On July 12, 2011, spacewalking astronauts Mike Fossum and Ron Garan successfully transferred the Robotic Refueling Mission module from the Atlantis shuttle cargo bay to an temporary platform on the International Space Station's Dextre robot.
Two weeks ago, while the astronauts on the International Space Station were sound asleep, Mathieu Caron was carefully putting Dextre into place from the safety of the Canadian Space Agency’s (CSA) control center in St. Hubert, Quebec. The robot — otherwise known as the Special Purpose Dextrous Manipulator — was preparing for the Robotic Refueling Mission, a test to see if robots could one day refuel satellites in space.
Dextre has its work cut out for it: Currently, United States Strategic Command is tracking more than 22,000 man-made objects in orbit around the Earth.
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“Maybe the new generation of satellites will be built with the consideration of being refueled by a robot, but that’s not the case with almost all of the satellites in orbit right now,” says Caron, senior operations engineer for the CSA.
Since the launch of Sputnik, satellites have taken one-way journeys into space with little hope of ever seeing a gas station. The result is a space junk traffic jam that can be hazardous to other satellites and people below.
If satellites could be refueled, operators on the ground could move them out of the way to make room for new satellites or bring them back to Earth to be safely disposed of. The problem? While the International Space Station is outfitted with special markings and durable parts meant to be manipulated by robots, most satellites aren’t, making refueling tricky business.
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“The point was to present Dextre with valves and wires and insulation blankets that you would find on a satellite, but were not designed to be handled robotically,” says Caron. Over the course of three days, Dextre passed its test with flying colors, carefully cutting razor-thin wires that held down valve caps on a mock satellite brought up by NASA.
Other planned tests over the year will see if Dextre can build on its repertory of skills, including the ability to unscrew caps and connect a fuel hose to a fuel valve. These might sound like simple tasks, but remember they are being done by a robot with 12-foot arms held by a 57-foot mechanical limb called Canadarm2.
The level of clearance the robot had to slide a hook under a wire to cut another wire? A single millimeter. Not a lot of room for error, especially considering the people doing the work are in NASA and CSA control rooms on Earth.
Building the thing was no easy task either; it was shipped up in nine different parts and had to be assembled by astronauts on space walks. In the end, it will be at least a year before Dextre actually refuels a satellite. Until then, its main duty will be repairing the International Space Station with instructions from its operators below, who will be busy working as the astronauts catch some Zs.
“The astronauts’ time is very precious,” says Caron. “We don’t want them to spend all of their time repairing the station. We want them there to carry out their main goal – scientific research.”