A new chapter in civil aviation

Growing urbanisation, increasing traffic congestion, and the need for smarter and more sustainable transport solutions has led to significant investment in urban air mobility solutions in recent years. Magnomatics’ chief executive officer, Gary Rodgers looks at what’s driving development in this field.

Urban air mobility (UAM), the concept of leveraging the airspace above cities to enable the safe and emission-free transport of people and products, is an innovative and exciting field. Whilst the idea may have seemed far-fetched just a few years ago, being able to zip through the air in a flying car is much closer than many realise.

In fact, 2023 saw the race between UAM developers intensify. According to the McKinsey’s Centre for Future Mobility, 72% and 64% of the 25 largest mainstream aerospace manufacturers and suppliers, respectively, are engaged in future air mobility technologies. Today, there are dozens of real prototypes flying around.

A taxi to the skies

Developments in eVTOL aircraft have been gaining traction due to their applications and potential benefits, which include not only passenger transport via air taxi, but also the transportation and delivery of goods, medical and humanitarian assistance, and even firefighting.

In October 2023, Wisk became the first air taxi company in the US to provide public flights, with autonomous passenger flights tested at Long Beach airport. In the same month, eHang became the world’s first fully certified electric vertical take-off and landing (eVTOL) air taxi cleared for commercial work, after being type-certified in China (it is only certified in China).

Additionally, Archer Aviation, widely regarded as the market leader in developing eVTOL aircraft, has plans to launch Midnight, a four-passenger aircraft designed to optimise point-to-point trips of approximately 20 miles, in 2025, and Joby Aviation is not far behind. Its aircraft, however, is expected to have a range of up to 150 miles. Backed by Uber, Joby plans to revolutionise the concept of ride-sharing, with plans to also start operating from 2025.

In line with these exciting announcements, Canada’s Jaunt Journey, which introduced its flagship eVTOL in 2020, launched an air corridor to offer indigenous communities faster and easier access to essential health and emergency services last year; similarly, California-based Jump Aero unveiled the design and specs for an aircraft set to reduce emergency response times in rural areas by bringing first responders to emergency sites.

While the concept of UAM is exciting, eVTOL aircraft bring with them many challenges. For example, they need to operate in complex airspace and over congested urban areas, which means the need for reliability and redundancy is critical. Additionally, composites technology is critical to the development and growth of this market as very strong yet lightweight materials are required to enable these aircraft to fly maximum distances with minimal electric power.

On the topic of electric power, a common feature shared by all UAM solutions is that they rely on multiple electric motors. The route to power density in electric machines has historically been to operate permanent magnet motors (PM) at higher speeds, often in excess of 10,000rpm. To become useful for air mobility aircraft, these speeds need to be geared down by as much as seven times. Conventionally this introduces the requirement for a mechanical gearbox, raising the issues of reliability, wear, maintenance, and noise.

NASA has been at the heart of UAM development and identified magnetic gears as being a potential technology for electric aircraft. In 2018, NASA embarked on a programme described in its paper ‘Magnetic Gearing Research for Electrified Aircraft Propulsion’. Its original focus was on pure magnetic gears, but in the 2020 paper ‘Outer Stator Magnetically Geared Motors for Urban Air Mobility Vehicles’ it stated that the concentric combination of a magnetic gear and a permanent magnet motor would be ideal for UAM aircraft, concluding that a magnetically geared motor was a highly effective solution to avoid the pitfalls of a mechanically geared high-speed electric motor.

Powering UAM solutions

While UAM systems are inherently complex, their performance can be significantly improved with intelligent system-level design. Magnetically geared motors are a key enabling technology for these solutions to ensure efficiency. Magnomatics’ revolutionary magnetic gears have been implemented in a range of innovative industry solutions, including offshore wind, marine propulsion, and light rail. Having achieved success at large scale, the company has turned its attention to much smaller machines, including drives for both UAM aircraft and personal micromobility vehicles.

The company’s patented Pseudo Direct Drive (PDD) – which is designed to overcome the torque limitations of conventional direct drive electrical machines – consists of a magnetic gear mounted inside a stator. The outer magnetics of the magnetic gear are attached to the inner bore of the stator, and copper windings in the stator are used to drive the inner rotor of the magnetic gear.

This is a relatively high-speed electric motor with a relatively low load, which results in low currents and hence, low temperatures. This in turn brings great efficiency, long life, and prevents demagnetisation of the outer magnet array. The torque in the inner rotor is then geared up in the novel polepiece rotor, typically by between 5 and 10:1. The result is a very compact and highly efficient electric motor, which is perfect for the UAM market.

The benefits of innovative magnetically geared motors such as PDD against conventional generator technology, particularly for this market, are drastic reductions in motor size, no minimum cooling requirements, and reduced maintenance requirements. Efficiency is also improved as there are no gearbox losses and, of course, gear wear is eliminated altogether.

The capabilities of UAM solutions are increasingly and successfully being tested, many thousands of hours of test flights have been conducted, and the aircraft’s potential to improve air mobility by moving people and cargo more quickly, quietly, and cost effectively are becoming ever clearer.

The realisation of flying cars, once the stuff of science fiction, marks a significant chapter in civil aviation history. With a vital contribution to make, Magnomatics continues to watch the exciting and rapidly developing UAM market with interest.

www.magnomatics.com