Engineering Week


The people from NASA were skeptical.  Should they entrust one of the most crucial aspects of the new shuttle program to a relatively untested engineering team from Canada?  Their decision, in 1975, to do just that has meant that Canadians are responsible for one of the most significant advances in space engineering -- the Canadarm.

Measuring 15.2 m (50 ft) in length with an earth weight of 410 kg (905) lbs, one of the Canadarm's most impressive engineering achievements is its ability to capture a free-flying payload in a zero gravity environment.  The slightest contact with an object in space, regardless of size, will send it spinning away.  The engineering team at SPAR developed a special grappling system for this unique environment. It consists of snares and a pin.  The pin is attached to the payload and the snares then close around it, much like a high-tech lasso.  The arm can then move the payload as required.  This elegant design was created specifically for the arm and has been sold to the Americans and the Japanese.

The team also engineered a very sophisticated control system.  Astronauts had to be able to control a 50-foot arm over a wide range of commands and for a wide range of payload sizes.  Operating the Canadarm may mean moving it very accurately and slowly over a distance of millimetres or it may mean moving it precisely over several metres at a very high speed.  This isn't possible if the arm and its joints have too much flex so the team designed an anti-backlash device within the joints which has resulted in zero backlash.

Safety is preeminent in the minds of SPAR's engineers.  There is no room for error in space.  Virtually every system in the Canadarm has built-in redundancy while the arm itself automatically performs built-in safety checks.  This has all been done without increasing its weight or size.  During more than 50 missions and after 7,000 orbits around the earth, the Canadarm has never malfunctioned.  Indeed, it is used to help solve other problems on the shuttle, everything from knocking ice off the fuselage of the Orbiter to fixing the Hubble Space Telescope.  And of course, it is instrumental in assembling the new international space station.  The Canadarm is truly one of the greatest Canadian engineering achievements.

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