The Convair B-58 Hustler grew out of a long series of design studies dating back to the years immediately following World War II. Early concepts called for small jet bombers carried aloft by B-36 or B-60 bombers, and would shed jet engine pods during the mission. These massively complex and expensive systems evolved over time to the somewhat more straightforward B-58 which was a single stage aircraft carrying an underslung pod containing both jet fuel and a single nuclear weapon. But even that was originally intended to be a rocket powered missile.
The B-58 evolved directly from the MX-1964 design from 1952. This is recognizably related to the B-58, but had the four jet engines in two pods rather than four, and a higher degree of integration between the pod and aircraft.
