Four-gate transistor analog multiplier circuit

A differential output analog multiplier circuit utilizing four G.sup.4-FETs, each source connected to a current source. The four G.sup.4-FETs may be grouped into two pairs of two G.sup.4-FETs each, where one pair has its drains connected to a load, and the other par has its drains connected to another load. The differential output voltage is taken at the two loads. In one embodiment, for each G.sup.4-FET, the first and second junction gates are each connected together, where a first input voltage is applied to the front gates of each pair, and a second input voltage is applied to the first junction gates of each pair. Other embodiments are described and claimed

Future Missions to Titan: Scientific and Engineering Challenges

Saturn’s largest moon, Titan, has been an enigma at every stage of its exploration. For three decades after the hazy atmosphere was discovered from the ground in the 1940s, debate ensued over whether it was a thin layer of methane or a dense shield of methane and nitrogen. Voyager 1 settled the matter in favor of the latter in 1980, but the details of the thick atmosphere discovered raised even more intriguing questions about the nature of the hidden surface, and the sources of resupply of methane to the atmosphere. The simplest possibility, that an ocean of methane and its major photochemical product ethane might cover the globe, was cast in doubt by Earth-based radar studies and then eliminated by Hubble Space Telescope and adaptive optics imaging in the near-infrared from large ground-based telescopes in the 1990s. These data, however, did not reveal the complexity of the surface that Cassini-Huygens would uncover beginning in 2004. A hydrological cycle appears to exist in which methane (in concert with ethane in some processes) plays the role on Titan that water plays on Earth. Channels likely carved by liquid methane and/or ethane, lakes and seas of these materials—some rivaling or exceeding North America’s Great Lakes in size—vast equatorial dune fields of complex organics made high in the atmosphere and shaped by wind, and intriguing hints of geologic activity suggest a world with a balance of geologic and atmospheric processes that is the solar system’s best analogue to Earth. Deep underneath Titan’s dense atmosphere and active, diverse surface is an interior ocean discovered by Cassini and thought to be largely composed of liquid water. Cassini-Huygens has provided spectacular data and has enabled us to glimpse the mysterious surface of Titan. However the mission will leave us with many questions that require future missions to answer. These include determining the composition of the surface and the geographic distribution of various organic constituents. Key questions remain about the ages of surface features, specifically whether cryovolcanism and tectonism are actively ongoing or are relics of a more active past. Ammonia, circumstantially suggested to be present by a variety of different kinds of Cassini-Huygens data, has yet to be seen. Is methane out-gassing from the interior or ice crust today? Are the lakes fed primarily by rain or underground methane-ethane aquifers (more properly, “alkanofers”) and how often have heavy methane rains come to the equatorial region? We should investigate whether Titan’s surface supported vaster seas of methane in the past, and whether complex self-organizing chemical systems have come and gone in the water volcanism, or even exist in exotic form today in the high latitude lakes. The presence of a magnetic field has yet to be established. A large altitude range in the atmosphere, from 400–900 km in altitude, will remain poorly explored after Cassini. Much remains to be understood about seasonal changes of the atmosphere at all levels, and the long-term escape of constituents to space. Other than Earth, Titan is the only world in our solar system known to have standing liquids and an active “hydrologic cycle” with clouds, rains, lakes and streams. The dense atmosphere and liquid lakes on Titan’s surface can be explored with airborne platforms and landed probes, but the key aspect ensuring the success of future investigations is the conceptualization and design of instruments that are small enough to fit on the landed probes and airborne platforms, yet sophisticated enough to conduct the kinds of detailed chemical (including isotopic), physical, and structural analyses needed to investigate the history and cycling of the organic materials. In addition, they must be capable of operating at cryogenic temperatures while maintaining the integrity of the sample throughout the analytic process. Illuminating accurate chemistries also requires that the instruments and tools are not simultaneously biasing the measurements due to localized temperature increases. While the requirements for these techniques are well understood, their implementation in an extremely low temperature environment with limited mass, power and volume is acutely challenging. No such instrument systems exist today. Missions to Titan are severely limited in both mass and power because spacecraft have to travel over a billion miles to get there and require a large amount of fuel, not only to reach Titan, but to maintain the ability to maneuver when they arrive. Landed missions have additional limitations, in that they must be packaged in a sealed aeroshell for entry into Titan’s atmosphere. Increases in landed mass and volume translate to increased aeroshell mass and size, requiring even more fuel for delivery to Titan. Nevertheless, missions during which such systems and instruments could be employed range from Discovery and New Frontiers class in situ probes that might be launched in the next decade, to a full-up Flagship class mission anticipated to follow the Europa Jupiter System Mission. Capitalizing on recent breakthroughs in cryo-technologies and smart materials fabrication, we developed conceptual designs of sample acquisition systems and instruments capable of in situ operation under low temperature environments. The study included two workshops aimed at brainstorming and actively discussing a broad range of ideas and associated challenges with landing instruments on Titan, as well as more focused discussions during the intervening part of the study period. The workshops each lasted ~4 days (Monday-Thursday/Friday), included postdoctoral fellows and students in addition to the core team members, and generated active engagement from the Caltech and JPL team participants, as well as from the outside institutions. During the workshops, new instruments and sampling methodologies were identified to handle the challenges of characterizing everything from small molecules in Titan’s upper atmosphere to gross mixtures of high molecular weight complex organics in condensed phases, including atmospheric aerosols and “organic sand” in dunes, to highly dilute components in ices and lakes. To enable these advances in cryogenic instrumentation breakthroughs in a wide range of disciplines, including electronics, chemical and mechanical engineering, and materials science were identified

