In everyday life, going higher means going up and coming back down. In orbit, altitude and speed are locked together in ways that break every terrestrial intuition. Understanding this relationship is the key to understanding everything else in orbital mechanics.
In everyday life, going higher means going up and coming back down. In orbit, altitude and speed are locked together in ways that break every terrestrial intuition. Understanding this relationship is the key to understanding everything else in orbital mechanics.
For a stable circular orbit, there is exactly one speed for each altitude. You can't choose independently. This comes directly from balancing gravitational pull against centripetal acceleration.
Imagine two satellites in the same orbit, one behind the other. The trailing satellite wants to catch up. Intuitively, it should speed up. But speeding up raises its orbit — and a higher orbit is slower. It actually falls further behind.
The differences in LEO are tiny — just fractions of km/s over hundreds of kilometres of altitude. But the difference between LEO and GEO is enormous: GEO satellites move at less than half the speed of LEO ones.
A satellite in a higher orbit travels faster because it has more energy
It does have more total energy, but its kinetic energy (speed) is lower. The extra energy is gravitational potential energy — height, not speed.
To deorbit, a satellite brakes like a car
A satellite fires its engines opposite to its motion (retrograde burn), which lowers the orbit. The perigee drops into the atmosphere, where drag does the actual braking.
This inversion of everyday intuition is the single most important concept in orbital mechanics. Once it clicks, maneuvers, rendezvous, and deorbit strategies all make sense.