When it comes to robots that perform internal inspections of water pipes, virtually all of them move along on rubber tires or treads. As that rubber grips against the inside of the pipe, however, it dislodges rust particles that ultimately end up coming out of peoples' taps. In an effort to address that problem, the European Union TRACT project is developing a propeller-driven inspection robot that keeps the pipe-touching to a minimum.

The current 3D-printed prototype was created by Norway's SINTEF research group (which has previously developed a wheeled pipe-inspection robot), along with Breivoll Inspection Technologies and industrial design firm Inventas.

It has an articulated segmented body, with propellers located at either end. While those props provide the power to move it, spring-loaded fins on its body do lightly brush against the inside of the pipe, just to keep the bulk of the robot from contacting it.

Depending on which prop is activated, the robot can move forward or backward through pipes as small as 10 cm (3.9 in) in diameter. It can travel up to 150 meters (492 ft) – making turns as sharp as 90 degrees as it goes – and then simply reverse back through the pipes to get to its starting point for retrieval.

The robot performs its inspections using 64 onboard ultrasound transducers. By emitting ultrasound signals into the pipe walls and then analyzing the reflected signals, it's able to determine the thickness of the metal. If a significant amount of that thickness has been lost to corrosion at any given location, the transducers will pick up on it.

The TRACT project started last December, and is due to wrap up next year. You can see the robot in action, in the video below.