Air Vehicle Design and Technology Considerations for an Electric VTOL Metro-Regional Public Transportation System

Abstract

This paper examines the potential of VTOL aircraft to supplement commuter rail services in a metropolitan or regional transportation system. An interdisciplinary study was conducted to examine the feasibility of integrating an aerial transport system into the existing airspace using a fleet of electrically powered rotorcraft. A notional network of stations and overall operating schedule were constructed based on the existing regional rail networks serving the San Francisco Bay Area. To define the VTOL vehicles, the rotorcraft sizing code NDARC has been modified to accommodate electric propulsion sizing. Initial sizing results indicate that battery technologies available by 2030, coupled with the "shorthop" ranges of the proposed aerial network, result in feasible aircraft designs. These vehicle designs, while significantly larger in gross weight than their Jet A powered turboshaft equivalents, may become economically viable in a business environment dominated by fuel costs. Finally, these initial study results are informing follow-on study efforts.

Technical and environmental assessment of all-electric 180-passenger commercial aircraft

“…The performance (efficiency) of a battery depends on the rate of discharge, which varies throughout the mission. Many analyses neglect battery efficiency or assume values of 98% or greater [10,134,155,156]. This implies that the rate of discharge has no impact on battery performance, which is fundamentally incorrect.…”

“…The name of this motor type can be misleading, as the power supply is DC, but a DC/AC inverter (controller) allows for variable frequency AC motor operation. Not using brushes or commutators has many benefits, including less maintenance, higher reliability, and the ability to operate in reverse The electric motor weight is scaled with shaft power, with HTS motors having more favorable scaling exponents[134,135]. The motors and electrical system are sized for takeoff, which is the most power demanding condition.…”

Scenario-Based Strategic Planning for Future Civil Vertical Take-off and Landing (VTOL) Transport

“…Because VTOL aircraft are an energy-intensive transportation mode for short distances, higher propulsion, and high-capacity battery technology was identified as two critical enablers to overcome current challenges with civil VTOL aircraft (German et al, 2013;Sinsay et al, 2012;Warwick, 2014). In consideration of current technological trend, the electric powered VTOL aircraft designs were foreseen to be available by 2030 (Young et al, 2011;Wang, Hou, Guo, & Gao, 2015).…”

“…While previous studies have shown that VTOL has the potential to improve airspace performance in capacity and delay based on an integrated fleet concept of operations, integrating VTOL aircraft into conventional airspace will be a complex issue. The study on VTOL mass transit feasibility jointly studied by NASA and Stanford (Sinsay et al, 2012) presented a conceptual design of an electric VTOL public transit system and network models using the existing railways and bus networks in the San Francisco metropolitan area. The simulations of a 30 seater VTOL operations carrying up to 30,000 passengers a day connecting eight potential multi-modal vertiports at population centers, with existing infrastructure of three airports, roads and rail links in the metropolitan area demonstrated the inevitable airspace management issues.…”

Greener Helicopters

“…There are substantial future challenges related to sustaining and improving efficient, cost-effective, and environmentfriendly transportation options for urban regions. A recently completed study by NASA and Stanford University investigated the feasibility of a rotorcraft solution for future urban transportation (Melton et al, 2014;Sinsay et al, 2012). Such an aerial transportation system could ideally tackle concerns related to urbanization, transportation gridlock, and fossil fuel emissions.…”