Search NASA⌕ Search

SEARCH · Search NASA

Results for “NETHERLANDS”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

An evaluation of proposed acoustic treatments for the NASA LaRC 4 x 7 meter wind tunnel

The NASA LaRC 4 x 7 Meter Wind Tunnel is an existing facility specially designed for powered low speed (V/STOL) testing of large scale fixed wing and rotorcraft models. The enhancement of the facility for scale model acoustic testing is examined. The results are critically reviewed and comparisons are drawn with a similar wind tunnel (the DNW Facility in the Netherlands). Discrepancies observed in the comparison stimulated a theoretical investigation using the acoustic finite element ADAM System, of the ways in which noise propagating around the tunnel circuit radiates into the open test section. The reasons for the discrepancies noted above are clarified and assists in the selection of acoustic treatment options for the facility.

Abrahamson, A. L.↗
NASA NTRS1983

Cryogenic infrared imaging beryllium telescope for Infrared Astronomical Satellite (IRAS)

The IRAS mission is the result of an international project involving the cooperation of the U.S., the United Kingdom, and the Netherlands. The Infrared Astronmical Satellite was placed into orbit on January 25, 1983. Its main function is to provide a survey of the entire sky as viewed in four octaves of infrared radiation in the wavelenth region from 8 to 120 microns. The cylindrical structure of the satellite contains a large dewar vessel with 70 liters of superfluid helium. The helium has the function to maintain the contents of the vessel at 2.5 K for the duration of the mission. The IRAS optics is a Ritchey-Chretien telescope of 24 inches aperture. Because of the operational requirements of the mission, it had been specified that all optical components should be beryllium. Attention is given to the cold performance test conducted with IRAS, plans for future infrared telescopes, and reflectance limits.

Devereux, W. P.↗
NASA NTRS1984

The first orbiting astronomical infrared telescope system Its development and performance

The Infrared Astronomical Satellite (IRAS) was launched on January 25, 1983, and has provided astronomers with their first extended views of the universe in the 8 to 120 micron wavelength region. The infrared telescope system is one of several United States contributions to this international project sponsored by the U.S.A., The Netherlands, and the U.K. This telescope employs four bands of detectors cooled to 2.4 K to achieve a noise equivalent flux density in the 10 to the -18th to 10 to the -19th watts/sq cm range and will operate for approximately eleven months before depletion of its supply of superfluid helium. This paper describes major problems, early flight results, and technical lessons learned during the course of the telescope's development and flight operations.

Conrad, A. G.↗
NASA NTRS1984

IRAS observations of cometary dust

It is pointed out that solid material present in the coma and tail of a comet is revealed by the scattering of sunlight and thermal emission of absorbed solar radiation. The large beam size and low background of the cold Infrared Astronomy Satellite (IRAS) telescope make it extremely well suited to the measurement of faint diffuse thermal emission from solid grains associated with comets. The IRAS project was conducted jointly by the Netherlands, the United Kingdom, and the U.S. Its basic objective involved a survey of the sky in four wavelength regions centered on 12, 25, 60, and 100 microns. The present paper is mainly concerned with IRAS observations of the coma-nucleus regions as defined by the maximum in the intensity distribution. Attention is given to circumstances of comet observations, dust production rates, and a discussion of the results.

Walker, R. G.↗
NASA NTRS1986

An overview of Dutch participation in the Spacelab D1 mission and the Columbus Space Station Project

Articles and a few short descriptions of recent developments in the field of space travel are discussed. Information on research and technology in space to facilitate contact between these two fields is provided. A description is given of the successful Spacelab D-1 flight and the standard instrument package. The Netherlands experiments in the D-1 mission, the next Spacelab flights, and the Columbus program are discussed.

Source record↗
NASA NTRS1985

A catalog of ultraviolet interstellar extinction excesses for 1415 stars

Ultraviolet interstellar extinction excesses are presented for 1415 stars with spectral types B7 and earlier. The excesses with respect to V are derived from Astronomical Netherlands Satellite (ANS) 5-channel UV photometry at central wavelengths of approximately 1550, 1800, 2500, and 3300 A. A measure of the excess extinction in the 2200-A extinction bump is also given. The data are valuable for investigating the systematics of peculiar interstellar extinction and for studying the character of UV interstellar extinction in the general direction of stars for which the extinction-curve shape is unknown.

Savage, B. D.↗
NASA NTRS1986

Relationships between dust grain components responsible for observed interstellar extinction and polarization

Ultraviolet extinction properties of interstellar dust are well observed. The amount of extinction measured in the visible (E(B-V)), at the 2200 A feature (E(BUMP)), and in the far ultraviolet (E(1550-V)) are only vaguely correlated indicating that at least 3 fairly independent populations of grains contribute to the overall extinction curve. A search of literature was made for polarimetric observations of the 1415 stars included in the extinction catalog derived from the Astronomical Netherlands Satellite (ANS) data. It was found that about 900 of the stars had at least one unfiltered polarimetric observation, p (%). In addition, 150 stars had calculated values of lambda sub max (wavelength at which maximum polarization occurs). The lambda sub max and p/E(B-V) parameters are discussed.

