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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 433 records · Page 24

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NASA NTRS1976

Effects of atomic oxygen on graphite ablation

It is shown that a previously derived semiempirical equation for describing observed ablation rates of isotropic graphites cannot be applied to low-density flows containing dissociated oxygen. Experimentally determined reaction probabilities of isotropic graphites to molecular and atomic oxygen are used to calculate heat-transfer rates and stagnation-point ablation rates for typical conditions. Integrated mass losses are computed for a group of flight trajectories which start from geosynchronous orbit and enter earth's atmosphere in a skipping motion following near-elliptic decaying orbits. A comparison of the results with those obtained by the equation under question shows excellent agreement for steep trajectories, but large discrepancies for shallow trajectories. The differences are attributed to surface oxidation by atomic oxygen.

Park, C.↗

NASA NTRS1977

The economic viability of pursuing a space power system concept

The development of a space power system requires no fundamental technological breakthroughs. There are, however, uncertainties regarding the degree to which necessary developments can be achieved or exceeded. An analysis is conducted concerning the implementation of a 5000 MW space-based solar power system based on photovoltaic conversion of solar energy to electrical energy. The solar array is about 13 km long and 5 km wide. Placed in geosynchronous orbit, it provides power to the earth for 30 years. Attention is given to the economic feasibility of a space power system, a risk analysis for space power systems, and the use of the presented methodology for comparing alternative technology development programs.

Hazelrigg, G. A., Jr.↗

NASA NTRS1976

Microwave holographic imaging of aircraft with spaceborne illuminating source

The conceptual development of a method for the high angular resolution and accurate angular position estimates for the surveillance and traffic control of aircraft is considered. A target volume several hundred kilometers in diameter is illuminated by a CW microwave source located on a satellite in geosynchronous orbit. Signals are received by a large array of random, conformally located receiving elements. Each element receives the direct signal from the satellite plus signals reflected from aircraft in the illuminated volume. Coherent combination of the signals received from the individual elements permits the equivalent of holographic imaging or multiple beam formation from which the useful target data can be obtained.

Berkowitz, R. S.↗

NASA NTRS1977

Cloud elevations in near real time

The paper shows how cloud elevations can be obtained from geosynchronous satellites within 15 min of an event and to an accuracy of less than 250 m. After careful consideration of pertinent factors, it is decided that a dual satellite system in parallel geosynchronous orbits would be the most feasible configuration for stereographic imaging of cloud systems. The discussion covers tracking accuracy, choice of imaging systems, data transmission and processing, image correlation, and proposed cloud heighting system. The described partially man-interactive system is substantially within the present state of the art and could be the basis for an interim system for cloud height determination.

Shull, C. W.↗

NASA NTRS1977

Alternative approaches to space-based power generation

Satellite Power Stations (SPS) would generate electrical power in space for terrestrial use. Their geosynchronous orbit location permits continuous microwave power transmission to ground receiving antenna farms. Eight approaches to the generation of the electrical power to be transmitted were investigated. Configurations implementing these approaches were developed through an optimization process intended to yield the lowest cost for each. A complete program was baselined for each approach, identifying required production rates, quantities of launches, required facilities, etc. Each program was costed, including the associated launches, orbital assembly, and maintenance operations. The required electric power charges to amortize these costs were calculated. They range from 26 to 82 mills/kWh (ground busbar).

Gregory, D. L.↗

NASA NTRS1977

Solar power satellite transportation

Preliminary studies and concepts are discussed relative to the feasibility and economics of developing the capability to transport a network of operational 10-GWe solar power satellites into geosynchronous orbit by A.D. 2025. The satellite is briefly described, and its space transportation options are presented. Launch vehicle requirements and concepts are discussed in relationship to the transportation task.

Davis, H. P.↗

NASA NTRS1977

The solar-terrestrial observatory as a major module of a space station

The solar-terrestrial environment is a dynamic, tightly coupled system in which variable solar energy is transmitted through electromagnetic radiation and the solar wind to the earth's magnetosphere and atmosphere. The constantly changing solar input and the continuous redistribution of energy near the earth combine to determine the characteristics of our global environment. An understanding and subsequent management of this environment will require a coordinated set of observations of solar processes and the accompanying magnetospheric and atmospheric responses. A major element in this observational plan should be a Solar-Terrestrial Observatory module of a manned Space Station in which instruments and experimental techniques developed during short-duration Spacelab flights will be applied to extended missions in both low-altitude and geosynchronous orbits.