Electro-Mechanical Systems for Extreme Space Environments

Exploration beyond low earth orbit presents challenges for hardware that must operate in extreme environments. The current state of the art is to isolate and provide heating for sensitive hardware in order to survive. However, this protection results in penalties of weight and power for the spacecraft. This is particularly true for electro-mechanical based technology such as electronics, actuators and sensors. Especially when considering distributed electronics, many electro-mechanical systems need to be located in appendage type locations, making it much harder to protect from the extreme environments. The purpose of this paper to describe the advances made in the area of developing electro-mechanical technology to survive these environments with minimal protection. The Jet Propulsion Lab (JPL), the Glenn Research Center (GRC), the Langley Research Center (LaRC), and Aeroflex, Inc. over the last few years have worked to develop and test electro-mechanical hardware that will meet the stringent environmental demands of the moon, and which can also be leveraged for other challenging space exploration missions. Prototype actuators and electronics have been built and tested. Brushless DC actuators designed by Aeroflex, Inc have been tested with interface temperatures as low as 14 degrees Kelvin. Testing of the Aeroflex design has shown that a brushless DC motor with a single stage planetary gearbox can operate in low temperature environments for at least 120 million cycles (measured at motor) if long life is considered as part of the design. A motor control distributed electronics concept developed by JPL was built and operated at temperatures as low as -160 C, with many components still operational down to -245 C. Testing identified the components not capable of meeting the low temperature goal of -230 C. This distributed controller is universal in design with the ability to control different types of motors and read many different types of sensors. The controller form factor was designed to surround or be at the actuator. Communication with the slave controllers is accomplished by a bus, thus limiting the number of wires that must be routed to the extremity locations. Efforts have also been made to increase the power capability of these electronics for the ability to power and control actuators up to 2.5KW and still meet the environmental challenges. For commutation and control of the actuator, a resolver was integrated and tested with the actuator. Testing of this resolver demonstrated temperature limitations. Subsequent failure analysis isolated the low temperature failure mechanism and a design solution was negotiated with the manufacturer. Several years of work have resulted in specialized electro-mechanical hardware to meet extreme space exploration environments, a test history that verifies and finds limitations of the designs and a growing knowledge base that can be leveraged by future space exploration missions

Development and Testing of Mechanism Technology for Space Exploration in Extreme Environments

The NASA Jet Propulsion Lab (JPL), Glenn Research Center (GRC), Langley Research Center (LaRC), and Aeroflex, Inc. have partnered to develop and test actuator hardware that will survive the stringent environment of the moon, and which can also be leveraged for other challenging space exploration missions. Prototype actuators have been built and tested in a unique low temperature test bed with motor interface temperatures as low as 14 degrees Kelvin. Several years of work have resulted in specialized electro-mechanical hardware to survive extreme space exploration environments, a test program that verifies and finds limitations of the designs at extreme temperatures, and a growing knowledge base that can be leveraged by future space exploration missions

