For more than a century, aeroplanes have relied on propellers and turbines to generate the thrust needed to fly. But what if an aircraft could move through the air without any rotating engines, almost silently, and without producing emissions from fuel combustion? Scientists are now bringing this idea closer to reality with a remarkable breakthrough in electric propulsion.
A research team led by Haofeng Xu has demonstrated that an aeroplane can achieve sustained, powered flight using electroaerodynamics, a technology that generates thrust through electrical forces rather than conventional moving engine parts. The team designed and flew a fixed-wing aircraft with a wingspan of five metres, successfully demonstrating steady, level flight on ten separate occasions.
The achievement provides important evidence that aircraft can fly using a solid-state propulsion system, potentially opening the door to quieter, mechanically simpler aircraft in the future.
What Is Electroaerodynamic Propulsion?
Electroaerodynamic propulsion is a method of generating thrust using electric fields to accelerate electrically charged particles, called ions, in the surrounding air.
Unlike conventional aircraft engines, this system does not depend on rotating propellers or turbine blades to push air backwards. Instead, it uses electrical energy to create movement in the air, producing a force that pushes the aircraft forward.
The basic principle involves creating an electric field strong enough to ionize air molecules. When these molecules become electrically charged, they respond to the electric field and accelerate. As the charged particles move, they collide with other air molecules and transfer momentum to them. This movement of air generates thrust.
In simple terms, the aircraft uses electrical forces to push air and move forward, rather than relying on spinning mechanical components.
This approach is particularly interesting because it could reduce the number of moving parts required for propulsion. It may also help reduce mechanical noise and eliminate emissions produced directly by burning fuel during flight.
A Five-Metre Aircraft Takes to the Sky
Although electroaerodynamic propulsion has attracted scientific interest for years, making it powerful and efficient enough to fly a heavier-than-air aircraft has been a major challenge.
Previous experiments demonstrated that electrical forces could generate thrust under controlled conditions. However, achieving enough thrust to support the weight of a complete aeroplane and maintain stable flight proved difficult.
The research team addressed this challenge by designing a fixed-wing aircraft powered entirely by an electroaerodynamic propulsion system.
The aircraft had a wingspan of five metres, making it a substantial demonstration compared with many earlier experimental setups. More importantly, the researchers did not rely on an external power supply to keep it flying.
Instead, the batteries and electrical power systems were carried onboard the aircraft. This allowed the team to test the technology as a complete airborne propulsion system rather than simply demonstrating thrust in a laboratory.
The aircraft successfully completed ten flights and demonstrated steady, level flight. These tests showed that electroaerodynamic propulsion could provide sufficient thrust to keep an aircraft moving through the air under the demonstrated conditions.
The results represent a significant step towards proving that this unconventional propulsion technology can work beyond small-scale experiments.
The Key Innovation: An Ultralight High-Voltage Power Converter
One of the most important parts of the project was the development of a specialised power converter.
Electroaerodynamic propulsion requires very high voltages to generate the electric fields needed to accelerate ions. However, the equipment used to produce these voltages can be heavy, making it difficult to use the technology in an aircraft.
Aircraft design is highly sensitive to weight. Every additional kilogram increases the amount of lift required and can make efficient flight more challenging. A propulsion system that produces thrust but requires excessively heavy electrical equipment may not be practical for aviation.
To overcome this problem, the researchers developed an ultralight high-voltage power converter capable of producing 40 kilovolts.
This component enabled the aircraft to operate its electrical propulsion system while carrying the necessary power equipment onboard.
The converter was crucial because the experiment required more than an electric field capable of generating thrust. The complete system also had to be light enough for the aircraft to fly.
By combining the specialised converter with onboard batteries and the propulsion system, the team demonstrated that these components could operate together during powered flight.
Overcoming a Major Challenge in Aircraft Propulsion
For years, researchers have faced two major obstacles when developing electroaerodynamic propulsion: thrust-to-power ratio and thrust density.
