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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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Data processing techniques useful for infrared astronomy data analysis systems are reported. This investigation is restricted to consideration of data from space-based telescope systems operating as survey instruments. In this report the theoretical background for specific point-source detection schemes is completed, and the development of specific algorithms and software for the broad range of requirements is begun.
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.
Fresh experimental bones can withstand greater bending forces and moments after 1.0 to 2.5 weeks of 3-G exposure. This appears more attributable to a 50% greater strength of bone material than to effects upon size or shape, and is most measurable for animals of 5 to 8 weeks of age. Experimental bone material seems to grow to its mature level at a younger age rather then there being so marked an effect upon the mature level itself. We simulated 3.1 G by chronic centrifugation of 66 albino rats and compared them to 63 1-G controls. Extrapolation of the simplest mathematical description of the present results to weaker, zero-G bones could be tested by a total of 60 space-based control and experimental animals. A flight of only 15 animals would be necessary for comparison to ground-based control animals. This is consistent with reports of bone demineralization during space-flight. In light of the differences in bone histology, however, extrapolation of these results to humans would be premature and, if at all applicable, are most likely to be so for children rather than adults.
Measurement accuracy goals of 2 cm rms range estimation error and 0.003 cm/sec rms range rate estimation error, with no more than 1 cm (range) static bias error are requirements for laser measurement systems to be used in planned space-based earth physics investigations. Constraints and parameters were defined for links between a high altitude, transmit/receive satellite (HATRS), and one of three targets: a low altitude target satellite, passive (LATS), and active low altitude target, and a ground-based target, as well as with operations with a primary transmit/receive terminal intended to be carried as a shuttle payload, in conjunction with the Spacelab program.
The requirements projected to the year 2000 for space-based communications facilities, including both personal communications and innovative services, are developed based upon anticipated demographic and economic growth for the seven major regions of the world. Projected growth requirements, when considered in light of operational factors such as orbit/spectrum crowding and the high investment costs of ground-based systems, suggest the need for new system concepts for communications. The concept of complexity inversion (placing high-cost systems in space and providing low-cost ground terminals to users) is examined and compared with the more conventional approach utiliizing land lines and extensive ground installations. The recommendation is made to develop the technology and capability to construct platforms in space, and the applicability of the Shuttle/Spacelab system in constructing large antenna systems in space is briefly considered.
A system definition study on the Solar Power Satellite System showed that a thin, 50 micrometers, silicon solar cell has significant advantages. The advantages include a significantly lower performance degradation in a radiation environment and high power-to-mass ratios. The advantages of such cells for an employment in space is further investigated. Basic questions concerning the operation of solar cells are considered along with aspects of radiation induced performance degradation. The question arose in this connection how thin a silicon solar cell had to be to achieve resistance to radiation degradation and still have good initial performance. It was found that single-crystal silicon solar cells could be as thin as 50 micrometers and still develop high conversion efficiencies. It is concluded that the use of 50 micrometer silicon solar cells in space-based photovoltaic power systems would be advantageous.
A long-lived space-based system that converts on-orbit solar and/or nuclear energy to a suitable form for distribution to using space systems is described. Mission applications, requirements, issues, problems, benefits, and technology thrusts are identified for the multipurpose power platform. Power levels of at least 10-100Kw are required for space manufacturing, satellites, and space station operations. Two Mw are needed for a proposed passive radar system. Propulsion system requirements are in the 100Kw-100Mw range.
The laser rocket systems investigated in this study were for orbital transportation using space-based, ground-based and airborne laser transmitters. The propulsion unit of these systems utilizes a continuous wave (CW) laser beam focused into a thrust chamber which initiates a plasma in the hydrogen propellant, thus heating the propellant and providing thrust through a suitably designed nozzle and expansion skirt. The specific impulse is limited only by the ability to adequately cool the thruster and the amount of laser energy entering the engine. The results of the study showed that, with advanced technology, laser rocket systems with either a space- or ground-based laser transmitter could reduce the national budget allocated to space transportation by 10 to 345 billion dollars over a 10-year life cycle when compared to advanced chemical propulsion systems (LO2-LH2) of equal capability. The variation in savings depends upon the projected mission model.
The results of the development of a unique modelocked laser device to be utilized in future NASA space-based, ultraprecision laser ranger systems are summarized. The engineering breadboard constructed proved the feasibility of the pump-pulsed, actively modelocked, PTM Q-switched Nd:YAG laser concept for the generation of subnanosecond pulses suitable for ultra-precision ranging. The laser breadboard also included a double-pass Nd:YAG amplifier and provision for a Type II KD*P frequency doubler. The specific technical accomplishment was the generation of single 150 psec, 20-mJ pulses at 10 pps at a wavelength of 1.064 micrometers with 25 dB suppression of pre-and post-pulses.
Recognizing a pressing need of the 1980s to optimize the two-way flow of information between a ground-based user and a remote space-based sensor, an end-to-end approach to the design of information systems has been adopted at the Jet Propulsion Laboratory. The objectives of this effort are to ensure that all flight projects adequately cope with information flow problems at an early stage of system design, and that cost-effective, multi-mission capabilities are developed when capital investments are made in supporting elements. The paper reviews the End-to-End Information System (EEIS) activity at the Laboratory, and notes the ties to the NASA End-to-End Data System program.
