Fuel

fuel is a substance used to pro­duce heat or power. Fuels con­tain energy that is usually obtained by burning the fuel. Aircraft and spacecraft use fuel to produce power. When fuel is burned inside an engine, it produces a lot of gas. The heat makes the gas expand rapidly, and this provides the power to propel the air­craft through the air. A variety of different fuels are used in aviation and spaceflight.

Aviation Fuels

There are many aviation fuels, each one a different mixture of chemicals. Extra chemicals called additives are included in the mixture to make it burn smoothly instead of exploding and to stop it from freezing solid or growing bacteria.

Early aircraft used the same sort of gasoline fuel as automobiles. When new types of engines were developed, new fuels were produced specially for them. Today, aircraft with piston engines (like automobile engines) use a type of gaso­line called Avgas. The first jet engines built in Germany used gasoline, too. Modern jet engines burn a different fuel, called kerosene.

The first fuel produced especially for jet engines was called Jet Propellant 1, or JP-1. When fuels were created for new military aircraft, each new fuel was given a JP number: JP-2, JP-3, etc. The U. S. Navy, for example, wanted to develop an aircraft fuel that would not

FUEL TANKS

Planes usually store fuel in tanks inside their wings. The Boeing 747­400 jumbo jet’s giant wings hold an enormous amount of fuel. There are three fuel tanks in each wing, anoth­er tank in the space where the wings join the fuselage, and another tank inside the horizontal stabilizer, or tailplane. When the tanks are all full, they hold more than 57,000 gallons (about 216,000 liters). This huge amount of fuel enables the 747-400 to fly a distance of more than 8,000 miles (12,872 kilometers) before it has to land and refuel.

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catch fire as easily as JP-1, so that it could be stored more safely on board ships. This new fuel was named JP-5.

Fuels for nonmilitary jets have differ­ent names. The most widely used fuels for commercial jets are Jet A-1 (most common worldwide) and Jet A (most used in the United States). A different jet fuel, Jet B, is sometimes used in the coldest parts of the world, including Canada and Alaska. Jet B is a mixture of gasoline and kerosene-the gasoline helps the fuel burn in very cold air.

When superfast spy planes were built in the 1960s, they were unable to use the same fuel as other jet planes. They flew at more than three times the speed of sound. At such a high speed, air rubbing
against a plane’s body heats it up. The wings of the new spy planes became so hot that fuel stored inside them could explode.

Chemists created a new fuel, JP-7, that could be heated to very high tem­peratures without exploding. It is said that a burning match dropped into JP-7 will actually go out.