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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
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NASA NTRS1991

VLBI astrometry and the Hipparcos link to the extragalactic reference frame

Intermediate results are reported from a program of VLBI radio observations designed to establish a link between the rotating reference frame of the ESA Hipparcos astrometric satellite and the extragalactic VLBI frame being developed by the International Earth Rotation Service. A group of 12 link stars have been observed at various epochs since 1982, and more observations are being undertaken during the 3-yr Hipparcos mission (1989-1992). Analysis of data on Algol indicates that phase-reference VLBI can determine an expected sky displacement of 4 marcsec with an uncertainty of 0.5 marcsec, even when the activity is only a few mJy.

Lestrade, J.-F.↗
NASA NTRS1990

The ISTP Program - An opportunity for collaboration in the investigation of solar-terrestrial relationships in the Americas

The ESA-NASA-ISAS International Solar Terrestrial Physics (ISTP) project has come to involve more than 2000 scientists worldwide; its investment of $2 billion by the U.S., the E.E.C., and Japan constitutes an excellent opportunity for participation of Latin American scientists in the analysis of geophysical observational data. The range of scientific problems addressed by ISTP are presently discussed with a view to the participation of Latin American researchers equipped with work stations of the requisite power.

Acuna, Mario H.↗
NASA NTRS1990

Tethered satellite systems - The 1991 STS-46 mission

The scope of a collaborative mission involving the implementation of a tethered satellite is described. The 1991 STS-46 mission, sponsored jointly by NASA, the ESA, and the Italian Space Agency involves the deployment of a tethered satellite on a Space Shuttle Discovery flight. The concept behind the tethered satellite is described, and extensive graphic descriptions of the mission profile and specifications are presented. The payload, the European Retrievable Carrier (Eureca), is explained in terms of its features and capabilities, as well as emergency considerations. A study of atmospheric composition will be the primary objective of the satellite project.

Chang Diaz, Franklin↗
NASA NTRS1991

Use of mercuric iodide X-ray detectors with alpha backscattering spectrometers for space applications

The authors present X-ray fluorescence (XRF) spectra of different extraterrestrial samples taken with a mercuric iodide (HgI2) spectrometer inserted into an alpha backscattering instrument identical to that used in the Soviet Phobos mission. The results obtained with the HgI2 ambient temperature detector are compared with those obtained using an Si(Li) cryogenically cooled detector. Efforts to design an optimized instrument for space application are also described. The results presented indicate that the energy resolution and sensitivity of HgI2 detectors are adequate to meet the performance needs of a number of proposed space applications, particularly those in which cooled silicon X-ray detectors are impractical or even not usable, such as for the target science programs on geoscience opportunities for lunar surface, Mars surface, and other comet and planetary missions being planned by NASA and ESA.

Iwanczyk, J. S.↗
NASA NTRS1991

Giotto Extended Mission (GEM)

The primary objectives of the Giotto Extended Mission (GEM), are to determine the composition and physical state of the Grigg Skjellerup Comet's nucleus; to determine the processes that govern the composition and distribution of neutral and ionized species in the cometary atmosphere. Giotto consists of a single European Space Agency (ESA) spacecraft that was launched in 1985 from Center Spatial Guyanis in French Guiana on an Ariane launch vehicle. After a successful launch into geostationary orbit and a heliocentric transfer trajectory, the spacecraft successfully encountered Halley's Comet in 1986. One month after encountering Halley's Comet, Mar. 1986, the spacecraft was placed in hibernation in a heliocentric orbit slightly less than 1 AU. Between Feb. and Jul. 1990 the spacecraft was successfully reactivated, checked out, and placed on a trajectory course to intercept comet Grigg Skjellerup. The spacecraft has been in hibernation since Jul. 1990. Information is presented in tabular form in the following areas: coverage goals, Deep Space Network Support, frequency assignments, telemetry, command, and tracking support responsibility.

Wilkins, D. E. B.↗
NASA NTRS1991

Enhanced EOS photovoltaic power system capability with InP solar cells

The Earth Observing System (EOS), which is part of the International Mission to Planet Earth, is NASA's main contribution to the Global Change Research Program which opens a new era in international cooperation to study the Earth's environment. Five large platforms are to be launched into polar orbit, two by NASA, two by ESA, and one by the Japanese. In such an orbit the radiation resistance of indium phosphide solar cells combined with the potential of utilizing five micron cell structures yields an increase of 10 percent in the payload capability. If further combined with the advanced photovoltaic solar array the payload savings approaches 12 percent.

