Satellite launch advantage due to Earth’s rotation When launching a satellite from the equator, the rotational velocity benefit of approximately 450–465 m/s is obtained in which launch direction?

Introduction / Context:
Earth’s rotation provides a “free” tangential velocity at the equator that can reduce the propulsive delta-v required for reaching orbit. Understanding which heading captures this boost is vital for efficient mission design and launch-site selection.

Given Data / Assumptions:

• Earth rotates eastward with surface linear speed ≈ 465 m/s at the equator.
• We neglect atmospheric drag and Earth’s oblateness for this conceptual question.
• Goal is to maximize effective inertial speed at liftoff

Concept / Approach:

The surface velocity vector due to rotation is tangential and eastward at the equator. A launch vector aligned with this direction adds the rotational speed to the vehicle’s inertial speed, reducing the additional orbital insertion speed required from the rocket.

Step-by-Step Solution:

Verification / Alternative check:

Launch sites near the equator (e.g., Kourou) favor eastward trajectories to capture the full rotational boost. Polar launches (north/south) forgo most of the benefit to achieve high inclinations.

Why Other Options Are Wrong:

Northward/southward (b,d) head toward polar orbits with minimal rotational gain. Westward (c) actively fights Earth’s rotation, increasing required delta-v. Upward (e) is not a compass direction and does not define a ground track heading.

Common Pitfalls:

Confusing “into the wind” considerations with inertial velocity; thinking maximum benefit occurs at higher latitudes (it drops as latitude increases).

Final Answer:

eastward