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The Mod-OA wind turbine blades were rotated for the first time on November 30, 1977, establishing the Mod-OA as the first wind-driven generator in 35 years to be continually tied into an electrical power system which services a community. Tower-mounted equipment and blade structural design and fabrication are discussed.
Dimensionless conservation equations, are presented and the theoretical basis of fluid behavior aboard orbiting satellites are reviewed with application to the processes of manufacturing crystals in weightlessness. The small amount of gravitational acceleration is shown to increase the separation of bands of varying concentration. Natural convection is shown to have no practical effect on crystallization from realistic conductions of weightlessness. The effects of surface tension become increasingly large, and suggestions are made for further research.
Two 60 foot long aluminum wind turbine blades were operated for over 3000 hours on the MOD-OA wind turbine. The first signs of blade structural damage were observed after 400 hours of operation. Details of the blade design, loads, cost, structural damage, and repair are discussed.
Operating loads and structural damage were monitored during operation of the MOD-OA electric generating system. The turbine was damaged locally between stations 48 and 125 after 2.8 million rotations. Loads due to degraded yaw stiffness and fretting at rib station 48 were identified as primary to this distress. The repaired blades operated an additional 4.8 million rotations without problems.
Engineering drawings and the detailed mechanical and electrical design of a horizontal-axis wind turbine designed for DOE at the NASA Lewis Research Center and installed in Clayton, New Mexico are discussed. The drawings show the hub, pitch change mechanism, drive train, nacelle equipment, yaw drive system, tower, foundation, electrical power systems, and the control and safety systems.
The machine configuration and its advantages and disadvantages, particularly as it affects reliability are discussed. The machine performance, both availability and power output characteristics are described. The Mod-OA operational experience is documented. The characteristics of the wind energy generated, the machine performance, and the subsystem strengths and weaknesses are discussed. An assessment of the project success in fulfilling its goals and objectives is also presented.
The windpowered generator, Mod-0A, and its advantages and disadvantages, particularly as it affects reliability, are discussed. The machine performance with regard to power availability and power output is discussed.
Future plans call for increasing the uplink and downlink frequencies used for communication with deep space probes from the present 2 GHz and 8 GHz bands into the millimeter band, 32-35 GHz.
The National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC) (Edwards, California) is developing a Hybrid-Electric Integrated Systems Testbed (HEIST) Testbed as part of the HEIST Project, to study power management and transition complexities, modular architectures, and flight control laws for turbo-electric distributed propulsion technologies using representative hardware and piloted simulations. Capabilities are being developed to assess the flight readiness of hybrid electric and distributed electric vehicle architectures. Additionally, NASA will leverage experience gained and assets developed from HEIST to assist in flight-test proposal development, flight-test vehicle design, and evaluation of hybrid electric and distributed electric concept vehicles for flight safety. The HEIST test equipment will include three trailers supporting a distributed electric propulsion wing, a battery system and turbogenerator, dynamometers, and supporting power and communication infrastructure, all connected to the AFRC Core simulation. Plans call for 18 high performance electric motors that will be powered by batteries and the turbogenerator, and commanded by a piloted simulation. Flight control algorithms will be developed on the turbo-electric distributed propulsion system.
This test bench represents a significant risk mitigation for creating the turbo-electric flying demonstrator.
There a few NASA funded electric and hybrid electric projects from different NASA Centers, including the NASA Armstrong Flight Research Center (AFRC) (Edwards, California). Each project identifies a specific technology gap that is currently inhibiting the growth and proliferation of relevant technologies in commercial aviation. This paper describes the design and development of a turbo-electric distributed propulsion (TeDP) hardware-in-the-loop (HIL) simulation bench, which is a test bed for discovering turbo-electric control, distributed electric control, power management control, and integration competencies while providing risk mitigation for future turbo-electric flying demonstrators.
Towers are an efficient structure commonly used to elevate systems against a gravity field, such as above the surface of a planet or the Moon. Towers can be used to elevate antennas, transmitters and sensors for communication, navigation, and observation infrastructure in support of surface operations. Near the Lunar poles, elevation of rotating solar panels enables nearly continuous panel illumination for solar power production despite the Sun remaining near the horizon year-round. Further, once technology is developed for tower assembly, this same technology can be extended to the assembly of a variety of structures including rocket blast containment shields, bridges, shelters, and habitats from either Earth-sourced or Lunar-sourced structural members. Environmental factors on the Lunar surface are vastly different than those found on Earth and have significant impact on the design of towers. Towers designed for the Lunar surface have no heritage nor Earth analog. The designs discussed herein are therefore breaking new ground creating a fundamentally new class of structures outside of current experience and intuition. The purpose of this paper is to: a) describe the unique environmental factors affecting tower design on the Lunar surface compared to Earth-based systems, b) evaluate two structural forms for the tower; telescoping tubes and an assembled truss, as well as c)provide recommendations on when each structural form is most suitable. A major contribution presented in the current paper is to provide parametric plots and supporting equations of mass and volume versus module power level and blanket height above the Lunar surface for the solar array application, to enable system level studies of optimum power module distribution and size. A secondary contribution are plots of the mass and volume of aluminum or structural glass required for assembled truss towers formed from Lunar derived structural members. An objective of achieving 1 MW of total power has been used to enable comparison of structural forms, because the total mass of solar arrays is consistent. It will be shown that for moderate module sizes, up to ~50 kW power modules, based on a telescoping tube tower have advantages, but for power modules from 50 kW to 200 kW an assembled truss tower can be created with half to one third of the tube tower mass. More significantly, when shipped from Earth, an assembled truss tower can be packed into 1/14th to 1/25th of the tube tower volume. Truss designs in the 100 kW to 200 kW range will be shown to be a favorable when assembled from either graphite-epoxy angles shipped from Earth or aluminum angles fabricated from Lunar materials. 50 kW towers are an attractive choice for both a telescoping or assembled tower with the solar arrays elevated 10 m above the Lunar surface, while increased solar array elevation favors 100 kW to 200 kW power modules.
