An orbit is the curved path that an object in space (such as a star, planet, moon, asteroid or spacecraft) takes around another object due to gravity. Gravity causes objects in space that have mass to be attracted to other nearby objects. If this attraction brings them together with enough momentum, they can sometimes begin to orbit each other. [1]https://www.esa.int/Enabling_Support/Space_Transportation/Types_of_orbits. There are three types of Earth’s orbit:
- Geostationary orbit (GEO): Satellites in geostationary orbit (GEO) circle Earth above the equator from west to east following Earth’s rotation – taking 23 hours 56 minutes and 4 seconds – by travelling at exactly the same rate as Earth. This makes satellites in GEO appear to be ‘stationary’ over a fixed position. In order to perfectly match Earth’s rotation, the speed of GEO satellites should be about 3 km per second at an altitude of 35 786 km. This is much farther from Earth’s surface compared to many satellites.
- Low Earth orbit (LEO): an orbit that is relatively close to Earth’s surface. It is normally at an altitude of less than 1000 km but could be as low as 160 km above Earth – which is low compared to other orbits, but still very far above Earth’s surface.
- Medium Earth orbit (MEO): Medium Earth orbit comprises a wide range of orbits anywhere between LEO and GEO. It is similar to LEO in that it also does not need to take specific paths around Earth, and it is used by a variety of satellites with many different applications.
According to Nasa[2]https://www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts121/launch/qa-leinbach.html, it takes the shuttle approximately 8 and a half minutes to get to orbit. And if you think about it, we’re accelerating a 4-1/2 million pound system from zero miles per hour to its orbital velocity of 17,500 miles per hour in those 8-1/2 minutes. So it’s a heck of a ride for the astronauts. They typically experience about three times the force of gravity during most of the ascent, and once we reach orbit, when the main engines cut off, they go from that three-G acceleration to zero acceleration virtually instantaneously, and that’s when they become weightless on orbit.