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Canadarm

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Canadarm

Canadarm or Canadarm1 (officially Shuttle Remote Manipulator System or SRMS, also SSRMS) is a series of robotic arms that were used on the Space Shuttle orbiters to deploy, manoeuvre, and capture payloads. After the Space Shuttle Columbia disaster, the Canadarm was always paired with the Orbiter Boom Sensor System (OBSS), which was used to inspect the exterior of the shuttle for damage to the thermal protection system.

In 1969, Canada was invited by the National Aeronautics and Space Administration (NASA) to participate in the Space Shuttle program. At the time what that participation would entail had not yet been decided but a manipulator system was identified as an important component. Canadian company DSMA ATCON had developed a robot to load fuel into CANDU nuclear reactors; this robot attracted NASA's attention. In 1975, NASA and the Canadian National Research Council (NRC) signed a memorandum of understanding that Canada would develop and construct the Canadarm.

NRC awarded the manipulator contract to Spar Aerospace (now MDA). Three systems were constructed within this design, development, test, and evaluation contract: an engineering model to assist in the design and testing of the Canadarm, a qualification model that was subjected to environmental testing to qualify the design for use in space, and a flight unit.

Anthony "Tony" Zubrzycki, a design engineer at DSMA ATCON, while seconded to SPAR, originated the concept for the Canadarm End Effector, inspired by an elastic band around his fingers. Zubrzycki formally presented this concept to NASA officials. Frank Mee, head of the SPAR mechanical development laboratory, built the end effector prototype based on Tony's concept and is credited by SPAR as the inventor of the Canadarm End Effector. The three-wire crossover design won over the claw-like mechanisms and others, such as the camera iris model, that were being considered.

The main control algorithms were developed by SPAR and by subcontractor Dynacon Inc. of Toronto. CAE Electronics Ltd. in Montreal provided the display and control panel and the hand controllers located in the Shuttle aft flight deck. Other electronic interfaces, servo amplifiers, and power conditioners located on the Canadarm were designed and built by SPAR at its Montreal factory. The graphite composite boom that provides the structural connection between the shoulder and the elbow joint and the similar boom that connects the elbow to the wrist were produced by General Dynamics in the United States. Dilworth, Secord, Meagher and Associates, Ltd. in Toronto was contracted to produce the engineering model end effector then SPAR evolved the design and produced the qualification and flight units. The Space Shuttle flight software that monitors and controls the Canadarm was developed in Houston, Texas, by the Federal Systems Division of IBM. Rockwell International's Space Transportation Systems Division designed, developed, tested, and built the systems used to attach the Canadarm to the payload bay of the orbiter.

An acceptance ceremony for NASA was held at Spar's RMS Division in Toronto on 11 February 1981. Here Larkin Kerwin, then the head of the NRC, gave the SRMS the informal name, Canadarm. The term was originally coined by Dr. Wally Cherwinski for use by Larkin Kerwin during his speech at the press conference. The NRC Canadarm Project Manager, Dr. Art Hunter, worked with colleagues, NASA and Spar, to add the Canadian flag and wordmark onto the arm to fly Canadian colours with those of the USA.

The first Canadarm was delivered to NASA in April 1981. Astronaut Judith Resnik developed the NASA software and onboard operating procedures for the system. In all, five arms – Nos. 201, 202, 301, 302, and 303 – were built and delivered to NASA. Arm 302 was lost in the Challenger accident.

The original Canadarm was capable of deploying payloads weighing up to 65,000 pounds (29,000 kg) in space. In the mid-1990s, the arm control system was redesigned to increase the payload capability to 586,000 pounds (266,000 kg) in order to support space station assembly operations. While able to maneuver payloads with the mass of a loaded bus in space, the arm motors cannot lift the arm's own weight when on the ground. NASA, therefore, developed a model of the arm for use at its training facility within the Johnson Space Center located in Houston, Texas. The Canadarm can also retrieve, repair and deploy satellites, provide a mobile extension ladder for extravehicular activity crew members for work stations or foot restraints, and be used as an inspection aid to allow the flight crew members to view the orbiter's or payload's surfaces through a television camera on the Canadarm.

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