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The strange story of D-Day and self heating soup.
The imposing cliffs of Pointe du Hoc overlook the Normandy beaches where Allied troops landed on June 6 1944. The assaults marked the beginning of the liberation of German-occupied Europe. And the cliff tops were the perfect spot for artillery pieces capable of devastating any troops who tried to attack the Omaha and Utah beachheads.
The Allied command knew this and so, to shore up the attack, the navy bombarded Pointe de Hoc. Afraid this might not be enough, they also had a backup plan. A team of US Rangers scaled the 30-metre cliffs and, after locating the weaponry, deployed grenades, destroying the guns. The key to success was the choice of thermite-based charges. These weren’t the kind of “high explosives” normally found in grenades, but instead used a chemical reaction that produced temperatures hot enough to melt the steel of firing mechanisms.
Surprisingly, the thermite the Rangers used is incredibly simple. It is just rust (iron oxide) and powdered aluminium. Mixed together they are entirely safe and stable — that is until the mixture is given an energetic kick, typically by lighting a magnesium metal fuse. And then the fireworks start. The aluminium grabs the oxygen from the rust and in the process produces iron and a huge burst of heat. The reaction can easily reach 2,500℃, hot enough to melt iron.
