Last year, Spectrum reported on Japan’s public-private initiative to create a new industry around electric vertical takeoff and landing vehicles (eVTOLs) and flying cars. Last Friday, start-up company SkyDrive Inc. demonstrated the progress made since then when it held a press conference to spotlight its prototype vehicle and show reporters a video taken three days earlier of the craft undergoing a piloted test flight in front of staff and investors.
The sleek, single-seat eVTOL, dubbed SD-03 (SkyDrive third generation), resembles a hydroplane on skis and weighs in at 400 kilograms. The body is made of carbon fiber, aluminum, and other materials that have been chosen for their weight, balance, and durability. The craft measures 4 meters in length and width, and is about 2 meters tall. During operation, the nose of the craft is lit with white LED lights; red lights run around the bottom to enable the vehicle to be seen in the sky and to distinguish the direction the craft is flying.
The SD-03 uses four pairs of electrically driven coaxial rotors, with one pair mounted at each quadrant. These enable a flight time of 5 to 10 minutes at speeds up to 50 kilometers per hour. “The propellers on each pair counter-rotate,” explains Nobuo Kishi, Sky Drive’s chief technology officer. “This cancels out propeller torque.” It also makes for a compact design, “so all the craft needs to land is the space of two parked cars,” he adds.
But when it came to providing more details of the drive system, Kishi declined, saying it’s a trade secret that’s a source of competitive advantage. The same goes for the craft’s energy storage system: Other than disclosing the fact that the flying taxi currently uses a lithium polymer battery, he’s also keeping details about the powertrain confidential.
Underlying this need for secrecy is the technology’s restricted capabilities. “Total energy that can be stored in a battery is a major limiting factor here,” says Steve Wright, Senior Research Fellow in Avionics and Aircraft Systems at the University of West England. “Which is why virtually every one of these projects is aiming at the air-taxi market within megacities.”
The SkyDrive video shows the SD-03 take off vertically then engage in maneuvers as it hovers up to two meters off the ground around a netted enclosure. The craft is shown moving about at walking speed for roughly 4 minutes before landing on a designated spot. For monitoring purposes and back-up, engineers used an additional computer-assisted control system to ensure the craft’s stability and safety.
Speaking at the press conference, Tomohiro Fukuzawa, SkyDrive’s CEO, estimated there are currently as many as 100 flying car projects underway around the world, “but only a few have succeeded with someone on board,” he said.
He went on to note that Japan lags behind other countries in the aviation industry but excels in manufacturing cars. Given the similarities between cars —especially electric cars—and VTOLs, he believes Japan can compete with companies in the United States, Europe, and China that are also developing eVTOLs.
SkyDrive’s advances have encouraged new venture capital investors to come on board and nearly triple investment to a total of 5.9 billion yen ($56 million). Original investors include large corporations that saw an opportunity to get in on the ground floor of a promising new industry backed by government. One investor, NEC, is aiming to create more options for its air-traffic management systems, while Japan’s largest oil company, Eneos, is interested in developing electric charging stations for all kinds of electric vehicles.
In May, SkyDrive unveiled a drone for commercial use that is based on the same drive and power systems as the SD-03. Named the Cargo Drone, it’s able to transport payloads of up to 30 kg and can be preprogrammed to fly autonomously or be piloted manually. It will be operated as a service by SkyDrive, starting at a minimum monthly rental charge of 380,000 yen ($3,600) that rises according to the purpose and frequency of use.
Kishi says the drone is designed to work within a 3 km range in locations that are difficult or time-consuming to get to by road. For instance, Obayashi Corp., one of Japan’s big five construction companies and an investor in SkyDrive, has been testing the Cargo Drone to autonomously deliver materials like sandbags and timber to a remote, hard-to-reach location.
Fukuzawa established SkyDrive in 2018 after leaving Toyota Motor and working with Cartivator, a group of volunteer engineers interested in developing flying cars. SkyDrive now has a staff of fifty.
Also in 2018, the Japanese government formed the Public-Private Conference for Air Mobility made up of private companies, universities, and government ministries. The stated aim was to make flying vehicles a reality by 2023. Tomohiko Kojima of Japan’s Civil Aviation Bureau told Spectrum that since the Conference’s formation, the Ministry of Land, Infrastructure, Transport and Tourism has held a number of meetings with members to discuss matters like airspace for eVTOL use, flight rules, and permitted altitudes. “And last month, the Ministry established a working-level group to discuss certification standards for eVTOLs, a standard for pilots, and operational safety standards,” Kojima added.
Fukuzawa is also targeting 2023 to begin taxi services (single passenger and pilot) in the Osaka Bay area, flying between locations like Kansai and Kobe airports and tourist attractions such as Universal Studios Japan. These flights will take less than ten minutes—a practical nod to the limitations of the battery energy storage system.
“What SkyDrive is proposing is entirely do-able,” says Wright. “Almost all rotor-only eVTOL projects are limited to sub-30-minute endurance, which, with safety reserves, equate to about 10 to 20 minutes flying.”
Source: IEEE Spectrum