"The motivation of our work is to help solve the global warming problems owing to humans' use of fossil fuel combustion engines to power machinery, such as cars and airplanes," study author Jau Tang, professor at Wuhan University in China, said in a news release. "There is no need for fossil fuel with our design, and therefore, there is no carbon emission to cause greenhouse effects and global warming."
Plasma, a mix of charged ions, is the fourth state of matter. Plasma can be found in lightning bolts and on the surface of the sun, but it can also be generated on Earth's surface. The new prototype produces plasma by compressing air under high pressures and exposing the air to microwaves, which ionize the pressurized air stream.
This isn't the first time scientists have demonstrated a thruster engine prototype fueled by microwave air plasmas. NASA's Dawn space probe uses a similar concept, but the space agency's engine relies on xenon plasma. In outer space, xenon plasma will work just fine, but on Earth's, xenon ions are unable to overcome friction to reach jet propulsion speeds.
The new design relies only on a high-temperature, high-pressure treatment combined with injected air and electricity -- no special gas.
The new prototype design uses microwaves to ionize compressed air and create jet-like thrust. Photo by Jau Tang and Jun Li
The prototype design features a thin quartz tube through which high-pressure air is pushed before being converted into a plasma jet by a microwave ionization chamber. Simulations showed the miniature thruster can lift a two pound ball over an inch-long tube -- scaled up, the equivalence of the thrusting pressure generated by a commercial airplane jet engine.
Currently, the team of engineers is working to improve the technology's efficiency. Moving forward, researchers plan to built and test actual real life thrusters with high-power microwave sources. The technology could ultimately be scaled up to a full-sized jet.
"Our results demonstrated that such a jet engine based on microwave air plasma can be a potentially viable alternative to the conventional fossil fuel jet engine," Tang said.