Space Station Robots Reach for Stars

 

It’s been a big week for robots living outside as well as inside the International Space Station.

Robonaut 2, NASA’s humanoid collaboration with U. S. automaker General Motors, however, may have to take a temporary backseat to DEXTRE, the two-armed Canadian handyman. Short for Special Purpose Dexterous Manipulator, DEXTRE removed and replaced an external circuit breaker over two late afternoons and nights – while the station’s six-member crew slept.

Both R2 and DEXTRE will gradually assume duties carried out by astronauts, routine activities that should free their human companions for more science research. In R2’s case, engineers expect to learn more about how safely humans and machines can work together, whether in space or on the Earth.

Both are designed to respond to commands from Mission Control as well as astronauts.

The 11.5 foot tall DEXTRE reached the space station in March 2008, as a space shuttle passenger. He was designed to work while anchored to the station, the tip ofCanada’s 57-foot-long robot arm, or as part of a small rail car that rides along the station’s solar power truss.

DEXTRE worked from the tip of the robot arm for the circuit breaker change out early this week on the inboard portion of the station’s power truss, a task that would typically be carried out by spacewalking astronauts. DEXTRE is likely to draw more work as a spacewalk substitute for routine maintenance of the station’s electrical, thermal control and data handling systems.

The robotic handyman will also participate in demonstrations of the Robot Refueling Mission, a U. S.satellite refueling demonstrator delivered to the space station aboard  NASA’s  final shuttle mission in July. The RRM was temporarily stored on DEXTRE during the July mission.

Refueling demonstration activities are tentatively scheduled to get under way in early 2012.

R2, a broad shouldered torso with two arms who resides on a stanchion in the station’s U. S. Destiny laboratory, was launched aboard the shuttle Discovery in February. He was awakened electronically on Aug. 22. This week, engineers and operators in Mission Control had hoped to command R2’s first movements in space.

However, they found his control systems, tuned originally in a NASA lab, need more tweaking in zero gravity before he is commanded to move his head, hands and arms.

“Before, we saw if Robonaut had a heartbeat,” said station astronaut Mike Fossum, a reference to the Aug. 22 power up, as he monitored the motion test early Thursday. “Today, we wake him up.”

But after two hours of testing, the R2 team in Mission Control decided the robot’s force sensors needed some adjustments.

“We had scheduled a set of motions to have the robot adaptively learn the difference between zero G and one G and configure parameters on the robot to move the joints in a certain fashion. We didn’t actually get to that today,” Nic Radford, NASA’s Robonaut deputy project manager, explained in a NASA TV interview.

“But what we did do was make sure that all the force sensors that are critical to the robot shutting down any inadvertent motions or keeping all our contact forces below certain thresholds approved by safety panels checked out. They looked great,” said Radford. “You can ask any crew member — moving in zero G is a lot different than moving around in a one G environment on Earth, and so our robot has to learn the difference.”

As R2 acclimates to weightlessness, he will begin to respond to programs that have him working in Destiny at a task board with his hands and tools. Eventually, R2 will be equipped with legs and assigned to cleaning chores – cleaning air filters and wiping down hand rails inside the station.

Someday, he is likely to venture outside the station, perhaps setting up a work site for spacewalking humans.

Meanwhile, on the ground NASA engineers are working on advanced versions of R2 that can join in the exploration of the moon, the asteroids and , perhaps one day Mars.