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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Fuel/engine/airframe tradeoff study, phase 1

The effects of broadening the specifications for JP-4 and JP-8 fueled on the performance and cost of all USAF aircraft presently using JP-4 as well as those expected to be introduced into the force structure by 1983 are investigated. Test results indicated that there was no impact on engine performance, turbine durability, and coking, however there was a small maintenance cost increase as a result of a small combustor life decrease. Using JP-4 as standard fuel will avoid the use of high demand middle distillate fuels and give producers flexibility. Extensive use of JP-8 in the United States will increase middle distillate demand and cause a slight increase in engine hot-section maintenance. It is also concluded that the maximum allowable freeze point of JP-4 or JP-8 cannot be increased without degrading system performance and safety as critical conditions are approached.

Peacock, A. T.↗
NASA NTRS1979

Tradeoff between picture element dimensions and noncoherent averaging in side-looking airborne radar

An experiment was performed in which three synthetic-aperture images and one real-aperture image were successively degraded in spatial resolution, both retaining the same number of independent samples per pixel and using the spatial degradation to allow averaging of different numbers of independent samples within each pixel. The original and degraded images were provided to three interpreters familiar with both aerial photographs and radar images. The interpreters were asked to grade each image in terms of their ability to interpret various specified features on the image. The numerical interpretability grades were then used as a quantitative measure of the utility of the different kinds of image processing and different resolutions. The experiment demonstrated empirically that the interpretability is related exponentially to the SGL volume which is the product of azimuth, range, and gray-level resolution.

Moore, R. K.↗
NASA NTRS1980

Single pilot IFR autopilot complexity/benefit tradeoff study

Five levels of autopilot complexity were flown in a single engine IFR simulation for several different IFR terminal operations. A comparison was made of the five levels of complexity ranging from no-autopilot to a fully coupled lateral and vertical guidance mode to determine the relative benefits vs. complexity/cost of state-of-the-art autopilot capability in the IFR terminal area. For the levels of progression tested, the heading select mode made the largest difference in decreasing workload and simplifying the approach task. It was also found that the largest number of blunders was detected with the most fully automated mode. The data also showed that, regardless of the autopilot mode, performance during an IFR approach was highly dependent on the type of approach being flown. These results indicate that some level of automation is desirable when making IFR approaches in a high workload environment, but also that some disturbing trends are associated with the higher levels of automation.

Bergeron, H. P.↗
NASA NTRS1980

SPS attitude control and stationkeeping: Requirements and tradeoffs

The dominant control requirements of solar power satellites change appreciably relative to small contemporary spacecraft. Trade studies and analyses illustrated preferred control approaches. It was found that the geosynchronous equatorial orbit is preferred over the alternative orbits considered, that the solar pressure orbit perturbation dominates stationkeeping propulsion requirements and that a combined AC and SK system using ion electric propulsion can satisfy the attitude control requirements. It was also found that control system/structural dynamic interaction stability can be obtained through frequency separation with reasonable structural dynamic requirements and simplify spacecraft design.

Oglevie, R. E.↗
NASA NTRS1980

Smaller SPS system sizing tradeoffs

The solar power satellite and associated microwave system was reoptimized with larger antennas (at 2.45 GHz), reduced output powers, and smaller rectennas. Four constraints were considered: (1) the 23 mw/sq cm ionospheric limit; (2) a higher (54 mW/sq cm) ionospheric limit; (3) the 23 KW/sq cm thermal limit in the antenna; and (4) an improved thermal design allowing 33% additional waste heat. The differential costs in electricity for seven antenna/rectenna configurations operating at 2.45 GHz and five satellite systems operating at 5.8 GHz were calculated. It is concluded that a larger antenna/smaller rectenna configurations are economically feasible under certain conditions; a transmit antenna diameters should be limited to 1 to 1.5 Km for 2.45 GHz operation and .75 to 1.0 Km for 5.8 GHz; the present ionospheric limit of 23 mw/sq cm is probably too low and should be raised after ionospheric heating tests and studies are completed; the 5.8 GHz configurations are constrainted by antenna thermal limitations, rather than ionospheric limits; and multiple (two to four) antennas on a single solar satellite are recommended regardless of the particular antenna/rectenna configuration chosen.

