Scientists have taken a major step towards creating an aircraft of the future, one powered by an ion drive rather than using moving parts and fuel like conventional aircraft.
In a paper published today in Nature, a team led by Steven Barrett from the Massachusetts Institute of Technology (MIT) described how they created a so-called electroaerodynamic-powered plane, one that uses solid-state propulsion, meaning no propellers or jet engines with expendable fuel.
“The future of flight shouldn’t be things with propellers and turbines,” Barrett says in the video below. “[It] should be more like what you see in Star Trek, with a kind of blue glow and something that silently glides through the air.”
This breakthrough has not been possible before because our technology simply wasn’t advanced enough. As far back as 1921, scientists have been unsuccessful in trying to develop something similar, once mistaken for anti-gravity technology. But now the team say that key technology advances have enabled this to happen.
In their tests from 2016 to 2018, they created an aircraft with a wingspan of 5 meters (16 feet) that weighed 2.45 kilograms (5.4 pounds). It has a number of thin electrodes running across its wings, and at the front of these are thin wires, while at the back is an aerofoil – a curved surface to produce the lift, like on a regular plane wing.
The thin wires at the front are charged to positive 20,000 volts, while the aerofoil at the back is charged to negative 20,000 volts, creating a strong electric field. At the front, electrons are removed from nitrogen molecules in the air to produce ions. And as these accelerate to the back, they produce an ionic wind, which gives the plane thrust.
“The basic idea is that if you ionize air, which means removing an electron from it, you can accelerate the air with an electric field,” Barrett told IFLScience. “Like the force you get if you rub a balloon on your head.”
Over the course of 10 test flights, the plane successful flew about 60 meters (200 feet) in about 12 seconds in a gym that the team hired to use, with a thrust efficiency of about 2.6 percent. But as the speed increases, the efficiency of the system increases, just like in a regular plane. Theoretically, at 670 miles (1,080 kilometers) per hour, faster than a passenger jet, it is 50 percent efficient.
The technique is similar to how ion engines are used in some spacecraft to travel through space. "There are some significant similarities," said Barrett. However, those spacecraft rely on ionizing a fuel – such as xenon gas – to produce thrust. The plane developed by the MIT team does not require propellant, instead relying only on the thin wires and an off the shelf lithium-polymer battery.
At the moment the technology is limited, with the plane being very much a prototype. But the future possibilities are exciting. In the near-term, this thrust system could be used to power small drones, making them near-silent as they wouldn’t have any propellers like regular drones.
“I don’t yet know whether you’ll see large aircraft carrying people any time soon, but obviously I’d be very excited if that was the case,” Barrett said in the video.
Tests on the plane are continuing, with the team now able to turn the plane in the air with a remote control rather than just flying in a straight line. Going forward, they want to try and remove the filaments that are hanging off the plane, with more tests to follow in the coming years.
At the end of their paper, the team compares the length of the plane’s flight (12 seconds) with that of the Wright Brothers in Kitty Hawk, North Carolina in 1904 (11 seconds), the world’s first heavier-than-air flight, although that one did include a pilot.
While this flight is perhaps not on the same magnitude, some of the future possibilities are certainly exciting. “It is possible to fly planes that are solid state, and we demonstrated that for the first time,” said Barrett.