The Mercedes-Benz Bionic Car has been developed by the company to explore the great potential which nature offers as a model for the development of automotive technology. The objectives are reduced drag, greater rigidity with low weight, undiminished levels of safety and the lowest possible fuel consumption and exhaust emissions.
Bionics – a combination of biology and technology – is recent field of interdisciplinary research which brings biology together with engineering science, architecture and mathematics. The basic principle is to make problem solutions which nature has developed in the long process of evolution usable for man.
In a new departure, Mercedes-Benz researchers and engineers looked at the natural world in order to find a model which, both in terms of its overall make-up and the details of its form and structure, was a close approximation to an aerodynamic, safe, comfortable and environmentally compatible car.
They found the boxfish, a highly skilled swimmer which, despite its box-like body, has outstandingly low flow resistance – a property which is extremely valuable with regard to aerodynamics. An accurate model of this tropical fish was found to have a drag coefficient (Cd) value of just 0.06.
A 1:4 scale car model with a shape largely corresponding to that of the boxfish attained a drag coefficient (Cd) value of 0.095. This is an unprecedentedly low figure for a car and corresponds to the kind of figure (Cd 0.09) which could normally only be obtained with a streamlined body. A prototype vehicle based on the boxfish design was found to have a drag coefficient more than 65 percent lower than that of today's compact cars.
Compared with the 1:4 model, it was necessary to compromise to a certain extent on the functionality, everyday usability and design of the roadgoing compact-car prototype which features two doors, four individual seats, a panoramic windscreen, a glass roof and a large tailgate. It measures 4.24 metres long, 1.82 metres wide and 1.59 metres high while its top speed is 190 km/h. Thanks to its outstanding aerodynamics (Cd 0.19), the Bionic Car is one of the most aerodynamically efficient vehicles in this size category.
The boxfish is also a model of rigidity and lightweight design. Its outer skin consists of numerous bony hexagonal plates which offer maximum strength for minimal weight. Translated to the Bionic Car by means of a special calculation process, this bionic approach to structural design reduces the weight of the bodyshell by about one third without diminishing its rigidity or crash safety at all.
As intended, the optimum aerodynamic characteristics and the lightweight bionic structure result in significantly lower fuel consumption: the 103 kW/140 hp direct-injection diesel engine uses just 4.3 litres per 100 kilometres in the European combined driving cycle. This figure is 20 percent lower than that for a comparable series-production model. And at a constant 90 km/h, fuel consumption drops to just 2.8 litres per 100 km.
The Bionic Car was also designed to generate the lowest possible level of exhaust emissions. As well as providing it with a standard oxidation catalyst and particulate filter, the design team followed the example set by the truck sector and equipped it with SCR (Selective Catalytic Reduction) technology as well. The heart of this system is a catalyst into which tiny quantities of "AdBlue" (an aqueous solution of urea) are injected in order to transform oxides of nitrogen into harmless nitrogen and water. In the European test cycle, this results in a reduction in NOx emissions of up to 80 percent.
