Mercedes Benz, Bionic Car, Boxfish and Thinking

In our post Nature Spotting Inspires Wild Ideas we argued that watching and enjoying nature get enriched by coming up with ideas about how nature’s ingenuity can be applied to everyday things. At times that can go terribly wrong, but that is not due to nature’s ingeniosity, but to the inadequate frames with which we perceive nature’s solutions, as in the example below. Mercedes-Benz completely misunderstood the fish behind its fish-inspired car.

In 1996, Dieter Gürtler and his colleagues from the Mercedes Technology Center in Sindelfingen, Germany, were looking for a model for a holistically conceived bionic car, respecting at once physics, design, and aerodynamics. The team’s first instincts were to use streamlined sharks, penguins, dolphins, and tunas. But on a visit to the museum, it became clear that their ideas of tunas and sharks were not useful to design cars. They turned to the boxfish, a small, tropical coral reef fish, as a model.

Engineers specifically took interest in the boxfish’s carapace and its shape, which were thought to have impressive hydrodynamic characteristics. The boxfish body, despite being a blocky, broad, rounded shape (conveniently similar to that of an automobile), was reported to have exceptionally low drag. Additionally, the carapace supposedly had unique, inherent, self-correcting stabilization properties, directing the flow of water in such a way that the swimming fish is kept on course even in roiling waves.

In 2005, Mercedes-Benz unveiled the Bionic, the concept car that resulted from this boxfish-inspired endeavor. The Bionic was widely interpreted as a symbol of the power of collaboration among biology, engineering, and design, and an example of the utility of drawing directly from the pool of inventions already shaped by millions of years of evolution.

The Boxfish Swimming Paradox

However, Mercedes-Benz may have completely misunderstood the boxfish. The company misinterpreted the fundamental hydrodynamic profile of this fish, and by logical extension, the Bionic concept car as well. Researchers at the University of Antwerp in Belgium, the University of Groningen in the Netherlands, and UCLA, contend that the boxfish body shape does not particularly excel at drag reduction. Not only that, but it actually promotes instability while swimming, rather than minimizing it. This contradicts the entire premise behind Mercedes-Benz’s bionics-driven concept car.

A Design Paradox

We asked Andew Taylor, a designer engineer, to comment on The Boxfish Paradox.

When engineers and designer tried to improve the manoeuvrability of fighter aircrafts they faced an interesting paradox. The thing that restricted manoeuvrability of fighter airraft was the shape of the aircraft, which was too streamlined, and tended to help it fly smoothly in a straight line, but resisted attempts to get it to turn quickly. To do sudden twists and turns, what you needed was an aircraft that would ‘fly like a brick’ – in other words one that was inherently unstable, but where the control surfaces (ailerons, rudder, elevator) were constantly being adjusted by a computer to get the aircraft pointing in the right direction.  

By having an unstable aircraft with all its control surfaces under computer control, you get a very manoeuvrable aircraft, perfect for quick turns in combat situations. Yet, if you switch off the flight control computers, the aircraft will immediately go back to behaving like a brick, and will fall from the sky.

The box fish is using the same principle. It is very un-streamlined and inherently unstable, but by constantly adjusting the force from its fins, it is highly manoeuvrable. It has its own built-in control computer – its brain!”

When using nature as inspiration, biomimicry, it is important to be aware of paradoxes or contradictions. The boxfish is very stable when its on a steady course but it is very wobbly when it is changing directions. Boxfish are shaped like bricks and the body shape actually promotes instability while swimming, rather than minimising it. Compared to a human swimmer, the boxfish slices through the water, but it produces at least twice as much drag as more conventional, “fish-shaped” fish. The boxfish does not lament the absence of a course correction mechanism, as its instability is one of its greatest assets on the reef, permitting it to swiftly whirl wherever it pleases .

Take Aways

Mercedes Benz’engineers looked at the boxfish from within known hydrodynamics, which failed to explain the boxfish´ movements. Apparently, they were not able to discover the design principle of the boxfish because the existing theories prevented them for noticing it. Moreover, in their thinking repertoire, it seems that the concept of a paradox or contradiction doesnot exist at all, so they didn´t notice that the boxfish is both stable on a steady course and at the same time very viable when changing direction.

In the literature about TRIZ it is supposed that Western engineers are educated to solve contradictions in terms of optimizing between two opposite features , in this case seeking an trade off between stability and manoeuvrability.

It would be interesting how Russian engineers had conduct the observation of the boxfish, because they are accustomed to define problems as contradictions. Their problem solving strategy is based on a complete removal of a contradiction. In Western society one could call this ¨providing an and/and solution¨: the Ideal Final Result of the design task is to obtain both great stability as well as great manoeuvrability.

At last, be careful not to project human explanatory models on nature´s brilliant solutions! Our understanding of the natural world is constantly changing. The understanding of the boxfish should be seen as a reminder to be careful before we try a new approach, it teaches us among other things the importance of thinkibility.

Sources

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