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The world's first scientific satellite in the history of space flight, Canada's Alouette I , was developed by Canadian scientists and launched in 1962 to study outer space. It carried new technology, a STEM antenna. (STEM stands for storable tubular extendible member.) The antenna was rolled up like a measuring tape then pushed out by an electric motor to form a tube after the satellite was in orbit.The antennas on Alouette were 23 - 45 metres long. Modern car radio antennas operate successfully by telescoping up a mere metre or so.
Alouette 1
Radio and television use electromagnetic signals to send information. Remember, in nature, there is a broad band of energies called the electromagnetic spectrum, consisting of radio waves, microwaves, infrared (heat), visible light, ultraviolet rays, x-rays and gamma rays.A radio signal can be sent through the atmosphere by varying the amplitude (strength) and/or the frequency . The radio signal is picked up by a piece of wire or metal post called an antenna. When a radio wave passes by the antenna a current (flow of electrons) is produced in the antenna at the same frequency as the wave. The radio amplifies the current; this drives the speaker and you hear a voice or music.
Students need to know that good design must be executed using careful construction and testing of components. Using the design process is an excellent way to solve problems. STEM was Canada's creative solution to the problem "build a stowable antenna". Invite students to use the design process to build their own Canadian antenna that can be extended by unfolding, telescoping or other means.
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Frequency:
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STEM antenna:
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Canada was the third country in space. When? What event signaled Canada's entry into the space race? Ask students to share what they know about Canadian satellites and how they affect their daily lives.
Ask students to identify where you would find an antenna.What does it look like? Could they bring one in? What is an antenna made of? A telescoping car antenna is an example of something that is stowable. Antennas need to be a certain length to be effective. Have someone listen to the radio with a shortened or stuck antenna and experience the poor reception that results.
Show the students a variety of stowable devices (e.g. a carpenter's measuring tape, folding ruler, collapsible umbrella, carpenter's chalk line, fishing rod reel, hose reel, telescoping pointer, telescoping painters handle, etc.).Allow students to handle the objects and test how they work. Encourage students to look for similar objects at home and bring them to class. Make a list of stowable objects.
Ask the students to explain how they might design an antenna for a spacecraft or satellite. Explore the possibilities, taking into consideration some of the constraints: it must be stowable because it has to fit in a small space and it must be light because the cost of launching baggage into space is high - $20,000 to $30,000 per kilogram.
Two to four students in groups
The photographs below show an antenna developed from a measuring tape. It is easily stowable, flexible and light. It was designed to attach to a simple vehicle or a rover, a strategy that will allow Challenges 2 and 3 to be combined.When the antenna is tilted (the rover goes down an incline), the ball bearing rolls off the antenna allowing it to unfold.
Ask the students to brainstorm in groups to come up solutions to the problem: How do you make a stowable antenna? Have the students record their ideas and make a list of materials required to construct the antenna. Bring materials from home and provide "found material", such as straws of various diameters, string, tape, cardboard tubes of various sizes, old tape measures, a builder ís snake, an old umbrella, spring loaded mechanisms, paper, foil, wire, scissors, cardboard, wood, plastic and other items from the recycling bin.
The finished antenna should conform to the following criteria: It must store in a container no longer than 15 to 30 cm and it must extend to a height of 60 to 75 cm. Releasing some sort of catch or pushing on a syringe or plunger should cause the antenna to extend by itself.You can increase the complexity of the activity by adding more criteria (e.g. the need for the antenna length to be increased, perhaps by a factor of two, or for the weight of the antenna to be halved).
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Antenna stowed
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Antenna extended
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Students test and observe the way their antennas deploy. They describe how they were able to set their antenna in motion.
Students could combine two methods of deployment such as a spring device and a pneumatic device to deploy more than one antenna at the same time.
