The Mercedes-Benz bionic car
• Unique research project by biologists and engineers
• Vehicle study with the streamlined contours of the boxfish
• Outstanding aerodynamics with a Cd value of 0.19
• Diesel engine with a particulate filter and innovative SCR technology
• Bionic design process for intelligent lightweight construction
Thinking the unthinkable. Looking beyond the horizon. Leaving familiar paths and giving new ideas a chance: that is the philosophy of DaimlerChrysler, the technological leader among automobile manufacturers.
For more than 100 years the technological lead of the Stuttgart company has been based on the creativity of its engineers – and on their enthusiasm for visions. None of this has changed to the present day, and Mercedes-Benz specialists take up the challenge to shape the future of the automobile on a daily basis. There are no limits here: in order to create trailblazing innovations for even more safety, environmental compatibility and comfort, they research all the possibilities offered by technology and science. For experience has shown that only free, interdisciplinary thinking leads to really outstanding results.
One such project was the Mercedes-Benz bionic car, a concept vehicle based on examples in nature, in which Mercedes-Benz has also transferred the diesel engine technology of the future to a fully functioning and practical car for everyday use.
Bionics – a combination of biology and technology – is a quite recent field of research which has nonetheless already made remarkable progress possible in different areas. Nature has provided ideas for high-strength materials, low-friction surfaces, dirt-repellent coatings and practical Velcro fastenings, for example.
Many of these inventions are based on more or less accidental discoveries from the animal and plant world. For the first time in the case of the Mercedes-Benz bionic car, the engineers at the Mercedes-Benz Technology Center (MTC) and DaimlerChrysler Research looked for a specific example in nature whose shape and structure approximated to their ideas for an aerodynamic, safe, spacious and environmentally compatible car. In other words, this was not a matter of detailed solutions but of a complete transfer from nature to technology – a first.
The boxfish – angular but nonetheless very streamlined
This required teamwork: biologists, bionics scientists and automotive researchers from various disciplines embarked on an extraordinary expedition into the animal kingdom which soon led them into the depths of the underwater world – and presented them with a surprise. It was not the fast, sleek swimmers such as the shark or dolphin that came closest to the ideals of the research engineers, but a creature that looks anything but streamlined and agile at first sight: the boxfish.
It has its home in the coral reefs, lagoons and seaweed of the tropical seas, where it has a great deal in common with cars in many respects. It needs to conserve its strength and move with the least possible consumption of energy, which requires powerful muscles and a streamlined shape. It must withstand high pressures and protect its body during collisions, which requires a rigid outer skin. And it needs to move in confined spaces in its search for food, which requires good manoeuvrability.
There is more to the boxfish than meets the eye: despite its angular body, it is an excellent swimmer whose cube-shaped structure is by no means a hindrance. On the contrary, the boxfish possesses unique characteristics and is a prime example of the ingenious inventions developed by nature over millions of years of evolution. The basic principle of this evolution is that nothing is superfluous and each part of the body has a purpose – and sometimes several at once.
The outer skin of the boxfish consists of numerous bony, hexagonal plates which are interlinked to form a rigid suit of armour. This bony, armour-plated structure gives the body of the fish great rigidity, protects it from injury and is also the secret of its outstanding manoeuvrability, as tiny vortices form along the edges on the upper and lower parts of the body to stabilise the fish in any position and ensure that it remains safely on course even in areas of great turbulence. It does not need to move its fins in the process, and can therefore conserve its strength.
Applied to automotive engineering, the boxfish is therefore an ideal example of rigidity and aerodynamics. Moreover, its rectangular anatomy is practically identical to the cross-section of a car body. And so the boxfish became the model for a so far unique automotive development project.
Cd value: boxfish almost as good as the ideal engineering shape
The first sub-project tackled by the engineers at the Mercedes-Benz Technology Centre and DaimlerChrysler Research concerned aerodynamics. In wind tunnels and water channels they examined how the attributes of the living model could be transferred to an automobile.
The results are impressive. Despite its angular structure, the boxfish has almost as good streamlining qualities as the water drop shape which specialists consider to be the standard for the ideal aerodynamic form. When exposed to an open flow, this streamlined shape has a Cd value of 0.04. Using computer calculations and wind tunnel tests with an accurate model of the boxfish, the Mercedes engineers achieved a value which came very close to this ideal, namely 0.06 – an outstanding result. It explains why the boxfish is such a good swimmer and is so manoeuvrable with minimal effort.
To make use of the aerodynamic potential the specialists in Stuttgart first created a 1:4 scale model car whose shape substantially corresponded to the boxfish. The angular outside contours of the living model were adapted in the area of the roof and side skirts, as was the prominent, descending rear end with its heavily scalloped sides and pronounced wedge shape.
In doing this they were disobeying important principles in automotive aerodynamics, and were all the more surprised at the results: the Cd value for the car was 0.095. In aerodynamic terms it was just as good as the shape – as measured on the ground – considered ideal by aerodynamics specialists (Cd 0.09).
The research model in the shape of a boxfish betters the drag coefficient of today’s compact cars by more than 65 percent.