Mercedes' fish-inspired car

Mercedes' fish-inspired car

(PopSci.comexternal link) -- When Mercedes-Benz began to contemplate its next generation of high-efficiency small cars, it sought aquatic inspiration.

But instead of considering obvious undersea hot rods like sharks, the Mercedes team turned to a fish that resembled a car: the tropical boxfish.

A native of the Indo-Pacific region, the Ostracion cubicus is surprisingly slick.

Wind-tunnel testing of a clay model revealed a drag coefficient (Cd) of just 0.06, startlingly close to the ideal 0.04 of a water droplet.

Like the droplet, the boxfish's face is small in proportion to its overall length, and its streamlined surfaces encourage air to move over it without creating the turbulence that robs aerodynamic efficiency.

Mercedes' Bionic concept vehicle mimics this functional form.

With a Cd of just 0.19, the four-seat Bionic is significantly more slippery than today's most aerodynamic production vehicle, Honda's two-seat Insight (Cd 0.25).

The design team eschewed expensive, complicated and heavy fuel-cell or hybrid powertrains, opting instead for a 1.9-liter four-cylinder direct-injection turbodiesel that pushes the fishmobile to 62 mph in 8.2 seconds with a combined city/highway fuel economy of 70 mpg.

At a constant 56 mph, the concept car will return an amazing 84 mpg.

Although the Bionic isn't coming to your local dealership, Mercedes does expect it to significantly influence the design language of its next generation of small cars.