Fuel value

The fuel value or relative energy density is the quantity of potential energy in fuel, food or other substance.

Some values:

• mass (total) 90 PJ/kg
• nuclear fusion 300 TJ/kg
• nuclear fission 2 TJ/kg
• hydrogen 120 MJ/kg
• gasoline 44 MJ/kg
• fat 38 MJ/kg
• coal 23 - 29 MJ/kg
• sugar 17 MJ/kg
• wood 15 MJ/kg
• TNT 4.6 MJ/kg

For rocket fuel a more relevant quantity is the energy per unit mass including oxidizer. For example, to burn 1 kg of hydrogen, 8 kg of oxygen is needed, so that the high fuel value reduces to 13.3 MJ per kg propellant.

Also relevant is the density: since that is very low for liquid hydrogen, the energy per unit volume is not so high, hence a large and therefore heavy tank is needed.

For projectiles, compare the value for TNT with the energy of a kinetic kill vehicle with a closing speed of e.g. 10 km/s, which is 50 MJ/kg.

Compare:

• specific heat of vaporization
• specific heat capacity
• specific melting heat
• specific orbital energy

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