometers with quantitative height measurements with relative and absolute accuracies on the order of + or - 0.5 km. It is noted that stereo height measurements detect cirrus anvil cloud decks at two altitudes corresponding to a lower stable layer and the main tropopause.

Hasler, A. F.↗
NASA NTRS1981

Comparative thermal fatigue resistance of several oxide dispersion strengthened alloys

The thermal fatigue resistance of several oxide dispersion strengthened (ODS) alloys has been evaluated through cyclic exposure in fluidized beds. The ODS nickel-base alloy MA 754 and ODS iron-base alloy MA 956 as well as four experimental ODS Ni-16Cr-4.5Al base alloys with and without Ta additions were examined. Both bare and coated alloys were subjected to up to 6000 cycles where each cycle consisted of a 3 minute immersion in a fluidized bed at 1130 C followed by a 3 minute immersion in a bed at 357 C. Testing revealed that the thermal fatigue resistance of the ODS nickel-base alloys was excellent and about equal to that of directionally solidified superalloys. However, the thermal fatigue resistance of MA 956 was found to be poor. Metallographic examination of tested specimens revealed that, in general, the post-test microstructures can be rationalized on the basis of previous diffusion, mechanical property, and oxidation studies.

Whittenberger, J. D.↗
NASA NTRS1981

Comparative analysis of CCMHD power plants

A study of Closed Cycle MHD (CCMHD) power generation systems has been conducted which emphasizes both advances in component conceptual design and overall system performance. New design data are presented for the high temperature, regenerative argon heaters (HTRH) and the heat recovery/seed recovery (HRSR) subsystem. Contamination of the argon by flue gas adsorbed in the HTRH is examined and a model for estimation of contamination effects in operating systems is developed. System performance and cost data have been developed for the standard CCMHD/steam cycle as powered by both direct fired cyclone combustors and selected coal gasifiers. In addition, a new CCMHD thermodynamic cycle has been identified.

Alyea, F. N.↗
NASA NTRS1980

Comparative petrology and origin of Governador Valadares and other nakhlites

The Governador Valadares is a cumulate augite achondrite showing many petrographic and geochemical similarities to the other known nakhlites, Nakhla and Lafayette. However, subtle differences in minor-element composition and textures suggest that each nakhlite is unique and probably represents a separate meteorite fall. Cumulus clinopyroxene compositions (En39FS23WO38) suggest crystallization from a common silica-saturated (tholeiite-like) liquid. Intercumulus mesostasis material shows evidence for a two-stage cooling history (slow, followed by quenching) and may represent highly fractionated, foreign pore liquid filtered into present nakhlites by compaction of lower-level cumulates.

Berkley, J. L.↗
NASA NTRS1980

The lunar regolith - Comparative petrology of the Apollo sites

A description is presented of the modal petrology of eight surface soils from the Apollo 11, 12, 14, 15, and 16 landing sites. One of the most striking features of the petrology of the considered soils is found to be the similarity in distribution of pyroxene composition between the soil and the local rock types. The considered investigation is concerned with certain difficulties with respect to an understanding of regolith evolution. Lunar soils contain material foreign to the local geology. The foreign material must have been transported over long distances. However, models of regolith formation on the moon indicate that lateral transport is inefficient. It is found in the investigation that the soil is predominantly of local derivation, that lateral homogenization is a minor process, that foreign material is present in the amounts indicated by bulk chemical mixing models, and that preferential transport of fine-grained material does not occur.

Labotka, T. C.↗
NASA NTRS1980

The lunar regolith - Comparative chemistry of the Apollo sites

In a grain-size study of various sections of the Apollo 17 drill core conducted by Laul et al. (1978, 1979), it was found that the fine fractions were consistently more enriched in highland material than the coarse fractions. Relative to the coarse fractions, the fine fractions contained 6-20% more KREEP material. In connection with these observations, an investigation was conducted to find out whether KREEP enrichment in fines occurs in soils from other sites. The investigation is also concerned with possibilities regarding any preferential lateral transport of the finest soil fractions relative to the coarser fractions. A description is presented of the chemical study of eight soils from five landing sites, taking into account also data on soil 70009 from the Apollo 17 drill core. Relative to the coarse fractions, no mare enrichment is found in the fines of highland soils. This argues strongly against preferential transport of fine fractions relative to coarse.

