Although Russia’s defense program marketing efforts may be among the most robust in the world, China is no slouch when it comes to making lofty claims about military capabilities through state-owned media outlets with global reach. China’s latest claim pertains to a new radar system that, according to reports, might render stealth technology obsolete.
In February, Chinese state-owned media reported on a spray-on coating they claimed had turned their J-16 into a “near-stealth” fighter. Although a radar-absorbent coating does play an important role in any stealth aircraft’s ability to evade detection, simply spraying it onto a platform prone to producing both large radar and IR returns does little to offset detection. However, according to Chinese media, the coating not only gave the aircraft stealth “capabilities,” it also made it nearly invisible to the naked eye.
“Brigade commander Jiang Jiaji, the first pilot to win the PLA’s Golden Helmet competition three times, told CCTV at the exercise that the silver-gray painting covering the J-16 is a kind of cloaking coating that gives the warplane a certain stealth capability, making it nearly invisible to the naked eye and electromagnetic devices,” China’s state-owned Global Times reported.
Now China claims to have developed a new radar array that can penetrate the stealth coating found on most low-observability aircraft, delivering radar returns that are precise enough to make a clear distinction between the types of aircraft that have been spotted. The radar array works by using terahertz radiation, which travels in a frequency range that’s higher than radio or microwaves but lower than infrared light waves. Theoretically speaking, terahertz radiation could penetrate the composite materials and radar-absorbent coating of a stealth aircraft, then bounce off of the metallic objects housed inside and produce a viable radar return.
The concept has some basis in reality. Terahertz radiation is already used as a commercial imaging tool than can penetrate materials like paper, plastic, and textiles to observe or inspect metallic objects housed inside. It has even been discussed for use in security applications, where terahertz radiation could be used to identify concealed weapons hidden under a subject’s clothes. However, these applications all depend upon an extremely close proximity between the antennae, object, and receiver, whereas detecting an aircraft would mean needing to transmit terahertz radiation waves over an extremely large expanse of airspace.
And therein lies the rub. Terahertz radiation simply does not have the range to be an effective means of aircraftdetection. In fact, it fails to do much of anything at all at distances greater than about 30 feet.
According to Carter M. Armstrong, a scientist serving as the vice president of engineering in the electron devices division of L-3 Communications:
For short-range operation—that is, for signals traveling 10 meters or less—the effects of the atmosphere and bad weather don’t really come into play. Try to send anything farther than that and you hit what I call the ‘terahertz wall’: No matter how much you boost the signal, essentially nothing gets through. A 1-watt signal with a frequency of 1 THz, for instance, will dwindle to nothing after traveling just 1 km. Well, not quite nothing: It retains about 10-30 percent of its original strength.”
If you’re thinking that the Chinese may have managed to overcome this obstacle by simply ramping up the power output on their terahertz radiation radar systems to astronomical levels, that also seems rather unlikely per Armstrong’s research.
So even if you were to increase the signal’s power to the ridiculously high level of, say, a petawatt, and then somehow manage to propagate it without ionizing the atmosphere in the process, it would be reduced to mere femtowatts by the time it reached its destination. Needless to say, there are no terahertz sources capable of producing anything approaching a petawatt; the closest is a free-electron laser, which has an output in the low tens of megawatts and isn’t exactly a field-deployable device.
China, however, claims to have already completed one prototype of their new radar platform with a successor on its way, though interestingly, even Chinese media points out that their terahertz-radar program probably won’t work. Oddly, this admission doesn’t come until nearly the end of the piece, despite apparently discrediting the rest of the article.
“Experts said the terahertz radiation decays very fast in the air, meaning the effective range of the radar is likely low and not sufficient for detecting an advanced stealth fighter jet in time before it launches attacks from beyond visual range,” the Global Times wrote.