Chappell, C. R.↗

NASA NTRS1977

Secondary emission conductivity of high purity silica fabric

High purity silica fabrics were proposed for use as a material to control the effects of electrostatic charging of satellites at synchronous altitudes. These materials exhibited very quiet behavior when placed in simulated charging environments as opposed to other dielectrics used for passive thermal control which exhibit varying degrees of electrical arcing. Secondary emission conductivity is proposed as a mechanism for this superior behavior. Design of experiments to measure this phenomena and data taken on silica fabrics are discussed as they relate to electrostatic discharge (ESD) control on geosynchronous orbit spacecraft. Studies include the apparent change in resistivity of the material as a function of the electron beam energy, flux intensity, and the effect of varying electric fields impressed across the material under test.

Belanger, V. J.↗

NASA NTRS1977

The effects of the geosynchronous energetic particle radiation environment on spacecraft charging phenomena

The energetic electron environment at the geosynchronous orbit is responsible for a variety of adverse charging effects on spacecraft components. The most serious of these is the degradation and failure of a complementary-metal-oxide-semiconductor (CMOS) electronic components as a result of internal charge-buildup induced by the energetic electrons. Efforts to accurately determine the expected lifetime of these components in this orbit are hampered by the lack of detailed knowledge of the electron spectrum and intensity, particularly of the more penetrating energies greater than 1.5 MeV. This problem is illustrated through the calculation of the dose received by a CMOS device from the energetic electrons and associated bremsstrahlung as a function of aluminum shielding thickness using the NASA AE-6 and the Aerospace measured electron environments. Two computational codes which were found to be in good agreement were used to perform the calculations. For a given shielding thickness the dose received with the two radiation environments differ by as much as a factor of seven with a corresponding variation in lifetime of the CMOS.

Reagan, J. B.↗

NASA NTRS1977

A space necklace about the earth

A space elevator is forecasted for the first quarter of the 21st century, that will consist of a cable attached at the earth's equator, suspended in space by an artificial satellite in geosynchronous orbit. It is stated that such a transport system will supplement rockets as the railway supplements aircraft. Specific aspects of the system are examined, including provisions for artificial gravity, the development special composite construction materials exhibiting high strength and low mass, and spacecraft launching from the elevator.

Polyakov, G.↗

NASA NTRS1978

Puncture discharges in surface dielectrics as contaminant sources in spacecraft environments

Spacecraft in geosynchronous orbits are known to become charged to large negative potentials during the local midnight region of the satellite orbit. Such discharges have been studied by the electron beam irradiation of dielectric samples in a vacuum environment. In addition to static measurements and photographic examination of the puncture discharges in Teflon samples, the transient characteristics of the electrical discharges are determined from oscillographs of voltage and current and by charged particle measurements employing a biased Faraday cup and a retarding potential analyzer. Using these latter techniques, studies of angular and energy distributions of charged particles have indicated an initial burst of high energy electrons (5 x 10 to the 13th power per discharge at energies greater than 300 eV) followed by a less intense burst of lower energy negative particles. Positive ions are emitted from the discharge site in an initial high velocity burst followed by a lower velocity burst tentatively identified as carbon.

Yadlowsky, E. J.↗

NASA NTRS1978

Geosynchronous Microwave Atmospheric Sounding Radiometer (MASR) feasibility studies. Volume 1: Management summary

The mission of the microwave atmospheric sounding radiometer (MASR) is to collect data to aid in the observation and prediction of severe storms. The geosynchronous orbit allows the continuous atmospheric measurement needed to resolve mesoscale dynamics. The instrument may operate in conjunction with this document, Volume 1 - Management, which summarizes the highlights of final reports on both the radiometer instrument and antenna studies. The radiometer instrument summary includes a synopsis of Volume 2 - Radiometer Receiver Feasibility, including design, recommended configuration, performance estimates, and weight and power estimates. The summary of the antenna study includes a synopsis of Volume 3 - Antenna Feasibility, including preliminary design tradeoffs, performance of selected design, and details of the mechanical/thermal design.

