The cleaner way to fly
It’s been more than 100 years since the first aeroplane took flight. Ever since, moving surfaces such as propellers and turbines have been used in combination with fossil-fuel combustion to noisily transport people and packages through the air.
Now, engineers have built a new type of plane that flies almost silently through the air. With no moving parts and no combustion, this invention could revolutionise air travel as we know it, all thanks to the power of ionic wind.
With people moving away from petrol and diesel cars to electric alternatives, the pressure to reduce emissions in transport is mounting. The aviation industry is following the automotive industry, spending millions of dollars on research into electric planes.
Air transport is one of the major contributors to climate pollution, generating more than 600 million tonnes of carbon dioxide a year. Aviation is potentially on the brink of a huge revolution thanks to advances in battery technology and lightweight materials.
The big players in the aviation industry, including Rolls-Royce and Airbus, have been modifying their planes to include a hybrid-electric propulsion system.
Similar to hybrid cars, these hybrid planes will combine traditional fuel-based turbines with power from on-board electric generators. Instead of hanging off a wing, these electricpowered fans could be distributed across several parts of the aircraft, giving designers more scope to make aeroplanes in very different shapes from those we are used to.
The traditional propeller-based flight mechanism raises some big challenges as aircraft convert to electric — current batteries have an energy density that is 60 times less than jet fuel, meaning that with current battery technology, the weight of the battery required for a fully electric flight would be almost three times the take-off weight limit of the aircraft.
To overcome this, researchers at MIT in Boston have been looking at powering flight in a very different way. This week, they published very promising results in the journal Nature.
Instead of using propellers or turbines, the researchers used electroaero-dynamics. The technology works by sending a current through an electrode, which electrically charges the molecules in the surrounding air. These charged molecules are then attracted towards a separate electrode on the aircraft — this movement of ions and neutral air particles generates an effect known as ionic or electric wind. By positioning an aerofoil in this air flow, lift can be generated, potentially allowing powered flight.
The ionic wind effect has been known about for almost 100 years, but until now has not been considered capable of providing enough propulsion for a large object like a plane.
However, after nine years of building, the MIT group created a prototype aircraft from carbon fibre and balsa wood — 2m in length with a 5m wingspan — which managed to fly independently for an average of 55m per flight.
Although this may not sound far, it is the first time that anything heavier than a couple of grams has ever been flown using this ionic wind effect, and opens up substantial new opportunities for people thinking differently about the physics involved in propelling large objects through the air.
Transferring this type of technology into commercial use is still a long way off for large airlines, but it could provide quieter alternatives for smaller, rotor-based drones in the shorter term as the move towards human-carrying drone taxis continues to gain momentum.
For now, the hope to reduce the aviation industry’s carbon emissions and meet government environmental targets through cleaner, cheaper commercial flights is one step closer thanks to the power of ionic wind.