A Motor Drive Electronics Assembly for Mars Curiosity Rover: An Example of Assembly Qualification for Extreme Environments

This paper describes the technology development and infusion of a motor drive electronics assembly for Mars Curiosity Rover under space extreme environments. The technology evaluation and qualification as well as space qualification of the assembly are detailed and summarized. Because of the uncertainty of the technologies operating under the extreme space environments and that a high level reliability was required for this assembly application, both component and assembly board level qualifications were performed

Universal programmable logic gate and routing method

An universal and programmable logic gate based on G.sup.4-FET technology is disclosed, leading to the design of more efficient logic circuits. A new full adder design based on the G.sup.4-FET is also presented. The G.sup.4-FET can also function as a unique router device offering coplanar crossing of signal paths that are isolated and perpendicular to one another. This has the potential of overcoming major limitations in VLSI design where complex interconnection schemes have become increasingly problematic

Future Missions to Titan: Scientific and Engineering Challenges

Saturn’s largest moon, Titan, has been an enigma at every stage of its exploration. For three decades after the hazy atmosphere was discovered from the ground in the 1940s, debate ensued over whether it was a thin layer of methane or a dense shield of methane and nitrogen. Voyager 1 settled the matter in favor of the latter in 1980, but the details of the thick atmosphere discovered raised even more intriguing questions about the nature of the hidden surface, and the sources of resupply of methane to the atmosphere. The simplest possibility, that an ocean of methane and its major photochemical product ethane might cover the globe, was cast in doubt by Earth-based radar studies and then eliminated by Hubble Space Telescope and adaptive optics imaging in the near-infrared from large ground-based telescopes in the 1990s. These data, however, did not reveal the complexity of the surface that Cassini-Huygens would uncover beginning in 2004. A hydrological cycle appears to exist in which methane (in concert with ethane in some processes) plays the role on Titan that water plays on Earth. Channels likely carved by liquid methane and/or ethane, lakes and seas of these materials—some rivaling or exceeding North America’s Great Lakes in size—vast equatorial dune fields of complex organics made high in the atmosphere and shaped by wind, and intriguing hints of geologic activity suggest a world with a balance of geologic and atmospheric processes that is the solar system’s best analogue to Earth. Deep underneath Titan’s dense atmosphere and active, diverse surface is an interior ocean discovered by Cassini and thought to be largely composed of liquid water. Cassini-Huygens has provided spectacular data and has enabled us to glimpse the mysterious surface of Titan. However the mission will leave us with many questions that require future missions to answer. These include determining the composition of the surface and the geographic distribution of various organic constituents. Key questions remain about the ages of surface features, specifically whether cryovolcanism and tectonism are actively ongoing or are relics of a more active past. Ammonia, circumstantially suggested to be present by a variety of different kinds of Cassini-Huygens data, has yet to be seen. Is methane out-gassing from the interior or ice crust today? Are the lakes fed primarily by rain or underground methane-ethane aquifers (more properly, “alkanofers”) and how often have heavy methane rains come to the equatorial region? We should investigate whether Titan’s surface supported vaster seas of methane in the past, and whether complex self-organizing chemical systems have come and gone in the water volcanism, or even exist in exotic form today in the high latitude lakes. The presence of a magnetic field has yet to be established. A large altitude range in the atmosphere, from 400–900 km in altitude, will remain poorly explored after Cassini. Much remains to be understood about seasonal changes of the atmosphere at all levels, and the long-term escape of constituents to space. Other than Earth, Titan is the only world in our solar system known to have standing liquids and an active “hydrologic cycle” with clouds, rains, lakes and streams. The dense atmosphere and liquid lakes on Titan’s surface can be explored with airborne platforms and landed probes, but the key aspect ensuring the success of future investigations is the conceptualization and design of instruments that are small enough to fit on the landed probes and airborne platforms, yet sophisticated enough to conduct the kinds of detailed chemical (including isotopic), physical, and structural analyses needed to investigate the history and cycling of the organic materials. In addition, they must be capable of operating at cryogenic temperatures while maintaining the integrity of the sample throughout the analytic process. Illuminating accurate chemistries also requires that the instruments and tools are not simultaneously biasing the measurements due to localized temperature increases. While the requirements for these techniques are well understood, their implementation in an extremely low temperature environment with limited mass, power and volume is acutely challenging. No such instrument systems exist today. Missions to Titan are severely limited in both mass and power because spacecraft have to travel over a billion miles to get there and require a large amount of fuel, not only to reach Titan, but to maintain the ability to maneuver when they arrive. Landed missions have additional limitations, in that they must be packaged in a sealed aeroshell for entry into Titan’s atmosphere. Increases in landed mass and volume translate to increased aeroshell mass and size, requiring even more fuel for delivery to Titan. Nevertheless, missions during which such systems and instruments could be employed range from Discovery and New Frontiers class in situ probes that might be launched in the next decade, to a full-up Flagship class mission anticipated to follow the Europa Jupiter System Mission. Capitalizing on recent breakthroughs in cryo-technologies and smart materials fabrication, we developed conceptual designs of sample acquisition systems and instruments capable of in situ operation under low temperature environments. The study included two workshops aimed at brainstorming and actively discussing a broad range of ideas and associated challenges with landing instruments on Titan, as well as more focused discussions during the intervening part of the study period. The workshops each lasted ~4 days (Monday-Thursday/Friday), included postdoctoral fellows and students in addition to the core team members, and generated active engagement from the Caltech and JPL team participants, as well as from the outside institutions. During the workshops, new instruments and sampling methodologies were identified to handle the challenges of characterizing everything from small molecules in Titan’s upper atmosphere to gross mixtures of high molecular weight complex organics in condensed phases, including atmospheric aerosols and “organic sand” in dunes, to highly dilute components in ices and lakes. To enable these advances in cryogenic instrumentation breakthroughs in a wide range of disciplines, including electronics, chemical and mechanical engineering, and materials science were identified

