Allow me to introduce myself. My name is Jacob, and I’m here to learn you some science. READY? GO!
Today I wanna talk to you about Stealth Technology. And because the word “stealth” can mean anything from “quiet” to “camouflaged” to “reduced radar signature”, let me qualify that by saying that today’s topic will be about aircraft stealth technology.
The objective of stealth tech, or “Low Observables” (LO) as we call it in the aerospace biz-nass, is principally to evade detection by radar (however LO concepts also apply to the visible spectrum as the name implies). Radar is basically just a certain range of electromagnetic radiation that happens to bounce off of metals with a particularly satisfying BOOP.
Ok, it doesn’t really make a BOOP, but it travels very long distances in reliably straight lines, so if you happen to see some of your own radar signal coming back at your face, there’s a good chance that it ran into something along the way!
So you need to get into your neighbor’s backyard pool with your RC airplane so you can snap a few pics of Naomi, who happens to be home from college before going off to Europe for a study-abroad. (Or if you’re a Paleo-Palette, to snap some pics of Eduardo, the mysterious Brazilian foreign exchange student) How do you do it without being detected by the overprotective, Electrical Engineer father/guardian who specializes in radar technology? Well my friend, you’ve come to the right place.
LO Technology comes in three main flavors: Geometry, Materials, and Electronic Countermeasures.
Since radar is a form of electromagnetic radiation, it’s reflection characteristics can be reliably predicted through fun and exciting calculations like Maxwell’s Equations, Fresnel Equations, and Brewster’s Angle.
They’re exciting because they have names! And even personalities! Me and Brewster go WAY back… I digress…
If you know how radar bounces off of a surface, then you can design an aircraft that will reflect radar AWAY from the source, no matter what the incidence angle is. For this, we defer to the Physical Theory of Diffraction (not a fun calculation, because it doesn’t have a name) discovered by a lone Soviet scientist named Petr Yakovlevich Ufimtsev. Considered useless research by the Soviets, Ufimtsev’s equations were able to figure out how to apply Maxwell and Fresnel’s Equations in an iterative manner to simple two and three-dimensional shapes.
The American’s quickly programmed their supercomputers to calculate Ufimtsev’s equations, and the result of this work was an aircraft which Lockheed engineers called “The Hopeless Diamond.” You might know it as the F-117 Nighthawk.
Each of the facets on the surface of the F-117 is specifically angled to reflect radar signals away from its source, and it does a pretty good job of it too. At the range that an enemy radar could easily detect an F-16, the radar operator MIGHT be able to discern a small metal ball bearing flying through the sky.
By the time he realizes that ball bearings don’t fly, the F-117 has already dropped a smart bomb, flown home, been refueled, read a bedtime story, and is just starting to dream of flying through space, with the stars reflecting off each of it’s beautiful facets…
Eventually the B-2 Spirit bomber followed, which, despite the obvious visual differences, actually has the same design principle; shape the aircraft to reflect radar signals away – no matter the direction of the source. You might even think of the F-117 as a “pixelated” or “low-res” version of the B-2.
(Aerospace Industry Anecdote: Apparently the lead designer of the B-2 was inspired after watching his children ride the “Mad Tea Party” teacup ride at Disney World. Apparently the smooth, continuous curvature of the teacups convinced him that continuous curvature could be just as effective as the faceted surfaces on the F-117.)
Before the F-117 was even imagined, and actually before World War Two was even over, the Germans realized that materials exist which can absorb a significant proportion of radar signals which impinge upon them.
The Horten Ho 229, built in March of 1944, incorporated a mixture of charcoal dust in the wood glue used in its construction, which actually absorbed a significant portion of the low-power radar signals used by the British at the time.
In the 1950’s and 60’s, the SR-71 Blackbird (Fact: Coolest aircraft ever made. Peer-reviewed, scientifically proven…) utilized graphite under its space-age titanium-alloy skin. The F-117 and B-2 followed with radar absorptive coatings which are painstakingly maintained and re-applied throughout the life of the aircraft.
Today, more durable coatings exist that can be applied to everything from the glass window of the cockpits to the 1st stage fan blades in a jet engine. Invisible to the naked eye, radar absorbing materials are a HUGE part of the LO technology portfolio.
The newest additions to the bag-o’-stealth tricks are electronic countermeasures, or EM. Typical EM aircraft, such as the EA-18G Growler, can complicate detection by obfuscating the radar signal.
Instead of completely avoiding detection like the F-117 or B-2, the Growler serves as a front-line jammer which can fly in a pack of blood-thirsty F-18 Super Hornets and keep the enemy from knowing anything except that “something is coming.”
You might not consider this to be “stealth technology”, but consider this: the F-22 Raptor, America’s newest jet fighter, employs highly advanced onboard radar and ECM system. By combining ECM technology with scanned-array radar, the F-22 could conceivably detect an incoming radar signal, absorb or reflect it, perform a few tricky calculations, and bounce back a modified radar signal to the source that would be interpreted as a totally different aircraft in a totally different position, at a different speed and a different altitude.
That’s right, the F-22 is basically David Blaine.
Now to be perfectly honest, I could talk all day about stealth tech (some fact, more speculation) but the real good juicy stuff is classified. That either means I can’t tell you about it, or I don’t know about it yet. I’ll leave that for your interpretation. ;-)
I hope you’ve learned something today… even if your intentions were mischievous (PERVERT!). Feel free to shoot me a question, or tell me I’m wrong about something, at Jacob@sciencesortof.com. If you’d like some references or some more fun aerospace industry anecdotes, I can certainly provide those as well.