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from the spreading-plasmas-everywhere-should-prove-exciting-in-a-thunderstorn dept.
Fossil fuel-free jet propulsion with air plasmas:
A team of researchers at the Institute of Technological Sciences at Wuhan University has demonstrated a prototype device that uses microwave air plasmas for jet propulsion. They describe the engine in the journal AIP Advances, from AIP Publishing.
"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," said author Jau Tang, a professor at Wuhan University. "There is no need for fossil fuel with our design, and therefore, there is no carbon emission to cause greenhouse effects and global warming."
[...] The researchers created a plasma jet by compressing air into high pressures and using a microwave to ionize the pressurized air stream.
[...] The prototype plasma jet device can lift a 1-kilogram steel ball over a 24-millimeter diameter quartz tube, where the high-pressure air is converted into a plasma jet by passing through a microwave ionization chamber. To scale, the corresponding thrusting pressure is comparable to a commercial airplane jet engine.
By building a large array of these thrusters with high-power microwave sources, the prototype design can be scaled up to a full-sized jet. The authors are working on improving the efficiency of the device toward this goal.
The article, "Jet propulsion by microwave air plasma in the atmosphere," is authored by Dan Ye, Jun Li and Jau Tang. The article will appear in AIP Advances on May 5, 2020 (DOI: 10.1063/5.0005814). After that date, it can be accessed at http://aip.scitation.org/doi/full/10.1063/5.0005814.
Without information about how much electrical power is used, it's impossible to say if this could be a realistic replacement for fossil-fuel jets.
(Score: 2, Insightful) by Anonymous Coward on Wednesday May 06 2020, @04:00PM (2 children)
not being "pro fossil fuel" or such but the comparison is a bit ... uhm errr ... misleading?
in a fossil fuel jet the energy source is both source of energy and thrust.
burning spilled jet fuel on a concret slap doesn't give you thrust.
you need a machinary (jet turbine) and a fuel source. for the jet turbine the fossile fuel IS the energy source to run the turbine and after doing work (compression on intake air and maybe driving a by-pass fan) the exhaust is still smart enough to provide thrust.
for the plasma jet in the article, the energy source is a electrical source. the "exhaust" plasma doesn't contribute to running the magnetron or the air compressor.
also, the fossile fuel jet gets lighter whilst the plasma airliner will arrive with the same weight as on take off.
a "correct comparison" would be if the battery would get combusted too.
the plasma jet, however, could turn into a real turbine, if instead of compressing and heating air, it would fuse hydrogen AND power the magnetron (at least) and have enough meaningful exhaust thrust left after that..?
(Score: 2, Interesting) by Anonymous Coward on Wednesday May 06 2020, @04:31PM (1 child)
Not arguing with all of your points. But this plasma jet IS producing thrust, but heating the air, using electricity as the energy source for the heat. It's not a cold plasma, nor is the plasma itself providing the thrust. So in an apples to apples comparison, it's exactly the same as a burning fossil fuel to generate energy only electricity is the fuel. It's not real clear from the description unless you read deeper into it, but their lab testing subtracts the force of the compressed air from the force of the resulting thrust to come up with the contribution caused by the plasma heating. It's really just another form of combustion chamber.
I could see this being used exactly like a standard jet engine. Compressor, a combustion chamber and a turbine only the plasma source is used in the place of the combustion chamber resulting in an "electric" jet engine. According to their calculations, they're implying that this kind of electric power source would be more efficient the currently available ducted fan electric power plants. And let's face it, no prop driven aircraft will ever reach a level of performance that a modern airliner or fighter jet needs. So that rules out electric powered aircraft from anything but small short hop flights. Not that there aren't plenty of valid use cases there.
I could also see this being used one day in some kind of ram jet engine with no moving parts. It's an exciting concept.
But it's also not much more than a hypothetical idea at this point anyway. Just because it works, doesn't make it practical for the same reason that electric power aircraft in general are still largely impractical for the points you mentioned. But who knows, where this idea might evolve into? Today's wright flyer, tomorrows jet fighter.
(Score: 1, Informative) by Anonymous Coward on Wednesday May 06 2020, @10:14PM
Electric plasma turbine engines aren't a new idea. Microwave boosting one might be, but the core concept is decades old. The difficulty, as always, is finding an adequate source of electricity.