Good Ideas: Stealth

Part 1 of our story saw a theoretical advance get loosed by Moscow and land on the desk of a Lockheed engineer. Wait, that makes the story sound simple and resolved, and misses the drama of the cliffhanger we ended on! Let’s try this again:

[cue Batman music] Da na na na na na

Last Batweek, the US had this Zen idea* of turning “See but Don’t Touch” into “Nobody Here but Us Chickens” by reducing a plane’s “RCS” (how big the plane appears on radar). Out of nowhere they find this paper that calculates the RCS for simple shapes. But simple shapes don’t fly. How do you bridge the difference between this and this. Will Batman survive his precarious position? Or will Penguin and the law of aerodynamics keep him a flightless bird?

Of course, the paper does describe how to compute the RCS of more complex shapes: you break them down into many simple shapes. But this comes at a cost: much more math. So much math that it would be faster just to build the shape and test it in real life.

Between 1962 (when the paper was written) and 1971 (when the paper was discovered), math became easier: computers. Lockheed programmed a computer to take a shape and calculate its RCS. Dying to impress the Air Force with technical wizardry, they tried a new way of making a plane.

On most airplane designs, the big dogs are the Aeronautics folks. They build the best flying machine they can and hand it off to the payload people, who have to fit in as many passengers/weapons/cargo/whatever. But on this plane, a whole different sort of nerd was in charge. The *electrical* engineers found the most invisible shape and handed if off to the plane builders. Now make it fly. Oh, but if you change a single angle or corner it will undo all the benefit of this plane.

And the results? Stupendous. At a radar testing range, the operator told them the model must have fallen off the pole. Then, a bird landed on top of the model plane (on top of the pole), and the operator “found the model”. The plane was invisible to a radar set that could pick up a small bird.**

This model turned into the F-117 Nighthawk. Which performed extraordinarily over the skies of Baghdad (surrounded by the finest air defense the Soviet Union could sell to its allies). And looked like the ugliest plane ever. No really, look:

Why is it so ugly and angular? Because computers in the 1970’s were so slow they could only calculate the RCS for moderately-complex shapes, engineers could only build approximations of complex shapes using simple triangles. This was all the shape 1970’s computers could manage. And just as faster computers have made video games look more realistic with higher resolution, they’ve also allowed stealth planes to be less blocky. Look at the second stealth plane:

The B-2 is still a weird looking plane (based on the flying wing concept). But 8 years (F-117 first flight 1981; B-2 1989) of computer development (the equivalent of 60 years of mechanical development or 290 dog years) allowed the plane to actually have curves. And after another 8 years, the F-22 (first flight: 1997) looks like a normal plane, just with a few wobbly, stealth-inducing contours.

In 20 years, Stealth went from being a plane’s defining characteristic (the F-117 was called the Stealth Fighter and the B-2 the Stealth Bomber) to just another factor in a plane’s design. Today, any new combat aircraft will be stealth, and will look normal.

*Is this actually Zen? I don’t know, because there’s no “Mad Props to Zen”.

**This anecdote specifically and much of this post’s material generally come from the book Skunk Works.

So That Happened: How a Russian Idea became an American technique

As World War II cooled in the 1940’s, the US built nuclear-armed planes to send deep into Russia. The Soviet Union responded in the 50’s by building Surface-to-Air Missiles that could fly up and intercept the planes faster than human-piloted planes. And so began an arms race. The US built planes that could fly higher. The USSR built missiles that could fly higher. In the 60’s, the US built planes that could fly faster. The USSR built missiles that could, well, you get the idea. And by the 70’s, there wasn’t any higher or faster left to fly. So, what was the US’s next move? The answer came from the USSR itself, in one of the more ironic (not just Alanis Morrisettical ironic) twists of the Cold War.

The reigning philosophy for military plane designers had been “See but Don’t Touch.” Planes that flew higher, flew faster, turned tighter, even planes that could send out distracting radar signals. But then, an idea. Radar operators had always known that different planes looked slightly different on radar. [Refresher: radar works by sending radio waves out, and seeing where they bounce back from. The more radio waves that bounce back, the bigger the dot on the screen looks] And that makes sense: bigger planes should look bigger. But... it wasn’t just size, or just amount of metal (the part of the plane that reflects radio). Some big planes looked small, and some small planes looked big. If they could figure out what it was that made a plane look big or small on radar, they could design a plane that looked invisible.

