By: Amaya

It used to be that robots in space was a theme for science fiction.  Now fiction has become fact - Dextre, the "way cool space bot" from Canada, is now standing on guard outside of the International Space Station.  Dextre is a small two-armed robot capable of handling the delicate assembly tasks currently performed by astronauts during spacewalks.  Recently, Dextre passed all of its installation tests - the power flows, the arms and wrists bend, and more importantly, they stop when "Dave" tells them to.

Astronauts from Space Shuttle Endeavour installed the $209 million robot, whose official name is "Special Purpose Dexterous Manipulator," this week on three spacewalks. They even gave the robot his own handyman's tool belt with space gadgets (mostly equipment for changing batteries and video cameras on the outside of the station).

NASA is ecstatic.  The U.S. space agency and influential American media are all captivated by the robot that will soon be able to prowl around the outside of the space station, travelling on rails aboard its own custom streetcar.    According to Daniel Rey, a project engineer at the Canadian space agency, "Dextre is able to do things automatically. It's not a 'smart' robot (one that works independent of humans), but Dextre has a brain, so it can insert or remove a unit without it jamming. It has a sense of touch." 

Rey is talking about Dextre's sophisticated arms.  The 1.5-ton, aluminium-titanium structure has seven joints that make up its shoulder, elbow and wrist. This gives Dextre's arms the freedom of movement to get into any position.  On the ends of the arms are Dextre's hands, or Orbital Replacement Unit/Tool Changeout Mechanisms.  Each hand consists of parallel retractable jaws, which are used to grip objects.

"Probably the most important thing in Dextre is what we call the force moment sensor," explains Richard Rembala from MacDonald, Dettwiler and Associates, the renowned Canadian robotics company that has led the development of Dextre.  "The sensor is located at the wrist on each arm, and this sensor really gives Dextre a sense of touch. As it's grabbing boxes, it can actually measure how hard it's pushing, how hard it's twisting.  This means it can limit the forces applied to structures so it doesn't break them."

Dextre is quite an apt robotic application -  a robot tailored to do what is a forbidding job for a human.  Having a robotic handyman means astronauts won't have to go outside in space as often.   Dextre can change bolts and batteries and cameras instead of human spacewalkers, who are always at the mercy of radiation, flying space debris and possible accidents.  Spacewalks are also quite time consuming for astronauts.  Says Rey, "It takes a week to prepare to go on a spacewalk and it takes a week afterwards to put all your stuff away."

Dextre also represents a solution to a long debated question about how to migrate repair robots around the outside of the space station.  One of the first suggestions was to attach suction cups to a robot's feet - but suction doesn't work in space.  Magnetic feet wouldn't work either - not all of the station is built with magnetic metals.  The ultimate solution came from the Canadian Space Agency - they built a system using customized trolled tracks.

Dextre is the final part in a three-component system built by the Canadians. The Canadarm2 was installed on an orbiting platform in 2001. (It is essentially a larger, more capable arm than the one currently used in the space shuttle's payload bay.)  In 2002, it was attached to a Mobile Base System - a trolley that can carry the Canadarm2 along rails running the length of the station. Dextre is the last addition. The two-armed robot will be picked up by its "head" by Canadarm2 and taken to wherever a job needs doing.  The whole system runs up and down a trolley track and is operated remotely by astronauts from inside the space station.

But putting the robot onto the station was not all fun and games.  Early on, Dextre ran the risk of a premature death in space when its electrical cable went down.  No power flowed into its internal heaters, needed for heating Dextre's joints, limbs and electronics. The $200 million machine could have been fatally damaged if left cold for too long. But luckily Canadian Space Agency engineers hustled and found a way to reroute power to Dextre through the space station's Canadarm2.
 

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