Doubly Self-Aligned DMOSFET in SiC for Microgravity Manufacture

The need exists for power electronics capable of operation at high temperatures in a high radiation environment, such as in deep space. There is a rationale for fabricating such devices from materials already in situ, such as building very large phased array antennas. Device manufacture on human-staffed microgravity platform presents a challenge to the tight lithographic alignment required for traditional fabrication methods. Presented here for the first time is a process sequence to produce high-mobility DMOS FETs with no masking steps requiring critical alignment, yet yielding channel lengths of 0.15 micron. The fabrication process is further designed to utilize and recycle materials expected to be available on certain classes of asteroids and within extinct comets, with minimal need for reagents from earth. One application is manufacture of the tens of millions of MMIC power amplifiers required for wireless power transfer to terrestrial customers from solar power satellites in geostationary earth orbit

Solar power satellite with no moving parts

The only solution to the global energy mess is sunlight captured in space. No other technology scales as well, and is as clean as Space Solar Power. Best of all, this is baseload power – “always on” – without the intermittency which will always plague ground-based solar and wind. Although invented in 1968, SSP designs have been impractical until now. A novel design architecture, relying on use of materials already in space, enables SSP at costs competitive with existing baseload power sources. And all this without greenhouse gas emissions. This work describes the technology and economics. The “tin can” solar power satellite is comprised of a cylindrical shell of solar panels. This configuration has integral thermal management by using the non-illuminated portions of the shell as a radiating heat shield, maintaining the solar cells within workable temperature ranges. The tethers holding the shell to the central conductor spire present a complex radiative environment which is studied further herein to obtain a more precise measurement of high and low temperature limits. Heat generated by the transmitting antenna and its power electronics is also studied to understand its impact on the requirements imposed on components and subsystems. Achieving a slow rotation of a very large diameter cylindrical shell with minimal internal strength interacts with the assembly process through tradeoffs between propellant, assembly jigs, and construction spacecraft. Vibrations induced in the cylindrical shell are studied including transient behavior during spin-up. The panel-to-panel forces expected during spin-up, and during on-going operations as gravity gradients excite low-frequency modes are studied in order to derive specifications for linkage rotation and strength. Finally, the results of imperfect assembly, lost parts, and meteorite strikes are investigated to assess risk to other spacecraft. Solar wind pressure is evaluated to determine station-keeping requirements. Assembly in an orbit slightly higher than GEO may be selected to minimize collateral damages, and means of adjusting the orbit are studied to derive overall architecture propellant requirements, anticipating a mixture of in situ propellant options versus earth-sourced propellants. This work charts a pathway to the ultimate energy source for all mankind for all time to come.Richard G. Lugar Center for Renewable Energ

Mentored, Unpaid Design Team Internship Experience

An international team of 7 undergraduate interns working pro bono during the summer made significant advances in several areas of Space Solar Power. Distinct from a capstone design effort, this study group revived the practice common in the 1970s and 1980s of considering broad topics of high relevance to public citizens and elected decision-makers. Significant obstacles to success included lack of research experience, lack of motivating paycheck, and a highly-complex system under study. Each student was assigned a mentor from the aerospace industry or academia to guide the creation of a research plan, and to periodically review progress. Team-building exercises were conducted to develop relationships, and weekly team workshops were held to teach interoperability with other subsystems. Student experiences shifted from excitement at the outset to a sense of being overwhelmed with the magnitude and difficulties associated with a space-based project running in the tens of billions of dollars. Yet, each student was able to overcome such mid-term concerns, and to make a meaningful contribution to a key research question. Their results were published at a national space conference with all students listed as co-authors. The present work assesses the formation of such an unpaid team and the management thereof, analyzes the techniques used to encourage desired outcomes, and finishes with post-project follow-up on perceptions and career choices. This approach may find interest among professors with limited funds who seek to develop solid preliminary data to make grant applications more competitive

Brownfield remediation powered by renewable energy

Subsurface contaminant plumes are a plague upon the earth. Some 1900 plumes remain after the go-fast atom bomb projects of the Cold War. Countless gasoline station sites dot our cities, leaching heavy metals and chlorinated solvents into drinking water. Superfund-type cleanup is so expensive that many sites languish while toxins continue to spread throughout the ecosystem. Federal funding for remediation research stopped 15 years ago. The only solution now is to move bad soil from one location to another. New advances in stem cell manipulation offer promise to clean up solvent-infused earth with a minimum of excavation at greatly reduced costs. Dielectrophoresis is the means by which polar molecules, in a matrix having a different dielectric constant, can be made to migrate along electric field gradients. A unique configuration called “pills and pillars” facilitates remediation of solvents. Electric field gradients originating in the deeply-driven “pillars” motivate solvents molecules towards the slightly-buried “pill”. When powered by renewable sources, such as solar panels, contaminants within a 1000 m3 volume can be concentrated within a 1 m3 volume at the pill, and then removed for disposal in a certified toxic waste repository. The pills and pillars are easily extracted for removal to a new site every 40 days. The solar panels are man-portable so that a single capital expenditure of a truckmounted kit can serve multiple sites simultaneously, and sequentially. The low labor overhead, the greatly reduced excavation, and the re-use of hardware contribute to make this novel method of brownfield remediation far cheaper than traditional, presently-available methods. Computer simulations including both vadose zone diffusion (natural spreading out) and drift via dielectrophoresis, demonstrate the effectiveness of this approach. The next research step is to build a benchtop model to validate the simulation model, followed by field trials with partners in the environmental remediation industry.Richard G. Lugar Center for Renewable Energ

