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Turboelectric propulsion is a technology that can potentially reduce aircraft noise, increase fuel efficiency, and decrease harmful emissions. In a turbo-electric system, the propulsor (fans) is no longer connected to the turbine through a mechanical connection. Instead, a superconducting generator connected to a gas turbine produces electrical power which is delivered to distributed fans. This configuration can potentially decrease fuel burn by 10% [1]. One of the primary challenges in implementing turboelectric electric propulsion is designing the power distribution system to transmit power from the generator to the fans. The power distribution system is required to transmit 40 MW of power from the generator to the electrical loads on the aircraft. A conventional aircraft distribution cannot efficiently or reliably transmit this large amount of power; therefore, new power distribution technologies must be considered.

A fuel cell powered airplane has been designed and constructed at the Georgia Insitute of Technology to develop an understanding of the design and implementation challenges of fuel cell-powered unmanned aerial vehicles (UAVs). A custom 448W net output proton exchange membrane fuel cell powerplant has been constructed and tested. A demonstrator aircraft was designed and built to accommodate this powerplant and the fuel cell powered aircraft has performed seven test flights to date. Test data show that the aircraft performance validates the models used for design and optimization and that the fuel cell aircraft is capable of longer endurance, higher performance test flights.

The environmental impact of aircraft, specifically in the areas of noise and NOx emissions, has been a growing community concern. Coupled with the increasing cost and diminishing supply of traditional fossil fuels, these concerns have fueled substantial interest in the research and development of alternative power sources for aircraft. In 2003, NASA and the Department of Defense awarded a five year research cooperative agreement to a team of researchers from three different universities to address the design and analysis of revolutionary aeropropulsion technologies.

This paper outlines a comprehensive, structured, and robust methodology for decision making in the early phases ofaircraft design. The proposed approach is referred to as the Technology Identification, Evaluation, and Selection (TIES) method. The seven-step process provides the decision maker/designer with an ability to easily assess and trade-off the impact of various technologies in the absence of sophisticated, time-consuming mathematical formulations. The method also provides a framework where technically feasible alternatives can be identified with accuracy and speed. This goal is achieved through the use of various probabilistic methods, such as Response Surface Methodology and Monte Carlo Simulations. Furthermore, structured and systematic techniques are utilized to identify possible concepts and evaluation criteria by which comparisons could be made.

As gas prices and climate change become the preeminent issues of today, more research effort is being directed towards the development of cheaper and cleaner alternative energy sources. These efforts have been further complemented with research into the applicability of these sources to air, land and sea borne vehicles. In this report a notional C-172R general aviation aircraft is retrofitted with a PEM power plant as a case-study. Lower bounds for useful load and range are set in such a way that the results can be useful in determining how much improvement in the technology would be required to power a useful general aviation vehicle. It is seen that even at the predicted 2015 fuel cell technology level (per US Department of Energy projections), PEM systems would still be infeasible for this vehicle due to low specific power. Further investigation revealed that a PEM-battery hybrid system had better chances of feasibility.

Our concept studies indicate that a set of reflectors floated in the upper atmosphere can efficiently reduce radiant forcing into the atmosphere. The cost of reducing the radiant forcing sufficiently to reverse the current rate of Global Warming, is well within reach of global financial resources. This paper summarizes the overall concept and focuses on one of the reflector concepts, the Flying Carpet. The basic element of this reflector array is a rigidized reflector sheet towed behind and above a solar-powered, distributed electric-propelled flying wing. The vehicle rises above 30,480 m (100,000 ft) in the daytime by solar power. At night, the very low wing loading of the sheets enables the system to stay well above the controlled airspace ceiling of 18,288 m (60,000 ft). The concept study results are summarized before going into technical issues in implementation. Flag instability is studied in initial wind tunnel experiments.

A direct solution to Global Warming would be to reflect a part of sunlight back into Space. A system tradeoff study is being developed with three of the concepts that are being evaluated as long-endurance high-altitude reflectors. The first concept is a high aspect ratio solar powered flying wing towing reflector sheets. This concept is named “Flying Carpet”. Second is a centrifugally stretched high altitude solar reflector (CSHASR). The CSHASR has 4 rotors made of reflector sheets with a hub stretching to 60 percent of the radius, held together by an ultralight quad-rotor structure. Each rotor is powered by a solar-electric motor. A variation on this concept, forced by nighttime descent rate concerns, is powered by tip-mounted solar panels and propellers with some battery storage augmenting rotational inertia as well as energy storage. The third concept is an Aerostatically Balanced Reflector (ABR) sheet, held up by hydrogen balloons.

The development of a universal personal air vehicle has been the dream of aeronautical visionaries since before the time of the Wright brothers' first flight. Through fits and starts the modern general aviation market developed both before and after the Second World War. However, the true personal airplane, one that rivals the automobile, has never emerged. There are a multitude of reasons for this; however, it is not possible to identify any single cause as the key component. Instead it is the complex interaction of regulations, market size, and technical and program risk. This paper shows that in the current environment there are few truly technical barriers to the development of a low-cost personal air vehicle. Instead, the market, regulatory, and program issues have come to dominate the problem. This means that the current impediment to the development of personal air vehicles is essentially an issue of finding a means to “close the business case.”

