Why are most satellites launched into prograde orbits?

• A. Launching in an easterly direction allows us to benefit from the speed of the earth's rotation.
• B. Most space launch ranges face east.
• C. Launching toward the north is easier than launching toward the south.
• D. Launching in a westerly direction allow us to benefit from the speed of the earth's rotation.

Answer: (A)

Leveraging Earth's rotation to gain extra velocity is what makes most satellites go into prograde, eastward orbits. When a rocket launches east, it starts with the planet’s spin adding to its speed. At the equator, that boost is about 465 meters per second, and it’s smaller at higher launch latitudes (scaling with the cosine of the latitude). That added speed means the rocket needs less extra delta-v to reach orbital velocity, allowing either a larger payload or a simpler, lighter rocket design.

That’s why launches are typically oriented eastward and why many launch sites are placed where an eastward flight over open ocean is safe. Launching westward would work against the rotation, making it harder to reach orbit and requiring more fuel. Launching north or south doesn’t provide the rotational boost, so it doesn’t offer the same efficiency for achieving a prograde orbit.