Urban Air Mobility: Welcome to the ‘Third Era of Aviation’
It’s a car, it’s a plane, it’s an air taxi — or something else. Aeronautical engineers haven’t agreed on a specific name for the emerging generation of vertically-flying, electrically-powered and autonomously-controlled vehicles being designed to streamline travel within cities and regions. Nor are they sure how the new flying machines will look; more than 200 design concepts have been proposed.
But I feel three things are certain: 1) Recent advances make urban air mobility (or UAM, the generic category) technologically feasible; 2) This transportation mode offers critical benefits; and 3) High-profile players are developing and testing diverse solutions.
Until recently, travel reminiscent of the Jetsons’ aerocar was out of reach due to energy constraints of batteries to power electric motors for flight, excessive noise of rotors on traditional helicopters, and concerns about safely controlling UAM vehicles.
Now, the situation has changed as enabling elements have converged to unleash a cascade of prototypes from the likes of Boeing, Bell, Airbus and numerous newer aerospace entrants. Greg Bowles, in his previous role as a vice president of the General Aviation Manufacturers Association, called UAM “the third era of aviation,” following propeller planes and then the jet age. [Bowles recently joined Joby Aviation, a startup developing eVTOL (electric vertical takeoff and landing) aircraft, as director of government relations.] As jet engines transformed how we travel around the country and across oceans, UAM will reshape travel across cities and regions.
Engineering Breakthroughs
UAM development is accelerating, thanks to these key engineering innovations:
· Much-improved batteries with enough energy to make a UAM vehicle fly for a useful time and distance
· Multiple electric motors that can power multiple propellers, making noise levels tolerable to city residents
· Advanced autonomy and automated software to control a UAM vehicle’s sophisticated features
Dramatic Benefits
Although it likely will cost more than ground taxi service, the emerging transportation mode is expected to be cheaper than current helicopter travel and provide tremendous time savings over ground-based alternatives. Those savings translate to a leap in productivity — essential for high-level decision-makers and potentially important for other passengers. Rather than waiting an hour in city traffic, a UAM vehicle could fly over that traffic in a few minutes.
In an example, Uber aims to launch Uber Elevate commercially in 2023 and begin testing it in cities as early as 2020. Initial plans call for fleets of small eVTOL aircraft in Dallas; Los Angeles; and Melbourne, Australia.
Extending this to regional travel, a longer-range eVTOL vehicle could whisk passengers from West Lafayette to Chicago in an estimated 20 minutes, versus about two hours driving, or from Albany to Manhattan in 30 minutes, versus three hours by car — enabling easy commuting with much lower housing costs.
Also important, regional eVTOL service could preclude the need for expensive, time-consuming investments in new rail lines or wider highways.
Myriad Solutions
Big-name players are presenting exciting concepts, with much progress this year. Most of these vehicles have some kind of powered lift and separate forward propulsion, but approaches vary. For example:
In January, Boeing’s autonomous Passenger Air Vehicle (PAV) prototype used eight electric-motor-powered propellers to ascend, hover and descend. The same month, Bell demonstrated its Bell Nexus, a hybrid with six propeller-like fans, scheduled for testing beginning in 2023.
Perhaps most unusual-looking is the Lilium Jet, tested in May and slated for availability in 2025. It seats five passengers; uses 36 swiveling, ducted fans for engines; and has a triple-redundant flight control computer.
Another alternative, demonstrated in May, is the four-seat CityAirbus, which boasts low environmental impact, quiet operation due to eight electrically-powered propellers, and remote piloting with advanced control systems.
Purdue Engineering Research
Recognizing the potential of urban air travel, as part of the Purdue Engineering Initiative in Autonomous and Connected Systems, we’re preparing to launch the Purdue UAS (Unmanned Aircraft Systems) Research and Test Facility. This testbed will house the world’s largest indoor motion-capture environment to measure aircraft position with high accuracy, which is needed as part of developing and implementing the safe and assured autonomous flight capabilities required for UAM operations.
What’s Next?
Pending further research, here are a couple of predictions:
1. UAM vehicles may be customized by region. For instance, the expansive Dallas-Fort Worth area may need an aircraft with wing-borne lift to support longer regional cruising distances, while a vehicle with powered lift may work better for short urban hops in the densely populated San Francisco Bay Area.
2. Regardless of the aircraft design, at first, automated systems will assist human pilots, eventually leading to full autonomy, in which a computer will convert passengers’ directions to flight control instructions. With proper testing and certification, self-piloting UAM vehicles may become reality within a decade.
By William Crossley, J. William Uhrig and Anastasia Vournas Head of Aeronautics and Astronautics, and Professor of Aeronautics and Astronautics at Purdue University
