# Why is jet fuel used as an aviation fuel in preference to dihydrogen gas? Does it make sense in terms of the energy yield?

Jun 27, 2016

Consider the mass of hydrogen, versus the mass of aviation fuel (which to a first approx. is kerosene).

#### Explanation:

${H}_{2} \left(g\right) + \frac{1}{2} {O}_{2} \left(g\right) \rightarrow {H}_{2} O \left(g\right) , \Delta {H}_{\text{rxn}} = - 286 \cdot k J \cdot m o {l}^{-} 1$

${C}_{12} {H}_{26} + 18 \frac{1}{2} {O}_{2} \rightarrow 12 C {O}_{2} + 13 {H}_{2} O$ $\Delta {H}_{\text{rxn}} = - 3506 \cdot k J \cdot m o {l}^{-} 1$

On a per gram basis, dihydrogen delivers much more energy. But how do you store the hydrogen on board? In the laboratory, hydrogen gas bottles are heavy steel cylinders (approx. 100 kg) that you can just lift. There is also the safety concern of using compressed gas in an aeroplane (as of course there is the safety concern of using compressed gas bottles in the laboratory).

The gas supply would have to be regulated (reduced to a sensible pressure), and supplied to the combustion engine on a gas tight loop - all large (and heavy) engineering requirements. On the other hand carburettor technology for the ICE with liquid fuels is a fairly mature field.