Posted on Jun 08, 2009 08:07:15 PM | Heather Smith | 0 Comments   

I’ve been learning more and more about the Colorado team’s experiment as I’ve watched them get everything assembled and talk through their questions and methods. As I usually am when interviewing students and writing about their projects, I’m impressed and in awe with what students come up with and build. The experiment from Colorado is actually inspired by an experiment that flew on Skylab III. The team is flying two Wilberforce pendulums – basically a spring with a mass, or weight, on one or both ends of the spring -- and will observe what happens to the pendulums when they are compressed and then released in microgravity. An excerpt and diagram from the team’s technical document explains the Wilberforce pendulum in more scientific detail: “A Wilberforce Pendulum is a mass-spring system that exchanges energy between two coupled oscillatory modes. The exchange in momentum is caused by the coupling of the modes where the longitudinal kinetic energy is converted into rotational kinetic energy.  The figure below illustrates this exchange.”   When hanging vertically, the mass causes the spring to bounce up and down and also spin. After a few seconds, the pendulum stops bouncing up and down and is only spinning. After another few seconds, it stops spinning and is only bouncing. It demonstrates the physics behind basic coupled modes and is quite amazing to watch. At one point it looks like it’s bouncing up and down but if you look closely it’s not -- the spring’s spinning action gives that illusion. For the reduced-gravity flight the pendulums will be mounted horizontally.   The students have done some pretty neat engineering work to make their project successful. They designed and ordered custom springs, but due to a manufacturing error they had to quickly go to plan B and find a ready-made spring. Just three weeks ago, Karina and Swarandeep started thinking of toys with compression springs with the hope that they could take apart the toy and use the springs for their pendulum. They tried a spring from a jack-in-the-box and another from a stuffed animal, but what ended up working for them was a spring from a toy gun that shoots foam balls. Another neat part of their project is the way they attach the steel wire that holds the pendulums to the framing of their box. The pendulums are mounted horizontally on two steel wires. In order to tighten the wires to the correct tension, the students used guitar tuning pegs so they could tighten the wires by just turning the pegs. When installing the wires during set-up last week, Karina even tested for the wires’ correct tension by plucking the strings and listening for a certain tone, just like when a musician tunes a guitar. (In addition to studying engineering, Karina also has a degree in music, so even this task uses her education.) I was quite impressed with how they figured out how to use the materials available to them to make their design work. After today’s Test Readiness Review, where they explained to NASA engineers how their device works, they loaded and secured the experiment into the aircraft. We were all fitted for our flight suits and briefed on avoiding motion sickness. Tomorrow – we fly!

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