Bailey, Sheila G.↗
NASA NTRS1991

Exobiological implications of dust aggregation in planetary atmospheres: An experiment for the gas-grain simulation facility

The Gas-Grain Simulation Facility (GGSF) will provide a microgravity environment where undesirable environmental effects are reduced, and thus, experiments involving interactions between small particles and grains can be more suitably performed. Slated for flight aboard the Shuttle in 1992, the ESA glovebox will serve as a scientific and technological testbed for GGSF exobiology experiments as well as generating some basic scientific data. Initial glovebox experiments will test a method of generating a stable, mono-dispersed cloud of fine particles using a vibrating sprinkler system. In the absence of gravity and atmospheric turbulence, it will be possible to determine the influence of interparticle forces in controlling the rate and mode of aggregation. The experimental chamber can be purged of suspended matter to enable multiple repetitions of the experiments. Of particular interest will be the number of particles per unit volume of the chamber, because it is suspected that aggregation will occur extremely rapidly if the number exceeds a critical value. All aggregation events will be recorded on high-resolution video film. Changes in the experimental procedure as a result of surprise events will be accompanied by real-time interaction with the mission specialist during the Shuttle flight.

Huntington, J. L.↗
NASA NTRS1991

A silicone column for GC analysis of polar and nonpolar chemicals

The investigation of the Saturnian System is being proposed jointly by NASA and the European Space Agency (ESA). The mission is scheduled for a launch in 1996. The mission provides an opportunity for close observation and exploration of Saturn's atmosphere, the complex Saturnian System of satellites and rings, Titan (Saturn's planet-sized moon), and Saturn's magnetosphere. The mission gives special attention to Titan which is blanketed by a thick, opaque atmosphere. An atmospheric probe will be deposited into the Titan Atmosphere for in situ measurement during a slow, three hour descent to the surface. The results from this analysis may provide the information which is important to the research of chemical evolution, and the origin of life. An analytical system was developed as a part of the Titan Aerosol Gas Experiment (TAGEX), a proposed experiment for the Cassini Mission. This system will use two highly sensitive detectors, the Metastable Ionization Detector (MID) and the Ion Mobility Spectrometer (IMS). Unfortunately, when commercial columns are utilized with these highly sensitive detectors, volatile components continuously bleed from the column and interfere with the detector. In addition, light columns must be able to separate polar and nonpolar organic chemicals within 10-15 minutes under isothermal conditions for the Titan Mission. Therefore, a highly crosslinked silicone polymeric packed column was developed which is able to efficiently separate amines, alcohols, and hydrocarbons with retention times less that 15 minutes at 100 C isothermal condition.

Shen, T. C.↗
NASA NTRS1991

Fluid seals technology at BHR Group Ltd.

A mathematical model was developed for ESA, which couples the rigid body dynamics in four degrees of freedom of a flexibly mounted stator (with Coulomb damping) of a turbopump face seal with the fluid film behavior. The interfacial film is assumed gaseous, and the model incorporates laminar/turbulent flow, inertia and sonic choking. Seal faces may be wavy and coned, while the rotating ring can be eccentrically mounted, misaligned with the shaft and oscillate axially at arbitrary frequency. The model is currently being coded into software. An experimental program using a high speed cryogenic/hot gas test rig is being conducted to verify the output of the computer program.

Leefe, Simon↗
NASA NTRS1991

Space mission support by NASA Space Network

Normal NASA operational considerations and Phase 1 of Space Network (SN) interoperability foresees S band cross support between user spacecraft and space networks or partnering agencies. A typical interoperable scenario for an S band user spacecraft of a partner space agency with the NASA SN is presented. ESA's Hermes Manned Spaceplane exemplifies a typical interoperable user. In order to demonstrate the support potential of the NASA SN, the internal and external interfaces of the TDRSS (Tracking and Data Relay Satellite System), ATDRSS (Advanced TDRSS), and supporting elements are examined. Communications and operational requirements for a typical mission supported by the NASA SN are discussed.

Godfrey, Robert↗
NASA NTRS1992

Ulysses/BATSE observations of cosmic gamma ray bursts

The gamma ray burst detector aboard the ESA-NASA Ulysses spacecraft, in operation since Nov. 1990, has detected numerous gamma bursts in conjunction with the BATSE experiment aboard the Compton Observatory. Initial results are presented on burst locations for three events (21 April, 2 May, and 3 May, 1991) obtained by arrival time analysis, and they are compared with the BATSE locations. The arrival time analysis annuli have typical widths of 5'. The preliminary analysis indicates that both experiments are likely to have unresolved systematic errors, but that further work will improve the location accuracy substantially.

Hurley, K.↗
NASA NTRS1992

The 1990 Hypobaric Decompression Sickness Workshop: Summary and conclusions

Decompression sickness resulting from exposure to the hypobaric environment was reviewed and discussed at a three day workshop in Oct. 1990. This milestone meeting, attended by over 50 participants representing the Dept. of Defense, NASA, ESA, and academia, updated the current understanding of altitude decompression sickness (DCS). Both research and operational aspects of this illness were addressed through presentations on the pathophysiology and clinical manifestations of DCS, its incidence in aviation and space operations, and existing and proposed measures for DCS prevention. Specific areas requiring further research were also identified. A summary is presented for the material given at the workshop.

