Tise
Flight dynamicsOrbital Mechanics
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01 · The central idea1 / 3

Falling around Earth

An orbit is not a place where gravity disappears. It is continuous free-fall with enough sideways velocity to keep missing Earth.

Gravity constantly bends a spacecraft’s path toward Earth. If its sideways speed is high enough, the planet curves away beneath it at the same rate. The result is a closed path rather than an impact.

Altitude and speed are linked. In a circular low-Earth orbit, a spacecraft typically travels near 7.8 km/s. Move to a higher circular orbit and the required orbital speed falls—even though the total energy increases.

Check your model01 question

Why does a spacecraft in low-Earth orbit not fall straight down?