The secret for these objects to remain in space, revolving around the Earth, is the “push” given by the rockets that put the satellites into orbit. After ascending into space, a thruster stage accelerates the satellite to a speed that is neither too small for it to fall to Earth nor too fast for it to escape the planet’s gravity. “If the velocity is applied correctly, the satellite continuously tries to move away from the Earth towards space, but at the same time it is pulled back by gravity. The result is as if it were always falling, but without touching the surface of the planet, describing a circular path around the globe”, says engineer Petrônio Noronha de Souza, from the National Institute for Space Research (INPE). In the table below, we show the principle that keeps satellites in the air, elucidated in the 17th century by the English physicist and mathematician Isaac Newton.
1. Speed is the key element in getting a satellite into orbit. If it is propelled at too low a speed, it soon falls, «pulled» by Earth’s gravity.
EXAMPLE – If the impulse speed is, say, 10 km/h, it falls after traveling only 687 meters in space
2. If the speed with which you throw the object is greater, it will fall farther and farther. But if the boost isn’t enough for the satellite to go around the Earth, it won’t be in orbit.
EXAMPLE – If the impulse speed is 10,000 km/h, it hits the surface after traveling 754 kilometers in space
3. Now, yes, our satellite has entered orbit. In our example, he is 300 km from the surface. If it is less than that, the atmosphere is denser and air resistance “stops” the satellite’s movement.
EXAMPLE – The ideal thrust for the satellite to enter orbit at an altitude of 300 km is 27 800 km/h
1- EQUATORIAL OR INCLINED CIRCULAR
ALTITUDE – from 300 to 1000 km
APPLICATION – Meteorology and scientific experiments
SPEED – 27 800 km/h
2- POLAR
ALTITUDE – 800 km
APPLICATION – Mapping
SPEED – 26 800 km/h
3- GEOSTATIONARY (ALWAYS ON THE SAME POINT)
ALTITUDE – 35 786 km
APPLICATION – Telecommunications (TV)
SPEED – 11 070 km/h (same as on Earth)