Pilmanis, Andrew A.↗
NASA NTRS1992

Effect of microgravity environment on cell wall regeneration, cell divisions, growth, and differentiation of plants from protoplasts (7-IML-1)

The primary goal of this project is to investigate if microgravity has any influence on growth and differentiation of protoplasts. Formation of new cell walls on rapeseed protoplasts takes place within the first 24 hours after isolation. Cell division can be observed after 2-4 days and formation of cell aggregates after 5-7 days. Therefore, it is possible during the 7 day IML-1 Mission to investigate if cell wall formation, cell division, and cell differentiation are influenced by microgravity. Protoplasts of rapeseeds and carrot will be prepared shortly before launch and injected into 0.6 ml polyethylene bags. Eight bags are placed in an aluminum block inside the ESA Type 1 container. The containers are placed at 4 C in PTCU's and transferred to orbiter mid-deck. At 4 C all cell processes are slowed down, including cell wall formation. Latest access to the shuttle will be 12 hours before launch. In orbit the containers will be transferred from the PTC box to the 22 C Biorack incubator. The installation of a 1 g centrifuge in Biorack will make it possible to distinguish between effects of near weightlessness and effects caused by cosmic radiation and other space flight factors including vibrations. Parallel control experiments will be carried out on the ground. Other aspects of the experiment are discussed.

Rasmussen, Ole↗
NASA NTRS1992

The Critical Point Facility (CPF)

The Critical Point Facility (CPF) is an ESA multiuser facility designed for microgravity research onboard Spacelab. It has been conceived and built to offer investigators opportunities to conduct research on critical point phenomena in microgravity. This facility provides the high precision and stability temperature standards required in this field of research. It has been primarily designed for the purpose of optical investigations of transparent fluids. During a Spacelab mission, the CPF automatically processes several thermostats sequentially, each thermostat corresponding to an experiment. The CPF is now integrated in Spacelab at Kennedy Space Center, in preparation for the International Microgravity Lab. mission. The CPF was designed to submit transparent fluids to an adequate, user defined thermal scenario, and to monitor their behavior by using thermal and optical means. Because they are strongly affected by gravity, a good understanding of critical phenomena in fluids can only be gained in low gravity conditions. Fluids at the critical point become compressed under their own weight. The role played by gravity in the formation of interfaces between distinct phases is not clearly understood.

Source record↗
NASA NTRS1990

Advanced multiple access concepts in mobile satellite systems

Some multiple access strategies for Mobile Satellite Systems (MSS) are discussed. These strategies were investigated in the context of three separate studies conducted for the International Maritime Satellite Organization (INMARSAT) and the European Space Agency (ESA). Satellite-Switched Frequency Division Multiple Access (SS-FDMA), Code Division Multiple Access (CDMA), and Frequency-Addressable Beam architectures are addressed, discussing both system and technology aspects and outlining advantages and drawbacks of either solution with associated relevant hardware issues. An attempt is made to compare the considered option from the standpoint of user terminal/space segment complexity, synchronization requirements, spectral efficiency, and interference rejection.

Ananasso, Fulvio↗
NASA NTRS1990

Payloads development for European land mobile satellites: A technical and economical assessment

The European Space Agency (ESA) has defined two payloads for Mobile Communication; one payload is for pre-operational use, the European Land Mobile System (EMS), and one payload is for promoting the development of technologies for future mobile communication systems, the L-band Land Mobile Payload (LLM). A summary of the two payloads and a description of their capabilities is provided. Additionally, an economic assessment of the potential mobile communication market in Europe is provided.

Perrotta, G.↗
NASA NTRS1991

Review of ESOC re-entry prediction results of Salyut-7/Kosmos-1686

An overview of activities at ESA/ESOC during the followup of the Salyut-7/Kosmos-1686 decay, and of related cooperations with space agencies, research institutes, and national bodies within the ESA Member States, within the U.S. and within the USSR, is presented. A postflight analysis indicated areas for improvement in the forecast procedures, especially during the last day of the orbital lifetime. Corresponding revised decay predictions are presented for Salyut-7/Kosmos-1686, and the improved procedures are verified by an analysis of the reentries of Kosmos-1402A and Kosmos-1402C.

Klinkrad, H.↗
NASA NTRS1991

Evaluation of sodium-nickel chloride cells for space applications

The status of the European Space Agency (ESA) program on sodium nickel chloride batteries is outlined. Additionally, the results of initial tests of two prototype space cells are reported. After 2800 cycles typical of a low-earth orbit (LEO) application without failure, the recharge ratio remained at unity, the round trip energy efficiency remained high (87 percent), and the increase in internal cell resistance was modest. Initial tear-down analysis data show no degradation whatsoever of the beta-alumina electrolyte tubes. The low-rate capacity did, however drop by some 40 percent, which needs further investigation, but overall results are encouraging for future use of this couple in geosynchronous (GEO) and LEO spacecraft.

Hendel, B.↗