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Aviation fuel
    Production of aviation fuel
    Jet fuel
    Energy content
    Chemical composition
    Safety precautions
Aviation Fuel Storage
Jet fuel
Aircraft Fuel System
What is a Fuel?

Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. A fuel contains energy, mostly heat, that can be released and then manipulated. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air. Other processes used to convert fuel into energy include various other exothermic chemical reactions and nuclear reactions, such as nuclear fission or nuclear fusion. Fuels are also used in the cells of organisms in a process known as cellular respiration, where organic molecules are oxidized to release usable energy. Hydrocarbons are by far the most common source of fuel used by humans, but many other substances, such as radioactive metals, are currently used as well.

What type fuel can be substituted for an aircraft if the recommended octane is not available?
The correct answer was:
C) The next higher octane aviation gas.

Subject Code: H307, Engine Operation in AC 61-23--Pilot's Handbook of Aeronautical Knowledge

Here are further guidelines.


Solid Fuels and their Characteristics
Liquid Fuels and their Characteristics
Gaseous Fuels and their Characteristics

Solid fuel

Bituminous Coal
Nuclear Power
Solid-fuel rocket technology

Propellant families

Black powder (BP) propellants
Zinc–sulfur (ZS) propellants
"Candy" propellants
Double-base (DB) propellants
Composite propellants
High-energy composite (HEC) propellants
Composite modified double base propellants
Minimum-signature (smokeless) propellants

Liquid fuel

Compressed natural gas
Liquefied petroleum gas (LPG)
Non-petroleum fossil fuels
Alcohols (Methanol)
Alcohols (Ethanol)
Alcohols (Butanol)

What is the difference between natural and manufactured fuels?
What are the merits and demerits of solid fuels?
What are the main constituents of wood?
What is the difference between ultimate analysis and proximate analysis of coal?
Mention the uses of different types of coal.
What are the characteristics of coke and briquette fuels?
Mention the composition of crude petroleum.
Mention the uses of different types of manufactured liquid fuels.
Mention the origin and composition of natural gas.
Mention the characteristics of the following gaseous fuels :
(i) Coal gas,
(ii) Water gas,
(iii) Producer gas, and
(iv) Blast furnace gas.

Q:What’s the difference between liquid and solid-fuel rockets?
A: There are two main types of rockets: liquid-fuel and solid-fuel. Liquid-fuel rockets consist of a fuel and oxygen (or other oxidizer) in liquid state. They are combined in a combustion chamber and ignited. The fuel flow to the engine can be controlled, the amount of thrust produced can be regulated and the engine can be turned off or on as needed. Solid-fuel rockets consist of a fuel and oxidizer that are pre-mixed in a solid form. Once the solid fuel is ignited, the resulting thrust cannot be regulated or turned off. This fuel system is simpler, safer, and cheaper—but less efficient—than that of a liquid-fuel rocket.

What kind of fuel do rockets use and how does it give them enough power to get into space?
A rocket works by exchanging momentum. Both the mass of the propellant and the high velocity of its exit from the engine system give the rocket its momentum. The propellant attains its velocity by burning with an oxidizer in a high-pressure chamber. The resultant high energy exhaust is then funneled through a converging or diverging nozzle. This velocity, coupled with the right mass properties of the propellant, provides the power, or energy, required to get the vehicle into space.

Scientists measure the efficiency of rocket propellants by what is termed vehicle specific impulse. This measures the impulse, or change in momentum, per unit of propellant expended. Thrust, or the force generated by the propellant, is another critical property related to the density of the propellant. Unfortunately, propellants that have high specific impulse do not have high-density or high-thrust properties and vice versa.

Although high specific impulse is a desired quality while moving in space, propellants with high specific impulse will not create sufficient thrust to get into space from Earth¿s surface. This is due to the larger fuel tanks necessary to contain a lower density propellant and the atmospheric drag that acts on the tanks when the rocket attempts to power beyond Earth's gravity. Other propellant considerations include ease of ignition, combustion stability, temperature, storability, reliability, toxicity, cost and availability. As a result, different propellants are used for different missions and differ among the stages of any given rocket.

Propellants can be in the form of a solid, liquid or gas, each with their own advantages and disadvantages. Solid propellants have higher density--and therefore thrust. They also are storable, transportable, reliable, less complex and can also contain their own oxidizer. Once ignited, however, solid propellants burn continuously, limiting the number of applications. Examples of rockets using solid propellants include the first stage of military missiles, commercial rockets and the first stage boosters that are attached to both sides of the liquid-fuel tank on the space shuttle. (Though attached, the two cylindrical boosters are separate units from the tank, which itself supplies the shuttle orbiter¿s own liquid-fuel engines.) Ammonium perchlorate mixed with powdered aluminum that is held together in a rubberlike matrix is the most common solid propellant.

Liquids, in particular low temperature liquids, offer the highest specific impulse values and can be started and stopped at will throughout a mission, which makes them the best candidates for space travel. For example, liquid hydrogen and liquid oxygen have a very high specific impulse and are used for the upper or second stages of a rocket. Dense liquids such as RP-1--similar to kerosene--are sometimes used for the first stage but lack the high specific impulse for use in space. Rounding out the propellant options, gaseous fuels lack density but can offer some performance and long-term storage advantages for space travel. Here are further guidelines.