The Feasibility of Large Electric Passenger Airliners

From the much-beloved Back to the Future to the sleek commuter aircraft of today, the idea of electric passenger airliners has long been a source of fascination. Many believe that the limitations of battery technology could make these planes an impractical dream, comparing them to current fuel-based jet engines in terms of speed and range. However, recent developments and innovative designs suggest that the future of electric air travel might be closer than we think.

Electric Airplanes vs. Jet Engines

One significant challenge for electric aircraft is the weight and energy density issue. The current best batteries have an energy density of approximately 120 watt-hours per kilogram (Wh/kg), while kerosene has an energy density of 12,000 Wh/kg. This makes kerosene 100 times more efficient in energy storage. Consequently, an electric airliner would need to allocate more of its carrying capacity to power, reducing the amount available for passengers or cargo. This is an economic non-starter for long-distance flights, which is why electric airplanes currently face challenges in competing with fuel-based jet engines in terms of speed and range.

However, the tide is shifting. Innovations such as ducted fans and new propeller designs are pushing the boundaries. NASA, for instance, is focusing on new prop designs that can operate up to at least Mach 0.8, which is very close to the typical cruise speeds of modern jet airliners (like the 787 Dreamliner, which cruises at approximately Mach 0.82, around 567 mph).

Range and Practicality

Range remains a significant hurdle for electric passenger airliners. Current battery technology limits practical ranges, meaning that flights over long distances, such as New York to Los Angeles, which spans 4,000 km, are not feasible. However, electric aircraft are making inroads in shorter routes, particularly in Europe. According to data from Quoran Christian Bull, many of the most popular flight routes within Europe are between 200 to 300 miles (320 to 480 km), making them ideal for electric propulsion.

In contrast, the average flight in the United States is significantly longer, with popular routes often exceeding 500 miles (800 km). Until battery technology improves substantially, electric passenger airliners will not be able to cover these distances efficiently. However, there is promising progress, and it is important not to dismiss the potential of electric aircraft entirely.

Unducted Fan Technology (UDF)

A new frontier in electric aviation is the development of unducted fan (UDF) technology. These airmass accelerators offer an efficiency advantage over both propellers and ducted fans but come with the drawback of increased noise levels. The development of UDF technology faced setbacks due to the decline in fuel prices, which made them less attractive commercially until the current environmental and technological focus shifted back to these systems.

While the future of UDF technology is unclear, advancements continue to drive the viability of electric aircraft. Innovations in battery technology, new aerodynamic designs, and ongoing research in energy density are paving the way for a future where electric passenger airliners become a more practical and feasible reality.