May 02, 2013
NASA flight controllers resumed activities with the Robotic Refueling Mission outside the International Space Station on May 1, using the Canadian robot arm/Special-Purpose Dextrous Manipulator (Dextre) combination to demonstrate a series of satellite repair capabilities.
The work — manipulating coaxial cable connectors, removing screws and insulation blankets that are representative of components found on spacecraft never designed for servicing in orbit — is scheduled to continue through the middle of next week, said Robert Pickle, NASA’s Robotic Refueling Mission lead in Mission Control at the Johnson Space Center.
The $22.6 million, three-year Robotic Refueling Mission (RRM), a washing machine-sized three dimensional task board with a tool kit developed by the Goddard Space Flight Center, was launched aboard the space shuttle on STS-135, NASA’s final station assembly mission, in July 2011. The hardware ultimately was placed on the station’s starboard truss Express Logistics Carrier 4 (ELC-4) to provide power and data connections for a spacewalk and subsequent robotic operations.
The latest round of demos follows a breakthrough round of ground-controlled activities in January using the 70-ft.-long Canadian robot arm/Dextre combination to sever lock wires and remove a mock fuel cap to flow 1.7 liters of ethanol fuel into the RMM.
“What we have coming up are some of the finer tasks for this payload,” Pickle said.
The two-armed Dextre extension was positioned over the ELC-4 work site on the eve of the latest exercise to demonstrate:
• Subminiature cap removal for simulated access to a satellite’s electrical data system to expose a component failure, much as a mechanic would attach a diagnostic display cable to an automobile computer to isolate an engine problem. Dextre will be commanded to remove simulated coaxial radio caps and stow them in a receptacle on the RRM module.
• Small screw removal and storage. The fasteners, which must be unthreaded as they would be with a handheld screwdriver, are of the sort that might hold a protective cover plate to a satellite. The removed plate could expose a faulty spacecraft component for replacement. As with the subminiature cap removal, safe stowage of the screws is considered essential.
• Non-destructive removal of multilayer insulation (MLI), the flexible, protective thermal blanketing that overlays fuel valves, access ports and potentially repairable components. The challenge is to cut, peel and fold MLI so that it can be re-applied as repair activities are completed.