Science Dimension volume 11 issue 2 1979

	.
An early demonstration of the Canadarm (Spar)

The Space Shuttle, the unique hybrid of rocket, spacecraft and airplane, being built by NASA, is getting a hand – and arm- from Canada: a complex, $95.4 million, remotely controlled manipulator arm, now in its final stages, and undergoing working demonstrations.

It resembles a magnified human arm - over 15 m long, articulated at shoulder, elbow and wrist, and ending in a cage-like hand. We move down its length, Lilliputians surveying Gulliver, dressed in the paper caps, slippers and lab coats required in a dust-free clean room. There are gear boxes, motors and servo-mechanisms intricately packed into each joint, linked by fat bundles of color-coded cables. The entire machine is laid on a frame which is free to move on air-bearing pads across the ice-smooth floor.

Standing at a control panel, a test engineer begins to put the mechanical arm through its paces. By means of two hand controls – one which he rotates, the other which he pushes and pulls – he issues commands, instantly transformed by computer into a coordinated stream of signals to all the system’s components. Smoothly, the arm bends at the elbow, poises, and then reaches towards a target, which, with a quiet whir of wire cables, it grasps.

It does not take a great leap of the imagination to see how maneuvers similar to this working demonstration will be used in space. A few years hence, remotely controlled from within the crew cabin of a Space Shuttle Orbiter, the arm will pluck telescopes or satellites out of orbit and place them in the spacecraft's large cargo hold; it will launch scientific and industrial payloads carried into orbit by the Shuttle; it will, in brief, help open up a new era in the exploitation of space.

No one has ever built or used anything quite like this before. For a number of years, engineers from a three-company consortium, led by Spar Aerospace Limited of Toronto and under contract to NRC, have been evolving the unique design. The precisely orchestrated process of finding elegant solutions to tricky problems passed two key milestones in 1978: a Critical Design Review and a working demonstration of a complete, assembled model of the arm.

.
	The end effector -- or hand -- of Canadarm (Spar)

Working demonstrations on earth are limited by the inexorable pull of gravity. Once in space, the environment for which it has been designed, the arm and the equipment which it manipulates will be weightless. Here on earth, however, it does not have enough strength to support its own weight, let alone that of a massive payload. The best that can be done to physically test the whole system before orbital flight is to place the arm on air-bearing pads (these minimize friction, allowing effortless, floating motions) and operate it only in a single plane, parallel to the floor. Despite these limitations, the tests now under way verify that the integrated system does perform as expected.

During the coming months, the $95.4 million Remote Manipulator System project enters its crucial final phases. The flight-ready hardware which Canada is contributing to the U.S. space agency is now being manufactured, and will be delivered later this year. NASA is negotiating an order for further manipulator systems with which to equip the planned space Shuttle fleet.

Space is not the only environment hostile to man in which such tools might prove useful. A joint Canada-West Germany study has found that an advanced manipulator for use on an underwater vehicle - to perform such tasks as repairing pipelines on the ocean floor - is not only technically feasible, but has a potential market.

But it is in space that the prototype arm will get its first full workout. Sometime early in 1980, a Space Shuttle will blast off on a flight largely devoted to giving the Remote Manipulator System its first, definitive, zero gravity test.

Reprinted courtesy of the National Research Council Canada