Dextre, Space Electrician: Swapping Out Failed Circuit Breaker Boxes

A typical task on a space robot's "To Do" list

Repairing failed circuit-breaker boxes is a routine chore on board the International Space Station (ISS). The circuit breakers (also known by the technical term "Remote Power Control Modules," or RPCMs) are an important part of the ISS's electrical system, and tend to fail occasionally. Up to now, swapping the boxes needed to be done by astronauts during spacewalks. That is, until the arrival of Dextre, the Space Station's robotic handyman.

Dextre was designed to do standard repairs on the Space Station's exterior to reduce the need for astronauts to do spacewalks (which always carry a certain level of risk), and free up the crew's time for more important activities, like conducting science experiments. Like the average home, as the Space Station ages, it will require more minor repairs and servicing to ensure that everything stays in working order. As the Station's resident handyman, Dextre will always be on call to keep the Station ship-shape.

On August 28, 29, 2011, Dextre performed the first successful replacement of a failed circuit breaker box by a robot. While perched on the end of Canadarm2, Dextre grasped and removed a brand new circuit breaker from a Cargo Transport Container (a small storage container) on his workbench. Using his free hand, he removed the broken circuit breaker from the ISS by unfastening the bolt that held it in place and sliding it out of its casing. Dextre then rotated at the waist so his workbench is turned away from the worksite, and installed the new circuit breaker, which was successfully powered up. The failed circuit breaker will then be put into an empty slot into the Cargo Transport Carrier. Once the task was completed, Canadarm2 will moved Dextre away from the worksite. The faulty circuit breaker will eventually be returned to Earth to help determine the cause of its failure.

This animation shows the accelerated sequence of operations Dextre performed when the robotic handyman replaced a failed circuit breaker box on board the International Space Station (ISS) in August 2011. (Credit: NASA TV)