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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 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

EMI survey for maritime satellite, L-band, shipboard terminal

The United States Lines 15,690-ton commercial-container ship, American Alliance, was selected as lead ship for an onboard EMI survey prior to installation of L-Band shipboard terminals for operation with two, geostationary, maritime satellites. In general, the EMI survey revealed tolerable interference levels onboard ship: radiometer measurements indicate antenna-noise temperatures less than 70 K, at elevation angles of 5 deg and greater, at 1559 MHz, at the output terminals of the 1.2-m-diameter, parabolic-dish antenna for the L-Band shipboard terminal. Other EMI measurements include field intensity from 3 cm- and 10 cm-wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars.

Taylor, R. E.↗
NASA NTRS1975

SEASAT economic assessment. Volume 7: Marine transporation case study

The studies conducted of the potential use of SEASAT ocean condition data and resulting forecasts by dry cargo ships and tankers reached the following conclusions. The SEASAT ocean condition data and resulting forecasts could be usefully employed to route ships around storms, thereby resulting in reduced adverse weather damage, time loss and the related operating costs, and occasional catastrophic losses. These benefits are incremental benefits beyond those which present and future conventional ship routing procedures can supply. The values of the benefits are listed.

Source record↗
NASA NTRS1975

L-band maritime experiments

Results are presented for the technical experiments conducted by the U.S. Maritime Administration (MARAD) using the ATS-6 satellite operating in the L-band fan beam mode. The MARAD experiments were conducted with satellite terminals placed on two commercial ships for evaluation of the communication service similar to that which will be available with a maritime commercial satellite system. Evaluation of position determination with a satellite was also made. Three modems having voice and digital data and a stabilized shipboard L-band antenna system were assessed. The ship antenna demonstrated successful tracking of the satellites for test period intervals of 4 to 6 hr without the need for operator adjustment. The ship position determination tests showed good measurement repeatability. The data analyzed supported the ability of future commercial satellite systems to achieve a probability of bit error of better than 0.00001.

Brandel, D. L.↗
NASA NTRS1977

Review of US Navy VSTOL handling qualities requirements

Handling qualities requirements for V/STOL operations from small ships are considered in terms of the ship operating environment. Turbulence, wind over the deck, ship motion, visibility, and severe weather and sea conditions are among the factors discussed.

Hutchings, D. E.↗
NASA NTRS1977

Active microwave measurement from space of sea-surface winds

Radar backscatter measurements from the ocean were made at 13.9 GHz from Skylab. The radar signal increased rapidly with wind speed over the entire range of winds encountered, and for angles of incidence of 30 deg larger. Signals observed were normalized to a nominal incidence angle and to a nominal upwind observation direction, using a theoretical model that has been verified as approximately true with aircraft experiments. Observations during the summer and winter Skylab missions were treated separately because of possible differences caused by an accident to the antenna between the two sets of observations. The results are in general agreement with the theory in all cases. The objective analysis method used for determining surface-truth winds in the Skylab experiment was tested by comparing results obtained at weather ships with the observations made by the weather ships themselves. In most cases, the variance about the regression line between objective analysis and weather-ship data actually exceeded that about the regression line between objective analysis and backscatter data

Young, J. D.↗
NASA NTRS1977

EMI survey for maritime satellite 1535-1645-MHz shipboard terminal

A 15,690-ton commercial container ship was selected as lead ship for an onboard electromagnetic-interference (EMI) survey prior to installation of 1535-1645-MHz (L-Band) shipboard terminals for communication via a maritime satellite. In general, the EMI survey revealed tolerable interference levels on board ship. Radiometer measurements indicate antenna-noise temperatures less than 70 K at elevation angles of 5 deg and greater at 1559 MHz at the output terminals of the 1.2-m diameter parabolic-dish antenna for the L-band shipboard terminal. Other EMI measurements include field intensity from 3-cm and 10-cm wavelength pulse radars, and conducted-emission tests of primary power lines to both onboard radars.

