The B-1B has a "variable-geometry" or swing-wing design: The wings are swept forwards, almost at right angles to the body, for take-off and landing and cruising.
Given a free hand in the design, his team developed a continuously variable transmission system that allows the petrol engine and electric motor to work separately or in tandem.
My last conversation with Adrian Bejan ended on the notion that if design in nature is a universal principle of the material world, then freedom is the key variable that determines how efficiently designs can evolve over time.