Adrian Bejan | Evolution of Airplanes, from Design in Nature
This video tells the story of how ideas for predicting movement and speed evolved from animals to sports and then to airplanes, showing how thinking about flow, shape, and hierarchy connects nature, engineering, and human design through personal experience and simple drawings. It begins with Jordan Charles, who linked animal speed to athletics, leading to published work and a career path through industry, Boeing, and, later, Blue Origin, where he served as Vice President of New Glenn.
The video then turns to airplanes, noting that commercial jet aircraft look similar even though they differ in size, following a pattern of few large and many small. It explains that flying structures are stressed, hierarchical, and bird-like because their wingspan and fuselage length are of the same order. Using very simple drawings, the video introduces proportions and degrees of freedom that describe the fuselage, wing, and their shapes without detailed measurements. The goal is to understand how drag, mass distribution, fuel, and range guide the evolution of airplanes in a way that feels intuitive and connected to earlier ideas.
The video describes Jordan Charles' experience where ideas about predicting speeds moved from animals to sports, leading to published work and long-term impact. This shows how practice and observation can connect to theory.
Commercial jet aircraft are said to look the same while differing in size, with a hierarchy of few large and many small. This hierarchy appears every year as new airplanes and new models are adopted.
Airplanes and birds are compared because their wingspan is of the same order as body or fuselage length. Similar does not mean identical, but it explains why flying things resemble each other.
A simple drawing of the fuselage and wing is used to introduce proportions, including shape, slenderness, and span relationships. These proportions are treated as degrees of freedom that can change.
The video explains that drag comes from the fuselage and wings, and that mass is divided between the fuselage and wings. This division is linked to fuel, range, and later engines, showing why design choices matter.
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Interesting how Bejan connects biomimicry to engineering constraints without getting mystical about it. The wingspan to fuselage ratio convergence across diferent manufacturers makes sense when you frame it through flow optimization rather than just trial and error. I worked adjacent to aerospace folks years back and the "few large many small" hierarchy was always chalked up to market forces, but seeing it as an emergent property of constrained optimization adds a useful lens. Curious how this framework holds up when you throw in supersonic designs where the rules change a bit.