Launching a Satellite


Although sophisticated technologies are involved in the process of launching a satellite, the principle it is built on is pretty simple. There are two steps involved in the process: how to launch the satellite, and how to keep it stable in its orbit.

The trick in launching a satellite is to find a way to kick it to reach a distance high enough to perform its job without losing the capsule in outer space. It is a delicate balance of push and pull, accomplished by the inertia of the moving object and the Earth's gravity. Usually this first "kick" is achieved using a massive powerful rocket; which carries the satellite to its orbit. The speed at which the satellite travels should be carefully calculated. If you launch a satellite at—for example—27,000 km/h, the forward momentum will balance gravity, and it will rotate around the Earth. If the satellite is launched faster than 38,000 km/h, it will leave the gravitational pull of the Earth and be lost in space.

The second step is how to force the satellite to stay in its orbit. The trick is to balance between two main factors: the velocity, or the speed at which it would travel in a straight line, and the gravitational pull between Earth and the satellite. This is just as simple as if you attach a small weight or a ball to a string and swing it around in a circle. If the string was to break, the ball would fly off in a straight line but because it is constantly pulled in—as gravity pulls a satellite—it keeps rotating.

Now imagine that you could climb an imaginary mountain whose summit pokes above the Earth's atmosphere. If you threw a baseball from the mountain top, it would fall to the ground in a curving path. Two motions act upon it: the ball tries to travel in a straight line while the Earth pulls it down to fall towards it. The result of these two forces will be a curving path between the straight line forwards and the straight line downwards. The stronger you throw the ball, the farther it will go before it hits the ground, meaning that it will travel for a longer distance before it reaches the Earth. According to scientists' calculations: if you could throw the ball at a speed of 27,000 km/h, the ball would not reach the ground. It would circle Earth in a curved path; it would be in orbit. To be exact, it would be traveling at 8 km/second which is the speed needed to put satellites into orbit.

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SCIplanet is a bilingual edutainment science magazine published by the Bibliotheca Alexandrina Planetarium Science Center and developed by the Cultural Outreach Publications Unit ...
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