Arndt, G. D.↗
NASA NTRS1982

Some tradeoffs in ingot shaping and price of solar photovoltaic modules

Growth of round ingots is cost-effective for sheets but leaves unused space when round cells are packed into a module. This reduces the packing efficiency, which approaches 95% for square cells, to about 78% and reduces the conversion efficiency of the module by the same ratio. Shaping these ingots into squares with regrowth of cut silicon improves the packing factor, but increases growth cost. The cost impact on solar cell modules was determined by considering shaping ingots in stages from full round to complete square. The sequence of module production with relevant price allocation guidelines is outlined. The severe penalties in add-on price due to increasing slice thickness and kerf are presented. Trade-offs between advantages of recycling silicon and shaping costs are developed for different slicing scenarios. It is shown that shaping results in cost saving of up to 21% for a 15 cm dia. ingot.

Daud, T.↗
NASA NTRS1980

Software cost/resource modeling: Software quality tradeoff measurement

A conceptual framework for treating software quality from a total system perspective is developed. Examples are given to show how system quality objectives may be allocated to hardware and software; to illustrate trades among quality factors, both hardware and software, to achieve system performance objectives; and to illustrate the impact of certain design choices on software functionality.

Lawler, R. W.↗
NASA NTRS1982

The B-747 flight control system maintenance and reliability data base for cost effectiveness tradeoff studies

Primary and automatic flight controls are combined for a total flight control reliability and maintenance cost data base using information from two previous reports and additional cost data gathered from a major airline. A comparison of the current B-747 flight control system effects on reliability and operating cost with that of a B-747 designed for an active control wing load alleviation system is provided.

Source record↗
NASA NTRS1982

Shuttle to GEO propulsion tradeoffs

An analysis has been made over a range of thruster, spacecraft and mission parameters to determine optimum electric propulsion requirements for LEO to GEO transfer missions. For this mission solar cell cover thicknesses of four to six mils each side appear to be an optimum compromise between mass and power loss due to radiation damage. The optimum range of thruster specific impulse for this mission is roughly from 1500 to 3000 seconds. Thrusters limited to much lower values of specific impulse and those requiring much higher specific impulse for good efficiency require substantially greater transfer times.

Dailey, C. L.↗
NASA NTRS1983

Preliminary assessment of the tradeoffs between the electric motor and the transmission in electric vehicles

The efficiency, weight, and cost of various propulsion system for 4-passenger electric vehicles are compared. These systems comprise the electric motor and the required speed reducing transmission to obtain the appropriate speed at the wheel. Three types of motors, dc synchronous, and squirrel-cage were considered at 6000 ycm and 24 000 rpm for a peak power of 40 kW. Two types of gearing selected were a single speed differential and a differential with a differential with a 4-speed gearbox. Only components that were readily realizable within present state-of-the-art were considered.

Levi, E.↗
NASA NTRS1982

Superfluid-supercritical helium tradeoff analysis for the Shuttle Infrared Telescope Facility (SIRTF)

A comparative study is made of three methods for obtaining the required cooling of the SIRTF. The first is a supercritical helium system in which the 2 K temperatures are obtained by a Joule-Thomson expander; the second is a superfluid (He II) helium system; and the third is a hybrid system in which supercritical helium provides the major cooling and small He II reservoirs supply specific detector cooling. The superfluid helium system is found to offer superior performance; it would be the system to use if funding were available. The comparative study gives equal weight to performance, operations, and cost. From this point of view, the hybrid system is selected as the best compromise to obtain an operational SIRTF.

