## Liftoff to Learning: Tethered Satellites
Table of Contents
To explain the dynamics of the tethered satellite system, the following equations appear in Part 1: Newton's Second Law of MotionForce equals mass times acceleration.
F=ma
500 kg x 20,000 m = 100,000 kg x 100 m
The following hands-on activities demonstrate some of the concepts presented
in these two programs. Rotating stool or rotating platform Two exercise hand weights (1 to 2 kg each) Background The Space Shuttle orbiter/tethered satellite system operates under the law of the conservation of angular momentum as it orbits the Earth. Angular momentum is a product of the rotational inertia of an object and its rotational speed. The system can be compared to a spinning ice skater. When the skater tucks his or her arms in tightly, rotational speed increases while rotational inertia decreases. Discounting frictional effects, the skater's angular momentum is conserved. When the skater's arms are extended, rotational speed decreases while rotational inertia increases. Again, angular momentum is conserved. Like a skater extending arms, when the tethered satellite is extended above the orbiter, its distribution of mass is changed. The rotational inertia of the system is conserved by decreasing its rotational speed while increasing its rotational inertia. The reduction of rotation speed actually lowers the orbiter in its orbit. However, when the tethered satellite is retrieved, rotational speed increases as rotational inertia decreases. Because angular momentum is again conserved, the orbiter actually raises its altitude. The following activity permits students to experience the conservation of angular momentum. Procedure
Discussion and Extensions
Seesaw
Background When a Space Shuttle orbiter deploys a tethered satellite, the center of mass of the two bodies remains in a constant orbit. What changes is the respective distance of the two bodies from that center of mass. Because it contains far less mass than the orbiter, the tethered satellite travels a great distance in one direction while the orbiter moves a short distance the opposite way. The orbiter has a mass of about 100,000 kg and the tethered satellite has a mass of 500 kilograms. When the tethered satellite is deployed to a distance of 20 kilometers, the orbiter moves about 100 meters in the opposite direction. The center of mass of these two bodies remains constant. Procedure (Follow the instructions that come with the Moment of Force Apparatus or use these instructions with the alternative apparatus)
Discussion and Extensions
Tether OscillationsMaterials Solid ball Elastic cord
Procedure
Discussion and Extensions
Procedure
Discussion and Extensions
Generating CurrentsMaterials Powerful magnet Copper wire Volt/ohm meter
Procedure
Discussion and Extensions
Commander STS-46: Loren J. Shriver (Col., USAF). Commander STS-75: Pilot STS-46 Andrew M. Allen (Lt. Colonel, USMC) Mission Specialist STS-46 and STS-75: Claude Nicollier (ESA). Mission Specialist STS-46: Marsha S. Ivins. Mission Specialist STS-46 and STS-75: Jeffrey A. Hoffman, Ph.D. Mission Specialist STS-46: Payload Commander STS-75: Franklin R. Chang-Diaz, Ph.D. Payload Specialist STS-46 (ASI): Franco Malerba, Ph.D. Pilot STS-75: Scott J. Horowitz (LTC, USAF, Ph.D.) Mission Specialist STS-75: Maurizio Cheli (ESA) Payload Specialist STS-75: Umberto Guidoni (ASI) To obtain biographic information, click on highlighted names |
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