A rocket may be a missile, spacecraft, aircraft or other vehicle which is pushed by a rocket engine. Some big rockets are launch vehicles and some are manned (e.g. Saturn V). Other rockets, for example missiles, are unmanned. ("Manned" means that a person is in it; "unmanned" means that the machine goes without a person.)
Most rockets can be launched from the ground because exhaust thrust from the engine is bigger than the weight of the vehicle on Earth. Some are used to bring satellites into orbit, for example from a spaceport. Some rockets such as ion thrusters are too weak and heavy to lift themselves. They work after other rockets bring them to outer space.
The Chinese invented the rocket using gunpowder.[1] The first rockets were shaped like arrows and weren't very fast. Most rockets still work by fire. The fire makes hot exhaust gases that expand and shoot out a nozzle, pushing the rocket forward.
Most rockets still use solid fuel to make the fire. The biggest ones use liquid fuel because it makes a hotter fire so the rocket is more powerful. However, handling the liquid fuel safely is difficult and expensive. Some satellite launch vehicles use both.
Manned rockets, similar to other manned flying machines, are designed to limit their acceleration and vibration to protect the crew. Unmanned rockets however are not bound by the limits of humans.
Some rockets go faster than the speed of sound (Mach 1 or 1,200 km/h or 760 mph). Those that go into Low Earth orbit go 30,000 km/h (19,000 mph).
