July 29, 2013
Dextre, the multipurpose dexterous manipulator that rides at the end of the International Space Station's (ISS) robotic arm, will acquire some new tools and tasks by year-end.
Among the cargo tucked into Japan's fourth H-II Transfer Vehicle scheduled for launch to the ISS Aug. 4 is Phase II hardware for NASA's Robotic Refueling Mission (RRM), a testbed the size of a window air conditioner bolted onto the station truss that mimics operational satellites.
After a good workout on the basics of satellite repair and refueling, the new gear will allow Dextre to practice more complex work—borescope inspections, cryogenic-refueling attachments, rewiring and the like.
Engineers at Goddard Space Flight Center, where the human-servicing missions for the Hubble Space Telescope were devised, developed the RRM to demonstrate that robotic tools are equal to the task of servicing satellites in orbit—repairing, relocating or refueling them to extend their service lives. They worked closely with robotics experts at the Canadian Space Agency (CSA), which supplies robotic technology for the station (see page 14).
“Demonstration in space is the only way to do this,” says Jill McGuire, the RRM project manager at Goddard. “We can do a lot of ground demonstrations with robots in our labs, and tell people until we're blue in the face that this will work. But actually showing them that it works in space is the key to buying down risk and giving them the confidence that you can repair their satellite.”
McGuire and her team designed a box studded with examples of the fixtures a servicing robot would find on the different satellites operating today, and produced a set of tools that use the torque Dextre generates to drive much smaller tools with the precision needed to manipulate the satellite interfaces.
The initial toolkit consisted of a wire cutter, a tool for removing safety caps, a nozzle to pump ethanol—a stand-in for hydrazine or other storable propellants—and a “multifunction tool” with heritage in the pistol-grip tool used by spacewalking astronauts.