Three fission chambers were tested at The Ohio State University Research Reactor (OSURR) to evaluate fission chambers for neutron flux and spectrum measurements. Two of the fission chambers are commercial Photonis CFUR43 fission chambers—one utilizing highly enriched uranium-235 fissile deposits for thermal neutron detection and the other with highly depleted uranium-238 for fast neutron detection. This experiment was also performed in collaboration with French Alternative Energies and Atomic Energy Commission (CEA) with CEA suppling a uranium-235 loaded fission chamber built from the Photonis CFPR CE8/9 kit. The fission chambers were irradiated in a movable 6.5 inch dry tube at reactor powers of 50 kW, 200 kW, and 450 kW at ambient temperature and at 350°C. While all sensors demonstrated good linear sensitivity to reactor power, a leakage current of 6 nA was measured for the CFUR43 detectors. Additionally, the measured signal ratios of the two CFUR43 detectors did not match the theoretical values and are subject to further investigation on individual signal contributors.
Projections for the total potential output of large wind turbines in the U.S. are reviewed. NASA has developed nine large windpowered generators, of 100 kW, 200 kW, 2 MW, and 2.5 MW capacities, with rotors 100-300 ft in diameter, and all with horizontal axes. Approximately 214,000 sq miles of the U.S. have been determined as having substantial wind regimes and terrain suitable for large wind turbine siting. This translates into 340,000 Mod 2 (2.5 MW) wind turbines producing 4.9 quads of electricity annually, equivalent to saving 2.5 billion barrels of oil/yr. The cost of electricity is seen as the critical factor in utility acceptance of large wind turbines, and the Mod 2 machines are noted to achieve the 2-4 cents/kWh (1977 dollars) COE which is necessary. Problems such as pollution, including visual, auditory, EM, and land use difficulties are considered, and solutions are indicated.
A 30-cell stack was tested for 7200 hours. At 6000 hours the stack was successfully refilled with acid with no loss of performance. A second stack containing the advanced Configuration B cell package was fabricated and assembled for testing in 1985. A 200-kW brassboard inverter was successfully evaluated, verifying the design of the two-bridge ASCR circuit design. A fuel processing catalyst train was tested for 2000 hours verifying the catalyst for use in a 200-kW development reformer. The development reformer was fabricated for evaluation in 1985. The initial test plan was prepared for a 200-kW verification test article.
Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency RF sources operating from a few hundred MHz to C-Band and power levels from tens to hundreds of kilowatts with the goal of providing MW-relevant sources. The efficiencies approach or exceed 80% with projected costs as low as $0.50/ Watt. Sources under development include magnetrons with phase and amplitude control, single and multi-beam klystrons, multi-beam power grid tubes, and multiple beam IOTs. A magnetron system achieved more than 80% efficiency with fast amplitude control using modulation of the phase locking signal. This would be a low cost, high efficiency RF source for superconducting accelerators. An L-Band, single beam klystron was built with simulated efficiency of 80%. The klystron has yet to be tested to confirm the simulation results. CCR is currently developing a multi-beam klystron to produce more than 200 kW CW at 80% efficiency. Also in development is a multiple beam triode to produce 200 kW CW from 300 MHz to approximately 1 GHz. Not only does the simulated efficiency exceed 75%, but it would be the lowest cost RF source in this frequency range. Finally, CCR recently concluded research for a multiple beam IOT at 700 MHz using third harmonic drive to boost efficiency toward 85%. Successful development and transition to production of these sources will significantly alter the cost/performance landscape for RF power generation.
Calabazas Creek Research, Inc. (CCR) and its collaborators are developing high efficiency, low cost RF sources. Phase and Amplitude Controlled Magnetrons: CCR, Fermilab, and Communications & Power Industries, LLC (CPI) recently developed a 100 kW, 1.3 GHz magnetron system with amplitude and phase control. The system operated at more than 80% efficiency and demonstrated rapid control of amplitude and phase. Multiple Beam Triodes: CCR, in collaboration with CPI and JP Accelerator Works, Inc., is developing 200 kW, pulsed and CW RF sources from 350 to 700 MHz with projected efficiencies exceeding 80% and cost of $0.50/Watt. Prototype tubes are scheduled for tests in spring 2021. High Efficiency Klystrons:CCR, CPI, and Leidos, Inc. are building a 1.3 GHz, 100 kW klystron operating at 80% efficiency. High power testing is scheduled for summer 2021. Multiple Beam IOTs: CCR and Georgia Tech Research Institute are developing MBIOTs with simplified input coupling and high efficiency. Simulations indicate that 3rd harmonic drive power can increase the efficiency 8-10 %. The program is developing a prototype tube to produce 200 kW peak, 100 kW average power at 704 MHz.
Two sixty-foot, low-cost, wood composite blades for service on 200 kW Mod-OA wind turbines were constructed. The blades were constructed of epoxy resin-bonded Douglas fir veneers for the leading edge sections, and paper honeycombcored, birch plywood faced panels for the afterbody sections. The blades were joined to the wind turbine hub by epoxy resin-bonded steel load take-off studs embedded into the root end of the blades. The blades were installed on the 200 kW Mod-OA wind turbine facility at Kahuku, Hawaii, The blades completed nearly 8,000 hours of operation over an 18 month period at an average power of 150 kW prior to replacement with another set of wood composite blades. The blades were replaced because of a corrosion failure of the steel shank on one stud. Inspections showed that the wood composite structure remained in excellent condition.