Academic Reading — Test 85

Reading passage

When the United States began designing its reusable Space Shuttle in the 1970s, it invited a small number of partner nations to contribute specialised hardware. Canada accepted the challenge of building a robotic arm capable of moving cargo into and out of the shuttle's payload bay while orbiting the Earth. The resulting device, formally named the Shuttle Remote Manipulator System but known to the public as the Canadarm, became the country's most celebrated contribution to human spaceflight and a lasting symbol of Canadian engineering. The first arm was delivered to the American space agency at no charge, a gesture intended to secure Canada a permanent place in the shuttle programme; later units were purchased outright. The engineering brief was unusually demanding. Because the arm would operate in the weightlessness of orbit, it did not need to lift heavy loads against gravity, yet it had to manoeuvre objects of enormous mass with great delicacy. Engineers therefore designed a long, slender limb roughly fifteen metres in length, constructed largely from lightweight carbon-fibre composite rather than metal. Despite weighing under half a tonne, the arm could handle payloads of many tonnes, including entire satellites. It possessed six joints, mirroring the movement of a human arm with its shoulder, elbow and wrist, and these allowed it to position objects with remarkable precision. An astronaut inside the shuttle controlled the limb using two hand controllers while watching through windows and television cameras mounted along its structure. A central difficulty was that the arm could never be tested at full load on the ground before launch. On Earth, its own weight would cause the slender structure to sag and even buckle under the pull of gravity, conditions that would never occur in orbit. To overcome this, the development team built elaborate simulators and suspension rigs that offset the effect of gravity, permitting engineers to rehearse manoeuvres in conditions resembling those of space. Software was written to model how the flexible limb would bend and oscillate when moving a massive payload, ensuring that operators would not accidentally set the structure swaying uncontrollably. This emphasis on careful simulation became a hallmark of the project. The Canadarm made its first flight in 1981 aboard the shuttle Columbia and performed reliably for three decades. Over that period it was used to release satellites into orbit, to retrieve malfunctioning spacecraft for repair, and to support astronauts working outside the shuttle. One of its most famous tasks was assisting in the servicing of the Hubble Space Telescope, where it held the observatory steady while crews replaced ageing instruments. The arm also proved valuable in unplanned situations; on several occasions it was used to inspect the shuttle's exterior for damage, a role that grew especially important following the loss of the shuttle Columbia in 2003. The success of the original design encouraged the development of a far larger and more sophisticated successor for the International Space Station. This second-generation system, commonly called Canadarm2, was longer, stronger and able to move along the exterior of the station by attaching itself to fixed points and effectively walking end over end. Unlike its predecessor, it could be operated remotely from the ground as well as by astronauts on board, and it played an indispensable role in assembling the station from components delivered by visiting spacecraft. It was later joined by a smaller, two-armed device nicknamed Dextre, designed to carry out delicate maintenance tasks that would otherwise require risky spacewalks. Beyond its practical achievements, the Canadarm carried considerable cultural and economic weight. Images of the arm, painted with the word CANADA and the national maple leaf, were broadcast around the world and instilled national pride. The programme nurtured a generation of engineers and established the country as a respected specialist in space robotics, a reputation that attracted further international contracts. The expertise developed for orbit was also adapted for use on Earth, most notably in medicine, where the precision technology inspired robotic systems used to assist surgeons. In this way an instrument built for the harsh environment of space came to influence work carried out much closer to home.