Operations to test new robotic satellite refuelling techniques on the International Space Station have run into a small problem.
NASA and the Canadian Space Agency (CSA) had planned a ten-day demonstration to test new satellite maintenance technology. Called the Robotic Refuelling Mission (RRM), the Canadian built Dextre robot and Canadarm 2 were to demonstrate different techniques on a testbed – called the RRM module – designed and built at the Goddard Space Center in Greenbelt Maryland. The plan was for Dextre to simulate the refueling of a satellite by transferring liquid ethanol into the RRM module.
Day 1 was completed successfully Monday. Day 2 operations were halted Tuesday evening by the glitch. The Canadian Space Agency media plan to post updates to their Twitter and Facebook accounts.
The RRM module was carried into orbit by the space shuttle Atlantis on the final shuttle mission in July 2011. The hardware on the RRM module is meant to simulate conditions found on a real satellite. Fuel tanks on satellites are triple-sealed to avoid hazardous leaks. To refuel a satellite, a series of seals, nuts and safety caps, must be released. Each piece must be tethered by a wire to prevent them from floating away.
The plan is that during operations, Dextre will be sitting on the end of Canadarm2 and will steady itself with one arm leaving the other free to perform the tasks. After completing several tasks to remove caps and valves, Dextre will attach the NASA-built nozzle tool (equipped with a 50-cm hose) onto a valve on the RRM module and then open a nut so that the fluid can be transferred to the RRM module. Operators at NASA’s Marshall Space Flight Center will then send the commands to transfer the fuel. Once complete, Dextre will back away, leaving behind a Quick Disconnect adapter on the valve to prevent the fluid from leaking.
The CSA’s Mathieu Caron explains the next phase of RRM in which Dextre will simulate refueling a mock satellite with liquid ethanol. (Video credit: CSA)
NASA Public Affairs Officer Josh Byerly conducts a phone interview with Benjamin Reed, Deputy Program Manager of NASA’s Satellite Servicing Capabilities Office, about this week’s Robotic Refueling Mission activities. (Video credit: NASA)
Here is the original 5-day itinerary for the demonstration – to be carried out during the period of January 14 – 23 :
Day 1: Tertiary Cap Removal
Grasp the wire-cutting tool from the RRM module and unstow it
Cut a safety wire on the tertiary cap
Using the other arm, grasp and unstow the multi-function tool and use it to remove the tertiary cap
Day 2: Wire Cuts
Stow the tertiary cap in its receptacle on the RRM module
Cut a safety cap wire
Cut a second wire hold an actuation nut in place
Stow the wire-cutting tool
Day 3: Tackle the Safety Cap
Stow the multi-function tool
Grasp the safety-cap tool and unstow it
Check out the safety-cap receptacle where used caps will be stowed
Day 4: Safety Cap Removal
Remove the safety cap
Stow the safety cap tool
Day 5: Refuelling
Dextre will use one of his arms to grab onto a nearby fixture for added stability
Grasp the nozzle tool and unstow it
Open an actuation nut
Fuel the RRM module
Release the nozzle, leaving behind a Quick Disconnect adapter to seal the valve and
Stow the nozzle tool and release the stabilization fixture
Day 1 activities were completed successfully on January 14.
Day 1 Highlights (Video Credit: NASA)
Day 2 activities were halted when a software issue became apparent in the space stations Canadian-built robotic arm.
According to the CSA website:
“The Canadian Space Agency (CSA) yesterday evening requested a temporary pause in the operations for the Robotic Refueling Mission. An intermittent difference in the software that controls of Canadarm2, the International Space Station’s Canadian-built Remote Manipulator System, requires further analysis to ensure safe operations. Canadarm2 and the Special Purpose Dexterous Manipulator, or Dextre, has temporarily been placed in a safe configuration while engineering teams on the ground assess the data. CSA will provide a status shortly to determine when work can safely resume.”
Update – 20:45 pm January 16
From the Canadian Space Agency:
RRM Robotics to Resume on Jan. 17
The Canadian Space Agency (CSA) has cleared the International Space Station’s robotic arm, Canadarm2, to continue work on the Robotic Refueling Mission (RRM) following a short delay to verify software settings in the robotic arm’s control system.
Robotics engineering teams had discovered an intermittent anomaly in the software that controls Canadarm2, which could potentially have caused the system to use the wrong parameters while in motion, a particular concern when the arm must work close to other structures (as is the case with RRM). After detailed analysis, the CSA identified steps that can be taken to ensure Canadarm2’s software selects the right parameters, thereby ensuring it is safe to proceed.
Canadarm2 and Dextre, the International Space Station’s robotic handyman, will resume Day 2 operations of RRM tomorrow. Because Dextre successfully stowed the tertiary cap in the RRM module on Tuesday, the robot’s next step will be to cut two sets of wires on the safety cap. The goal of RRM is to demonstrate how robots could service and refuel satellites to extend their useful lifetime.