Taylor, R. E.↗
NASA NTRS1980

The winds of the comparison data set for the Seasat Gulf of Alaska Experiment

Ship and data buoy winds used for comparison in the validation of Seasat-derived winds are described in terms of the time series of hourly wind observations from the buoys and in terms of the techniques used to produce 20- and 30-min average winds from the ships. Attention is given to the comparison data, the synoptic scale wind, turbulence concepts, the data buoy winds, Ocean Weather Station PAPA, the oceanographer data, and the results from Ocean Station PAPA Ship Quadra and from the oceanographer. Sources of scatter in the comparison data are reviewed.

Pierson, W. J.↗
NASA NTRS1983

VTOL shipboard letdown guidance system analysis

Alternative letdown guidance strategies are examined for landing of a VTOL aircraft onboard a small aviation ship under adverse environmental conditions. Off line computer simulation of shipboard landing task is utilized for assessing the relative merits of the proposed guidance schemes. The touchdown performance of a nominal constant rate of descent (CROD) letdown strategy serves as a benchmark for ranking the performance of the alternative letdown schemes. Analysis of ship motion time histories indicates the existence of an alternating sequence of quiescent and rough motions called lulls and swells. A real time algorithms lull/swell classification based upon ship motion pattern features is developed. The classification algorithm is used to command a go/no go signal to indicate the initiation and termination of an acceptable landing window. Simulation results show that such a go/no go pattern based letdown guidance strategy improves touchdown performance.

Phatak, A. V.↗
NASA NTRS1985

Large-scale sea surface temperature variability from satellite and shipboard measurements

A series of satellite sea surface temperature intercomparison workshops were conducted under NASA sponsorship at the Jet Propulsion Laboratory. Three different satellite data sets were compared with each other, with routinely collected ship data, and with climatology, for the months of November 1979, December 1981, March 1982, and July 1982. The satellite and ship data were differenced against an accepted climatology to produce anomalies, which in turn were spatially and temporally averaged into two-degree latitude-longitude, one-month bins. Monthly statistics on the satellite and ship bin average temperatures yielded rms differences ranging from 0.58 to 1.37 C, and mean differences ranging from -0.48 to 0.72 C, varying substantially from month to month, and sensor to sensor.

Bernstein, R. L.↗
NASA NTRS1985

Blended SST fields combined SMMR/ship data (summary of technique)

All remote sensors have bias problems which vary in space and time. The infrared measurements are very sparse in cloudy areas: the SMMR has coverage limitations due to the interference of land areas and only half time operation. If one simply averaged the data from these various sources, the combination of the biases and varying sampling would introduce artifacts into the analyzed product which would reflect the sampling and which could be quite misleading. The remote sensors provide reasonable estimates of gradients of SST over length scales greater than the sensor resolution but smaller than hemispheric. Ships can be considered unbiased but are poorly distributed on small scales except in the densest shipping lanes. An analysis scheme based on a suggestion by Holl was developed which exploits just this approximately complementarity to provide an improved SST analysis. The resulting accuracy appears to be in the required approx. 0.5 C range for the particular case of using SMMR and ship data to produce two degree latitude by two degrees longitude monthly analyses.

Wilheit, T. T.↗
NASA NTRS1985

Assessing the capability of EOS sensors in measuring ocean-atmosphere moisture exchange

As part of the Science Synergism Studies to identify interdisciplinary Scientific studies, which could be addressed by the Environmental Observing System (EOS), the techniques being developed to measure ocean-atmosphere moisture exchanges using satellite sensors were evaluated. Studies required to use sensors proposed for EOS were examined. A method has been developed to compute the moisture flux using the wind speed, sea surface temperature, and preciptable water measured by satellite sensors. It relies on a statistical model which predicts surface-level humidity from precipitable water. The Scanning Multichannel Microwave Radiometer (SMMR) measures all 3 parameters and was found to be sensitive to the annual cycle and large interannual variations such as the 1982 to 1983 El Nino. There are systematic differences between geophysical parameters measured by Nimbus/SMMR and in situ measurements. After quadratic trends and crosstalks were removed from the parameters through multivariate regressions, the latent heat fluxes computed from SMMR agree with those computed from ship reports to within 30 W/sq m. The poor quality of ship reports may be the cause of a portion of this scatter. Similar results are found using SEASAT/SMMR data. When the scatterometer winds were used instead of the SMMR winds, the difference between the satellite fluxes and the ship fluxes was reduced.

