Steering the International Space Station
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Orbiting 250 miles above Earth is the largest structure ever put into space, the International Space Station. It is flying exactly 17,500 miles per hour. The reason that it flies exactly 17,500 miles per hour is to create a perfect balance with the Earth’s gravity. It doesn’t fall back to Earth and it doesn’t fly off into outer space. It’s the same principle that works if you have a glass of water and spin it over your head. If you spin it at the right speed the water stays in the glass, but if it rotates too slow, you get wet.
The International Space Station is the size of a football field, and even though it is 250 miles above Earth, the atmosphere at that altitude can still exert enough drag to slow it and cause it to lose altitude. Also degrading the orbit are the huge solar arrays, they must swivel and rotate to track the sun.
The space station was built using a long truss in which modules could be attached and this is its also its central axis. So as the station orbits planet Earth once every 90 minutes, the station slowly rotates on that axis to keep communication antennas pointing towards Earth at all times.
The International Space Station is the size of a football field, and even though it is 250 miles above Earth, the atmosphere at that altitude can still exert enough drag to slow it and cause it to lose altitude. Also degrading the orbit are the huge solar arrays, they must swivel and rotate to track the sun.
The space station was built using a long truss in which modules could be attached and this is its also its central axis. So as the station orbits planet Earth once every 90 minutes, the station slowly rotates on that axis to keep communication antennas pointing towards Earth at all times.
Gyroscopic Stabilizers
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The station must keep a constant sense of its altitude, position, and velocity. This takes place using GPS receivers, Russian navigation satellites, and sensors that collect information on the sun, stars, and the horizon. All of this information tells the computers that the station may need to turn or even be boosted into its normal orbit.
Gyroscopes monitor how fast the station’s position is changing, but other gyroscopes do a lot more than that. The station’s position needs correction, it doesn’t have rockets that turn the station. What are the computers on the station going to do? Located along the backbone of the station are four gyroscopes with four-foot-diameter stainless steal flywheels that spin at 6,600 revolutions per minute. Station computers turn the huge wheels in unison and their combined angular momentum cancels, or absorbs, the torque that gravity or other disturbances impart on the station.
Gyroscopes monitor how fast the station’s position is changing, but other gyroscopes do a lot more than that. The station’s position needs correction, it doesn’t have rockets that turn the station. What are the computers on the station going to do? Located along the backbone of the station are four gyroscopes with four-foot-diameter stainless steal flywheels that spin at 6,600 revolutions per minute. Station computers turn the huge wheels in unison and their combined angular momentum cancels, or absorbs, the torque that gravity or other disturbances impart on the station.
Orbital Correction
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Typically, the station falls about 300 feet in its orbit every day and if nothing is done, the station would eventually fall into thicker air where it would break apart. So every three months the station needs a boost.
The station must get resupply ships for the crew to survive. The supply comes in cargo ships like the Russian Progress ships or Europe’s Automated Transfer Vehicles. These vehicles dock at the Russian Zvezda Service Module located at the Station’s aft end so that these vehicles can give the station the boost it needs. The rocket fires for 20 minutes, increasing the orbital speed and therefore its altitude. The Zvezda module is also the only module on the ship that has reaction thrusters so that should there be a need to to avoid space debris it can do so.
DIAGRAMS-Popular Science Magazine
Article and Photoshop-Steve Miller
The station must get resupply ships for the crew to survive. The supply comes in cargo ships like the Russian Progress ships or Europe’s Automated Transfer Vehicles. These vehicles dock at the Russian Zvezda Service Module located at the Station’s aft end so that these vehicles can give the station the boost it needs. The rocket fires for 20 minutes, increasing the orbital speed and therefore its altitude. The Zvezda module is also the only module on the ship that has reaction thrusters so that should there be a need to to avoid space debris it can do so.
DIAGRAMS-Popular Science Magazine
Article and Photoshop-Steve Miller