Unfortunately, the promises of efficient, clean, quiet power that fuel cells offer are balanced by extremely low power densities and great infrastructure-related challenges. Studies by government and industry have investigated their feasibility for primary propulsion in light aircraft. These studies have produced mixed results but have tended to rely on integrating fuel cells into existing airframes, with respectably-performing light sport planes being turned into underpowered show planes with horribly compromised range and payload capabilities. Fuel cells today are in the earliest phases of technological development. As an aircraft propulsion system, they are as advanced as the Wright's reciprocating engine was a hundred years ago.

This paper attempts to assess the benefits of a unique distributed propulsion concept, known as the Multi-Gas Generator Fan (MGGF) system, over conventional turbofan engines on civilian vertical takeoff and landing (VTOL) applications. The MGGF-based system has shown the potential to address the fundamental technical challenge in designing a VTOL aircraft: the significant mismatch between the power requirements at lift-off/hover and cruise. Vehicle-level performance and sizing studies were implemented using the Grumman Design 698 tilt-nacelle V/STOL aircraft as a notional personal air vehicle (PAV), subjected to hypothetical single engine failure (SEF) emergency landing requirements and PAV mission requirements.

This paper describes a machine to quarry construction material, sinter walls, and assemble future space station modules. In prior work, we explored the solar energy requirements to build a 50m diameter, 50m high, cylindrical module out of pulverized rock from a Near-Earth Object, using tailored radio wave fields. In this paper, we describe the issues in the conceptual design of the robotic construction machines. The 4-legged Rock breaker is designed to fit the payload bay of a modern heavy-lift booster to reach Low Earth Orbit, and primary solar-sail propulsion for most of its journey. It uses beamed microwave energy for its cutting operations. Rotating, telescoping arms use integrated laser/plasma jet cutter arrays to dig trenches in spiral patterns which will form blocks of material. Cut blocks are sent into a toroidal cloud of material for use in the force field tailoring for automatic module formation.

In this paper, we discuss our experiences with applying an approach called Activity-Based Life-Cycle Assessment (LCA) in industrial settings. In contrast to other Life-Cycle Assessment approaches, we have taken modern cost management practices such as Activity Based Costing as a basis for our approach to environmental impact assessment. The resulting method, Activity-Based LCA, is an extension of Activity-Based Costing as it handles costs, energy consumption and waste generation simultaneously under the presence of uncertainty in a single framework.

The objective of this paper is to develop a generalized loss management model to account for the usage of thermodynamic work potential in vehicles of any type. The key to accomplishing this is creation of a differential representation for vehicle loss as a function of operating condition. This differential model is then integrated through time to obtain an analytical estimate for total usage (and loss) of work potential consumed by each loss mechanism present during vehicle operation. The end result of this analysis is a better understanding of how the work potential initially present in the fuel, batteries, etc. is partitioned amongst all losses relevant to the vehicle's operation. The loss partitioning estimated from this loss management model can be used in conjunction with cost accounting systems to gain a better understanding of underlying drivers on vehicle manufacturing and operating costs.

The interest in flying cars comes with the question of characterizing aerodynamic loads on shapes that go beyond traditional aircraft shapes. When carried as slung loads under aircraft, vehicles can encounter severe aerodynamic loads, which may also cause them to go into divergent oscillations that can threaten the vehicle and aircraft. Slung loads can encounter the wind at arbitrary attitudes. Flight test certification for every vehicle-aircraft combination is prohibitive. Characterizing the aerodynamic loads with sufficient resolution for use in dynamic simulation, has in the past been extremely arduous. Sharp changes that drive instabilities arise over small ranges of yaw and pitch. With the Continuous Rotation technique developed by our group, aerodynamic load characterization is viable and efficient. With two well-chosen attitude sweeps and appropriate transformations, the entire 6-DOF load map can be obtained, for several rates.

Loads slung under aircraft can go into divergent oscillations coupling multiple degrees of freedom. Predicting the highest safe flight speed for a vehicle-load combination is a critical challenge, both for military missions over hostile areas, and for evacuation/rescue operations. The primary difficulty was that of obtaining well-resolved airload maps covering the arbitrary attitudes that a slung load may take. High speed rotorcraft using tilting rotors and co-axial rotors can fly at speeds that imply high dynamic pressure, making aerodynamic loads significant even on very dense loads such as armored vehicles, artillery weapons, and ammunition. The Continuous Rotation method demonstrated in our prior work enables routine prediction of divergence speeds. We build on prior work to explore the prediction of divergence speed for practical configurations such as military vehicles, which often have complex bluff body shapes.

Hybrid-electric gas turbine generators are considered a promising technology for more efficient and sustainable air transportation. The Ohio State University is leading the NASA University Leadership Initiative (ULI) Electric Propulsion: Challenges and Opportunities, focused on the design and demonstration of advanced components and systems to enable high-efficiency hybrid turboelectric powertrains in regional aircraft to be deployed in 2030. Within this large effort, the team is optimizing the design of the battery energy storage system (ESS) and, concurrently, developing a supervisory energy management strategy for the hybrid system to reduce fuel burn while mitigating the impact on the ESS life. In this paper, an energy-based model was developed to predict the performance of a battery-hybrid turboelectric distributed-propulsion (BHTeDP) regional jet.