What is the difference between orbital and sub-orbital spaceflight?
What is the difference between orbital and sub-orbital spaceflight?
The biggest difference between the two is their speed. An orbital spaceflight has to achieve 'orbital velocity', while a sub-orbital rocket flies at a lower speed. Orbital velocity is the speed at which an object must remain in order to revolve around a planet. It is as if you throw a ball from the ground. If you throw it at normal speed, it goes a little higher in the air and comes back and falls on the ground.
Sub-orbital rockets do not have enough power to reach Earth's orbit. It goes up to a certain height depending on its speed and then comes back down after the engine is switched off.
Suppose you have to throw a stone. If you throw it slowly, it will go some distance and fall down. But if you throw it too fast, it will go far and remain in the air for some time. Orbital spaceflight is like a stone thrown very fast. It will reach such a height that it will start revolving around the Earth. Sub-orbital spaceflight is like a stone thrown with less force. It will go up, stay in the air for some time and then come back down.
If a spacecraft has to revolve about 200 kilometers above the Earth, then it will have to move at a very high speed (about 28,000 kilometers per hour). This is a very high speed and is the reason why space flights are so difficult and expensive.