You're absolutely right! As a rocket travels upwards, its engine thrust remains constant, but its mass decreases. This is the key principle behind rocket propulsion, and here's why:

* Thrust: Thrust is the force that propels the rocket forward. It's generated by the engine burning fuel and expelling hot gas out the nozzle. This force remains constant as long as the engine is firing at a steady rate.

* Mass: The rocket's mass decreases as it burns its fuel. The fuel is the primary source of mass for the rocket. As it's consumed, the total mass of the rocket decreases.

Why is this important?

The relationship between thrust and mass is crucial for rocket acceleration:

* Newton's Second Law: This law states that force (thrust) equals mass times acceleration (F = ma).

* Increasing Acceleration: Since the thrust remains constant, but the mass decreases, the acceleration of the rocket increases. This means the rocket gets faster and faster as it burns its fuel.

The Rocket Equation:

The relationship between thrust, mass, and acceleration is formalized in the Tsiolkovsky rocket equation. This equation shows that the final velocity of a rocket depends on the initial mass, final mass, and exhaust velocity.

In short: The constant thrust of a rocket engine acting on a decreasing mass results in ever-increasing acceleration, propelling the rocket to higher speeds and altitudes.