What is a
rocket?
The American Heritage dictionary says that a rocket is "Any device propelled by ejection of matter, esp. by the high-velocity ejection of gaseous combustion products". Say What?
OK, the rocket is a mechanical and chemical device which harnesses the power of burning gasses to propel an object into the atmosphere. This same propulsion system can be used in space to alter the orbit of a spacecraft, or land it on an asteroid.
How does it
work?
There are two main types of chemical rocket engines, Liquid Fueled, and Solid Fueled. The United States Space Shuttle uses both types of systems. Liquid fueled engines work by combining a very flammable fuel (sometimes hydrogen) with a very good supply of oxidizer, such as liquid oxygen. Pumps mix the two materials together in a nozzle and ignite them. The result is an ongoing explosion which is directed in a straight line behind the craft, and causes the craft to move rapidly in the opposite direction. A solid fuel engine works in much the same way, but the fuel and oxidizer are already mixed together in a solidified form. When they are ignited they produce a very similar force to the liquid fueled engines, but you cannot "turn off" a solid fuel engine. Once it has been ignited, you have no choice but to let it burn, come what may.
In What Shapes and
Sizes do they
come?