Changing Rocket engine

Liquid fuel rocket engines often require complex [[pump]]s and [[valve]]s to properly move (and pressurize) the liquids from the fuel tank to the actual engine. These machines must work in extreme temperatures and pressures. Liquid oxygen is very cold (-223˚C) while the engine is very hot (3000˚C), and the pressure is oftentimes hundreds of times higher than the surrounding [[Atmospheric pressure|air pressure]]. Because of these conditions, liquid fuel rocket engines are often very complex, expensive, and require very specialised materials ([[Alloy|metal alloys]], [[ceramic]]s, etc.).

Solid fuel rocket motors have the fuel (called [[propellant]]) as a solid mixture of an oxidizer and fuel. An [[oxidizer]] supports the burning of fuel much like oxygen supports burning. The common oxidizer is powdered [[Ammonium perchlorate|Ammonium Perchlorate]], while the common fuel is powdered [[aluminum]] metal. The two powders are stuck together with a third component known as the binder. The binder is a [[rubber]]y solid that also burns as a fuel. Since their design is so simple, solid rocket engines are usually much cheaper than other rocket engines, but their main disadvantage is that they cannot be turned off, their control is very limited, and they are more likely to [[explode]] than liquid rocket engines. Solid rockets also provide a smaller [[specific impulse]] (a measure of efficiency for rocket engines), hence must be heavier to launch the same payload.