Clayton, G. C.↗
NASA NTRS1986

A comparison of the acoustic and aerodynamic measurements of a model rotor tested in two anechoic wind tunnels

Two aeroacoustic facilities--the CEPRA 19 in France and the DNW in the Netherlands--are compared. The two facilities have unique acoustic characteristics that make them appropriate for acoustic testing of model-scale helicopter rotors. An identical pressure-instrumented model-scale rotor was tested in each facility and acoustic test results are compared with full-scale-rotor test results. Blade surface pressures measured in both tunnels were used to correlated nominal rotor operating conditions in each tunnel, and also used to assess the steadiness of the rotor in each tunnel's flow. In-the-flow rotor acoustic signatures at moderate forward speeds (35-50 m/sec) are presented for each facility and discussed in relation to the differences in tunnel geometries and aeroacoustic characteristics. Both reports are presented in appendices to this paper. ;.);

Boxwell, D. A.↗
NASA NTRS1986

Solar VLBI

In April, 1981, radio telescopes at Dwingeloo (The Netherlands) and Onsala (Sweden) were used as a long-baseline interferometer at a wavelength of 18 cm. The baseline of 619 km gave a spatial resolution on the Sun of about 45 km. The major problems of Solar Very Long Baseline Interferometry are discussed.

Tapping, K. F.↗
NASA NTRS1986

A comparison of the acoustic and aerodynamic measurements of a model rotor tested in two anechoic wind tunnels

Two aeroacoustic facilities - the CEPRA 19 in France and the DNW in the Netherlands - are compared. The two facilities have unique acoustic characteristics that make them appropriate for acoustic testing of model-scale helicopter rotors. An identical pressure-instrumented model-scale rotor was tested in each facility and acoustic test results are compared with full-scale-rotor test results. Blade surface pressures measured in both tunnels were used to correlated nominal rotor operating conditions in each tunnel, and also used to assess the steadiness of the rotor in each tunnel's flow. In-the-flow rotor acoustic signatures at moderate forward speeds (35-50 m/sec) are presented for each facility and discussed in relation to the differences in tunnel geometries and aeroacoustic characteristics. Both reports are presented in appendices to this paper.

Boxwell, D. A.↗
NASA NTRS1986

Characteristics and performance of the ESTEC large space simulator cryogenic system

The final concept and performance characteristics of the Large Space Simulator (LSS) at ESTEC, The Netherlands are discussed. The LSS cryogenics system has proven its operational capabilities under simulated heat load conditions and provides sufficient margin for future elevated requirements. The acceptance test proved that nominal operating pressures can be lower than the design parameters, providing increased system safety and reliability. The ease of access for repair and the incorporated redundancy will limit system downtime. Finally, the system design resulted in a low consumption of LN sub 2, which is an important factor in keeping the operational costs at a low level.

Amlinger, H.↗
NASA NTRS1989

Design and status of the detector block for the ISO-SWS

The Short Wave Spectrometer (SWS) is one of the two spectrometers for the Infrared Space Observatory (ISO). It consists of a pair of grating spectrometers and a Fabry-Perot interferometer. Together, the grating spectrometers cover the wavelength range 2.4 to 45 microns, at a resolution between 1000 and 2000. The Fabry-Perot interferometer, in series with one of the grating spectrometers, provides a resolution of about 20,000 at the wavelengths between 15 and 35 microns. The SWS is being built by the Space Research Organization of the Netherlands and the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. The spectrometer has 52 discrete detectors, most of which are bulk detectors. In the design of the spectrometer, the main emphasis is on the sensitivity of the individual channels, rather than on the number of detectors. This was one of the main reasons to select non-destructive read-out circuits, with a separate heated-JFET pre-amplifier for each individual detector. The signals are amplified and filtered in parallel. The engineering tests on the SWS detector block have not yet been completed. The design of the detector block is described and the present problem areas are indicated.

Luinge, W.↗
NASA NTRS1990

International programs - A growing trend

The National Aeronautics and Space Administration has collaborated successfully in space science missions with a multiplicity of partners, including the European Space Agency, Federal Republic of Germany, the Netherlands, United Kingdom, Japan, and the Soviet Union, among others. These collaborations generally arise out of common scientific goals and in the interest of economizing to take advantage of skills and capabilities among the partners. A trend towards increased cooperation in space is expected to continue as the global scientific community works together to plan future space science missions and the missions become more sophisticated.

