How Rockets Reach Orbit
ராக்கெட்டுகள் சுற்றுப்பாதையை எப்படி அடைகின்றன?
Reaching orbit is less about going up and more about going sideways very fast. Here is how rockets manage it.
Many people picture a rocket as something that simply flies upwards until it reaches space. In fact, going up is the easy half. To stay in orbit, a spacecraft must also travel sideways at enormous speed, and getting up to that speed is what a rocket’s job is really about.
How a rocket pushes
A rocket burns fuel and throws hot gas out of its engine at very high speed. As the gas is pushed one way, the rocket is pushed the other way. This is Newton’s third law of motion: every action has an equal and opposite reaction. Because the rocket pushes against its own exhaust, it doesn’t need air to push against, which is why rockets work perfectly well in the vacuum of space.
Space has no air, so a rocket must carry both its fuel and the oxygen needed to burn it. At lift-off, most of a rocket’s weight is propellant.
Why sideways matters
A satellite in orbit is not floating above gravity. Earth’s gravity is still pulling on it. The satellite stays up because it is moving sideways so fast that, as it falls towards Earth, the curved surface of the planet falls away beneath it. It keeps falling and keeps missing the ground. Close to Earth, this takes a speed of roughly 28,000 kilometres per hour.
That is why a rocket doesn’t climb straight up for long. It rises through the thickest air first, then gradually tilts over, so that more and more of its push goes into building sideways speed.
Dropping weight along the way
Carrying empty fuel tanks all the way to orbit would waste energy. So most rockets are built in stages. When the first stage has used up its fuel, it separates and falls away, and the next stage, which is lighter, takes over. Some modern rockets are designed so that a stage can land and be flown again.
Weightless, but not free of gravity
Astronauts inside a spacecraft in orbit float because they and the craft are falling together. Gravity has not gone away. They are in constant free fall around the Earth.
Key points
- Reaching orbit is mostly about gaining sideways speed, not just height.
- A rocket works by throwing exhaust one way so that it moves the other, and needs no air to do it.
- Rockets are built in stages so they can drop weight they no longer need.
- Things in orbit are not beyond gravity. They are falling around the Earth without ever landing.
