Radar stealth used to mean a $2.1 billion bomber and a secret only governments could keep. China now sells it by the kilogram, cheap enough to spray on a throwaway drone
For most of the last 40 years, radar stealth has been shorthand for two things: enormous amounts of money, and secrets nobody outside a cleared facility was allowed to see. A B-2 Spirit runs about $2.1 billion a copy, the most expensive aircraft anyone has ever built, and the F-117 that opened the whole stealth story spent years as a black program before the public knew it existed. Making an airframe hard to see on radar meant controlled factories, exotic materials, and a budget only a handful of governments could write.
Sold in 1, 5 and 10 kilogram tubs
Star-Navi, a company based in Shenzhen, is now selling a version of that capability in a tub. Its XRAM-C Series is a sprayable radar-absorbing coating that, by the company's own numbers, takes roughly half the reflected radar power off a coated surface, and it comes packaged the way you'd buy industrial paint: 1, 5, and 10 kilogram containers, applied with a spray gun. The Defence Blog, which first detailed the product, described it as selling "core technology by the kilogram." That phrase, not the performance figure, is the part worth paying attention to.
The XRAM-C line is a black-gray liquid you spray onto a prepared surface and let cure, and Star-Navi splits it into three formulas aimed at different radar bands. The XRAM-C105 targets the X and Ku bands, which is where a lot of fire-control radars live, along with the millimeter-wave sensors inside modern counter-drone systems. The XRAM-C112 goes after the S and C bands used by the surveillance radars that build the first picture of what's in the sky. The XRAM-C113B trades peak performance at any single frequency for broadband coverage across C and X band, for an operator who doesn't know which radar he'll be hiding from.
The physics is ordinary
The physics is the same physics every stealth program uses. A bare metal or composite skin bounces most of an incoming radar pulse straight back to the receiver, which is exactly what lets an operator find you, track you, and shoot at you. Radar-absorbing material sits on top and turns that energy into heat instead of reflecting it, so the return signal gets weaker and the target looks smaller than it is.
Star-Navi's published spec sheet, reported by The Defence Blog, claims at least 3.0 decibels of reflection loss across 8 to 12 gigahertz and at least 3.5 decibels across 2 to 6 gigahertz, at a coating thickness between 0.40 and 0.60 millimeters.
The company says the coating stays under 1.1 kilograms per square meter at the thin end, survives 250 degrees Celsius for 100 hours, and passes a 2,000-hour salt-spray corrosion test, which is the kind of number you quote when you want to sell to a navy as well as a drone shop.
What 3 decibels is actually worth
Three decibels does mean what it sounds like. A 3 dB cut halves the reflected power reaching the radar. The trouble is that "half" is a far smaller deal in stealth than it is on, say, your power bill.
Serious radar-absorbing treatments are generally reckoned to take 20 to 30 decibels off a return, and the math there is unforgiving. A coating that delivers 20 dB is handing back about one percent of the radar energy that hit it. Star-Navi's 3 dB is still handing back roughly half. One of those makes you genuinely hard to find. The other makes you slightly harder to find.