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The Mobile Servicing System (MSS) is a sophisticated robotic system critical to the assembly of the International Space Station.The MSS (see photo) will put together the parts of the station mating motor-home-sized laboratories built by different countries 350 to 450 kilometres above the Earth. It will play a key role in 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 is made up of the following parts:
Students should carry out this design-and-build activity using the same procedures outlined in Challenges 2 and 3.The arm is a complex machine that is tubular in appearance. It looks and acts much like a human arm, with joints and a grasping hand. Review Canadarm and MSS features, including the end effector, or hand mechanism, and the arm made out of segments with connecting joints.
Ask students to find out how the arm is to be used in space. Gather information on Mission STS-100 (www.space.gc.ca), when Col. Hadfield will activate the SSRMS. Explore how the SSRMS and other parts of the MSS will be used during the construction of the International Space Station. Did you know that STS-100 is one of 45 separate missions required to assemble the station? Or that Col. Hadfield's space walk is one of 162 space walks (or 1,100 hours of walks) required to construct the 110-metre-long station? Once built, the International Space Station will be the third brightest object in the sky after our moon and the planet Venus.
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End Effector:
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Strut:
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Hydraulics:
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Truss:
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In 2001 Canada's Col. Chris Hadfield will unpack and assemble the new International Space Station robotic arm, called the Space Station Remote Manipulator System (SSRMS).This arm, its dexterous hand (SPDM), base (MBS) and transporter (MT) will slide along a truss or mini railway over the length of the station (about 1.4 Canadian football fields in length).
Have students do some research into the robotic arm industry (www.mdrobotics.ca and www.space.gc.ca).Ask them to identify the similarities and differences between Canadarm and the SSRMS. Show a movie or video demonstrating how Canadarm works. (Canadian videotape on Canadarm, MSS and space missions cost $10 each and are available from the Canadian Space Resource Centre, 1-877-449-2772.)
Students are asked to design and build a mechanical arm with at least three hinged joints that can travel along a truss or track and grasp an object. Depending on your available class time, you may wish to modify the challenge to eliminate one or two of the above requirements. Review how Canadarm is made.
Four to six students
Corrugated cardboard, mailing tubes, Foamcore, Coroplastic, thin plywood, chop sticks, Popsicle sticks, thread spools, pencils, bamboo garden stakes, coat hangers, metre rules, materials for a track (model train track, etc.), construction sets such as LEGO and K'NEX.
Challenge the students to build a space arm according to the provided specifications or your own criteria. Use your own arm as a model. Show the students photographs of robots that have arm-like, hinged features (www.ai.mit.edu/projects). You may encounter bending of the arm when making sections that exceed a certain length.The use of struts in triangular formation for the cross section may give extra stability over the length.
Remember that the first section of the arm has to support the weight of the next section and ultimately, the end effector. Use counter weights to offset the weight of the arm. Make hinge points as smooth and frictionless as possible. Try combining different materials or using construction toys and incorporate hydraulics (syringes) to move the arm.
The space arm can be relatively small, so that other devices already designed and built by the class (e.g. end effector, hinged joints) can be attached.
Alternatively, the arm can be a large demonstration-type model with some flexibility and ability to grasp objects.With a larger model students could use cardboard (sono-type) tubing, flexible dryer venting or other large-diameter material. It may require support or a base-like system that can run on rails (trusses) or be suspended. For more ideas, consult the Internet, local engineers and other resources (e.g. Suited for Spacewalking NASA-1998-03-112-HQ) and sites where robots are in use (e.g. Ontario Science Centre and Science North).
Students test and refine their robotic arm designs and record the way their arm performs tasks. Students carefully document their difficulties and describe how they were able to correct design problems. Recognize student effort by displaying the student robotic arms. Have a "launch the arm" party when the STS-100 mission is in orbit. Invite the media and inform the local community about Canadian robotics and the way the space station is being assembled.
Explore how MD Robotics and other Canadian companies have adapted space arm technology to solve problems here on Earth.
Ask the class to make a replica arm that has flexible joints and a way of grasping or snaring objects and a means of locomotion to move it along a track.Think of a two-pulley system washing line, with the arm affixed like a piece of washing on the line. Place the pulley/line arrangement flat on a table top, with one pulley on each end of the table. Place the arm base on the table between the pulley wheels.Tie the string or cord to one side of the arm base and extend the line around both pulleys and back to be tied to the opposite side of the base. When the string is pulled, the base plus arm will move (like washing on a line). To reduce friction, some small wheels or casters can be affixed to the arm base.