Laul, J. C.↗
NASA NTRS1980

The Apollo 16 regolith - Comparative petrology of the greater than 20 micron and 20-10 micron soil fractions, lateral transport and differential volatilization

The present investigation is concerned with questions regarding a preferential transport of finer-grained material on the lunar surface. Attention is also given to a possible appearance of volatization effects in the case of fine-grained glass beads. It is found that preferential lateral transport of fine-grained material is not efficient over the distances required to introduce mare material into the Apollo-16 (A-16) lunar highlands. The presence of granitic glasses found in the 20-10 micron fractions is attributed to comminution of mesostasis. The composition of mesostasis and the silica-rich phases contained within it reported by other investigators supports this conclusion. No evidence could be found of increased volatilization in the finer grained samples.

Kempa, M. J.↗
NASA NTRS1982

Low-latitude cloudiness and climate feedback - Comparative estimates from satellite data

Three studies of the relative albedo to the IR components of cloud amount feedback are reviewed, and an approach to the seasonal variability in low-level cloud numbers is presented. Comparisons are made and uncertainties calculated for the predictions of cloud amounts from satellite data sets for outgoing IR flux. IR data is used directly for a linear regression analysis and seasonal and latitudinal variations are considered in terms of monthly-annual means for particular latitude zones. Investigations of NOAA-NESS satellite data revealed that cirrus clouds are transparent in the 10.5-12.5 microns range and cloud albedos decrease at wavelengths greater than 0.7 micron, which suggests a possibility of cloud-sky and clear-sky albedo comparisons at 0.5-0.7 micron. The inclusion of Rayleigh scattering and atmospheric water vapor absorption of sunlight is recommended to test the effects on observed contracts.

Cess, R. D.↗
NASA NTRS1981

The optical and probe measurement of NO - A comparative study

Measurements were made of NO formation in both subsonic turbulent and nonturbulent media generated from gaseous and liquid fuels. Quartz and metallic, cooled and uncooled probes were employed, and optical measurements were made in the UV with narrow-line and continuum lamps. The extent of systematic error bias in these methods was studied over a wide range of conditions. High resolution measurements were made only on flat flames using a high pressure Xe lamp, while low resolution measurements were done with a hollow cathode lamp on flat flame, swirl burner and jet combustor exhausts. Optical data were reduced using a first principles spectral model and multiple zone treatment of the optical path. No major discrepancies related to processes occurring in probes were identified. Good agreement can be expected in measurements made in subsonic exhaust streams up to 2000 K.

Zabielski, M. F.↗
NASA NTRS1982

A comparative Rb-Sr, Sm-Nd, and K-Ar study of shocked norite 78236 - Evidence of slow cooling in the lunar crust

The sample 78236 was chipped from the top of a norite boulder at Station 8 by the Apollo 17 landing team. Jackson et al. (1975) concluded that this rock formed at a depth of 8-30 km in the lunar crust and suggested that it was excavated by a large basin-forming impact event. A petrographic description of the boulder is provided, and isotopic analyses are discussed. Attention is given to a chronology for 78236 which seems to be most consistent with radiometric and other evidence. It is proposed that cumulate norite 78236 formed deep in the lunar crust approximately 4.4 AE ago. The rock cooled slowly in the crust until it was excavated by a major basin-forming event. Excavation may have occurred about 4.2 AE ago, but the time of this event is not well constrained.

Nyquist, L. E.↗
NASA NTRS1982

The lunar regolith - Comparative studies of the Apollo and Luna sites. Petrology of soils from Apollo 17, Luna 16, 20, and 24

A progress report is presented concerning an investigation involving a comprehensive chemical and petrologic study of surface soils from all nine lunar sampling sites. The soils selected for this study are part of the lunar highlands soils suite and represent the soils at each site that contain abundant highland-derived material. The current report takes into consideration, in addition to the eight soils discussed by Labotka et al. (1980) and by Laul and Papike (1980), three Apollo 17 soils (72501, 76501, and 78221), and three Luna soils (21000, L-16; 22001, L-20; and 24999, L-24). Attention is given to the modal petrology of the 1000-90 micrometer fraction of all 14 soils, and the modes and mineral and glass chemistries of the 90-20 and 20-10 micrometer fractions of the Apollo 17 and Luna soils. In an evaluation of the obtained results, it is found that except for rare, large-scale impacts, lateral mixing is an inefficient process. Comminution and vertical mixing appear to be the dominant process.

Simon, S. B.↗
NASA NTRS1982

A study comparing several isocyanate and isothiocyanate derivatives of Porasil C for the separation of lower hydrocarbons by GC

Several isocyanate and isothiocyanate derivatives of Porasil C were synthesized and evaluated for the separation of the low-molecular-weight saturated and unsaturated hydrocarbons. It was shown that different functional groups significantly affect the retention behavior of the more polar unsaturated hydrocarbons, and that reproducible results can be obtained if dry carrier gas is used.

Pollock, G. E.↗