摘要:

The rationale for Wireless Power Transmission (WPT) technology applications is presented to meet the needs of the growing global population. These applications include high‐altitude, long‐endurance aircraft to supplement communication satellites, power relay satellites to acess large‐scale terrestrial renewable energy sources, and solar power satellites to meet global energy demands without increasing stresses on the Earth’s ecology. An overview of past developments and demonstrations of WPT is provided and international activities in Europe, Japan, United States and the former USSR in this field highlighted. These ongoing activities are considered to provide opportunities for a growth path for commercial endeavors with defined milestones so as to gain public acceptance. The conclusion is presented that WPT technologies can provide the impetus for international cooperation to meet global energy demands, and for effective management of both terrestrial and extraterrestrial resources on an unprecedented scale. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47165

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

This paper describes unmanned missions planned in support of NASA’s Space Science Enterprise over the next ten years. It focuses on smaller, focused missions employing advanced technology in order to achieve significant science return at a reduced cost and duration such as the Discovery and Small Explorer programs now in place and the next generation of small missions now being planned. These next generation missions will continue to build upon the expeditionary nature of the original flagship missions through the focused investigation of specific phenomena or features of interest, using small, inexpensive, highly integrated spacecraft, costing an order of magnitude less than past missions and developed in a fraction of the time. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47117

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Over the past five years, the U.S. Government has provided research and development ‘‘seed money’’ for a number of important small satellite developments and initial demonstrations. As a result, the United States today leads the world in the development and deployment of military, civil and commercial small satellite systems. This paper recommends a path for future small satellite development by focusing resources on technologies which will deliver higher performance and higher reliability and refocusing the involved Federal laboratories on the development of compact, high‐performance payload instruments. This work was sponsored by Spectrum Astro, Inc. and was performed at Spectrum Astro’s headquarters located in Gilbert, Arizona. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47225

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Matrixed field emission devices have been fabricated using a modification of standard integrated circuit fabrication techniques. The emtter‐to‐gate spacing is fixed by the thickness of a deposited oxide and not by photolithograpnic techniques. Functioning triodes have been fabricated using this deposited oxide spacer spproach. Measured emission current to a collector electrically and physically separated from the matrixed emission array follows Fowler‐Nordheim behavior. Modeling of the potential field near the emitter and gate structures as well as the emitted electron trajectories with a two‐dimensional, Poisson solver, finite‐differnce code was used to evaluate and improve field emission structures. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47164

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report on two novel high temperature and potentially highly neutron and gamma radiation resistant electronc technologies that are suitable for nuclear and space applications. The operational effects on these technologies from gamma radiation doses up to 10 megarads and 1‐MeV equivalent neutron fluences up to 1014neutrons/cm2are examined using a calibrated (to appropriate ASTM standards) irradiation chamber in the University of Utah TRIGA Nuclear Reactor. The first high temperature, harsh environment technology is based on microminiature vacuum (MTV) devices. The second high temperature technology is gallium arsenide (GaAs) metal semiconductor field effect transistor (MESFET)‐based devices and circuits that can operate at temperatures up to 350 °C. This MESFET‐based technology also allows a wide range of control with respect to the MESFET’s enhanced resistance to breakdown at elevated temperatures. The MESFET‐based technology has general applicability and works equally well with both enhancement and depletion n‐channel MESFET’s. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47178

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A SiC high temperature amplifier circuit has been developed using discrete SiC depletion mode transistors. The amplifier open loop gain decreases by only 4 dB over the temperature range of 298 to 573 K at 1 kHz. From radiation effects results on the discrete devices included in this paper it is expected that this amplifier could survive a severe radiation environment to a total dose of 100 Mrad and neutron fluence exceeding 1015n/cm2. The radiation results also suggest that the amplifier will be less susceptible to radiation at high temperatures. ©1995 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47186

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The paper describes the details of a majority voted fault tolerant shunt regulator for a 6 kW thermionic nuclear reactor. The shunt regulator compensates for spacecraft load changes to maintain a constant load on the reactor. Power not used by the loads or to recharge the spacecraft battery is dissipated in externally mounted resistors. The excess power control is done by sequentially switching the shunt resistors for coarse control. The fine adjustment of the excess power is done using a multistage linear sequential shunt. The shunt regulator is designed to handle multi‐kilowatt load transients and is tolerant to any single failure in the control electronics. The power handling capability can be increased by increasing the number of the digital switched shunts. The breadboard test and analysis results are presented. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47196

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Electrical measurements have been performed on the TOPAZ 2 V‐71 and Ya‐21 Reactors, in order to characterize the source impedance as a function of DC operating point and frequency. The response of the reactor to step changes in load current, as well as the frequency content of the electrical noise generated by the reactor have also been measured. These parameters are important to know in order to design power regulation circuitry which maintains a constant load on the reactor during spacecraft operations for any flight application of the TOPAZ 2 reactors. Voltage spikes at the reactor interface induced by load transients must be limited; the power regulation circuitry must have adequate bandwidth to compensate for spacecraft load dynamics. The methods used to make these measurements will be discussed. Results of the measurements on the Ya‐21 reactor indicate the source impedance is dominated by a series resistance and inductance. The equivalent DC leakage resistance from the reactor output to structure was also measured. The self generated noise of the reactor is benign; load induced transients will be sufficiently controlled with capacitive filtering and active regulation circuitry external to the reactor/power distribution system. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47136

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thermal systems for space applications based on two phase flow have several advantages over single phase systems. Two phase thermal energy management and dynamic power conversion systems have the capability of achieving high specific power levels. However, before two phase systems for space applications can be designed effectively, knowledge of the flow behavior in a ‘‘0‐g’’ acceleration environment is necessary. To meet this need, two phase flow experiments were conducted by the Interphase Transport Phenomena Laboratory Group (ITP) aboard the National Aeronautics and Space Administration’s (NASA) KC‐135, using R12 as the working fluid. The present work is concerned with modeling of two‐phase pressure drop under 0‐g conditions, for bubbly and slug flow regimes. The set of data from the ITP group includes 3 bubbly points, 9 bubbly/slug points and 6 slug points. These two phase pressure drop data were collected in 1991 and 1992. A methodology to correct and validate the data was developed to achieve high levels of confidence. A homogeneous model was developed to predict the pressure drop for particular flow conditions. This model, which uses the Blasius Correlation, was found to be accurate for bubbly and bubbly/slug flows, with errors not larger than 28%. For slug flows, however, the errors are greater, attaining values up to 66%. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47145

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Thermal management systems for space applications based on two phase flow have attractive advantages over single phase systems including reduced mass and increased heat transfer rates. However, before two phase systems for space can be designed effectively, knowledge of two phase flow behavior through real engineering components in reduced gravity is necessary. This work shows typical plots from an experimental study of two phase flow pressure drops through 1.25 m corrugated flexible bellows and quick disconnect attachments in reduced gravity. Three components are examined: a 10.41 mm minimum inner diameter flexible bellows, a 4.7 mm minimum inner diameter flexible bellows, and a quick disconnect apparatus between two 10.41 mm bellows sections. These components were tested simultaneously with a 1.25 m smooth glass tube of identical inner diameter for comparison. The smooth glass tubes were filmed using a digital imager for flow regime determination. These data were obtained from a test package using R12 as the working fluid and flown aboard NASA’s KC‐135. For the data used in these figures, pressure drops in the quick disconnect section increase 30–40% in microgravity, while in both sizes of bellows sections, pressure drops are seen to decrease 10–20%. © 1995American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.47154

出版商:AIP    

年代:1995

数据来源: AIP