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This scientist says he's built a jet engine that turns electricity directly into thrust:
This past autumn, a professor at Wuhan University named Jau Tang was hard at work piecing together a thruster prototype that, at first, sounds too good to be true.
The basic idea, he said in an interview, is that his device turns electricity directly into thrust — no fossil fuels required — by using microwaves to energize compressed air into a plasma state and shooting it out like a jet. Tang suggested, without a hint of self-aggrandizement, that it could likely be scaled up enough to fly large commercial passenger planes. Eventually, he says, it might even power spaceships.
Needless to say, these are grandiose claims. A thruster that doesn't require tanks of fuel sounds suspiciously like science fiction — like the jets on Iron Man's suit in the Marvel movies, for instance, or the thrusters that allow Doc Brown's DeLorean to fly in "Back to the Future."
But in Tang's telling, his invention — let's just call it a Tang Jet, which he worked on with Wuhan University collaborators Dan Ye and Jun Li — could have civilization-shifting potential here in the non-fictional world.
"Essentially, the goal of this technology is to try and use electricity and air to replace gasoline," he said. "Global warming is a major threat to human civilization. Fossil fuel-free technology using microwave air plasma could be a solution."
He anticipates this happening fast. In two years, he says, he thinks Tang Jets could power drones. In a decade, he'd like to see them fly a whole airplane.
That would all be awesome, obviously. But it's difficult to evaluate whether Tang's invention could ever scale up enough to become practical. And even if it did, there would be substantial energy requirements that could doom aerospace applications.
One thing's for sure: If the tech works the way he hopes, the world will never be the same.
Journal Reference:
Dan Ye, Jun Li, Jau Tang. Jet propulsion by microwave air plasma in the atmosphere [open], AIP Advances (DOI: 5.0005814)
(Score: 5, Insightful) by Anonymous Coward on Saturday July 04 2020, @08:19AM (6 children)
Editor - the subject is misleading. This is not "Electricity Directly Into Thrust". Directly means something. This is electricity directly into EM radiation, which is absorbed by a material which expands.
So, that's misleading and unfortunate. But this tech is also not, at first face, plausibly useful. Consider how hot plasma is; the difference between ambient and plasma temp is what the EM has to deliver. When a plasma jet exhausts, its heat is lost. Maybe one might think "a heat exchanger!" but that's perpetual motion machine thinking; you can't cool the jet below the plasma threshold or it won't thrust - not as a plasma jet.
As for "even in space" - I don't know what kind of air supply they think will conveniently be available in space, before even touching energy density issues (which might be handwaved away with "but future micronuclear plants" or "but terrestrial or spacecraft power plants that beam EM (lasers!) to be converted to electricity to be converted to EM" or "but solar panels")
And I'm sorry, I read TFA. It has such gems as:
and
Yes folks; that's 7.8 MW sustained electric. And that's assuming the tech scales up without any loss in efficiency. The mind boggles.
(Score: 3, Interesting) by theluggage on Saturday July 04 2020, @11:55AM (1 child)
Even? It's already in space [wikipedia.org] - with the superficially similar ion thruster [wikipedia.org] even more commonplace...
Of course, that's in spaaaace where (a) there's tons of always-on solar energy (and you can sometimes get away with radioisotopes), (b) combustion engines don't get half their fuel free from the atmosphere and (c) with no air friction or gravity you can get useful delta-v from a gnat's fart, if the gnat can keep farting continuously for a year. In space, specific impulse (where ion & plasma drives rule) trumps total thrust...
Nah, it's "even on Earth" - where thrust is king - that's the problem, and even if the technical problems can be solved you're up against the old problem that the energy density and convenience of combustible fuel is hard to beat without going nuclear.
(Score: 0) by Anonymous Coward on Saturday July 04 2020, @10:41PM
Good points. But note that TFA's invention doesn't make efficiency claims against other plasma drives.
(Score: 1, Interesting) by Anonymous Coward on Saturday July 04 2020, @03:32PM (1 child)
It might get more efficient when scaled up. Regular jet engines do. And airplane engines only run at full power for takeoff, if even then. Of course it's still not anywhere near as efficient as it would have to be.
In space, obviously you would have to bring the reaction mass with you. But that is true for all rockets. But it could potentially replace chemical or ion thrusters for orbital maneuvering, all of which currently require fuel that is some combination of toxic, corrosive, or made of rare chemicals. A thruster that runs on harmless and abundant nitrogen gas might have value even if it doesn't perform quite as well.
(Score: 0) by Anonymous Coward on Saturday July 04 2020, @09:43PM
We need to know how much thrust / force per watt can be produced so that we can compare it to existing technologies. Without numbers how can I tell if it's more efficient or not?
(Score: 2) by bzipitidoo on Saturday July 04 2020, @06:59PM
This article maybe should have been cast as more of a cautionary tale about magical thinking, with this Tang Jet as a recent example, rather than focusing on the jet itself. The first thing that leaped to my mind was the debacle over Cold Fusion.
I've had my share of discovering things that were too good to be true. At first, it looks like a great idea. Then, you start to realize that if it really does work, it violates the laws of thermodynamics, the lower limits of entropy, and so on. You know there has to be something wrong with the idea. You missed something, somewhere. When I've found the thing I overlooked, sure enough, the fantastic idea turns out to be not so fantastic after all.
I could give an example, if anyone wants to hear it. Like, a way to represent numbers with fewer bits than the standard Arabic numeral style representation. If that had been possible, then it would be possible to compress uncompressable files.
(Score: 1) by khallow on Sunday July 05 2020, @12:32AM
That's why it expands first, converting that heat into thrust.