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Rocket • A rocket is a type of engine that pushes itself forward or upward by producing thrust. Unlike a jet engine, which draws in outside air, a rocket engine uses only the substances carried within it. As a result, a rocket can operate in outer space, where there is almost no air. A rocket can produce more power for its size than any other kind of engine.
Rocket Engines Produce Thrust • Rocket engines generate thrust by expelling gas. Most rockets produce thrust by burning a mixture of fuel and an oxidizer, a substance that enables the fuel to burn without drawing in outside air. This kind of rocket is called a chemical rocket because burning fuel is a chemical reaction. The fuel and oxidizer are called the propellants.
Propellants • A chemical rocket can produce great power, but it burns propellants rapidly. As a result, it needs a large amount of propellants to work for even a short time.
Rockets • Rockets are the only vehicles powerful enough to carry people and equipment into space.
How Rockets Work • Rocket engines generate thrust by putting a gas under pressure. The pressure forces the gas out the end of the rocket. The gas escaping the rocket is called exhaust. As it escapes, the exhaust produces thrust according to Newton’s Laws of Motion.
Newton’s Third Law of Motion • Newton's third law of motion states that for every action, there is an equal and opposite reaction. Thus, as the rocket pushes the exhaust backward, the exhaust pushes the rocket forward.
Parts of a Rocket The four major parts of a rocket are: • payload = the cargo, passengers, and equipment the rocket carries • propellants = the fuel and oxidizer (make up about 90% of the weight at liftoff) • the chamber = the area of the rocket where propellants are put under pressure • the nozzle = the opening at the end of the chamber that allows the pressurized gases to escape
Launch Vehicles • Rockets launch spacecraft carrying astronauts that orbit Earth and travel into space. These rockets, like the ones used to launch probes and satellites, are called launch vehicles.
