Could the friction from a plane crash generate enough energy to start a thermite reaction?
TestAmerica Expert: Larry Penfold
Expert's Response:
Thermite reactions are chemical reactions between a zero valence metal and a metal oxide. The one I remember from my school days involved iron oxide (rust) and powdered aluminum, which requires an ignition source with a temperature of something like 2,500 to 3,000 degrees Centigrade. The reaction generates a lot of heat quickly and, unlike a paper fire, doesn’t need any air to keep it going. The oxygen that sustains the burning is coming from the iron oxide. It’s a chemistry experiment that requires extra fire precautions - I can remember a demonstration given by one of my university chemistry professors that was much more exciting than he expected.
In regards to a plane crash, the total energy of an airplane crash is certainly more than enough to start a thermite reaction. A little Fourth of July sparkler is enough if all of the ingredients are carefully prepared in the right proportions, and it is the question about the right proportions that is the key to the answer to your question.
I would guess that the aluminum skin in the nose of the crashing airplane could simply melt and burn in the atmosphere without any metal oxide being present. In other words, a spray of high temperature aluminum combining rapidly with the oxygen in the air is a likely reaction. Spontaneous combustion of materials in air is sometimes called a pyrophoric reaction, not quite the same as a thermite reaction. If there were some iron rust present where the aluminum from the nose of the plane is burning, then it could add its oxygen to the burning and there would be a little bit of a thermite reaction going on. But unless there almost as much rust as aluminum, I wouldn’t think that would be the main effect because the ratio of the ingredients, the stoichiometry, is not right.
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