Air taxis: A wide range of concepts are on approach

More than 100 companies worldwide are working on air taxis. Their concepts vary considerably in their use cases and their technical details. Six approaches.

04.2020 | Text: Denis Dilba

Text:
Denis Dilba holds a degree in mechatronics, is a graduate of the German School of Journalism, and founded the “Substanz” digital science magazine. He writes articles about a wide variety of technical and business themes.

The race for the airspace beneath the clouds is well underway: almost daily, we hear stories about start-ups and older companies alike claiming to have developed an air taxi (usually fully electric and autonomous) that is on the cusp of breaking through. Often these reports are exaggerated, and many blueprints are destined to return to the drawer they came from—but the sheer variety of different projects is leading experts and other observers to believe that it won’t be long before the first air taxis are ready for service. A current study by management consulting firm Horváth & Partners, for example, is founded on the assumption that air taxis will already be carrying passengers on initial, defined routes in big cities as early as 2025. Indeed, test operations are expected to begin in just a few months’ time. However, use of the small aircraft need not be restricted to congested metropolises: companies also see useful application scenarios in areas where the infrastructure is not as well developed, such as islands and mountain regions. In short, wherever a direct route through the air saves a lot of time. Companies can smell a big business opportunity. Analysts from Morgan Stanley Research estimate that the market for autonomous air taxis could reach 1.36 trillion euros by 2040. It remains to be seen which concepts will have proved successful by then. MTU ­AEROREPORT presents six representative development approaches.

Cora: The vertical takeoff aircraft has 12 rotors on its wings that span 11 meters. Since 2017, the Cora self-flying air taxi has completed over 1,000 test flights.

Cora by Wisk: Founded in 2019, Wisk is a joint venture between airframer Boeing and start-up Kitty Hawk.

Kitty Hawk Cora—Rotors on the wing

In October 2017, the Cora air taxi could already be found circling in the skies of New Zealand’s South Island. At the time, only aviation experts knew what they were looking at. It took another six months before the U.S. start-up Kitty Hawk, which is financed by Google cofounder Larry Page, confirmed the secret test flights of its fully electric and autonomous aircraft. Twelve rotors on the two wings, which span around eleven meters, enable Cora to take off vertically. With a further propeller at the rear, it flies like a conventional aircraft once airborne. Kitty Hawk gives its initial range as “40 kilometers plus reserves.” At the same time, the company announced a commercial air taxi service in New Zealand. Although Kitty Hawk would not be drawn on a specific launch date, Prof. Florian Holzapfel, Chair of the Institute of Flight System Dynamics at the Technical University of Munich (TUM), estimates that test operation will begin in 2020: “The Cora project is at a very high stage of maturity and will probably be one of the first commercial air taxis in the skies.”

Volocopter 2X: The 18-rotor prototype recently took to the skies above Singa­pore. In the future, it’s set to fly in San Francisco, too.

Volocopter GmbH: In 2011, software engineer Stephan Wolf co-founded Volocopter GmbH with his childhood friend and entre­preneur Alexander Zosel. Their company is based in Bruchsal, near Karlsruhe in Baden-Württemberg. It now employs over 150 people and has offices in Munich and Singapore.

Volocopter—Drone with multiple rotors

Another contender hoping for the title of “first commercial air taxi” is the German manufacturer Volocopter. The company, in which the automobile groups Daimler and Geely have a stake, already made aviation history back in 2011 when it completed the first ever manned flight of an all-electric vertical takeoff and landing craft. In mid-August 2019, the company unveiled the fourth generation of the aircraft, which goes by the name of VoloCity. It is due to start scheduled service in Singapore in 2021. A cross ­between a drone and a helicopter for two people, the aircraft has 18 rotors and is slated to fly 35 kilometers on power obtained from ­lithium-ion batteries. Although this makes the range ­comparatively small, Volocopter claims that its configuration makes it “the ideal on-­demand air taxi for the city center.” Expert Florian ­Holzapfel sees such helicopter-type concepts as at a ­disadvantage to air taxis that can use wings for cruising. “Winged aircraft are a much more efficient solution, at least as regards the big advantages in terms of range.”

This jet is set to provide direct connections between cities in the future.

Lilium GmbH: Founded in 2015, the young start-up from Weßling near Munich already employs some 350 people.

