Ion thrusters have been around since the 1960's, but until now they've been considered as low-efficiency devices. Now their potential may be realized, with efficiency far outweighing that of the jet engine.
Electrohydrodynamic thrust, or Ionic wind, is a phenomenon first identified in the 1960’s. Since then, it has had limited applications beyond hobbyists, primarily being conceptualized as a low-energy, low-thrust spacecraft propulsion system. The problem ionic thrusters have had until now is that they require a massive amount of electricity to produce enough thrust to drive a vehicle.
Researchers at MIT however, have discovered that this may not be the case. After running their own efficiency tests on ion thrusters, they’ve discovered that it may in fact be much more efficient than conventional jet engines. Their experiments found that ionic wind could produce thrusts of up to 110 Newtons per kW, as compared to the jet engines 2 Newtons per kW.
This astounding revelation may change propulsion forever. Steven Barrett, an assistant professor in aeronautics and astronautics at MIT, suggests that Electrohydrodynamic thrust could one day be used to power light aircraft, and due to it being completely silent and invisible in the infrared, they may be excellent candidates to power surveillance vehicles.
Another step towards making my life more like Star Wars – good work, science!
An ionic thruster is composed of three principal components: A thin copper electrode, called an emitter; a collector, essentially an aluminum tube; and an air gap between the two. When an electric voltage is applied, the air molecules in the thruster are stripped of their electrons. The charged ions then begin moving in an electric field – away from the electrode, and towards the collector tube. As they do this, they collide with other air molecules, creating a wind, or thrust.
The research team was able to measure the thrust of the ionic wind by suspending the thruster from a scale and measuring the difference in weight as the device began lifting off the ground. The distance between electrode and collector was varied during the test in order to find optimal working conditions. The most efficient thrust was observed while the device was producing a low velocity wind. This is because higher velocity winds are turbulent and leave a lot of unused kinetic energy in its wake.
Currently, there are still a few difficulties with deploying these thrusters to power aircraft. First and foremost, they require a lot of voltage to work; the necessary range lies in the hundreds, or even thousands of kilovolts. "The voltages could get enormous," Barrett says. "But I think that's a challenge that's probably solvable." Another problem is that the thrust is directly proportional to the size of the air gap in the device. This means that to power an aircraft, the thrusters would likely have to encompass the entire vehicle.