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CCotW: Mercedes Bionic (2005)

14 December 2018 | by Karl Smith

In 2005, at the Daimler Innovation Symposium in Washington DC, Mercedes introduced a strange-looking little snub-nosed car. Called the Bionic, it was a car that was inspired by natural forms and processes, rather than traditional automotive design cues. Mercedes explained: “For the first time, the engineers specifically looked for a role model in nature, which lends itself to an aerodynamically efficient, safe, comfortable and environmentally compatible automobile not just in detail features but in its overall form and structure. They found this role model in the boxfish.”


The Boxfish (Ostracion cubicus) – a model for the Mercedes Bionic car

The boxfish is a reef-dwelling fish that lives in warmer waters in the Atlantic, Pacific, and Indian Oceans. Its ungainly, squarish body, made up of hexagonal plates that create a box-like carapace, is surprisingly agile. The boxfish spends its life flitting about reefs, able to turn rapidly and even spin on its vertical axis like a top with almost zero turning radius. This allows it to dart in and out of the coral searching for food and avoiding predators.

Studies on the boxfish’s form revealed a surprisingly aerodynamic (or, more to the point, hydrodynamic) shape. And unlike most fish, which are thin, the boxfish actually encloses a body of some volume, curiously like that of a car. Mercedes would characterise the boxfish as “a prime example of the ingenious inventions developed by nature over millions of years of evolution”.


The Bionic sported an aerodynamic form with a Kamm back

The form of the boxfish was simplified to create a concept body that could be tested in a wind tunnel. In a free flow of air the shape approached that of an optimum aerodynamic body. Even after wheels were added and concessions made for occupants, it still proved very sleek indeed.


The design evolution of the Bionic

The structure of the car was created with a innovative computer program that analysed critical areas and increased structure there, while reducing it in other areas. Mercedes explained: “ In consultation with bionics experts, a process was developed to transfer the growth principle used by nature to automobile engineering.

“Based on the Soft Kill Option (SKO), computer simulation is used to configure body and suspension components in such a way that the material in areas subject to lower loads can be made thinner, and perhaps even eliminated (‘killed’), while highly stressed areas are specifically reinforced. This process enables an optimal component geometry to be identified that meets the requirements of lightweight construction, safety and durability in equal measure. The bone-plate skeleton of the boxfish demonstrates how nature is able to achieve maximum strength with a lightweight design.”


The Bionic on the turntable at its introduction. Box Car, MPV, or Coupé? All of the above, it seemed

The end result of all this study was a stubby little four-seat coupe. Although it looked tiny in photos it was over four metres in length, placing it (theoretically) in the C-segment; it was actually larger than the Mercedes A-Class cars of the time.

The side profile was a teardrop with a truncated rear, the shape of which would have made Wunibold Kamm proud. The tiny front snout emulated the mouth of the fish. The Bionic sported an ultra-low Cd of 0.19.


Simple interior with a panoramic windscreen. Note the rear view camera, top left

The interior was a simple affair with vaguely aquatic shapes outlining the IP controls, steering and centre stack. The high box shape meant plenty of glasshouse and the windscreen swept up into the roof, providing a panoramic view out of the front of the car.

Underneath the tiny hood Mercedes installed a 1.9-litre BlueTEC diesel engine, the first in a passenger car (they were installed on Mercedes commercial vehicles that year for the first time). Hailed as the engine of the future, with unparalleled efficiency and clean emissions, it was seen as the saviour of internal combustion.


Bionic from above – lots of glass made for panoramic views

The Bionic got an enormous amount of press coverage for a car introduced well away from mainstream auto shows. Motoring and popular press outlets, and even some science magazines, picked up the story, as the cute little boxfish lead-in was too good to pass up.

The Bionic would appear once again in the 2008 Museum of Modern Art exhibit, ‘Design and the Elastic Mind’, which displayed all sorts of projects using non-traditional and cross-disciplinary design techniques. Once again, it was a popular story with a variety of newspapers, blogs and magazines. And then it quietly fell off Mercedes’ agenda. They were never going to sell anything resembling the fishy little car, and so it was back to more traditional concepts for the German traditionalists.

Still, the research which underpinned the Bionic proved that nature can provide valuable lessons for automotive design, and that the boxfish in particular pointed a way forward in aerodynamic design.

Or did it?

The scientific community looked on the Bionic project with bemusement. News articles profiling the little car circulated for years, prompting discussion about the car and the studies behind it. And some were skeptical that the boxfish was actually the hydrodynamic miracle it had been portrayed as.


Simplified Boxfish form used by Mercedes for aerodynamic testing

Finally, some scientists from the University of Antwerp, the University of Groningen and UCLA collaborated on a study and paper that extensively researched and modelled the boxfish and its close cousins, the trunkfish and the puffer fish. What they found contradicted Mercedes’ conclusions. The boxy carapace, while strangely hydrodynamic, was actually unstable rather than stable. Its highly celebrated manoeuvrability was actually the result of de-stabilising vortices of water flowing over the boxy carapace which the boxfish used, in conjunction with its fins, to enable its lightning fast turns and bursts of speed.


The Boxfish is ideally suited for reef life

But the boxfish is not a speedster in open water, or very efficient for lengthy swims in a straight line. Its hydrodynamics do not produce stability or speed. For protection when exposed in open water it relies on its boxy carapace and the poison it secretes out of its skin when threatened.

It is unlikely that Mercedes would develop a car with manoeuvrable fins or poison secretions (though some might pay for those options to clear a path through motorway traffic), so the boxfish model was at best incomplete and at worst completely misunderstood. Does this mean the whole car design was a sham?


Computer-generated models of the boxfish and its cousins were used to analyse swimming patterns

Not at all. There were important lessons learned in the study of an aero-box form, even if they don’t match the realities of the boxfish. The Soft Kill Option (terrible name) as a way of creating body structure was very valuable, as was the BlueTEC engine, even as diesel, once championed as the saviour of the automobile, now seems doomed as a powertrain option for the future.


The 2019 Toyota Prius – the Bionic, realised in production form?

Some thought the Bionic might be the next version of the A-Class, with a more bio-futuristic monoform shape. But the A-Class moved to a more traditional architecture. And yet the Bionic architecture lives on, in a slightly different form, in the Toyota Prius, which has a similar profile. No doubt Toyota engineers experimented with some of the same forms in the wind tunnel, though the boxfish has never been referenced.

Nature metaphors for automotive design are just that – metaphors. They can only be extended so far, because a fish is a fish, a bird is a bird, a jaguar is a jaguar and a car is a car; a machine in a natural and artificial ecosystem every bit as complex as the natural world.

Even a boxfish knows that.