Nuclear Power from Lunar ISRU

Thorium on the lunar surface can be transmuted into fissile uranium suitable for a controlled chain reaction to provide heat. Thorium is fertile, requiring bombardment by neutrons to become a suitable nuclear fuel. Oxides of thorium are dense and can be concentrated and beneficiated from comminuted regolith via inertial or thermal means. A neutron flux can be provided by encasing thoria within a beryllium and graphite vessel, which emits neutrons upon exposure to gamma rays or galactic cosmic rays. After a brief period at protactinium the transmuted material becomes U-233, a desirable fuel because decay product half-lives are below 100 years. When compressed into fuel pellets the uranium oxide is configured into a reactor through which a working fluid can extract thermal power. With regolith tailings as shielding such a reactor can operate safely for 30 years. A century later, the site can be harvested for specialty elements and then made available for other uses. The advent of launch-safe nuclear rockets in space greatly expands the potential for in situ resource utilization, a space-based economy, and profitable exploitation of the asteroid belt

Removing Crop Residues Without Hurting Soil

Agricultural residue, the organic matter left over after grain harvesting, has the potential to replace a large fraction of our petroleum and coal use, making this a significant national benefit. However, agricultural residues also serve a useful function in farm soils, so it is important to understand the impact of removing some of these residues

Robust Automated Airbag Module Calibration

Increasing sophistication of electronic safety systems requires more advanced tools for design and optimization. Systems of safety products already being designed are becoming too interdependent to calibrate as stand-alone modules. Compounding this difficulty is the trend towards fewer test crashes and more sophisticated regulatory requirements. This paper presents a unified calibration approach to produce robust performance. First, the set of crash samples are extended using statistical techniques. Then an automated calibration tool using Genetic Algorithms is used to provide robust performance against deployment requirements. Finally, an expert systems is employed to ensure logical behavior. Together, these powerful methods yield calibrations which out-perform manual calibrations and can be completed in far less time

Costs, Organization, and Roadmap for SSP

Space Solar Power will be too expensive until it is too late to afford it. Politicians shy away from projects that last longer than they will remain in office. Governments are reluctant to fund projects where there are no short-term paybacks. Militaries will not sponsor work that cannot be used to fight wars. Corporate investment in long-term projects without a proven return are unlikely. Environmentalists, status quo defenders, and established energy interests alike will resist large-scale projects, driving up costs and costing time. There is presently no consensus on an optimal SSP architecture; nor is there an agreed-upon cost; nor is there an organization charged with achieving either. Therefore, SSP needs a miracle. By definition, miracles cannot be predicted, or counted upon. However, it is possible to prepare for miracles, so that when they do arise, action can begin immediately. This paper describes how to prepare for the miracle

Plasma Extraction of Metals in Space

Extraction of purified metals from extraterrestrial materials can be accomplished in several ways, such as beneficiation, hydrogen reduction, recovery of spent rockets, direct melting of iron meteorites, and plasma isotope separation. Presented here is a method for multiple simultaneous extraction of multiple metals and metalloids from regolith. Two patented approaches are described which can operate on a planetary surface, or in the microgravity environment of orbit. This approach to isotope separation applies to regolith fines but is advantageously applied to the effluent of a patented oxygen extraction method. In this way, a plurality of valuable raw materials can be obtained with a single system, suitable for operation on the Moon or at the surface of an asteroid. Silicon is of interest for studies of purity due to its importance in photovoltaics. A silicon-aluminum aerospace alloy can be produced directly, called Silumin, which has value in construction of habitats and space craft in space. Silicon can also be combined with carbon to form the wide-bandgap semiconductor SiC from which high-power and radiation-tolerant power transistors can be fabricated. Furthermore, this method lends itself to additive manufacturing whereby specific shapes of purified metals can be formed directly from the plasma extraction process

Distributed Bio-Hydrogen Refueling Stations

Hydrogen fuel cell cars are now available for lease and for sale. Renewable hydrogen fuel can be produced from water via electrolysis, or from biomass via gasification. Electrolysis is power-hungry with high demand from solar or wind power. Gasification, however, can be energy self-sufficient using a recently-patented thermochemical conversion technology known as I-HPG (indirectly-heated pyrolytic gasification). I-HPG produces a tar-free syngas from non-food woody biomass. This means the balance of plant can be small, so the overall system is economical at modest sizes. This makes it possible to produce renewable hydrogen from local agricultural residues; sufficient to create distributed refueling stations wherever there is feedstock. This work describes the specifics of a novel bio-hydrogen refueling station whereby the syngas produced has much of the hydrogen extracted with the remainder powering a generator to provide the electric power to the I-HPG system. Thus the system runs continuously. When paired with another new technology, moderate-pressure storage of hydrogen in porous silicon, there is the potential to also power the refueling operation. Such systems can be operated independently. It is even possible to design an energy self-sufficient farm where all electric power, heat, and hydrogen fuel is produced from the non-food residues of agricultural operations. No water is required, and the carbon footprint is negative, or at least neutral