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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Modification of a variational objective analysis model for new equations for pressure gradient and vertical velocity in the lower troposphere and for spatial resolution and accuracy of satellite data

Since late 1982 NASA has supported research to develop a numerical variational model for the diagnostic assimilation of conventional and space-based meteorological data. In order to analyze the model components, four variational models are defined dividing the problem naturally according to increasing complexity. The first of these variational models (MODEL I), the subject of this report, contains the two nonlinear horizontal momentum equations, the integrated continuity equation, and the hydrostatic equation. This report summarizes the results of research (1) to improve the way the large nonmeteorological parts of the pressure gradient force are partitioned between the two terms of the pressure gradient force terms of the horizontal momentum equations, (2) to generalize the integrated continuity equation to account for variable pressure thickness over elevated terrain, and (3) to introduce horizontal variation in the precision modulus weights for the observations.

Achtemeier, G. L.↗
NASA NTRS1986

Characterization of 2.5 microns HgCdTe detectors for low-background applications

A program of testing aimed at the evaluation of systems that have the potential to provide the level of performance required for use in space-based instruments was undertaken and their usefulness appraised for astronomy. The results of the first phase of the program to characterize selected pixels of a HgCdTe photovoltaic array detector were reported.

Depoy, D. L.↗
NASA NTRS1986

Preliminary measurements of very low dark currents in MLA/SWIR HgCdTe/DRO arrays

In infrared astronomy observations, one of the key detector performance parameters is the dark current which, together with the optics, establishes the fundamental limit of a space-based instrument. This technical note summarizes an effort to measure dark current performance of the MLA/Short Wave Infrared photovoltaic HgCdTe array (2.5 micron cutoff) at temperatures from 65 to 120 K. The preliminary results indicate that dark current decreased systematically to 100 K, then the value became measurement-limited at about 3.0 E-18 A/pixel, or 19 electrons/sec/pixel.

Yang, B. T.↗
NASA NTRS1986

Tethered orbital refueling study

One of the major applications of the space station will be to act as a refueling depot for cryogenic-fueled space-based orbital transfer vehicles (OTV), Earth-storable fueled orbit maneuvering vehicles, and refurbishable satellite spacecraft using hydrazine. One alternative for fuel storage at the space station is a tethered orbital refueling facility (TORF), separated from the space station by a sufficient distance to induce a gravity gradient force that settles the stored fuels. The technical feasibility was examined with the primary focus on the refueling of LO2/LH2 orbital transfer vehicles. Also examined was the tethered facility on the space station. It was compared to a zero-gravity facility. A tethered refueling facility should be considered as a viable alternative to a zero-gravity facility if the zero-gravity fluid transfer technology, such as the propellant management device and no vent fill, proves to be difficult to develop with the required performance.

Fester, Dale A.↗
NASA NTRS1987

Solar power absorption in a glass tube

The optics of a glass tube to be used in near-Earth space at the focus of a solar concentrator has been examined, and an equation for the power absorbed from multiple-reflected light beams in the tube wall has been developed. The equation has been used to calculate the power absorbed by a highly transmissive form of fused silica. The equilibrium temperature reached by the tube with only radiative cooling has also been examined, and it shows a significant rise with large solar concentrations. The results apply specifically to cylindrical containment vessels for space-based solar-pumped lasers and generally to any similarly irradiated tubes.

Williams, Michael D.↗
NASA NTRS1987

Advanced long term cryogenic storage systems

Long term, cryogenic fluid storage facilities will be required to support future space programs such as the space-based Orbital Transfer Vehicle (OTV), Telescopes, and Laser Systems. An orbital liquid oxygen/liquid hydrogen storage system with an initial capacity of approximately 200,000 lb will be required. The storage facility tank design must have the capability of fluid acquisition in microgravity and limit cryogen boiloff due to environmental heating. Cryogenic boiloff management features, minimizing Earth-to-orbit transportation costs, will include advanced thick multilayer insulation/integrated vapor cooled shield concepts, low conductance support structures, and refrigeration/reliquefaction systems. Contracted study efforts are under way to develop storage system designs, technology plans, test article hardware designs, and develop plans for ground/flight testing.

Brown, Norman S.↗
NASA NTRS1986

Technical aspects of the United States Space Station

The design and development of the Space Station are described. The proposed design of the Station is a dual keel configuration which will include manned facilities and unmanned free flying platforms. The Station is to be utilized as a space-based laboratory for basic research and observations, a depot for repair and servicing of spacecraft, a strorage area, and a manufacturing facility. International participation in the Space Station program and technological developments applicable for the Station are discussed. A diagram of the Space Station configuration and a Space Station development schedule are provided.

Herman, D. H.↗
NASA NTRS1986

Containerless processing technology

Ground- and space-based containerless processing levitation devices are described. Experiments performed in the MSFC drop tube, the JPL drag-free drop facilities, a single-axis tuned cavity acoustic levitator furnace on TEXUS-I, and a three-axis acoustic levitator and furnace on the STS-11 mission are discussed. Neither acoustic interference nor aerodynamic levitation trials have yielded promising results in sounding rocket and STS based experiments. An electrostatic levitator has furnished a high degree of positioning control with multiple objects in a terrestrial laboratory.

