Letters: September 2012

When considering the viability of electric-powered aircraft, it’s important to note the huge difference between the internal combustion (IC) engine that burns hydrocarbon fuels and an electric motor that relies on a battery energy source. The ratio of air mass to fuel mass at efficient combustion (stoichiometry) is about 14.6. That is, for every pound of fuel burned, 14.6 pounds of air are consumed. But you don’t have to carry the air since it is available in the atmosphere. Fuel weighs about 6 pounds per gallon, so 16 gallons of fuel weigh about 100 pounds. Over 1400 pounds of air will be consumed in burning that amount of fuel. An electric motor requires that all of the energy be contained in the battery. Since the energy density of lithium batteries is about 26 times less than the energy of gasoline, there is nowhere for electric propulsion to go. It is interesting to note that gasoline has 10 times the energy density of TNT that needs to carry its oxidizer within.