251 SYSTEMS: ROBOTICS—THE CONSTRUCTION EQUIPMENT FOR THE INTERNATIONAL SPACE STATION CHAPTER 15 Robotic Systems on the International Space Station As part of a longstanding partnership between NASA and the Canadian Space Agency (CSA), Canada’s main contribution to the ISS has been the robotic systems. Canada already had an established capability in space robotics. The Canadian government managed and funded the design of the Shuttle Remote Manipulator System (SRMS), commonly referred to as Canadarm. The first shuttle-based Canadarm was launched on Space Transportation System (STS)-2 in November 1981, with operational responsibility residing with the NASA Flight Operations Directorate. After President Ronald Reagan’s invitation in 1984 for international friends and allies to participate in the Space Station Freedom Program, Canada chose to contribute a suite of robotics elements that would be critical to space station assembly and maintenance. The formal agreements were signed between the United States and Canada on September 29, 1988—the same day the space shuttle returned to flight following the post- Challenger hiatus. The centerpiece of the ISS MSS is the Space Station Remote Manipulator System (SSRMS), dubbed Canadarm2 by the CSA. Since it is larger than the shuttle arm by 2.0 m (6.6 ft) and wider by 2.0 cm (0.8 in.), it is also referred to as the “big arm.” Although similar to the shuttle arm in many respects, the new space station arm represented an evolutionary step forward. Table 1 lists the key characteristics of the SSRMS with an overview of the MSS shown in Figure 1. Table 1. Summary of the SSRMS properties, based on data provided by CSA (http://www.asc-csa.gc.ca/eng/iss/canadarm2/c1-c2.asp). Detail International Space Station Mobile Servicing System (Canadarm 2) Mission Profile Permanently in space. Range of Motion Moves end-over-end to reach many parts of International Space Station in an inchworm-like movement limited only by number of Power and Data Grapple Fixtures (PDGFs) on the station. PDGFs located around the station provide power, data, and video to the arm through its Latching End Effectors (LEEs). The arm can also travel the entire length of the space station on the Mobile Base System. Fixed Joint No fixed end. Equipped with LEEs at each end to provide power, data, and video signals to arm. Degrees of Freedom 7 degrees of freedom. Much like a human arm: shoulder (three joints), elbow (one joint), and wrists (three joints). However, Canadarm2 can change configuration without moving its “hands.” Joint Rotation Full joint rotation. Joints (7) rotate 540 degrees. Larger range of motion than a human arm. Senses Force moment sensors provide a sense of touch. Automatic self-collision avoidance. Length 17.6 m (57.7 ft) Weight 1,800 kg (3,968 lbs) Diameter (exterior diameter of composite boom) 35 cm (13.8 in.) Mass Handling Capacity 116,000 kg (255,736 lbs)—design case handling payload. Speed of Operations Unloaded: 37 cm /sec (1.21 ft /sec) Loaded: Station Assembly—2 cm/sec (.79 in./sec) EVA Support—15 cm/sec (5.9 in./sec) Orbiter—1.2 cm/second (.47 in./sec) Composition 19 plies of high strength carbon fiber—thermoplastic Repairs Designed to be repaired in space by replacing Orbital Replacement Units. Built-in redundancy. Control Ground operation or astronaut control Cameras Four color cameras (one at each side of the elbow, the other two on the LEEs) Early assembly of the ISS (including supporting spacewalks) was