Electronic drive and acquisition system for mass spectrometry

The present invention discloses a mixed signal RF drive electronics board that offers small, low power, reliable, and customizable method for driving and generating mass spectra from a mass spectrometer, and for control of other functions such as electron ionizer, ion focusing, single-ion detection, multi-channel data accumulation and, if desired, front-end interfaces such as pumps, valves, heaters, and columns

High Temperature Boost (HTB) Power Processing Unit (PPU) Formulation Study

This technical memorandum is to summarize the Formulation Study conducted during fiscal year 2012 on the High Temperature Boost (HTB) Power Processing Unit (PPU). The effort is authorized and supported by the Game Changing Technology Division, NASA Office of the Chief Technologist. NASA center participation during the formulation includes LaRC, KSC and JPL. The Formulation Study continues into fiscal year 2013. The formulation study has focused on the power processing unit. The team has proposed a modular, power scalable, and new technology enabled High Temperature Boost (HTB) PPU, which has 5-10X improvement in PPU specific power/mass and over 30% in-space solar electric system mass saving

Long-Term Reliability of a Hard-Switched Boost Power Processing Unit Utilizing SiC Power MOSFETs

Silicon carbide (SiC) power devices have demonstrated many performance advantages over their silicon (Si) counterparts. As the inherent material limitations of Si devices are being swiftly realized, wide-band-gap (WBG) materials such as SiC have become increasingly attractive for high power applications. In particular, SiC power metal oxide semiconductor field effect transistors' (MOSFETs) high breakdown field tolerance, superior thermal conductivity and low-resistivity drift regions make these devices an excellent candidate for power dense, low loss, high frequency switching applications in extreme environment conditions. In this paper, a novel power processing unit (PPU) architecture is proposed utilizing commercially available 4H-SiC power MOSFETs from CREE Inc. A multiphase straight boost converter topology is implemented to supply up to 10 kilowatts full-scale. High Temperature Gate Bias (HTGB) and High Temperature Reverse Bias (HTRB) characterization is performed to evaluate the long-term reliability of both the gate oxide and the body diode of the SiC components. Finally, susceptibility of the CREE SiC MOSFETs to damaging effects from heavy-ion radiation representative of the on-orbit galactic cosmic ray environment are explored. The results provide the baseline performance metrics of operation as well as demonstrate the feasibility of a hard-switched PPU in harsh environments