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Canadarm End Effector

In this activity, students build a replica of the Latching End Effector on Canadarm 2 out of foam cups, string and tape.

Canada’s contribution to the International Space Station (ISS) (a research laboratory that orbits the Earth) is the Mobile Servicing System (MSS): a three-part robotics system that built and now maintains the ISS. Astronaut Dr. Judith Resnik developed the NASA software and onboard operating procedures for the system. Because of this MSS, scientists from Canada, the United States, Japan, Russia and Europe can work together to conduct research in space.

There are three parts to the Mobile Servicing System:

  • the Mobile Base
  • Canadarm 2
  • Dextre

The Mobile Base is a platform that stores equipment and slides around the outside of the space station, taking the Canadarm with it.

You may have already heard about the Canadarm 2, a 17m long robotic arm, with a Latching End Effector (LEE). The Canadarm can carry a large payload, an astronaut on a spacewalk, or Dextre (a.k.a. the “Canada Hand”).

Dextre, nicknamed the Canada Hand, is a robotic “handyman” that performs tasks like changing batteries and replacing cameras that would otherwise have to be done by an astronaut.

The combination of the Mobile Base and the long reach of the Canadarm allow maintenance and repair work to occur at all parts of the ISS.

The Latching End Effector on the Canadarm is a relatively simple but very important part. Think of the End Effector as the Canadarm’s “wrist”… with a twist. The wrist on your body attaches your hand to your arm, but the End Effector can attach to the Canada Hand (Dextre), or grasp objects like a payload, an astronaut or the ISS itself. Its simple 3-wire design means it is both effective in safely holding onto a variety precious cargo as well as being easy to fix if it ever becomes damaged.


  • Investigate technology used in space exploration and build models.


  • Per Student:
    2 Styrofoam cups (same size)
    3 pieces of string, 12cm long
    6 pieces Scotch Tape®

Key Questions

  • What part of the Canadarm is the end effector?
  • What does the end effector hold onto? (Payloads of various kinds, machinery, video cameras, astronauts, the ISS)
  • What shapes can the end effector grab onto? What would that mean for you if you were designing it? How it would carry a payload?
  • Why is it advantageous to have a simple design?
  • What are the advantages of using robotic technology to do construction and maintenance on the ISS?

What To Do

Part 1: Building the End Effector

  1. Nest the two cups together and cut through both cups as evenly as possible; about halfway down the outside cup.
  2. Cut three pieces of string 12cm long.
  3. Tape the end of the first string to the inside of the inner coffee cup (near the top of the edge where it was cut). Then loop it over and tape the other end of the string to the outside of the cup, opposite where the piece was taped to the inside cup.
  4. Repeat this step twice, evenly spacing the strings around the cut edge of the cups.
  5. Hold the drinking edge of the inner cup, and rotate the outer cup until the three strings just begin to cross each other. The strings will have some slack. You may need to make adjustments by re-positioning and re-taping some of the strings.

Part 2: Using the End Effector

  1. See for yourself just how tight a grip this end effector can achieve by putting a friend’s finger in it and tightening the strings around the finger. To do this:
  • Rotate the end effector so that the strings are crossing each other but form a large triangle shape in the centre.
  • Slip the end effector (triangular opening) over their finger.
  • Hold the outer cup and rotate the inner cup until the strings grasp their finger firmly.
  1. Challenge yourself to use the end effector to pick up objects around the room (e.g. a pencil).


  • Build a model of the entire Mobile Servicing System.
  • Find out more about the technology aboard the ISS. What functions do they perform? Can you think of any other technologies that could be helpful?

Other Resources

Canadian Space Agency |Canadarm 2

Canadian Space Agency | Flight History of Canadarm

NASA | For educators | Train like an astronaut

Canadian Space Agency | Junior Astronauts
These activities are designed for youth in grades 6 to 9. They  focus on three streams—science and technology, fitness and nutrition, and communications and teamwork.