Watch a clip of Dextre's first repair job on the International Space Station. Video provided by NASA TV. From You Tube.
Specifications of the Canadarm
While the mechanical arm, mounted in the shuttle's cargo bay, is the most visible part, the system also has an ASTRONAUT control station inside the shuttle, which includes hand controllers, a display and control panel and a signal processing-interface box, all to allow easy control of the Canadarm from the shirt-sleeve environment of the shuttle's cabin. A TV camera (or eye) located on the wrist - and an optional second TV camera at the elbow - are part of the shuttle's closed-circuit television system that provides visual cues when an astronaut is operating the manipulator. One of the five on-board shuttle COMPUTERS provides the "brain" of the arm.
Sophisticated computer programs enable automatic operations or allow the astronaut to operate the arm in several control modes, ranging from complete end-point control (where the astronaut "flies" the end of the arm) to moving one joint at a time. The arm also has a contingency back-up mode that can be used to complete missions, if the primary control system fails.
The Canadarm was designed to have a minimum lifetime of 10 years and to be used for up to 100 missions. It weighs under 450 kg and cannot support itself in normal gravity; hence, a complex simulation facility (SIMFAC) had to be developed to verify its operation in space before its first flight and to facilitate astronaut training. On Earth, the assembled arm could only be tested in one plane at a time by using a special air-bearing cradle operating on a specially designed flat-floor area.
The $110-million Canadarm development program was largely carried out by Canadian industry, under the direction of the NATIONAL RESEARCH COUNCIL OF CANADA. The industrial team, led by SPAR AEROSPACE LIMITED, included CAE Electronics Ltd and DSMA Atcon Ltd. (The Space Robotics Division of Spar Aerospace was acquired by MacDonald Dettwiler in 1999.) The export-oriented, industrial returns achieved include the sale and maintenance of four Canadarm systems to NASA (one of the five built was donated); the sale of robotic components to Japan and Europe; the sale of simulators; and the development of robotic systems for the nuclear industry. Canadarm has allowed the establishment in Canada of an industrial capability in the HIGH-TECHNOLOGY fields of advanced manipulator systems and ROBOTICS.
Canadarm in Space
The first arm was signed over to NASA in February 1981, at Spar's Toronto plant, where it was built. After being carefully trucked to the Kennedy Space Center, it was integrated into the space shuttle Columbia in June. The arm first flew on 13 November 1981 on STS-2, the second space shuttle flight, and performed well, exceeding all design goals. It was declared operational one year later, after three successful test flights. Since it first flew, Canadarm has become an important symbol of Canadian prowess in technological fields and was installed on the other four space shuttles (Challenger, Discovery, Atlantis and Endeavour), becoming an integral part of every shuttle mission.
The Canadarm is capable of maneuvering payloads of nearly 30 000 kg mass in space at speeds (depending on the payload mass) of up to 60 cm/s. It can place such payloads in any position, with an accuracy of approximately 5 cm. Each joint is powered by an optically commutated, brushless DC motor driven by a specially designed servo-power amplifier. To obtain the high joint torques needed from the small, high-speed joint motors, a high-reduction gearbox with an epicyclic/planet system is used in each joint. Gear ratios range from 1842:1 to 739:1 on different joints.
Demanding stiffness and strength requirements, coupled with volume constraints imposed by the shuttle, dictated extensive use of the latest AEROSPACE materials (eg, TITANIUM, stainless steel, ultra-high modulus graphite epoxy). The harsh environment necessitated special attention to thermal design and lubrication. The arm is entirely covered with a multilayer insulation system, consisting of alternate layers of goldized kapton, dacron scrim cloth and a beta cloth (fibre glass) outer covering. In extremely cold conditions, thermostatically controlled electric heaters protect critical electronics.
The best-known tasks carried out with Canadarm have been the capture, repair and deployment of several satellites, including missions to the Hubble Space Telescope; the docking of the space shuttle to the Russian Mir space station; the knocking-off of ice growths that were causing a blockage to a waste exit on the shuttle; and, along with the Mobile Servicing System also developed by Canada, Canadarm's role in the construction of the International Space Station.
The next generation of the Canadarm is Canadarm 2, the Space Station Remote Manipulator System (SSRMS), a bigger and "smarter" version of the original. Canadarm 2 was launched on STS-100 in April 2001. It is 17.6 m long when extended fully and has seven joints. It played an important role in the construction of the International Space Station and remains on the station for conducting maintenance on the station, moving equipment and supplies, supporting astronauts working in space and handling payloads attached to the space station. It has a Latching End Effector that allows it to be attached to complementary ports on the station's exterior.
The Mobile Base System (MBS) is a work platform that moves along rails running the length of the space station. It provides lateral mobility for the Canadarm 2 and was added to the station during STS-111 in June 2002. Both Canadarms can be used in tandem, a process that has been nicknamed the "Canadian handshake" in the media.
On 16 March 2008, the Special Purpose Dexterous Manipulator (Dextre) was added to the space station. It is essentially a robot handyman used for a range of tasks outside the orbiting station, including many of the routine tasks done by astronauts during risky spacewalks. It can be moved around at the end of Canadarm 2 or by the MBS. Dextre has two arms more than 3 m long, each with seven joints that allow movement in all directions. It has "hands" - grippers that work much like the components in a pocket knife. Each gripper has sensors that give it a human-like sense of touch, as well as retractable tools, a camera and lights, and a retractable umbilical connector to provide power and data connections when the robot manipulates electronic equipment or conducts experiments.
Author KARL DOETSCH and GARRY LINDBERG Revised: LAURA NEILSON
Links to Other Sites
Top 10 Things Canadians Should Know About Canada
Click on the 101things.ca link to discover the top 10 things people should know about Canada, a list developed from a national survey of what Canadians felt were the 101 people, places, symbols, events and innovations that most define our nation. From the Historica-Dominion Institute.
Canadarm - A Technology Star
This CBC website features amazing video clips of the Canadarm and Canadarm2 robotic arms working in outer space.
See how the 17-metre long Canadarm2 was designed and built and view an impressive collection of photos and videos depicting the Canadian robotic arm in operation during space missions. From the Canadian Space Agency.
This site highlights one of Canada's greatest engineering feats, the development and deployment of the "Shuttle Remote Manipulator System," commonly referred to as the “Canadarm.” Click on the links at the bottom of the page to see a history of this project, illustrations, and technical details about the system's components and operation. From the website for the Institute of Electrical and Electronics Engineers Canada.
The Space Vision System
A feature article about Canadarm's Space Vision System, a device that was designed by Alberta engineer Dr. Lloyd Pinkney. From the website "Alberta Inventors and Inventions."
Canada in Space
This site highlights Canadian achievements in space technology. From the Canada Science and Technology Museum.