The solution was “Method of Edge Wave in the Physical Theory of Diffraction”, an obscure technical paper from 10 years earlier and half a world away. Published by Petr Ufimtsev, chief scientist of the Moscow Institute of Radio Engineering, it described how to calculate a shape’s “Radar Cross Section” (i.e., how big it looks on radar).

So given this gem of insight into our physical world, what did the Soviet higher-upniks do? Did they build a whole new generation of invisible planes and fly them from Havana to Washington? No. But, they had a different strategy, so the Dr. Strangelovean fleets of bombers was never really their jam. OK. So, did they classify it as a state secret and stack it up in the Russian equivalent of that warehouse with the Lost Ark? No. Because Ufimtsev’s work was only practical to determine the RCS of simple shapes. And you can’t fly a cube.

Well, maybe, you say, it’s because the USSR just really believed in openness. And, well, no. Not really. They classified huge amounts of aeronautics research. They kept secret all the data that came out of their testing programs. But anyone in the US could replicate testing data (testing data is when you carve a shape out of soap or balsa wood, throw it in a wind tunnel, and write down the numbers). No one in the US was figuring out the math of “Method of Edge Wave in Boring Theory Yadda Yadda.” The US’s coup de grace Cold War plane design is due to a Soviet Censor stamping “looks fine” on a seminal theoretical advance.

Tomorrow, we’ll cover how engineers in the US took this nugget of egghead-ness and ran with it. Ran with it to the tune of 4 awesome planes and 200 billion dollars.

Airplanes are Awesome: a Manifesto

Airplanes are Awesome. Like chocolate. Why? First off, they fly. Awesome.

Then, some do more. Like, fly faster than a speeding bullet. Or transport 500 people. Or carry the Space Shuttle. Like adding peanut butter to chocolate, this only makes planes more awesome.

This blog is a celebration of their awesome.

Now, lots of people write about planes. From the deep analysis to the gossip, the world already has enough commentary on planes and all that surrounds them. But these are “industry” blogs. They write for the writers of other airplane blogs, or the executives they’re reporting on, or the engineers making the decisions. Their writing isn’t impenetrable, but the authors aren’t trying to expand the club.

After years of diligent reading and late-night Wikipedia-ing, I’ve learned the awesome. And when something new happens, I can chortle with Mihai or Bernardo. But why no one else? These are great stories! This is underappreciated awesome here.

I won’t relate every bit of revealed information or industry updates. I just want to take the best bits, rip them out of the jargon and the lingo, and make them interesting and accessible. So, what’s interesting about these beasts of steel and birds of industry?

First, what they can do. I’ll talk about specific planes, and why each is cool. Names that might be familiar like 707, 737, 747, 767, 787 (that’s one pattern) and A320, A330, A350, A380 (another pattern). A wider range of more esoteric military planes (SR-71, F/A-18, YC-14, and longer alphabet soups). And I’ll talk about how planes relate to one another (and how they’re different).

Second, how people interact with planes. For most people, this means airlines and airports. How you board them. How you should board them. How airplanes work. How frequent flier programs function. We’ll talk some about how frequent fliers function (and a lot more about their dysfunction).

Third, how planes are made. Which, stay with me, is awesome in its own way. Why? Planes are the largest, most expensive item made on an assembly line. Making planes has its own drama and interest. From the small (how much can one piece matter? a lot) to the large (it’s cheaper to buy Frontier Airlines than one of its planes) to the geopolitical (Boeing vs. Airbus. We’ll get there).

So who’s my ideal reader?

• You don’t know much about planes

• You don’t particularly want to know much about planes

• But you do like hearing cool anecdotes and analyses. And if you have to learn a bit about planes to do so, well, that’ll do.

So if you already love planes, by all means, stick around and enjoy the superiority you feel at correcting my every misstep and foible. But if you don’t love planes? Well I’m jealous of you, cause you’re about to mainline the niftiest factoids about those that fly.