URBAN AIR MOBILITY (UAM)

from 35 Must Know Terms in Sustainable Aviation

THE EU EMISSIONS TRADING SYSTEMS (ETS)

Urban Air Mobility (UAM) is a new air transportation system for passengers and cargo in and around densely populated and built-up environments, made possible by small, electric vertical takeoff and landing aircraft (eVTOL).

UAM is seen as a potential solution to urban congestion, reducing travel times and emissions while increasing mobility. However, the development and deployment of UAM require significant technological, regulatory, and infrastructure challenges to be overcome.

Considering the excitement around UAM, several big airlines are forming partnerships and placing pre-orders with different companies.

• Our UAM Power List report unpacks the hype behind these aircraft and identifies their possible use cases.

eVTOL

Electric vertical takeoff and landing (eVTOL) aircraft are small aircraft that are capable of vertical takeoff and landing, similar to helicopters. However, eVTOLs are powered by batteries or fuel cells, making them much quieter and more efficient than traditional helicopters.

They have the potential to revolutionise urban transportation by providing fast, efficient, and environmentally friendly transportation options for short-range trips.

Popularly known as ‘air taxis’, eVTOLs promise to bring all our Jetsons dreams true by changing the nature of flying itself. American aerospace company Archer Aviation focuses on designing and developing eVTOLs, which they believe will “unlock the skies”, and enable everyone to reimagine how they live, travel and manage time. Other notable eVTOL manufacturers are Joby, Eve, Supernal and Wisk.

• Read our article about how the introduction of eVTOLs can transform aviation, based on a discussion at this year’s SXSW Festival.

REGIONAL AIR MOBILITY (RAM)

Urban Air Mobility (UAM) and Regional Air Mobility (RAM) are emerging paradigms in aviation, though they serve distinct geographical and functional scopes.

While UAM focuses on improving connectivity within dense, urban areas, RAM extends beyond city limits and is targeted towards regional transportation. It focuses on connecting cities, towns, and other geographical areas within a region, usually within a range of about 100 to 500 miles.

RAM vehicles can be larger and potentially hybrid, due to the longer distances involved. The goal is to provide a faster, more efficient mode of transportation between regional locations, making use of existing small and medium-sized airports and reducing reliance on ground transportation or major airline hubs.

Regional Air Mobility is likely to be driven largely by electric and hydrogen (along with hybrid versions) aircraft.

Electric Aircraft

Electric aircraft are planes that run on electric power instead of fuel. The idea is similar to electric cars. Just like how an electric car uses batteries to power the motor, an electric aircraft uses batteries to run its propellers.

There are multiple benefits of electric aircraft:

• They are non-polluting and do not release greenhouse gases. As a result, they can reduce air pollution and fight climate change.

• Electric planes could be cheaper to run because electricity can cost less than jet fuel.

• They will likely be easier to maintain and operate, reducing the lifetime costs of the plane.

• Finally, they are expected to be significantly quieter than jet and propeller planes, reducing noise pollution and making them capable of flying to many airports without community-based restrictions.

However, there are also challenges with the biggest one being the battery. Batteries for electric aircraft need to be light, but they also need to store a lot of energy which is hard to accomplish with today's technology. For example, the energy density of the best batteries available today is nearly 20 times lower than conventional jet-A fuel.

Another significant hurdle is that electric planes need a place to charge their batteries, just like electric cars. Creating such an infrastructure can be challenging and expensive.

While the technology for electric long-haul travel is still far off, for short-haul travel electric aircraft, like Heart Aerospace’s ES-30, could prove revolutionary. The 30-seater aircraft includes a reserve-hybrid configuration and is projected to operate with zero emissions and low noise. Commercial passenger flights on the ES-30 are expected to commence in 2028. Other notable electric aircraft manufacturers include Cosmic Aerospace, Maeve and Ampaire

• Learn more about how electric aircraft can transform regional aviation in our interview with Heart Aerospace’s CEO and Founder Anders Forslund.

Hydrogen Aircraft

Hydrogen aircraft are planes that use hydrogen as a power source. This can be potentially done in two ways:

• To burn the hydrogen in jet engines, much like the kerosene in conventional aircraft.

• To use hydrogen to power a fuel cell, which then produces electricity to drive the aircraft's propellers.

At first glance, hydrogen looks to be a good solution for flying without wrecking the climate. Whether it is used to power a fuel cell to generate electricity or directly combusted for power, the only byproduct is clean water, not greenhouse gases.

Hydrogen is also more energy-dense than traditional aviation fuels – three times more than conventional jet fuel, and more than a hundred times that of lithium-ion batteries

But there are big disadvantages with using hydrogen for aircraft:

• One of the main ones is the storage of hydrogen – hydrogen gas takes up a lot of space, even when compressed, which is a problem on an airplane where space is at a premium.

• It also requires very cold temperatures to remain a liquid, adding to the complexity of storage.

• Another challenge is safety – hydrogen is highly flammable, which means it has to be handled and stored very carefully.

• The lack of infrastructure for hydrogen fuel. We would need new systems at airports to store and deliver hydrogen fuel, and that would require major investments.

There's also the fact that most hydrogen currently available is "grey" hydrogen made from natural gas, which isn't environmentally friendly. We would need to significantly scale up production of "green" hydrogen, made using renewable energy, for hydrogen aviation to truly be sustainable.

The State of the Industry

Even though hydrogen performs three times better than conventional jet fuel, using it with traditional aircraft, however, is not as straightforward.

In our podcast, Universal Hydrogen’s co-founder John-Paul Clarke pointed out that aircraft would require significant tweaking of the engines to make the transition to this clean fuel. As a result, aircraft manufacturing startup ZeroAvia has resorted to retrofitting existing aircraft with hydrogen-electric power trains.

Giants like Airbus are betting big and working on clean-sheet aircraft designs that don’t depend on existing technology or infrastructure. In 2020, Airbus revealed three concepts for zero-emission commercial aircraft – all code-named “ZEROe” – that could enter service by 2035.

• Learn more about Airbus’ investments in hydrogen in our interview with the airframer’s Vice President for Research & Tech (Americas), Amanda Simpson.

Listen to more insights on our podcast

Want more sustainable aviation insights? Sustainability in the Air is the world’s first sustainable aviation podcast. Hosted by SimpliFlying Shashank Nigam, the show has featured airline CEOs such as Scott Kirby and Tony Douglas.

But as part of the podcast, Shashank has also talked to innovators developing new kinds of aircraft and engines, such as Heart Aerospace CEO Anders Forslund, ZeroAvia CEO Val Miftakhov and Archer Aviation CEO Adam Goldstein.