Liu, W. T.↗
NASA NTRS1985

Large-scale sea surface temperature variability from satellite and shipboard measurements

A series of satellite sea surface temperature intercomparison workshops were conducted under NASA sponsorship at the Jet Propulsion Laboratory. Three different satellite data sets were compared with each other, with routinely collected ship data, and with climatology, for the months of November 1979, December 1981, March 1982, and July 1982. The satellite and ship data were differenced against an accepted climatology to produce anomalies, which in turn were spatially and temporally averaged into two-degree latitude-longitude, one-month bins. Monthly statistics on the satellite and ship bin average temperatures yielded rms differences ranging from 0.58 to 1.37 C, and mean differences ranging from -0.48 to 0.72 C, varying substantially from month to month, and sensor to sensor.

Bernstein, R. L.↗
NASA NTRS1989

The browse file of NASA/JPL quick-look radar images from the Loch Linnhe 1989 experiment

The Jet Propulsion Laboratory (JPL) Aircraft Synthetic Aperture Radar (AIRSAR) was deployed to Scotland to obtain radar imagery of ship wakes generated in Loch Linnhe. These observations were part of a joint US and UK experiment to study the internal waves generated by ships under partially controlled conditions. The AIRSAR was mounted on the NASA-Ames DC-8 aircraft. The data acquisition sequence consisted of 8 flights, each about 6 hours in duration, wherein 24 observations of the instrumented site were made on each flight. This Browse File provides the experimenters with a reference of the real time imagery (approximately 100 images) obtained on the 38-deg track. These radar images are copies of those obtained at the time of observation and show the general geometry of the ship wake features. To speed up processing during this flight, the images were all processed around zero Doppler, and thus azimuth ambiguities often occur when the drift angel (yaw) exceeded a few degrees. However, even with the various shortcomings, it is believed that the experimenter will find the Browse File useful in establishing a basis for further investigations.

Brown, Walter E., Jr.↗
NASA NTRS1991

Heterogeneous distributed databases: A case study

Alternatives are reviewed for accessing distributed heterogeneous databases and a recommended solution is proposed. The current study is limited to the Automated Information Systems Center at the Naval Sea Combat Systems Engineering Station at Norfolk, VA. This center maintains two databases located on Digital Equipment Corporation's VAX computers running under the VMS operating system. The first data base, ICMS, resides on a VAX11/780 and has been implemented using VAX DBMS, a CODASYL based system. The second database, CSA, resides on a VAX 6460 and has been implemented using the ORACLE relational database management system (RDBMS). Both databases are used for configuration management within the U.S. Navy. Different customer bases are supported by each database. ICMS tracks U.S. Navy ships and major systems (anti-sub, sonar, etc.). Even though the major systems on ships and submarines have totally different functions, some of the equipment within the major systems are common to both ships and submarines.

