# How Stealth Works

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.

So how does stealth work?

![a large airplane flying through a blue sky](https://images.unsplash.com/photo-1643392873687-783ecb05dd1f?crop=entropy&cs=tinysrgb&fit=max&fm=jpg&ixid=M3wzMDAzMzh8MHwxfHNlYXJjaHwyfHxzdGVhbHRoJTIwYWlyfGVufDB8fHx8MTc2NTE4Nzg4N3ww&ixlib=rb-4.1.0&q=80&w=1080)

*Photo by* [*Steve Harvey*](https://unsplash.com/@trommelkopf) *on* [*Unsplash*](https://unsplash.com/)

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.

![](https://substackcdn.com/image/fetch/$s_!5XSI!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F4facbbf9-80af-43ba-a5f6-f52c485046aa_1600x1051.png)

*Picture courtesy of Katelynn Bennett over at* [*bifocal bunny*](https://bifocalbunny.substack.com/)

So how would you evade radar? You can try to:

*   Blast a bunch of radio waves in all directions (“[jamming](https://en.wikipedia.org/wiki/Radio_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](https://www.lockheedmartin.com/en-us/who-we-are/business-areas/aeronautics/skunkworks.html) 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](https://en.wikipedia.org/wiki/Perpendicular) to you).

![](https://substackcdn.com/image/fetch/$s_!sebk!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F3336952e-ccab-46d0-a8c4-c210cb7eefde_2266x1488.jpeg)

*Illustration by Katelynn Bennet*

Tilted a few fractions of a degree off, and you don’t see your own reflection!

![](https://substackcdn.com/image/fetch/$s_!0fDc!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2Ff5113ea7-63fd-412d-afc2-16162e2f0a74_2266x1488.jpeg)

*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 surfaces[^1^](https://linch.substack.com/p/how-stealth-works#footnote-1-181026663).

Put another way, the best stealth airplane is a plane. Not an airplane, a *plane.* The [Euclidean kind](https://en.wikipedia.org/wiki/Euclidean_plane). 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^](https://linch.substack.com/p/how-stealth-works#footnote-2-181026663) 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!

![](https://substackcdn.com/image/fetch/$s_!UDHl!,w_1456,c_limit,f_auto,q_auto:good,fl_progressive:steep/https%3A%2F%2Fsubstack-post-media.s3.amazonaws.com%2Fpublic%2Fimages%2F5301c607-c4b4-49d9-aca1-7d07b7acbc8d_1600x1067.png)

[*F-117 Nighthawk*](https://en.wikipedia.org/wiki/Lockheed_F-117_Nighthawk)

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](https://en.wikipedia.org/wiki/First_strike_(nuclear_strategy)) 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*](https://linch.substack.com) *to read my upcoming full review of* [*Skunk Works*](https://www.amazon.com/Skunk-Works-Personal-Memoir-Lockheed/dp/0316743003) *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.*