From 1957 to 1963, the design team went through at least 12 iterations of the form of the shells trying to find an economically acceptable form (including schemes with parabolas, circular ribs and ellipsoids) before a workable solution was completed.
The design team went through at least 12 iterations of the form of the shells (including schemes with parabolas). This was from 1957 to 1963. The design team went through at least 12 iterations of the form of the shells (including schemes with circular ribs). This was from 1957 to 1963. The design team went through at least 12 iterations of the form of the shells (including schemes with ellipsoids). This was from 1957 to 1963. These shells were trying to find an economically acceptable form (including schemes with parabolas). These shells were trying to find an economically acceptable form (including schemes with circular ribs). These shells were trying to find an economically acceptable form (including schemes with ellipsoids). A workable solution was completed.