In 2007, the University Research Engineering and Technology Institute and the National Aeronautics and Space Administration teamed up to investigate how electric propulsion schemes could one day power all-electric airborne vehicles. In a traditional aero turbine engine, torque and speed are coupled for speed control. That limits propulsion. The study's participants discovered that electric propulsion can be achieved by designing multiple "propulsors," in this case propellers, which remotely connect to an electric generator. Place several fans in the aircraft fuselage, and you increase the combined contribution of each to the total power of the all-electric plane. The idea begins in the design concept.
The URETI results showed that all-electric planes, using superconducting motors and generators, could not only match the power density of turbine engines, they could actually reach higher power densities at relatively low power levels, according to Cesar Luongo, senior fellow for the Institute of Electrical and Electronics Engineers. That said, both NASA and URETI concede that electrical components within the superconductor need enhanced power density. Naturally, potential needs further research with convincing track results before any carrier could viably and commercially convert to it. As of the time of publication, NASA's five-year research project continued to study these possibilities.
So how would all of this apply? Researchers tested the electric propulsion concept in the worst-case scenario facing a Cessna 172: power failure. According to Luongo's study of superconductors, a "squirrel cage," the rotor of an AC induction engine, could provide enough power (35 percent) for an overheated electric plane to make it to the nearest airport. Meanwhile, NASA and the Georgia Institute of Technology developed an integrated electromagnetic-thermal model that could integrate electric and aeropropulsion system designs. In effect, researchers have discovered how to bridge the turbine-to-electric engine divide.
To facilitate the most positive impact on the environment, Luongo and other researchers suggested applying super-conduction engine models to two types of aircraft: small regional transport planes, and large transcontinental or intercontinental transports. To do this, existing turbine engines would drive superconducting generators, and propulsion would be distributed to multiple electric motors on each wing. However, researchers acknowledge configuration challenges. For instance, existing aircraft would need hybrid wing-body design and short takeoff and landing capabilities.
