Alan Brown of Ufimtcev work:
Now I’ve got to back up a little bit on
the theory of that we developed on the theory of
that we developed for calculating radar cross
section. As I mentioned it was all based on the
radar return from a flat plate. If you illuminate a
flat plate at any arbitrary angle with a radar which
is coming in with a uniform electromagnetic
distribution then any element on that flat plate will
re radiate identically to a first approximation
which is caused physical optics. Now in real life it’s
not quite that simple because the edges of the plate
have the energy flow around them and those
flowing around the corner generates another signal
which we call diffraction. Just like diffraction
optically. And that diffraction term then gives a
stronger signal than the signal that comes from the
main part of the plate. So all around the periphery
of the plate if you were to illuminate it like a
window frame you get a bigger return from the
frame than you do from the body of the plate in
the middle. But we didn’t know how to calculate
that. Now the Air force has a group of people
called foreign technology division also at Wright
Patterson Air force Base whose sole job is to look at
foreign documents, determine if they’re of interest,
translate them, and get them out to our military
and our military contractors. And one of the ones
that they did, and they translated this in 1971 was
the work by a Russian physicist predominately
done initially for his PhD thesis had at I think the
Institute of Theoretical Physics in Moscow, I’m not
sure the exact title of the institution, and his name
was Petr Ufimtcev. And he came up with the
theory of physical diffraction which is one step
beyond our physical optics. The Air force translated
it in 1971 because this material had never been
kept classified by the Soviet Union. The most likely
reason was twofold. One is I mentioned earlier you
have to drop the radar cross section by at least a
1,000 to maybe 10,000 to be really effective against
modern radars compared to conventional aircraft.
That will probably be seen to be a ridiculous
impossibility at best. So that was probably the main
reason. The second reason, of course, is that
Russia’s predominant military posture was defense
of mother Russia more than designing airplanes to
be able to penetrate American air space. They were
thinking more in terms of ICBMs for that job
anyway. So there’s probably less interest in the
subject than we had, and also a general feeling that
it wasn’t practical anyway.
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