Bunner, A. N.↗
NASA NTRS1990

The acoustic results of a United Techologies scale model helicopter rotor tested at DNW

An initial summary is presented of the acoustic measurements acquired for some of the different configurations of a 1/6 geometrically and aeroelastically scaled UTC model helicopter rotor which was tested in the open-jet anechoic test section of the Duits-Nederlandse Windtunnel in the Netherlands. Of particular interest are high-speed impulsive noise and blade-vortex interaction. An analysis is provided of baseline swept tip rotor acoustic characteristics in the regimes of high-speed forward flight, where high-speed impulsive noise dominates, and low-speed descent, where severe blade vortex interaction noise occurs. Also discussed are more recent studies of data which involve the animation of the acoustic field upstream of the rotor to evaluate the detailed radiation patters caused by BVI and HSI noise sources. The trends of these primary noise sources are examined as the first step in validating the data for release and application.

Liu, Sandy R.↗
NASA NTRS1990

The acoustic results of a United Technologies scale model helicopter rotor tested at DNW

In a major cooperative program between U.S. Government agencies (represented by the U.S. Army Aeroflightdynamics Directorate and NASA Ames and Langley Research Centers) and United Technologies Corp., a 1/6 geometrically and aeroelastically scaled UTC model helicopter rotor was tested in the open-jet anechoic test section of the Duits-Nederlandse Windtunnel in the Netherlands. As the fourth entry under the Aerodynamic and Acoustic Testing of Model Rotors Program, several comprehensive acoustic and aerodynamic databases were obtained relating the important aerodynamic phenomena to both the near- and far-field acoustic radiation. In particular, high speed impulsive noise and blade-vortex interaction are of primary interest. This paper provides an initial summary of the acoustic measurements acquired for some of the different configurations tested. A review of the baseline swept tip rotor acoustic characteristics in the regimes of high speed forward flight, where high speed impulsive noise dominates, and low speed descent, where severe blade vortex interaction noise occurs, is presented. The trends of these primary noise sources are studied as the first step in validating the data for release and application.

Liu, Sandy R.↗
NASA NTRS1991

Relationship between gas exchange, wind speed, and radar backscatter in a large wind-wave tank

The relationships between the gas exchange, wind speed, friction velocity, and radar backscatter from the water surface was investigated using data obtained in a large water tank in the Delft (Netherlands) wind-wave tunnel, filled with water supersaturated with SF6, N2O, and CH4. Results indicate that the gas-transfer velocities of these substances were related to the wind speed with a power law dependence. Microwave backscatter from water surface was found to be related to gas transfer velocities by a relationship in the form k(gas) = a 10 exp (b A0), where k is the gas transfer velocity for the particular gas, the values of a and b are obtained from a least squares fit of the average backscatter cross section and gas transfer at 80 m, and A0 is the directional (azimuthal) averaged return.

Wanninkhof, Richard H.↗
NASA NTRS1991

Airborne precursor missions in support of SIR-C/X-SAR

The NASA DC-8 and DLR E-SAR airborne imaging radars have been deployed over several sites in Europe and the U.S. in support of SIR-C/X-SAR (Shuttle Imaging Radar-C/X-Synthetic Aperture Radar) science team investigations. To date, data have been acquired in support of studies of alpine glaciers, forests, geology, oceanography, and calibration. An experimental campaign with airborne sensors will take place in Europe in June to July 1991 which will allow multitemporal surveys of several Europeans sites. Current plans are for calibration and ecology experiments to be undertaken in Germany, the Netherlands, Italy, France, and the United Kingdom. Coordinated multitemporal aircraft and ground campaigns are planned in support of hydrology experiments in Italy, the United Kingdom, and Austria. Data will also be acquired in support of oceanogrqhy in the Gulf of Genova, North Atlantic, Straits of Messina and the North Sea. Geology sites will include Campi Flegrei and Vesuvio, Italy.

Evans, D.↗
NASA NTRS1991

Multi-frequency and polarimetric radar backscatter signatures for discrimination between agricultural crops at the Flevoland experimental test site

We describe the calibration and analysis of multi-frequency, multi-polarization radar backscatter signatures over an agriculture test site in the Netherlands. The calibration procedure involved two stages: in the first stage, polarimetric and radiometric calibrations (ignoring noise) were carried out using square-base trihedral corner reflector signatures and some properties of the clutter background. In the second stage, a novel algorithm was used to estimate the noise level in the polarimetric data channels by using the measured signature of an idealized rough surface with Bragg scattering (the ocean in this case). This estimated noise level was then used to correct the measured backscatter signatures from the agriculture fields. We examine the significance of several key parameters extracted from the calibrated and noise-corrected backscatter signatures. The significance is assessed in terms of the ability to uniquely separate among classes from 13 different backscatter types selected from the test site data, including eleven different crops, one forest and one ocean area. Using the parameters with the highest separation for a given class, we use a hierarchical algorithm to classify the entire image. We find that many classes, including ocean, forest, potato, and beet, can be identified with high reliability, while the classes for which no single parameter exhibits sufficient separation have higher rates of misclassification. We expect that modified decision criteria involving simultaneous consideration of several parameters increase performance for these classes.

Freeman, A.↗