The current push for Urban Air Mobility (UAM) is predicated on the feasibility of novel aircraft types, which will be enabled by the near-term availability of mature technology for high performance subsystems. A number of candidate concept aircraft are presently being designed to meet a set of UAM requirements, in order to quantify the tradeoffs and performance targets necessary for practical implementation of the UAM vision. In examining these vehicles, performance targets and recurring technology themes emerge, which may guide investments in research and development within NASA, other government agencies, academia, and industry.

With high incomes, long commutes, severe ground geographic constraints, severe highway congestion during peak commute times, high housing costs, and near perfect year-round weather, the Silicon Valley is positioned to be an excellent early adopter market for emerging aviation On-Demand Mobility transportation solutions. Prior efforts have attempted to use existing aviation platforms (helicopters or General Aviation aircraft) with existing infrastructure solutions, or only investigated new vehicle platforms without understanding how to incorporate new vehicle types into existing built-up communities. Research has been performed with the objective of minimizing door-to-door time for "Hyper Commuters" (frequent, long-distance commuters) in the Silicon Valley through the development of new helipad infrastructure for ultra-low noise Vertical Takeoff and Landing (VTOL) aircraft. Current travel times for chosen city-pairs across urban and suburban commutes are compared to future mobility concepts that provide significantly higher utilization and productivity to yield competitive operating costs compared to existing transportation choices. Helipads are introduced near current modes of transportation and infrastructure for ease-ofaccess, and maximizing proximity. Strategies for both private and public infrastructure development are presented that require no new land purchase while minimizing community noise exposure. New VTOL concepts are introduced with cruise speeds of 200 mph, which yield a greater than three times improvement in overall door-to-door time when compared to current automobiles, and in some cases, improvements of up to 6 times lower trip times.

The purpose of this study was to explore advanced airframe and propulsion technologies for a small regional transport aircraft concept (~50 passengers), with the goal of creating a conceptual design that delivers significant cost and performance advantages over current aircraft in that class. In turn, this could encourage airlines to open up new markets, reestablish service at smaller airports, and increase mobility and connectivity for all passengers. To meet these study goals, hybrid-electric propulsion was analyzed as the primary enabling technology. The advanced regional aircraft is analyzed with four levels of electrification, 0% electric with 100% conventional, 25% electric with 75% conventional, 50% electric with 50% conventional, and 75% electric with 25% conventional for comparison purposes. Engine models were developed to represent projected future turboprop engine performance with advanced technology and estimates of the engine weights and flowpath dimensions were developed. A low-order multi-disciplinary optimization (MDO) environment was created that could capture the unique features of parallel hybrid-electric aircraft. It is determined that at the size and range of the advanced turboprop: The battery specific energy must be 750 Wh/kg or greater for the total energy to be less than for a conventional aircraft. A hybrid vehicle would likely not be economically feasible with a battery specific energy of 500 or 750 Wh/kg based on the higher gross weight, operating empty weight, and energy costs compared to a conventional turboprop. The battery specific energy would need to reach 1000 Wh/kg by 2030 to make the electrification of its propulsion an economically feasible option. A shorter range and/or an altered propulsion-airframe integration could provide more favorable results.

In this paper, a novel hybrid electric regional aircraft is presented that strategically locates multiple electric and hybrid electric propulsors to obtain aerodynamic benefits. This concept is called the Parallel Electric-Gas Architecture with Synergistic Utilization Scheme (PEGASUS) aircraft. The use of the alternative propulsive systems coupled with their potential aerodynamic benefits presents modeling challenges for conventional aircraft analysis tools. These challenges are addressed by two methods that quantify the potential benefits of the PEGASUS concept. The results of both methods suggest that when compared to other hybrid electric regional aircraft, the PEGASUS concept has the potential to decrease the total energy required to complete a mission while also reducing the vehicle gross weight.

Vehicle Sketch Pad (VSP) is a parametric geometry modeling tool that is intended for use in the conceptual design of aircraft. The intent of this software is to rapidly model aircraft configurations without expending the expertise and time that is typically required for modeling with traditional Computer Aided Design (CAD) packages. VSP accomplishes this by using parametrically defined components, such as a wing that is defined by span, area, sweep, taper ratio, thickness to cord, and so on. During this phase of frequent design builds, changes to the model can be rapidly visualized along with the internal volumetric layout. Using this geometry-based approach, parameters such as wetted areas and cord lengths can be easily extracted for rapid external performance analyses, such as a parasite drag buildup. At the completion of the conceptual design phase, VSP can export its geometry to higher fidelity tools. This geometry tool was developed by NASA and is freely available to U.S. companies and universities. It has become integral to conceptual design in the Aeronautics Systems Analysis Branch (ASAB) here at NASA Langley Research Center and is currently being used at over 100 universities, aerospace companies, and other government agencies. This paper focuses on the use of VSP in recent NASA conceptual design studies to facilitate geometry-centered design methodology. Such a process is shown to promote greater levels of creativity, more rapid assessment of critical design issues, and improved ability to quickly interact with higher order analyses. A number of VSP vehicle model examples are compared to CAD-based conceptual design, from a designer perspective; comparisons are also made of the time and expertise required to build the geometry representations as well.