When it is completed in 2011, the International Space Station will weigh some 400 tons and measure about 110 meters long. A collaborative effort involving engineers and scientists from more than a dozen countries, including Russia, Japan, 10 European nations and the United States, it constitutes the largest international technological project of all time.
Among countless other challenges, in recent years engineers have had to figure out a way to adequately maintain the station given that the number of supply missions has been considerably reduced following the Space Shuttle Columbia disaster in 2003. To address this problem, the European Space Agency (Paris) has decided to employ what it calls a “Eurobot” to augment the efforts of what is often a minimal three-member crew. This highly customized robot will perform inspections, and assist in spacewalks and other repairs.
As part of the development process, the prototype for the mobile, three-armed system needs to undergo dozens of hours of underwater tests at the German Aerospace Center (Cologne, Germany) where both it and the astronauts working with it can experience a kind of simulated zero gravity weightlessness. This, in turn, requires that the test robot be waterproof and capable of withstanding the chlorine and other chemicals in the water that keep it algae free.
This proved to be highly problematic for project members Thales Alenia Space Italia (Rome, Italy) and EADS Astrium (Paris), especially with respect to the rotary modules controlling the robot’s “head,” which is equipped with video cameras that play a crucial role in coordinating its movements. On the one hand, according to EADS Astrium Bremen project director Dr. Stephane Estable, there are plenty of underwater rotary modules on the market, but none of them is precise enough for this kind of application. On the other, the rotary modules that offer the requisite precision lack the means of preventing the ingress of water when submerged.
To solve the problem, Alenia Space Italia and EADS Astrium contacted work-holding and automation equipment manufacturer SCHUNK Inc. (Morrisville, NC), which modified a number of its PR 70 series modules for the application.
Specifically, SCHUNK equipped each module with new cable glands and an additional set off seals at each joint. It also replaced the modules’ standard external housing screws with threaded fasteners fabricated from especially corrosion-resistant steel.
The revamped rotary modules are now capable of withstanding an overpressure of 1.2 bar. In addition, they have been equipped with an encoder system with referencing capability that can record the angular position of the head to within 0.02 degree to help the robot’s control unit navigate its way through the space station.
“The modified rotary modules from SCHUNK have proven themselves comprehensively during the test phase,” Estable says. She adds that when the actual robot blasts into orbit some time in the future, it may very well be equipped with SCHUNK rotary encoders as well.
For more on automation, visit www.schunk-usa.com.