Lilium—swiveling ducted fans

Although the Lilium Jet will need a few years before it’s ready for autonomous, all-electric scheduled service, its developers are so convinced of its potential that they have already ­announced the building of an air taxi factory. As of 2025, several hundreds of the jets are to be ­produced each year near the headquarters of ­Lilium GmbH in Oberpfaffenhofen near Munich. The five-seater aircraft with 36 electric engines and the same number of swiveling ducted fans made its first unmanned flight in May 2019. ­According to information from Lilium, the aircraft successfully completed its first test phase at speeds of up to 100 kilometers an hour. However, many aviation experts are skeptical as to whether the vertical takeoff and landing aircraft mini jet will actually reach a top speed of 300 km/h and then ­travel 300 kilometers on one battery charge, as the company boldly claims. But Lilium CEO Daniel Wiegand maintains that development work has progressed swiftly as planned. Starting in 2025, the company plans to launch passenger operations at several locations worldwide.

A total of 36 all-electric jet engines provide the five-seater vertical takeoff air taxi with a maximum output of 2,000 hp.

The Silent Air Taxi transports four passengers, plus pilot, for a range of up to 500 kilometers without making a stop. A flyover by the aircraft cannot be distinguished from everyday background noise thanks to its ultra-low-noise fan.

e.SAT GmbH: The hybrid electric aircraft manufacturer was founded in 2018. Headquarted in Aachen, the company is headed by three RWTH professors: Frank ­Janser, Peter Jeschke and Günther Schuh.

Silent Air Taxi—straightforward, quick to implement

Unlike other air taxis, the Silent Air Taxi (SAT) cannot take off and land vertically; neither is it fully electric, nor will it fly autonomously, at least initially. But that is exactly how the company e.SAT from Aachen, which is developing the aircraft, says it wants it to be: capable of flying at 300 km/h and with a range of up to 500 kilometers, the small aircraft has a hybrid electric powertrain, space for four passengers plus pilot, and is to enable direct services between existing airfields starting in 2024. “We don’t have to build any new infrastructure, and neither do we need any new regulations—moreover, our hybrid drive minimizes the need for heavy bat­teries,” says e.SAT co-CEO Prof. Peter Jeschke. MTU will ­participate in the development and construction of the hybrid powertrain. Detailed engineering is due to begin in 2021. “We hope to be able to take off for the first time in 2022,” Jeschke says.

The aircraft’s maximum payload will be 450 kilograms—which is sufficient to carry five people.

Alaka’i Technologies: Founded in 2015, the start-up is based in ­Hopkinton, Massachusetts.

Skai: With their fuel cell powertrain concept, the people behind Skai take a different approach to other air taxi projects.

Skai—taking off with hydrogen

In the opinion of start-up Alaka’i Technologies from Massachusetts, lithium-ion batteries are too heavy as an energy source for air taxis—and so the company has based its concept, which was developed jointly with BMW Designworks, on fuel cells. Skai, the prototype unveiled at the end of November 2019, has space for five passengers, is powered by six electric motors, and is planned to offer a range of 640 kilometers. Such distances are possible, says company founder Brian Morrison, because a pound of compressed hydrogen contains 200 times more energy than a battery of the same weight. At an average speed of 137 km/h, Skai can fly for four hours on electric power, says the start-up. The prototype is fully functional, the company adds, and the first flight will take place soon.

Although TUM researcher Florian Holzapfel does not rule out such a fuel cell powertrain on principle, he observes that “without additional batteries capable of rapid discharge, a fuel cell air taxi won’t be able to lift off. Taking off requires a lot of energy all at once—that’s simple physics.”

Skai takes less than ten minutes to refuel with enough hydrogen to fly 640 kilometers.

Uber Air will take off and land from what are known as vertiports—found, for example, on the roofs of parking lots.

Uber Air: The San Francisco-based provider of ridesharing services is working to expand into air transportation.

Uber Air—the design surprise

Ridesharing company Uber also plans to take to the skies from 2023: “Uber Air,” the San ­Francisco-based company’s air taxi service, is due to launch in the U.S. cities of Dallas and Los ­Angeles and in the Australian city of ­Melbourne. Test flights are already planned there for 2020. However, it is still unclear what the aircraft that will be taking off then will look like: although Uber has designed three different reference models and created technical specifications for them, the ­development of the air taxis will be handled by various partner companies, ­including ­Aurora Flight Sciences (Boeing), Bell, ­Pipistrel and ­Embraer. What is clear at this stage is that the Uber aircraft are supposed to carry four ­passengers plus the pilot just under 100 ­kilometers at a speed of around 240 km/h. The company does not rule out an autonomous flight option in the future.

The big difference with the proposed Uber Air service, which will take off from and land on ­platforms on top of high-rise buildings, ­parking lots, or multi-story mega-skyports, is price: flights are meant to cost no more than an ­ordinary Uber ride in a car.

The final design of the Uber air taxi is still a work in progress—but it could look something like this.

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