The full potential of infrared astronomy can be realized only through observations made with space-based telescopes cooled to cryogenic temperatures. The paper outlines the scientific mission, system description, and focal plane requirements for two cryogenic telescopes: the Infrared Astronomical Satellite (IRAS) and the Shuttle Infrared Telescope Facility (SIRTF). IRAS, a 60-cm superfluid-helium-cooled telescope system, will perform a one-year 8-120-micron IR sky survey; it will provide results of high reliability and sensitivity, produce the first complete survey data for the 30-120-micron region, and fill in missing portions (spectrally and spatially) of previous surveys short of 30 microns; its focal plane assembly is being designed to approach background-limited performance with an array of 62 discrete detectors. The SIRTF design will allow detailed follow-up studies in the 1-1000-micron range with a 116-160-cm observatory-class instrument. The Shuttle sortie capability introduces the unique SIRTF concept of an easily refurbishable or replaceable focal plane instrument complement in an orbiting cryogenic telescope.
Concepts for space-based conversion of space radiation energy into useful energy for man's needs are developed and supported by studies of costs, material and size requirements, efficiency, and available technology. Besides the more studied solar power satellite system using microwave transmission, a number of alternative space energy concepts are considered. Topics covered include orbiting mirrors for terrestrial energy supply, energy conversion at a lunar polar site, ultralightweight structures for space power, radiatively sustained cesium plasmas for solar electric conversion, solar pumped CW CO2 laser, superelastic laser energy conversion, laser-enhanced dynamics in molecular rate processes, and electron beams in space for energy storage.
As major elements of life-cycle costs (LCC) having critical impacts on the initiation and utilization of future space programs, the areas of vehicle design and operations are reviewed in order to identify technology requirements. Common to both areas is the requirement for efficient integration of broad, complex systems. Operations technologies focus on the extension of space-based capabilities and cost reduction through the combination of innovative design, low-maintenance hardware, and increased manpower productivity. Design technologies focus on computer-aided techniques which increase productivity while maintaining a high degree of flexibility which enhances creativity and permits graceful design changes.
A space-based orbital transfer vehicle has been sized for a 50-metric-ton payload delivery from low-earth-orbit to a geosynchronous orbit. Space basing effected substantial reductions in cryogenic insulation, tank, and body structure. The tank and body structural masses are shown to be lower for space basing because of the larger difference in acceleration loads between the on-orbit case (0.2 g's) and delivery (3.0 g's), the latter applying to ground-based vehicles which are delivered to orbit fully loaded with propellants. Insulation masses are lower because of the absence of an atmosphere and the attendant heat transfer losses. Insulation systems masses are also reduced because of the elimination of the problem of liquefaction and freezing of moisture on the tanks.
The requirements projected to the year 2000 for space-based global service systems, including both personal communications and innovative services, are developed based on historic trends and anticipated worldwide demographic and economic growth patterns. The growing demands appear to be best satisfied by developing larger, more sophisticated space systems in order to reduce the size, complexity, and expense of ground terminals. The availability of low-cost ground terminals will, in turn, further stimulate the generation of new services and new customers.
The paper reports on some correlative features of two sets of space-based atmospheric measurements which are globally distributed with good statistical coverage. One set of data, pertaining to tropospheric processes, is lightning occurrence frequency derived from measurements aboard the DMSP satellite. The second set of data, pertaining to thermospheric processes, is the occurrence frequency of wavelike structures in neutral atmospheric density profiles derived from measurements aboard AE-C and AE-D. A significant correlation was found between the occurrence patterns of dawn lightning, which is indicative of massive long-lived tropospheric convective activity, and the occurrence patterns of wavelike structures in the thermosphere.
A microprocessor controlled lidar system under construction at the NASA Goddard Space Flight Center is described and the problems in making space-based measurements of tropospheric ozone are considered. The differential absorption lidar using a dual wavelength, pulsed CO2 laser and direct detection receiver can significantly improve the existing global data base on tropospheric ozone burden. Sensitivity to tropospheric ozone can be obtained in the spaceborne version of lidar by selecting laser lines located in the wings of the target zone lines. Simulation studies using various laser line pairs in the P-branch of the CO2 9.4 micron band show that the ozone burden retrieval may be weighted to particular altitude regions. These simulation studies are based on numerical integration of differences in absorption coefficient at the two selected laser wavelengths using the AFGL absorption line parameter compilations, U.S. Standard Atmosphere ozone profile, and laser software. Simulation, data collection and reduction are performed by a microprocessor subsystem of the CO2 lidar.
A preliminary design of a space-based decimeter accuracy ranging instrument is described along with the ranging subsystem, the pointing subsystem, and attitude reference. The measurement capabilities including ranging accuracy, the signal-to-noise ratio for water, ice, and solid Earth, footprint size, and atmospheric effects are defined and the overall system with its advantages and disadvantages are summarized.