Stewart, Tracy R.↗
NASA NTRS1992

Data availability and data archeology from the former Soviet Union

Acquisition of data on the ocean is believed to start in 1872, when the Royal Navy ship 'Challenger' performed oceanographic stations in its round-world voyage (1872-1876). The first oceanographic studies of the World Ocean refer to the 80s second half of the 19th century. During its round-world expedition 'Vityaz' (1886-1889) headed by S.O. Markov, performed hydrological measurements in the Baltic Sea, Atlantic and Pacific Oceans. According to information available the regular expedition observations (prototype of future complex international program on the ocean research) started in the second half of 80s last century under the auspice of Kiev commission for exploration of German Seas. Systematic hydrological observations were organized by Hydrographic Department of Russia in 1876-1879 according to the program similar to the Kiev one and observations were regularly made by ships of custom service over the Russian area of the Baltic Sea. The increasing demands in oceanographic data contributed to considerable progress in exploration of the World Ocean during current century whole tendency to increase and become more significant has been observed for the last 30-40 years. Most probably various expeditions which were carried out during International Geophysical Year in different regions of the World Ocean are to be reference point in performing intensive oceanographic observations of Marine environment. In the former USSR oceanographic observations are made by research and hydrographic vessels, commercial and fishery ships as well as oil production platforms, coastal hydrometeorological station and other observing platforms. Oceanographic observations data, available from main sources of information on the ocean-research vessels, are also considered in the report.

Sychev, Yuri↗
NASA NTRS1993

Radar backscatter measurements from Arctic sea ice during the fall freeze-up

Radar backscatter measurements from sea ice during the fall freeze-up were performed by the United States Coast Guard Icebreaker Polar Star as a part of the International Arctic Ocean Expedition (IAOE'91) from Aug. to Sep. 1991. The U.S. portion of the experiment took place on board the Polar Star and was referred to as TRAPOLEX '91 (Transpolar expedition) by some investigators. Before prematurely aborting its mission because of mechanical failure of her port shaft, the Polar Star reached 84 deg 57 min N latitude at 35 deg E longitude. The ship was in the ice (greater than 50 percent coverage) from 14 Aug. until 3 Sep. and was operational for all but 6 days due to two instances of mechanical problems with the port shaft. The second was fatal to the ship's participation in the expedition. During the expedition, radar backscatter was measured at C-band under a variety of conditions. These included measurements from young ice types as well as from multiyear and first-/second-year sea ice during the fall freeze-up. The sea ice types were determined by measurement of the ice properties at several of the stations and by visual inspection on others. Radar backscatter measurements were performed over a large portion of the ship's transit into the Arctic ice pack. These were accompanied by in situ sea ice property characterization by the U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) at several stations and, when snow was present, its properties were documented by The Microwave Group, Ottawa River (MWG).

Beaven, S.↗
NASA NTRS1992

Oceanwide gravity anomalies from Geos-3, Seasat and Geosat altimeter data

Three kinds of satellite altimeter data have been combined, along with 5 x 5 arcmin bathymetric data, to calculate a 0.125 deg ocean wide gridded set of 2.3 x 10 exp 6 free-air gravity anomalies. The procedure used was least squares collocation that yields the predicted anomaly and standard deviation. The value of including the bathymetric data was shown in a test around the Dowd Seamount where the root mean square (rms) difference between ship gravity measurements decreased from +/- 40 mgal to +/- 20 mgal when the bathymetry was included. Comparisons between the predicted anomalies and ship gravity data is described in three cases. In the Banda Sea the rms differences were +/- 20 mgal for two lines. In the South Atlantic rms differences over lines of 2000 km in length were +/- 7 mgal. For cruise data in the Antarctica region the discrepancies were +/- 12 mgal. Comparisons of anomalies derived from the Geosat geodetic mission data by Marks and McAdoo (1992) with ship dta gave differences of +/- 6 mgal showing the value of the much denser Geosat geodetic mission altimeter data.

Rapp, Richard H.↗
NASA NTRS1925

Forces on Airships in Gusts

In this report it is shown that determining the instantaneous angle of pitch, the acceleration of the gust is as important as its maximum velocity or yaw. Hitherto it has been assumed that the conditions encountered in gusts could be approximately represented by considering the airship to be at an instantaneous angle of yaw or pitch (according to whether the gust is horizontal or vertical), the instantaneous angle being tan to the (-1) power (v/v), where v is the component of the velocity of the gust at right angles to the longitudinal axis of the ship, and v is the speed of the ship. An expression is derived for this instantaneous angle in terms of the speed and certain aerodynamic characteristics of the airship, and of the maximum velocity and the acceleration of the gust, and the application of the expression to the determination of the forces on the ship is illustrated by numerical examples.

Burgess, C P↗