Ahmad Hammoud

Performance of surface-mount ceramic and solid tantalum capacitors for cryogenic applications

Low temperature electronics are of great interest for space exploration programs. These include missions to the outer planets, earth-orbiting and deep-space probes, remote-sensing and communication satellites. Terrestrial applications would also benefit from the availability of low temperature electronics. Power components capable of low temperature operation would, thus, enhance the technologies needed for the development of advanced power systems suitable for use in harsh environments. In this work, ceramic and solid tantalum capacitors were evaluated in terms of their dielectric properties as a function of temperature and at various frequencies. The surface-mount devices were characterized in terms of their capacitance stability and dissipation factor in the frequency range of 50 Hz to 100 kHz at temperatures ranging from room temperature (20/spl deg/C) to about liquid nitrogen temperature (-190/spl deg/C). The results are discussed and conclusions made concerning the suitability of the capacitors investigated for low temperature applications.

Electronic components and systems for cryogenic space applications

Electronic components and systems capable of operation at cryogenic temperatures are anticipated in many future NASA space missions such as deep space probes and planetary surface exploration. For example, an unheated interplanetary probe launched to explore the rings of Saturn would reach an average temperature near Saturn of about −183 °C. In addition to surviving the deep space harsh environment, electronics capable of low temperature operation would contribute to improving circuit performance, increasing system efficiency, and reducing payload development and launch costs. Terrestrial applications where components and systems must operate in low temperature environments include cryogenic instrumentation, superconducting magnetic energy storage, magnetic levitation transportation systems, and arctic exploration. An on-going R&D program at the NASA Glenn Research Center focuses on the development of reliable electronic devices and efficient power systems capable of surviving and operating in low tempera...

Electronic components and circuits for extreme temperature environments

Planetary exploration missions and deep space probes require electrical power management and control systems that are capable of efficient and reliable operation in very low temperature environments. At present, spacecraft operating in the cold environment of deep space carry radioisotope heating units in order to maintain the surrounding temperature of the on-board electronics at approximately 20/spl deg/C. Electronics capable of operation at cryogenic temperatures will not only tolerate the hostile environment of deep space but also reduce system size and weight by eliminating or reducing the radioisotope heating units and their associated structures; thereby reducing system development as well as launch costs. In addition, power electronic circuits designed for operation at low temperatures are expected to result in more efficient systems than those at room temperature. This improvement results from better behavior and tolerance in the electrical and thermal properties of semiconductor and dielectric materials at low temperatures. The Low Temperature Electronics Program at the NASA Glenn Research Center focuses on research and development of electrical components, circuits, and systems suitable for applications in the aerospace environment and deep space exploration missions. Research is being conducted on devices and systems for reliable use down to cryogenic temperatures (as low as -243/spl deg/C or 30 K). Some of the commercial-off-the-shelf as well as developed components that are being characterized includes passive and active devices and circuits. An overview of the NASA Glenn Research Center Low Temperature Electronic Program is presented in this paper. Selected data obtained through in-house components and circuits testing is also discussed.

Performance evaluation of low power DC/DC converter modules at cryogenic temperatures

Power electronics capable of operating at cryogenic temperatures is anticipated to play an important role in future NASA deep space missions. Besides having the ability to survive a very cold environment, low temperature electronics could contribute to improving system performance, and reducing development and launch costs. As part of the NASA Glenn Research Center Low Temperature Electronics Program, several commercial-off-the-shelf, low power, DC/DC converter modules were evaluated under various test parameters as a function of temperature in the range of 20/spl deg/C to -190/spl deg/C. Due to the significant amount of data generated during the investigations, only selected data pertaining to some of the tested converters is presented and discussed in this paper.

Efficiency and regulation of commercial low power DC/DC converter modules at low temperatures

DC/DC power converters that are capable of operating at cryogenic temperatures are anticipated to play an important role in the power systems of future NASA deep space missions. Design of these converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. At the NASA Glenn Research Center Low Temperature Electronics Laboratory, several commercial off-the-shelf DC/DC converter modules were evaluated for their low temperature performance. Various parameters were investigated as a function of temperature, in the range of 20/spl deg/C to -190/spl deg/C. Data pertaining to the efficiency and voltage regulation of the tested converters is presented and discussed.

