Some nuances I decided not to include in the main post:
1. The first stealth airplanes were mostly dominated by shape by not entirely. They also used radar absorbing materials. Maybe 3 OOMs shape, 1 OOM absorption was an estimate given by an expert. So shape gets most of the Shapley but not entirely. 2. Flat surfaces were the main design principle of first-gen stealth airplanes but modern software have allowed people to figure out curved surfaces that still doesn't reflect radio echoes to the sender-receiver. Still, if you look at pictures of modern stealth airplanes they still look much more angular and flat than old airplanes, or passenger aircraft. 3. Modern stealth airplanes and radar detection have to adapt in a sort of Red-Queen race situation so the simple bouncing technique doesn't fully work anymore. I didn't closely investigate why. 4. I simplified stealth as "evading radar" but of course there are other detection methods (sight, sonar, thermal detection). Eg reducing your jet planes' heat signatures is important to modern stealth as well. But I didn't think it's as relevant to the main argument. 5. My argument/analysis here works for any sender-receiver style. Eg it also works for echolocation and bats (interestingly, and sadly in my view, bats often die by killing themselves on stealth airplanes). Radar has structural advantages over sonar (sound waves) and light. This is why militaries use them. I didn't bother clarifying this as it is not relevant to the core of stealth technology.
Stealth technology is cool. It’s what gave the US domination over the skies during the latter half of the Cold War, and the biggest component of the US’s information dominance in both war and peace, at least prior to the rise of global internet connectivity and cybersecurity. Yet the core idea is almost embarrassingly simple.
When we talk about stealth, we’re usually talking about evading radar. How does radar work?
Radar antennas emit radio waves in the sky. The waves bounce off objects like aircraft. When the echoes return to the antenna, the radar system can then identify the object’s approximate speed, position, and size.
Picture courtesy of Katelynn Bennett over at bifocal bunny
So how would you evade radar? You can try to:
Blast a bunch of radio waves in all directions (“jamming”). This works if you’re close to the radar antenna, but kind of defeats the point of stealth.
Build your plane out of materials that are invisible to radio waves (like glass and some plastics) and just let the waves pass through. This is possible, but very difficult in practice. Besides, by the 1970s, if the entire physical plane was invisible to radar, modern radar can easily detect signals that bounce off the pilot from miles away.
US and Soviet missiles can track a “live hawk riding the thermals from 30 miles away” (Skunk Works by Ben R. Rich, pg 3)
Build your plane out of materials that absorb the radio waves. This dampening effect is possible but expensive, heavy, and imperfect (some waves still bounce back).
What Lockheed’s Skunk Works discovered in the 1970s, and the core principle of all modern stealth planes, is something devilishly simple: make the waves reflect in a direction that’s not the receiver.
How do you do this? Think of a mirror. You can see your reflection from far away if and only if the mirror is facing you exactly (ie, the mirror is perfectly perpendicular to you).
Illustration by Katelynn Bennet
Tilted a few fractions of a degree off, and you don’t see your own reflection!
Illustration by Katelynn Bennett
In contrast, if an object is curved, at least some of it at any given point is tilted 90 degrees away from you.
This is why stealth planes all have flat surfaces. To the best of your ability, you want to construct an airplane, and any radar-evading object, out of flat surfaces1.
Put another way, the best stealth airplane is a plane. Not an airplane, a plane. The Euclidean kind. A flat airplane design trades off a tiny chance of a huge radar echo blast (when the plane’s exactly, perfectly, perpendicular to the radar antenna), against a 99.99%+ chance that the echo is deflected elsewhere. In other words, a flat plane design allows you to correlate your failures.
Unfortunately, a single plane (the Euclidean kind) can’t fly [citation needed]. Instead, you need to conjoin different planes together to form an airplane’s surface. Which creates another problem where the planes meet: edges. Edges diffract radio waves back, which is similar to but not exactly like reflection. Still detectable however! Hmm.
The solution comes from being able to predict edge behavior precisely. The Physical Theory of Diffraction (PTD)2 allows you to calculate exactly how much radar energy any edge will scatter, and in what direction. While implementing the theory is mathematically and computationally complex, the upshot is the same: PTD lets you design edges that are pointed in the same direction. This correlates the failures again, trading off a huge radar echo blast when the edges are pointed directly at you against the very high probability the radar waves are simply deflected elsewhere. Pretty cool!
This simple idea revolutionized much of conventional warfare. Stealth spy planes can reliably gather information about enemy troop movements and armament placements without being detected (and thus shot down) themselves. Stealth fighters can track enemies from far away while being “invisible” themselves, winning aerial dogfights before enemy fighters even recognize an engagement is afoot. Stealth bombers and missiles have a huge first-strike advantage, allowing nations to bomb military targets (and cities) long before the panicked defenders have a chance to react.
But while the idea is simple, the implementation is not. Building an airplane almost completely out of flat surfaces trades off aerodynamicity for stealth. How do you make a stealth plane that actually flies? How do you do so quickly, and, well, stealthily, without leaking your technological secrets to your geopolitical enemies? How do you run an organization that reliably generates such bangers as stealth planes without resting on your laurels or succumbing to bureaucratic malaise? And finally, what were the intelligence, military, and ethical implications of these deadly innovations?
To learn more, subscribe to The Linchpin to read my upcoming full review of Skunk Works by Ben R. Rich, the Director of Lockheed’s Advanced Research and Development department during the development of the world’s first stealth airplane, and the man arguably singularly most responsible for heralding a new era of aerial warfare for over 50 years.
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