Gier, H. L.↗
NASA NTRS1985

Attitude Control Tradeoff Study Between the Use of a Flexible Beam and a Tether Configuration for the Connection of Two Bodies in Orbit

Sometimes it is necessary to mount a payload remotely from the main body of a spacecraft or space station. The reasons for this vary from vibration isolation to avoidance of measurement contamination. For example the SP-100 project, which grew out of the increased interest in nuclear power in space for space stations and for deep space explorations, requires separation of the nuclear reactor from the user because of vibration, heat and radiation. The different attitude control problems for beam and tether configurations are discussed. The beam configuration uses a conservative design approach. The vibration, beam flexibility and deployment concerns are analyzed. The tether configuration offers some very attractive design features, but not without several thorny problems. These problems are analyzed. One configuration will be recommended for the main thrust of the SP-100 design effort based on attitude control considerations.

Graff, S. H.↗
NASA NTRS1984

Flat-plate module efficiency versus cost tradeoffs

The Five Year Research Plan energy cost methodology and in depth analyses based on the extensive data that are relevant to PV systems are used to facilitate the accomplishment of the $0.15/kWh energy cost goal. An equation is given for the five year energy cost methodology. The allocation guidelines are designed to be consistent with flat solar array (FSA) milestones for module cost, module efficiency, and the programmatic goal for energy cost. They are research targets that appear to be achievable, given prior accomplishments and planned activities in the areas of low cost silicon purification, low cost sheet material, high efficiency cell processing, low cost, long life encapsulants, and automated fabrication method. Extensive sensitivity analysis work has been performed that shows that these guidelines represent an efficient way to meet the intent of the DOE program.

Aster, R. W.↗
NASA NTRS1985

Tradeoff analysis of technology needs for public service helicopters

The design requirements for a family or type of Public Service Helicopter (PSH) is examined which will satisfy the needs of municipal and state governments in the following mission areas: Emergency Medical Service--Airborne Rescue Squad; Law Enforcement; Search and Rescue; and Environmental Control (Fire Fighting, Pollution, Resource Management). The report compares both design and performance requirements as specified by the PSH user's group against current technological capabilities, RTOPS and US Army LHX design requirements. The study explores various design trade-offs and options available to the aircraft designer/manufacturer in order to meet the several criteria specified by the PSH user's group. In addition, the report includes a brief assessment of the feasibility of employing certain advanced rotorcraft designs to meet the stringent combination of operational capabilities desired by the Public Service Helicopter Users.

Bauchspies, J. S.↗
NASA NTRS1986

Performance tradeoffs in static and dynamic load balancing strategies

The problem of uniformly distributing the load of a parallel program over a multiprocessor system was considered. A program was analyzed whose structure permits the computation of the optimal static solution. Then four strategies for load balancing were described and their performance compared. The strategies are: (1) the optimal static assignment algorithm which is guaranteed to yield the best static solution, (2) the static binary dissection method which is very fast but sub-optimal, (3) the greedy algorithm, a static fully polynomial time approximation scheme, which estimates the optimal solution to arbitrary accuracy, and (4) the predictive dynamic load balancing heuristic which uses information on the precedence relationships within the program and outperforms any of the static methods. It is also shown that the overhead incurred by the dynamic heuristic is reduced considerably if it is started off with a static assignment provided by either of the other three strategies.

Iqbal, M. A.↗
NASA NTRS1985

Design tradeoffs for a Space Station solar-Brayton power system

Mass, area, and station-keeping propellant needs have been estimated for a typical system. And, although important criteria such as cost, Shuttle packaging, and erection/deployment schemes were not considered, the documented trends should aid in many of the design choices to be made. Effects on system characteristics were examined for: three heat storage salts with melting temperatures from 743 to 1121 K; parabolic and Cassegrainian mirrors; module power levels of 20 and 40 kW; and, alternate pumped-loop, tube-and-fin radiator configurations, with and without micrometeoroid armoring.

Klann, J. L.↗
NASA NTRS1987

Maximum Entropy/Optimal Projection (MEOP) control design synthesis: Optimal quantification of the major design tradeoffs

The underlying philosophy and motivation of the optimal projection/maximum entropy (OP/ME) stochastic modeling and reduced control design methodology for high order systems with parameter uncertainties are discussed. The OP/ME design equations for reduced-order dynamic compensation including the effect of parameter uncertainties are reviewed. The application of the methodology to several Large Space Structures (LSS) problems of representative complexity is illustrated.

Hyland, D. C.↗