Power Electronic Components, Circuits and Systems for Deep Space Missions

Power electronic circuits are widely used in space missions in the areas of power management, conditioning, and control systems. Circuits designed for deep space applications and outer planetary explorations are required to operate reliably and efficiently under extreme temperature conditions. This requirement is dictated by the fact that the operational environments associated with some of the space missions would encompass extremely cold temperatures. The development and utilization of electronics capable of low temperature operation would not only fulfil the advanced technology requirements, but also would contribute to improving circuit performance, increasing system efficiency, and reducing development and launch costs. These benefits are generally achieved by the improved intrinsic properties of some of the electronic materials at low temperature, reduced device losses, and the elimination of heating elements used in conventional systems at low temperatures. In this paper, the performance of commercially available and custom-made power electronic components and circuits was investigated under extreme-cold temperature conditions. The devices included semiconductor switches, magnetic cores, capacitors, pulse-width-modulation (PWM) controllers, and advanced commercial DC/DC converter modules. Different properties were determined as a function of temperature in the range of 20degC to - 196degC, at various voltage, current and frequency levels. The experimental procedures along with the experimental results are presented and discussed

Performance of power converters at cryogenic temperatures

Power converters capable of operation at cryogenic temperatures are anticipated to play an important role in the power system architecture of future NASA deep space missions. Design of such converters to survive cryogenic temperatures will improve the power system performance, and reduce development and launch costs. Aerospace power systems are mainly a DC distribution network. Therefore, DC/DC and DC/AC converters provide the outputs needed to different loads at various power levels. Recently, research efforts have been performed at the NASA Glenn Research Center (GRC) to design and evaluate DC/DC converters that are capable of operating at cryogenic temperatures. This paper is a summary of the research performed to evaluate the low temperature performance of five DC/DC converters. Various parameters were investigated as a function of temperature in the range of 20/spl deg/C to -196/spl deg/C. Data pertaining to the output voltage regulation and efficiency of the converters is presented and discussed.

Power electronics in harsh environments

The environmental temperature in many NASA missions, such as deep space probes and outer planetary exploration, is significantly below the range for which conventional commercial-off-the-shelf electronics is designed. Presently, spacecraft operating in the cold environment of such deep space missions carry a large number of radioisotope or other heating units in order to maintain the surrounding temperature of the on-board electronics at approximately 20 /spl deg/C. Electronic devices and circuits capable of operation at cryogenic temperatures -does not only tolerate the harsh environment of deep space but also reduces system size and weight by eliminating or reducing the heating units and their associate structures; thereby reducing system development cost as well as launch costs . This improvement results from better behavior in the electrical and thermal properties of some semiconductor and dielectric materials at low temperatures. An on-going research and development program on low temperature electronics at the NASA Glenn Research Center focuses on the development of efficient electrical systems and circuits capable of surviving and exploiting the advantages of low temperature environments. In this paper, the performance of some power electronic components and circuits was investigated under low temperature. These include semiconductor switches, inductors, capacitors, pulse-width-modulation (PWM) controllers, and advanced commercial DC/DC converter modules. Different properties were determined as a function of temperature in the range of 20 /spl deg/C to -196 /spl deg/C, at various current and voltages levels. The experimental procedures along with the experimental results are presented and discussed.

Cryogenic evaluation of an advanced DC/DC converter module for deep space applications

DC/DC converters are widely used in power management, conditioning, and control of space power systems. Deep space applications require electronics that withstand cryogenic temperature and meet a stringent radiation tolerance. In this work, the performance of an advanced, radiation-hardened (radhard) commercial DC/DC converter module was investigated at cryogenic temperatures. The converter was investigated in terms of its steady state and dynamic operations. The output voltage regulation, efficiency, terminal current ripple characteristics, and output voltage response to load changes were determined in the temperature range of 20/spl deg/C to - 140/spl deg/C. These parameters were obtained at various load levels and at different input voltages. The experimental procedures along with the results obtained on the investigated converter are presented and discussed.

Preliminary evaluation of polyarylate dielectric films for cryogenic applications

Polymeric materials are used extensively on spacecraft and satellites in electrical power and distribution systems, as thermal blankets and optical surface coatings, as well as mechanical support structures. The reliability of these systems when exposed to the harsh environment of space is very critical to the success of the mission and the safety of the crew in manned-flight ventures. In this work, polyarylate films were evaluated for potential use as capacitor dielectrics and wiring insulation for cryogenic applications. Two grades of the film were characterized in terms of their electrical and mechanical properties before and after exposure to liquid nitrogen (−196 °C). The electrical characterization consisted of capacitance and dielectric loss measurements in the frequency range of 50 Hz to 100 kHz, and volume and surface resistivities. The mechanical measurements performed included changes in tensile Z(Youngs modulus, elongation-at-break, and tensile strength) and structural properties (dimensional change, weight, and surface morphology). The preliminary results, which indicate good stability of the polymer after exposure to liquid nitrogen, are presented and discussed.