The thrust-to-power ratio describes how much thrust a propulsion system produces for a given amount of power. A system with a low ratio consumes substantial electrical power while generating relatively little thrust.
Thrust density refers to how much thrust a system can produce within a given volume or area. If the system cannot generate enough thrust in a compact and lightweight design, it becomes difficult to integrate into a practical aircraft.
These limitations have led scientists to question whether electroaerodynamics could ever provide enough propulsion for a heavier-than-air aeroplane.
The new demonstration challenges the idea that these limitations make the technology impossible to use for aircraft propulsion.
By achieving sustained, level flight, the researchers showed that the obstacles can be overcome sufficiently for a working aircraft under experimental conditions.
However, this does not mean that all efficiency and engineering challenges have been solved. More research will be needed to determine how the technology performs across different aircraft sizes, flight conditions and operating requirements.
Could This Technology Make Aircraft Quieter and Cleaner?
One of the most attractive features of electroaerodynamic propulsion is its potential to reduce noise.
Conventional aircraft generate noise from several sources, including rotating propellers, turbine engines and the movement of air around the aircraft. A propulsion system without conventional rotating engine components could reduce some of this mechanical noise.
The technology could also simplify certain aspects of aircraft design by reducing dependence on moving propulsion parts. Fewer moving components may offer advantages in maintenance and mechanical complexity, although the complete system would still require careful inspection and servicing.
Another potential benefit is the absence of direct combustion emissions from the propulsion process. Because the system generates thrust through electrical forces rather than burning aviation fuel, it does not produce the same exhaust emissions associated with conventional combustion engines.
However, the environmental benefits would depend partly on how the electricity used to charge the aircraft's batteries is generated. Battery production, material use and the overall energy requirements of the aircraft would also need to be considered.
Therefore, electroaerodynamic propulsion could offer a cleaner alternative in certain applications, but its overall environmental performance must be evaluated through further research.
What Comes Next for Electroaerodynamic Aircraft?
Despite the successful demonstration, electroaerodynamic propulsion is still an experimental technology. The researchers have established that a five-metre fixed-wing aircraft can achieve powered, steady-level flight using this approach, but many questions remain.
Future studies will need to investigate how the system performs during take-off, climbing, turning and other demanding flight conditions. Researchers will also need to improve its energy efficiency, increase its thrust output and examine how it can be scaled for larger aircraft.
Safety and reliability will be equally important. High-voltage electrical systems must operate consistently under changing weather conditions, while aircraft designs must meet strict aviation requirements.
If these challenges can be addressed, the technology could eventually find uses in specialised aircraft, experimental flying platforms and aerodynamic devices where low noise and mechanical simplicity are valuable.
Conclusion
The successful flight tests by Haofeng Xu and his team mark an important milestone in the development of unconventional aircraft propulsion.
By flying a five-metre-wingspan aeroplane ten times using an onboard electroaerodynamic system, the researchers demonstrated that electrical forces can provide enough thrust to sustain powered flight under experimental conditions.
The achievement does not mean that propellers and turbines will disappear anytime soon. Conventional aircraft propulsion remains highly developed, and electroaerodynamic systems still face significant challenges involving efficiency, thrust and scalability.
Nevertheless, the experiment offers a new direction for aviation research. If scientists can make the technology more powerful, efficient and practical, it could help pave the way for aircraft that are quieter, mechanically simpler and free from direct fuel-combustion emissions during propulsion.
The idea of an aeroplane flying without conventional propellers or turbines is no longer just a theoretical possibility. It has now been demonstrated in flight, bringing scientists one step closer to exploring a different future for aviation.
Reference: Xu, H., He, Y., Strobel, K.L. et al. Flight of an aeroplane with solid-state propulsion. Nature 563, 532–535 (2018). https://doi.org/10.1038/s41586-018-0707-9
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