The Basics
* Low Earth Orbit (LEO): This is the region of space around Earth where satellites orbit at relatively low altitudes, usually between 160 and 2,000 kilometers (100 to 1,200 miles).
* Orbital Velocity: To stay in orbit, an object needs to travel at a specific speed, called orbital velocity. This velocity depends on the altitude of the orbit and the gravitational pull of the planet.
* Minimum Orbital Velocity for LEO: The minimum orbital velocity for a stable low Earth orbit is approximately 7.8 km/s (4.8 miles/s). This speed is crucial for the object to balance Earth's gravity and prevent it from falling back to the ground.
What Happens if the Speed is Less Than 7.8 km/s
If an object launched into space doesn't reach the minimum orbital velocity for LEO:
1. Trajectory: The object won't achieve a stable circular orbit. Its path will be more like an elongated ellipse, with its furthest point (apogee) lower than its closest point (perigee).
2. Gravity: Because the object isn't moving fast enough to counteract Earth's gravity, it will gradually lose altitude.
3. Atmospheric Drag: As the object descends, it will encounter more atmospheric drag, slowing it down even further.
4. Re-Entry: Eventually, the object will re-enter the Earth's atmosphere, likely burning up due to friction.
Example: Imagine throwing a ball straight up. It goes up, then comes back down. If you throw it harder, it goes higher, but still comes back down. To keep it from falling back down, you need to throw it so fast that it goes into orbit, continuously falling around the Earth.
In Summary
An object needs to reach a minimum orbital velocity of around 7.8 km/s to achieve a stable low Earth orbit. If it doesn't, it will follow a trajectory that leads to a gradual descent and eventually re-entry into the atmosphere.
