A Helping Hand for the Space Station
Artist's version of Dextre attached to the station's robot arm

Dextre can be attached to the end of the space station’s Canadarm2. Image Credit: NASA

Following NASA's recent addition of the Harmony node, the International Space Station is becoming more international than ever. The European Space Agency's Columbus laboratory module was connected to Harmony in February 2008, and Japan's Kibo module is about to be added as well.

As part of that international expansion, the space station will be getting a helping hand from Canada on the STS-123 mission of space shuttle Endeavour.

Canada has long been the leading source for robotic space appendages. The original Canadarm Remote Manipulator System, or "robot arm," is an important part of the space shuttle's equipment, useful for retrieving satellites and, now, for the construction of the space station.

The Canadarm's "big brother," the Canadarm2, was installed on the space station in 2001, during another mission of the space shuttle Endeavour. This larger arm, with new features, was designed to be one component in the Mobile Servicing System, a three-part system to help build and service the space station.

The second part of the system, the Mobile Base System, was added to the space station in June 2002, also by Endeavour. This part is essentially a "train" that can carry the Canadarm2 along rails running the length of the station.

Now, on STS-123, Endeavour is carrying the final part of the system, the Special Purpose Dexterous Manipulator, or "Dextre."

More than just a hand, Dextre is a robot with two smaller arms. It is capable of handling the delicate assembly tasks currently performed by astronauts during spacewalks.

Detailed image of Dextre robotic hand

Dextre somewhat resembles a person, with a head, a torso and arms. Image Credit: NASA

The two arms will allow Dextre to transport objects, use tools, and install and remove equipment on the space station. Dextre also is equipped with lights, video equipment, a tool platform and four tool holders. Sensors will allow the robot to "feel" the objects it is dealing with and automatically react to movements or changes. Four mounted cameras will allow the crew to observe what is going on.

Dextre can be attached to the end of the Canadarm2 and placed in position for the work it needs to do. Or it can ride on the Mobile Base System rail system, and the Canadarm2 can deliver equipment to it.

Astronauts will operate Dextre remotely from inside the space station. The robot is designed to function as a part of a spacewalk team, working with astronauts, or to work independently on tasks that previously would have required a spacewalk, allowing the crew to remain inside the station. This will increase crew safety and could free up more time for astronauts to perform other tasks.

Dextre's design somewhat resembles a person. The robot has an upper body that can turn at the waist and shoulders that support arms on either side. Each arm is 11.5 feet in length and has a total of seven joints, allowing a wide range of possible movements. The arms are able to handle masses of up to 1,327 pounds. Each arm has a "hand" with parallel retractable jaws that can grip objects, a retractable motorized socket wrench, lights and a camera.

To keep the arms from bumping into each other, only one arm can move at a time. This constraint provides greater stability for the robot, because the hand not being used fastens onto the station, anchoring Dextre in place.

Many astronauts have said that spacewalks are some of the more memorable parts of their spaceflight experiences. But, with Dextre, the crew will have the option of staying inside while some of the work is done outside. And when the astronauts do go out, they'll have the benefit of the Canadian helping hand.

Related Resources
Canadarm2 and the Mobile Servicing System
Canadian Space Agency   →
NASA Education Web Site   →

David Hitt/NASA Educational Technology Services