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    ISS Elements: Mobile Servicing System (MSS)

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    Sources: NASA, CSA

  • System Description
  • Related Links
  • News
  • Mobile Servicing System Subsystems
  • Shuttle Robotic Arm vs. Station Robotic Arm
  • NASA MSS NASA MSS Operations Documents
  • NASA MSS Interface Control Documents (ICD)

    System Description

    (Source: NASA)

    The Mobile Servicing System (MSS) is a robotic system used for space station assembly and maintenance: moving equipment and supplies around the station, supporting astronauts working in space, and servicing instruments and other payloads attached to the space station. The MSS includes facilities on Earth for mission support and astronaut training. Built at a cost of U.S. $896 million (over 20 years)

    The MSS is composed of three separate components:

    1. Canadarm2, also known by its technical name, the Space Station Remote Manipulator System (SSRMS). The SSRMS as part of Canada's contribution to the ISS. The next generation Canadarm is a bigger, better, smarter version of the Space Shuttle's robotic arm. It is 17.6 meters (57.7 feet) long when fully extended and has seven motorized joints. This arm is capable of handling large payloads and assisting with docking the space shuttle. The Space Station Remote Manipulator System, or SSRMS, is self-relocatable with a Latching End Effector, so it can be attached to complementary ports spread throughout the station's exterior surfaces.

    The SSRMS is comprised of long composite booms made from PEEK/IM7 (PolyEtherEtherKetone / Carbon fibre) composite, which are manufactured by FRE Composites Inc.

    2. The Special Purpose Dexterous Manipulator (SPDM), a smaller, highly advanced detachable two-armed robot that can be placed on the end of the space arm. It will perform sophisticated operations including installing and removing small payloads, such as batteries, power supplies and computers.

    This robot can also handle tools, such as specialized wrenches and socket extensions, for delicate maintenance and servicing tasks, provide power and data connectivity to payloads, as well as manipulate, remove and inspect scientific payloads. The SPDM is also equipped with lights, video, equipment, a tool platform and four tool holders.

    This robot will be able to touch and feel much like humans. It can sense various forces and moments on a payload and, in response, can automatically compensate to ensure payloads are moved smoothly. The SPDM will be controlled by the ISS crew via the Robotic Workstation, and can perform a great many of the tasks that would otherwise require an astronaut to perform during spacewalks.

    3. The final component is the Mobile Remote Servicer Base System (MBS), a movable platform for Canadarm2and the SPDM that slides along rails on the Space Station's main truss structure to transport Canadarm2 to various points on the Station, providing lateral mobility for the Canadarm as it traverses the main trusses. It is equipped with four Power Data Grapple Fixtures and a Latching End Effector to hold payloads (or alternatively, the SPDM).

    Related Links

  • Canadarm2 Deployment on the ISS, SpaceRef.TV (Real Player required)
  • Canadarm2, CSA
  • Building in space: Canadarm 2, Discovery Channel Canada
  • Canadarm2, MacDonald Dettwiler Space and Advanced Robotics
  • Canadarm2 Images & Videos, MacDonald Dettwiler Space and Advanced Robotics
  • STS-100 Media Handbook, CSA (Acrobat)
  • NASA/KSC Newsroom Space Station Remote Manipulator System Photograph Archives


    (Source: NASA)

  • 19 April 2001: Combine Chris Hadfield, Two Spacewalks and the Canadarm2 and you get a Great Canadian Mission, SpaceRef
  • 19 April 2001: MacDonald Dettwiler Back in Canadian Control, SpaceRef
  • 18 April 2001: Canadarm2 Ready For Launch, MacDonald Dettwiler
  • 18 April 2001: The Amazing Canadarm2, NASA MSFC
  • 16 April 2001: Le Ministre Brian Tobin Assistera au Lancement de Chris Hadfield et du Canadarm2, CSA
  • 16 April 2001: Lancement du Canadarm2 et de l'Astronaute de l'ASC Chris Hadfield a Board de la Navette Spatiale Endeavour, CSA
  • 16 April 2001: Launch of Canadarm2 and CSA Astronaut Chris Hadfield aboard the Shuttle Endevour, CSA
  • 16 April 2001: Minister Brian Tobin to Attend Launch of Chris Hadfield and Canadarm2, CSA
  • 12 April 2001: STS-100 Web Cast with Marc Garneau, CSA
  • 12 April 2001: Mission STS-100 Activities for Media Leading up to Launch Day, CSA
  • 5 April 2001: Endeavour Launch Set for April 19; Mission Will Expand Human Reach in Space with Canadian International Space Station Robotics, NASA

