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Dextre achieves robotic refuelling milestone on station

Elizabeth Howell, News Writer
Jan 28, 2013, 0:00 UTC

Sen—NASA and the Canadian Space Agency achieved a robotic refuelling on January 24, marking a crucial step for future missions to refuel dead satellites without going to the expense or risk of sending humans.

Dextre, which is a robotic "hand" aboard the International Space Station, successfully fuelled an experimental module attached to the station on a task that is part of the robotic refueling mission (RRM).

"Dextre just proved that robots can refuel sats in space! It’s the future, and it’s possible!" the Canadian Space Agency wrote on Twitter.

"Ladies and gentlemen, #RRM IS REFUELING!," added NASA's satellite services capability office on Twitter. "Fluid is moving through the nozzle tool through the closed-loop system in the module."

NASA and several private-industry firms are currently contemplating refuelling spent satellites while they are orbiting Earth. Running out of gas is a common reason for satellites to cease being useful to controllers.

Since Sputnik launched in 1957, satellites - for the most part - have been considered disposable. NASA did launch a handful of shuttle missions in the 1980s to service satellites, but the idea was abandoned after the 1986 Challenger explosion due to the expense and danger involved for the astronauts.

More than 1,000 satellites currently orbit the Earth, and with each new one launched comes the risk of incurring space debris through inadvertent collisions. Because it is an expensive proposition to design, test, build and launch satellites, NASA touts the RRM as a possible way to save money and time down the line.

The demonstration mission, however, was not without its challenges. Balky readings on Day 2 of the multi-day mission threatened to derail the schedule. The test was also pushed back from a date earlier in January due to software problems with Canadarm2, the robotic arm on which Dextre sits.

"Dextre removed two safety caps, cut through two sets of thin retaining wires, and finally transferred a small quantity of liquid ethanol into the washing machine-sized module. The latter manoeuvre was particularly tricky, since handling liquids in space required perfect precision to prevent dangerous leaks," the Canadian Space Agency said in a statement.

"Adding to the level of difficulty was the fuel hose itself, which adds additional forces that tend to pull Dextre’s hands. It took the combined skills of the experienced NASA and CSA robotics controllers to pull off this first-of-a-kind space refueling demonstration successfully and without any mishap."

Last week's milestone follows on from a highly successful mission that Dextre performed in March of last year.

In three days of work, the robot picked up tools, unlatched locks on the mock satellite, and cut several wires that were holding down a mock gas cap.

"The Robotic Refueling Mission required surgical precision and Dextre succeeded each task on the first attempt," said Steve MacLean, President of the Canadian Space Agency, after the March mission.

"It's the robotic equivalent of threading a needle while standing on the end of a diving board. With thirty years of experience flowing through the iconic Canadarm, Canadarm2 and now Dextre, Canada has honed its skills in space robotics to millimetre precision."

Astronauts toted the RRM module to the station during the final space shuttle mission, STS-135, in July 2011. As for Dextre, astronauts put the robot together from nine parts shipped up to the station.

January's RRM attempt required participation from the Canadian Space Agency, which controls Dextre from Quebec, as well as the NASA Johnson Space Center and NASA Goddard Space Flight Center.