Naumann, R. J.↗
NASA NTRS1986

Comparison of a tethered to a zero-gravity refueling facility

The space-based orbital transfer vehicle will require a large cryogenic fuel storage facility at the Space Station. An alternative to fuel storage on-board the Space Station is on a tethered orbital refueling facility (TORF) which is separated from the Space Station by a sufficient distance to induce a gravity gradient to settle the propellants. Overall costs and benefits of a particular tethered facility design have been defined relative to a representative zero-gravity facility on the Space Station. Results indicate that the TORF hardware and operations costs are roughly 40 percent higher than the comparable zero-g facility costs. The cost difference is negligible when compared to the launch cost of the fuel over the facility 10-year lifetime.

Kiefel, E. R.↗
NASA NTRS1986

Measurements of lower stratospheric/upper tropospheric water vapor by the SAGE II instrument

Preliminary, unvalidated data are discussed from early measurements of water vapor profiles in the upper troposphere/lower stratosphere by means of SAGE II satellite sensors. Zonal means for April 1985 are discussed and compared with previous, separate data sets for water vapor profiles for the 100 mbar and 300 mbar levels determined from space-based IR and rawinsonde data. Techniques employed to correct for noisy measurements due to the presence of clouds in the SAGE II scenes are described, noting the slant path transmission methods applied to generate the water vapor profiles.

Larsen, J. C.↗
NASA NTRS1985

Space Station - Implications for space manufacturing

Space-based materials processing R&D is examined. It is proposed that the Space Station's Microgravity and Materials Processing Facility will be utilized by academic, government, and commercial customers. Users requirements for materials processing in space are discussed. Consideration is given to the time allocation of the facility, charges to users, and the property rights of the users.

Tingey, D. L.↗
NASA NTRS1986

High-resolution optical and ultraviolet absorption-line studies of interstellar gas

Recent progress in the characterization of the interstellar medium (ISM) by means of optical and UV spectral data is summarized. The gas is studied by focusing on background stars whose spectra can be accurately modeled to provide the light source for the absorption-line scans. The capabilities of earth- and space-based instruments which have been and are used for the surveys are delineated. The distributions of diffuse gas densities and characteristics of the cold, warm and hot gas in the Galaxy are described in terms of the elemental abundances, kinetics and distributions of the gas. Particular note is taken of gas in the solar neighborhood and around SNR, and of absorption-line data of cosmological significance.

Cowie, Lennox L.↗
NASA NTRS1986

Evaluation of on-orbit cryogenic propellant depot options for the orbital transfer vehicle

An orbital cryogenic propellant storage facility will be required for a space-based Orbital Transfer Vehicle. The facility tanks will have features to permit fluid acquisition and transfer in low gravity and to limit cryogen boiloff caused by environmental heating. Boiloff management features will include thick multilayer insulation, vapor-cooled shields, low conductance structural supports and penetrations, and possibly refrigeration systems.

Schuster, J. R.↗
NASA NTRS1986

A conceptual design for a microwave active phased array SAR

The active phased array radar is well known for its assets of rapid electronic beam steering and adaptability to limited degrading influences. In a spaceborne synthetic aperture radar (SAR) application, therefore, it should be possible to provide for rapid beam control in the cross-track (variable incidence angle) and along-track (spot-light mode) directions, as well as allowing for possible relaxation of antenna structural requirements. A design study has been conducted at Stanford University for a conceptual spaceborne C-band SAR application operating in the early to mid-1990's time frame. This study was intended to identify principal design issues, as well as unique features associated with an active phased array antenna SAR. A hypothetical design is used to illustrate these issues. Some of this work should have generic application to space-based communications activities.

Gilchrist, Brian E.↗
NASA NTRS1986

Simple method for designing or analyzing an optical communication link

A simple method is described for determining the performance of a free space optical communication link. The method can be used either in the system design (synthesis) mode, or in the performance evaluation (analysis) mode. Although restricted to photo counting based detection (e.g., photomultiplier tube or equivalent) of pulse position modulated signals, the method is still sufficiently general to accommodate space-based, as well as ground-based, reception.

Lesh, James R.↗
NASA NTRS1987

Isophotal diameters of galaxies at high redshifts

New ultraviolet observations and archival spectra are presented for the bright disk of the galaxy NGC 4736 to derive the ultraviolet surface brightness profile. This is used to predict the appearance of such a galaxy at high redshift. The profiles in red light of 100 galaxies determined by S. Kent (1984) are used with assumed ultraviolet spectra to predict the isophotal diameters of these galaxies as a function of redshift. The results show that, for ground-based imagery, normal spiral galaxies should be resolvable to the largest redshifts (z roughly 1). For space-based imagery, much smaller but brighter galactic disks characterized by extensive star formation will be those resolved at the highest redshifts (z roughly 2.5).

Weedman, Daniel W.↗
NASA NTRS1986

Remote sensing of the biosphere

The current state of understanding of the biosphere is reviewed, the major scientific issues to be addressed are discussed, and techniques, existing and in need of development, for the science are evaluated. It is primarily concerned with developing the scientific capabilities of remote sensing for advancing the subject. The global nature of the scientific objectives requires the use of space-based techniques. The capability to look at the Earth as a whole was developed only recently. The space program has provided the technology to study the entire Earth from artificial satellites, and thus is a primary force in approaches to planetary biology. Space technology has also permitted comparative studies of planetary atmospheres and surfaces. These studies coupled with the growing awareness of the effects that life has on the entire Earth, are opening new lines of inquiry in science.

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