    Mobile Servicing System Subsystems

    (Source: NASA)

    Technical DetailRemote
    Manipulator System
    Arm Length17.6 meters (57.7 feet)3.5 meters (11.48 feet) linear stroke5.7 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)
    1,662 kilograms
    (3,664 pounds)
    1,450 kilograms
    (3,196.7 pounds)
    Mass Handling/Transportation Capacity116,000 kilograms
    (255,736 pounds)
    600 kilograms
    (1,322.77 pounds)
    20,900 kilograms
    (46,076.61 pounds)
    Degrees of Freedom715Fixed
    Peak Power (operational)2,000 W2,000 W825 W
    Avg. Power (keep alive)435 W600 W365 W
    Applied Tip Load Range0-1,000 N0-111 NN/A
    Stopping Distance (under max. load)0.6 meters
    (1.96 feet)
    0.15 meters
    (5.9 inches)

    Shuttle Robotic Arm vs. Station Robotic Arm

    (Source: NASA)

    DetailSpace Shuttle Robotic Manipulator System
    International Space Station Mobile Servicing System (Canadarm 2)
    Mission Profile Returns to Earth after every shuttle mission.Permanently in space.
    Range of MotionReach 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.
    SensesNo sense of touch.

    Force moment sensors provide a sense of touch.

    Automatic vision feature for capturing.
    Automatic collision avoidance.
    Length15 meters (49.2 feet)17.6 meters (57.7 feet)
    Weight410.5 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.
    Recently 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
    (2.36 inches / second)
    EVA Support - 15 centimeters / second
    (5.9 inches / second)
    Orbiter - 1.2 centimeters / second
    (.47 inches / second)
    Composition16 plies of high modulus carbon fiberˇepoxy19 plies of high strength carbon fiberˇthermoplastic
    RepairsRepaired on EarthDesigned to be repaired in space by replacing ORUs (Orbital Replacement Units). Built-in redundancy.
    ControlAutonomous operation or astronaut controlAutonomous operation or astronaut control
    Cameras2 (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)

    NASA MSS Operations Documents

  • International Space Station, Robotics Group, Robotics Book, All Expedition Flights, JSC-48540, April 13, 2001, Mission Operations Directorate, Operations Division [14 MB Adobe Acrobat]

    This 541 page documents contains procedures for the operation of the SSRMS robotic system aboard the ISS. It also contains drawings that show Space Vision System (SVS) targets on all ISS elements.

    NASA MSS Interface Control Documents (ICD)

  • Space Station Manned Base (SSMB) to Mobile Servicing System (MSS) Interface Control Document, SSP 42003 Revision F, May 22, 1997, Part [1] [2] (Adobe Acrobat)

    The Space Station provides a Mobile Servicing System (MSS) to assist in the assembly and external maintenance of the Space Station. The MSS is used to transport hardware and payloads about the Space Station and support Extravehicular Activity (EVA) operations. This Interface Control Document (ICD) defines and controls the interfaces between the Space Station and the Mobile Servicing System. Included in this ICD are drawings, physical specifications, environmental requirements, and mechanical and electrical interfaces between EVA systems and other ISS systems.

  • Mobile Servicing System (MSS) to User (Generic) Interface Control Document, May 22, 1997, SSP 42004 Revision E, Part [1] [2] (Adobe Acrobat)

    This Interface Control Document (ICD) defines and controls the physical and functional interfaces which shall be provided by the Mobile Servicing System (MSS) for users. Included in this ICD are drawings, physical specifications, environmental requirements, and mechanical and electrical interfaces between EVA systems and other ISS systems.

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