Source record↗

NASA NTRS1977

NASCAP, a three-dimensional Charging Analyzer Program for complex spacecraft

A computer code, NASCAP (NASA Charging Analyzer Program), has been developed by Systems, Science and Software under contract to NASA-LeRC to simulate the charging of a complex spacecraft in geosynchronous orbit. The capabilities of the NASCAP code include a fully three-dimensional solution of Poisson's equation about an object having considerable geometrical and material complexity, particle tracking, shadowing in sunlight, calculation of secondary emission, backscatter and photoemission, and graphical output. A model calculation shows how the NASCAP code may be used to improve our understanding of the spacecraft-plasma interaction.

Katz, I.↗

NASA NTRS1978

NASA Charging Analyzer Program - A computer tool that can evaluate electrostatic contamination

The data from the ATS-5 and -6 Auroral Particles Experiments have shown that the environment at geosynchronous orbit can charge spacecraft surfaces to appreciable negative values. Such surface charges could have undesirable effects on satellite equipment and the data obtained in satellite experiments. A computer program, the NASA Charging Analyzer Program (NASCAP), has, in this connection, been developed to determine the surface charging of spacecraft when encountering geomagnetic substorm conditions. Once a model of a spacecraft has been developed in the NASCAP code, the surface charging can be computed for any environmental input flux. On the basis of the obtained information regarding the surface charging, charged particle trajectories can be computed to determine if it is possible for a particle to return to a satellite surface. It is pointed out that the computer runs conducted with the NASCAP code represent the first attempts to use a self-consistent program to study the behavior of spacecraft surfaces experiencing a geomagnetic substorm condition.

Stevens, N. J.↗

NASA NTRS1978

Applications Technology Satellite program

The Applications Technology Satellite (ATS) program has involved geosynchronous spacecraft technology made possible by the increased capability of the Atlas-Agena launch vehicle. The ATS-1-5 program developed spin stabilized and gravity gradient stabilized spacecraft for geosynchronous orbit, earth-oriented antennae for increased antenna gain, earth-scanning meteorological experiments for continuous weather monitoring, and made possible satellite communications to mobile terminals. The ATS-6 program developed a space-deployed, high-gain antenna for color television broadcast to low-cost ground terminals and precise spacecraft attitude control for pointing, slewing, and tracking applications. All of the ATS program objectives were successfully met, except for the gravity gradient experiments. ATS-1, -3, -5, and -6 are in orbit and operational.

Mcceney, P. J.↗

NASA NTRS1978

Design concept of geostationary platform

The payload efficiency of communication satellites has typically averaged 25 to 30% while meteorology and earth observation satellites range from 30 to 35%. Improvement in solar cell efficiency, batteries, electric propulsion for stationkeeping, and solid-state circuitry will increase this efficiency in the future, but it will still be advantageous in the Shuttle era to reduce the expenditure for support systems. A platform that provides all the support functions could reduce the initial cost due to economics of scale and also reduce transportation cost. Three alternate configurations of a platform for geosynchronous orbit communications and meteorology missions are presented

Hamilton, E. C.↗

NASA NTRS1978

Microwave power transmitting phased array antenna research project

An initial design study and the development results of an S band RF power transmitting phased array antenna experiment system are presented. The array was to be designed, constructed and instrumented to permit wireless power transmission technology evaluation measurements. The planned measurements were to provide data relative to the achievable performance in the state of the art of flexible surface, retrodirective arrays, as a step in technically evaluating the satellite power system concept for importing to earth, via microwave beams, the nearly continuous solar power available in geosynchronous orbit. Details of the microwave power transmitting phased array design, instrumentation approaches, system block diagrams, and measured component and breadboard characteristics achieved are presented.

Dickinson, R. M.↗

NASA NTRS1978

Satellite Power Systems (SPS) Concept Definition Study. Volume 1: Executive Summary

The evolution of a total satellite power is described as well as major subsystem alternatives. Trade study results are given for satellite concepts, ground receiving antennas, satellite construction sites, and transportation. Point design definition, end-to-end analysis, and programmatics are covered. The GaAlAs photovoltaic concept is recommended as the current preliminary baseline satellite concept with silicon photovoltaic and Rankine cycle solar-thermal concepts as viable alternatives. Geosynchronous orbit is preferred for the construction of the satellite. A horizontal takeoff and landing air breathing rocket HLLV concept is preferred for earth-to-LEO transportation, with vertical takeoff options as viable alternatives. An argon electric orbit transfer vehicle is preferred for cargo transport from LEO and GEO orbit, and a chemical LH2/L02, two-stage orbit transfer vehicle is recommended for crew transport. A stripline rectenna array is the current preferred concept.

Hanley, G.↗