Why many launches head east
Earth's rotation already gives a launch site eastward speed. A rocket heading into a suitable eastward orbit can use that initial motion, reducing the extra speed it must supply. The benefit is greatest near the equator, but the destination orbit and safe flight path can make another direction necessary.
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The launch pad is already moving
A point on Earth's surface moves eastward as the planet rotates. Near the equator, that motion is roughly 465 metres per second relative to Earth's centre.
A launch towards an appropriate prograde orbit can make use of this existing velocity. At higher latitudes, the surface's rotational speed is smaller because the point travels around a smaller circle.
Rotation is a useful contribution, not a rule that every rocket must follow. Polar and other specialised orbits require different launch directions.
- Latitude affects the available rotational speed.
- The target orbit determines the desired direction.
- Safety and geography constrain the flight corridor.
Changing an orbital plane later can be costly in propulsion. Launch planners therefore balance the rotation benefit against reaching the correct orbit in the first place.