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When the ramps rolled out from the Pathfinder landing craft allowing the Sojourner rover (see photo) to descend to the Martian surface, Canadian-designed technology was in use. The ramps were built by Astro Aerospace, a subsidiary of Spar Aerospace, now MD Robotics, located in Brampton, Ontario. Sojourner rolled down the ramp and began its exploration of the surface of Mars. It was the first mobile vehicle to roam another planet, moving at a top speed of 0.4 metres/minute.
The Pathfinder Lander carried three, one-metre ramps strong enough to carry the 11 kg rover, yet flexible enough to be rolled up like a carpet into a roll less than 5 cm in diameter. Look closely at the picture of the ramp and you will see two shiny metal rods at the edges. Guess what they are: STEM antennas or storable tubular extendible members.The ramp was built using other interesting products, including Velcro and Kevlar.
The Sojourner rover is surprisingly small (63 cm x 48 cm x 28 cm). Its rocker-bogie suspension with a six-wheel and axle system, operates as a lever to allow Sojourner to travel over bumps and gullies. On Mars, Sojourner used a 0.25 square metre solar panel to gather the sun's energy and nine non-rechargeable Lithium D-cell batteries.The batteries were designed to keep the rover working for 30 days but, in fact, operated for more than twice that long. Sojourner was controlled from Earth like a remote control car, but there was a time delay of 11 minutes. Mars is at least 58 million km from Earth, and it takes that much time at the speed of light (300,000 km/sec) for signals to cover the distance.
The rover explored about 200 square metres of the surface of Mars and sent back 550 photographs, 16 chemical analyses of rocks and 8.5 million individual temperature, pressure and wind measurements.
What did we learn about Mars from the Pathfinder Mission? Have students do some research and report their findings. Show a movie or a simulation of the mission. Participate in the Canadian National Marsville Program (http://mars2000.enoreo.on.ca/).
Complex machines are made up of simple machines and new or old technologies integrated to perform tasks for which the machine is designed. In achieving the Mars rover challenge, levers, wheels and axles, pulleys, gears and/or motors can be combined to produce a machine that will roll down a ramp and over the rough terrain of Mars.
The Mars rover can be designed to resemble Sojourner, or it can be configured to meet the parameters set out in this activity. In either case, thoughtful planning and design must be followed by careful construction and testing of all components of the machine. The design process should be followed in developing the Mars Rover.
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Bevel gears:
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Rack and pinion gears:
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Sprocket gears:
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Spur gears:
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Worm gears:
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Rocker-bogie system:
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STEM antenna:
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In 1997 when NASA successfully landed a rover on Mars, Canadian technology was involved. Check the Pathfinder Mission website (http://mpfwww.jpl.nasa.gov/rover/about.html) to gather information and photos about Mars. Show a movie or simulation about the mission (contact the Canadian Space Resource Centre at 1-877-449-2772). For more information on Mars, use the Mars Pathfinder/Sojourner Slide Set #JPL-27 available by calling 1-281-486-2172 or order online at www.finley-holiday.com).
Set up an obstacle course. Have one student (Mission Control Earth) direct another student (Sojourner Mars Rover) through the course with voice commands. Have a 10-second delay between the command and response. Add to the challenge by blindfolding Mission Control Earth and having another student (Pathfinder Mars Lander camera) describe the scene in front of Sojourner.
Ask students to design and build a Mars rover capable of descending a ramp (approximately 0.3 metres high and 1 metre long) and negotiate at least 1 metre of rough Mars terrain.
Two to four students in groups.
The ramp can be built of plywood or parallel boards resting on a step, blocks or books.
Also consider the K'NEX radio-controlled Control-A-Bot kit or LEGO MindStorms light-and-touch sensor-responsive Robotics Discovery Set.
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Rover made of cardboard and wood
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Rover made of LEGO
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Ask students to brainstorm in groups to solve the problem of how to make a Mars Rover that will be able to descend the ramp and negotiate the terrain. Show them a variety of rover devices from books, magazines, the Internet or other sources, or have teams of students gather information themselves after learning about Sojourner.
Have the students record their ideas and make a list of material required to construct the rover. They can use "found material" or building/construction toys, such as K'NEX or LEGO.
A simplified rocker-bogie system can be made by creating a triangle-shaped frame, attaching two wheels to the two base corners of the triangle and making a pivot point at the apex of the triangle. Two of these triangles can be hung from the same fulcrum to create the back four wheels of the rover. Note that the two triangles must be allowed to rotate independently.
The rough Mars terrain can be replicated by scattering Styrofoam packing, peanuts, small paper balls, LEGO pieces or other objects on the floor. If you have a tile floor (or other smooth surface), consider covering the floor with a towel or other material so that the rover climbs over the Mars "rocks" rather than pushes them along the ground. Make the ramp available during the construction phase of the project so students can test their rovers for design modifications.
The teacher and/or a group of students should set design standards such as rover size, dimension limits, time to complete the prototype and testing period, rover weight restrictions, ramp dimensions and materials or any other criteria the group decides to impose. The group can increase the complexity of the activity by adding more criteria (e.g. self propulsion).
If students choose to build a motorized rover, they may find construction toys like LEGO and K'NEX the best choice of building material. If the wheels are rotating too fast or if there isn't enough force to get a vehicle moving, consider using gears to solve the problem. Put a small gear on the motor and a large gear on the axle. This will give the rover wheels more force but less speed.When two gears are linked together, they turn in opposite directions. It may be necessary to develop a gear train (a series of four or more gears connected together) to slow down the axle sufficiently.
Students repeatedly test their designs and observe the way their rovers behave. They record their difficulties and describe how they were able to correct design problems.
An evaluation committee could award certificates of merit to rovers that were able to complete certain tasks.The culminating challenge is designed as an extension of this activity. Follow the development of the "Red Rover Goes to Mars Project" and the "Mars Exploration Rovers" new space initiatives. See more at www.planetary.org.
Another way to extend the activity would be to use solar energy to power a K'NEX rover. Solar or photovoltaic cells are usually made of silicon.When light strikes the cell, some of the energy is absorbed by the silicon.The energy knocks some electrons loose allowing the electrons to flow freely. This flow of electrons is called current. By placing metal contacts on the cell, you can use the current to power a motor. See www.howstuffworks.com/solar-cell.htm for more information on solar cells.
