During the next few weeks, the team created a computer program which could evaluate the RCS of possible designs. The RCS-prediction software was called "ECHO 1". As tests with the program proceeded, it became apparent that edge calculations by the program were incorrect due to diffraction. In 1964, Pyotr Ufimtsev, the chief scientist of the Moscow Institute for Radio Engineering, published a seminal paper titled "Method of Edge Waves in the Physical Theory of Diffraction". The work was translated by the Air Force Systems Command's Foreign Technology Division; subsequently, Overholser incorporated elements of Ufimtsev's work to refine the software. ECHO 1 allowed the team to quickly decide which of the 20 possible designs were optimal, finally settling on the faceted delta-wing design. However, many within the division were skeptical of the shape, giving rise to the name "Hopeless Diamond" – Kelly Johnson said to Rich, "Our old D-21 drone has a lower radar cross-section than that goddamn diamond".