Jun 042011

Some day in the future, it’s possible that an unmanned rover may go trundling across the Martian landscape not on wheels, but on three rotating steel coils.

While able to traverse rugged terrain without getting stuck, it could also move sideways to get around obstacles, would be unlikely to malfunction as it would have very few moving parts, and could perhaps even remain mobile if it were to take a tumble and flip over. Although such a vehicle might not be exploring Mars any time particularly soon, a fully-functioning prototype does already exist here on Earth, and its design could find terrestrial applications.

The basic device

Wisconsin engineer Tim Lexen built and designed the rover. At its heart is a flat triangular PVC main body (measuring about 7 inches/17.8 cm per side) that houses three electric servo motors, battery packs, and electronics. These independently power its three 8-inch (20.3-cm) stainless steel helical coils, also known as screws, each one extending horizontally from one corner of its body. The screws incorporate a low-friction outer coating that keeps them from getting stuck against rough surfaces while their augering action allows them to push or pull against those surfaces to move the rover in any desired direction. For this reason, it works best on textured surfaces such as dirt, grass, sand, or gravel, as opposed to completely flat, smooth surfaces.

The proof-of-concept device is remotely-piloted by a human operator, via a standard hobbyist’s radio-control system.


Screw-driven ground vehicles in and of themselves are certainly nothing new, having been around since at least the 1860s – one relatively well-known example is the Russian ZIL off-road vehicle. Almost all of these, however, have utilized pairs of longitudinally-mounted pontoons with sharp-edged augers coiling around their outer surfaces. While these did a decent job of moving the vehicles forward over rough or sloppy terrain, they required the vehicles to face whatever direction they were turning.

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