Space Station Assembly

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Canadarm2 and the Mobile Servicing System

The Expedition 11 crew aboard the International Space Station flexes the robotic arm, Canadarm2, while flying approximately 225 miles above Cape Horn. Image Credit: NASA.

Launched on STS-100 in April 2001, the next generation robot arm, called Canadarm2, is a bigger, better, smarter version of the robotic arm that was on the space shuttles. It is 57.7 feet long when fully extended and has seven motorized joints. This arm is capable of handling large payloads and helped build the entire orbiting complex. It has latches on either end, allowing it to be moved by both ground controllers and the Expedition crews to various portions of the station. It has even been used to move astronauts around during spacewalks.

The Mobile Base System is a work platform that moves along rails covering the length of the space station. It provides lateral mobility for the Canadarm2 as it traverses the main trusses. It has four grapple fixtures on board that can hold cargo carriers, Canadarm2 and Dextre. The Mobile Base System was added to the station during STS-111 in June 2002.

Canadarm2 and Mobile Base System Specifications

Technical Detail Remote
Manipulator System
Arm Length 17.6 meters (57.7 feet) 5.7 meters x 4.5 meters x 2.9 meters
(18.7 feet x 14.76 feet x 9.5 feet)
Mass (approx.) 1,800 kilograms
(3,968 pounds)
1,450 kilograms
(3,196.7 pounds)
Mass Handling/Transportation Capacity 116,000 kilograms
(255,736 pounds)
20,900 kilograms
(46,076.61 pounds)
Degrees of Freedom 7 Fixed
Peak Power (operational) 2,000 W 825 W
Avg. Power (keep alive) 435 W 365 W
Applied Tip Load Range 0-1,000 N N/A
Stopping Distance (under max. load) 0.6 meters
(1.96 feet)

Shuttle Robotic Arm vs. Station Robotic Arm

Detail Space Shuttle Robotic Manipulator System (Canadarm) International Space Station Mobile Servicing System (Canadarm 2)
Mission Profile Returns to Earth after every shuttle mission. Permanently in space.
Range of Motion Reach limited to length of arm. Moves end-over-end to reach many parts of International Space Station in an inchworm-like movement; limited only by number of Power 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 Fixed to the shuttle by one end. No fixed end. Equipped with LEEs at each end to provide power, data and video signals to arm.
Degrees of Freedom
6 degrees of freedom.
Similar to a human arm: shoulder (2 joints), elbow (1 joint) and wrists (3 joints).
7 degrees of freedom.
Much like a human arm: shoulder (3 joints), elbow (1 joint) and wrists (3 joints). However, Canadarm2 can change configuration without moving its hands.
Joint Rotation Limited elbow rotation (limited to 160 degrees).
Full joint rotation.
Joints (7) rotate 540 degrees.
Larger range of motion than a human arm.
Senses No sense of touch.
Force moment sensors provide a sense of touch.
Automatic vision feature for capturing.
Automatic collision avoidance.
Length 15 meters (49.2 feet) 17.6 meters (57.7 feet)
Weight 410.5 kilograms (905 pounds) 1,800 kilograms (3,968 pounds)
Diameter (exterior diameter of composite boom) 33 centimeters (13 inches) 35 centimeters (13.8 inches)
Mass Handling Capacity
29,484 kilograms (65,001 pounds) - design case handling payload.
Upgraded to 266,000 kilograms (586,429 pounds)
116,000 kilograms (255,736 pounds) - design case handling payload.
Speed of Operations
Unloaded: 60 centimeters / second
(1.97 feet / second)
Loaded: 6 centimeters / second
(2.36 inches / second)
Unloaded: 37 centimeters / second
(1.21 feet / second)
Station Assembly - 2 centimeters / second
(.79 inches / second)
EVA Support - 15 centimeters / second
(5.9 inches / second)
Orbiter - 1.2 centimeters / second
(.47 inches / second)
Composition 16 plies of high modulus carbon fiber—epoxy 19 plies of high strength carbon fiber—thermoplastic
Repairs Repaired on Earth Designed to be repaired in space by replacing ORUs (Orbital Replacement Units). Built-in redundancy.
Control Autonomous operation or astronaut control Autonomous operation or astronaut control
Cameras 2 (one on the elbow and one on the wrist) 4 color cameras (one at each side of the elbow, the other two on the Latching End Effectors)