Rockets enter and maintain orbits through a combination of speed and gravitational forces. When a rocket is launched into space, it initially ascends vertically to overcome Earth's gravity and then gradually tilts its trajectory to achieve the desired orbital path. Let's break down the process:
Launch: A rocket is launched vertically from the surface of the Earth, typically using powerful engines to provide the necessary thrust. The goal during the initial phase is to reach a certain altitude and gain enough horizontal speed to enter orbit.
Gravity turn: As the rocket gains altitude, it begins to tilt its trajectory sideways in a maneuver called the gravity turn. This turn allows the rocket to take advantage of Earth's rotation and gradually align its path with the desired orbit.
Circularization burn: Once the rocket reaches the desired altitude, it performs a circularization burn. This burn is executed when the rocket's trajectory is at its highest point (apogee). By firing the engines prograde (in the direction of travel) at apogee, the rocket increases its speed and enters a circular orbit.
Orbital maintenance: Once in orbit, the rocket continues to move at a high velocity tangentially to the Earth's surface. The centrifugal force generated by this velocity balances out the gravitational pull from Earth, resulting in a stable orbit. To maintain the orbit, occasional corrective burns may be required to compensate for factors like atmospheric drag or gravitational perturbations from the Moon and the Sun.
It's important to note that achieving a stable orbit requires reaching a certain velocity, known as orbital velocity, which varies depending on the desired altitude and type of orbit. Achieving the correct combination of altitude and velocity is crucial to establish and maintain a stable orbit around a celestial body, such as the Earth.