What is required to transition from a higher orbit to a lower orbit?

To transition from a higher orbit to a lower orbit, retrothrust is required. This process involves firing the spacecraft's engines in the opposite direction of its current motion. By doing so, the spacecraft decreases its velocity, which allows it to fall into a lower orbit due to the influence of gravity.

In orbital mechanics, maintaining a stable orbit involves balancing gravitational pull with the inertia of the orbiting body. When transitioning to a lower orbit, you need to reduce your speed so that the gravitational forces can pull the spacecraft into a lower and faster orbit. This is fundamentally different from what is needed for higher orbit transitions, where you would need to increase speed to counteract gravitational forces.

While launch thrust might propel a spacecraft into space initially, it is not applicable when modifying an existing orbital position. Inertia adjustments and acceleration boosters are not appropriate terms in this context; they do not accurately describe the necessary maneuver. Thus, retrothrust is clearly the necessary method to effectively transition to a lower orbit, as it directly relates to the critical action of decreasing orbital speed.