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Chinese Researchers Reveal Active Stealthy Material (popsci.com)
hackingbear writes: Even after billions and billions of dollars spent on the stealthy skin used on F-22, F-35 and B-2, the material has weaknesses, and one of those is ultra-high-frequency (UHF) radar, which can pick up traces of the plane that other radar misses. Chinese researchers came to the rescue and created a material just 5/16 of an inch thick that can safeguard stealth planes against UHF detection. The material tunes itself to a range of detection frequencies, protecting against a large swath of radar scans. What's even more amazing? They published this seemingly top secret invention wide open in the Journal of Applied Physics .
As with almost any tuned system, it works very well and damping a particular frequency, but very poorly off resonance. The article describes a "broad-band" anti-reflective material, which is misconstrued in the summary. In fact they made a material which can be tuned over a relatively large frequency band ("0.7-1.9GHz) by adjusting a bias voltage. In reality, at any given time the bandwidth is only ~0.2GHz. Moreover, their structure only absorbs one polarization of radiation, and was tested only at normal incidence.
If this thing works, how did anyone notice it?
This is a physics paper and the road to engineering is as big as the ocean.
Translation: 5/16 Inch = 8mm
expansionist? China is VERY expansionist. South China Seas? Multiple islands? Eastern India. vietnam? ALL of Chinese neighbors, either fear china or do exactly what they want.
I prefer the "u" in honour as it seems to be missing these days.
Radars have been wideband (wider than the absorption peak of this new material) for at least 30 years, and probably longer. Pulse compression with multi-hundred MHz bandwidth is a standard thing, and has been for a very long time. The SPY-1 on Aegis cruisers is a good example.. It's L-band (where this material seems to be designed) and the bandwidth is very wide. (hundreds of MHz). And the frequency on modern radars is agile. The air traffic radars at 5GHz that have the interference problem with WiFi are another example.
We've come a long way since the old magnetron based systems.
The other problem is that this material shows good absorption for normal incidence. As soon as the signal comes in from an angle, it doesn't work as well, because it's relying on the wavelength and the classic 1/4 wavelength thick absorber (but not actually 1/4 wavelength, just simulating it). If the signal comes in from 45 degrees, now you need an absorber that's 1.4 times thicker.
Kind of a neat idea, but it's not going to change stealth airplanes.
The Russian physics paper was very theoretical and derived the equations needed to show that this technology was possible. The equations could not, and probably still can not, be directly solved. However, this paper was translated by the US Air Force as were many such technical publications and circulated through channels to aircraft manufacturers, and others. It was an engineer at Lockheed who realized that you could implement this technology without solving the equations if you were willing to devote huge amounts of computer resources to doing numerical solutions, which, are great for engineers, but frowned upon by theorists. We had the computer power to do this and the USSR did not. Even then the F117, sometimes called the wobbly goblin, had to sacrifice much in terms of aerodynamics and flight characteristics to implement the first true stealth aircraft.
With all the cheap drones with super high end cameras and AI, a stealth bomber could be found by the US military with just simple optics. Just literally find a flying black object that's like 25 feet long.