how space shuttle stayed in orbit without burning fuel

The Space Shuttle, like other spacecraft in Earth's orbit, did not stay in orbit by continuously burning fuel. Instead, it used a combination of initial propulsion to reach orbit and then relied on the principles of orbital mechanics and the absence of atmospheric drag to remain in orbit. Here's how it worked -

1. Orbital Velocity: To achieve and maintain orbit, a spacecraft like the Space Shuttle must reach a specific speed called orbital velocity. Orbital velocity depends on the altitude of the desired orbit and is the speed at which an object travels in a circular or elliptical path around the Earth. It is calculated to be sufficient to counteract the pull of Earth's gravity, allowing the spacecraft to continuously "fall" around the planet without crashing into it.

2. Initial Propulsion: The Space Shuttle used its main engines and solid rocket boosters during launch to accelerate to orbital velocity. These engines burned liquid fuel, and the solid rocket boosters provided additional thrust to reach the required speed. Once the desired velocity was achieved, the main engines were shut down, and the empty solid rocket boosters were jettisoned.

3. Orbital Mechanics: After reaching orbital velocity, the Space Shuttle followed a specific trajectory that placed it in a stable orbit around the Earth. This trajectory took advantage of the principles of orbital mechanics, which describe how objects in space move under the influence of gravity. Essentially, the Space Shuttle was placed in a continuous state of free fall, which kept it in orbit.

4. Absence of Atmospheric Drag: In orbit, the Space Shuttle and other spacecraft operate in the near-vacuum of space, where there is very little air or atmosphere. This absence of atmospheric drag means that there is no resistance to slow down the spacecraft. Unlike an airplane, which relies on engines to overcome drag and stay in flight, spacecraft in orbit can coast indefinitely as long as they maintain their orbital velocity.

5. Periodic Adjustments: While in orbit, the Space Shuttle did require periodic adjustments to its trajectory and orbit. Small thrusters, known as Reaction Control System (RCS) thrusters, were used for these adjustments. The RCS thrusters expelled small amounts of propellant to change the spacecraft's orientation or make course corrections.

6. Deorbit and Reentry: When it was time to return to Earth, the Space Shuttle's main engines were reignited to slow it down and reduce its velocity. This change in velocity caused it to begin descending from orbit. The Space Shuttle then reentered Earth's atmosphere, where it experienced atmospheric drag, further slowing it down. The orbiter's heat shield protected it during reentry, and it glided to a safe landing.