The most important document in the history of stealth aircraft was not written in California or at a secret desert airfield. It was written in Moscow, in Russian, by a Soviet physicist — and the Soviet Union let it go abroad because it decided the work was of no military use whatsoever. His name was Pyotr Ufimtsev, and without him there might be no F-117, no B-2, and no modern stealth at all.

A paper about edges

In 1962, Ufimtsev published a dense theoretical work with the unpromising title Method of Edge Waves in the Physical Theory of Diffraction. It was pure mathematics: a way of precisely calculating how electromagnetic waves — including radar — scatter off the edges and flat facets of a shape. To the Soviet military establishment of the day it looked like abstract academic physics with no obvious weapon attached, so there was no objection to it being openly published.

In 1971 the US Air Force's Foreign Technology Division at Wright-Patterson Air Force Base translated the book into English. And there it sat, in the technical literature, until the right person read it.

The engineer who understood what it meant

That person was Denys Overholser, a radar specialist at Lockheed's legendary Skunk Works. In the mid-1970s Lockheed was trying to work out how to build an aircraft that radar could not see, and the problem was fiendish: nobody could reliably predict how radar would bounce off a complex three-dimensional shape. Reading Ufimtsev, Overholser realised the Soviet physicist had already handed him the tool. His equations made it possible to calculate the radar reflection of a shape made of flat panels — and to design that shape so the reflections went anywhere except back at the enemy radar.

Because the computers of the day could only handle flat surfaces, the resulting aircraft came out looking like a faceted gemstone. That aircraft was the F-117 Nighthawk. Overholser later, famously, credited Ufimtsev as the true father of stealth. The story of the ugly little prototype that proved it all works is told in our piece on Have Blue.

The great irony

The same theory later underpinned the smoothly-curved B-2 Spirit, once computers grew powerful enough to model curved surfaces. In other words, the mathematical foundation of America's entire first generation of stealth aircraft — the machines that would one day fly against Soviet-designed air defences — came from a Soviet scientist's freely published book.

And Ufimtsev's own story has a fitting final twist. After the Cold War he moved to the United States and took up an academic post at UCLA in California — living and teaching in the country his work had quietly transformed.

It is one of the great what-ifs of the Cold War: had a single Soviet review board decided that a paper about radar edges was worth classifying, the shape of modern air power might look completely different.