Pointe de Hoc is a cliff that overlooks the Normandy beaches, where Allied troops landed in June 1944. These assaults were the start of liberating German-occupied Europe. The cliffs provided the ideal location for artillery pieces that could destroy any troops who attempted to attack the Omaha or Utah beachheads.
To reinforce the attack, the Allied command bombarded Pointe de Hoc. They also had a backup plan in case this wasn’t enough. After locating the weapons, a team of US Rangers climbed the 30-meter-high cliffs and then deployed grenades to destroy the guns. The choice of thermite charges was crucial to the success. Thermite-based charges were not the “high explosives” found in grenades. Instead, they used a chemical process that heated the firing mechanism to temperatures high enough to melt it.
The thermite used by the Rangers is actually incredibly simple. Thermite is made of rust (iron dioxide) and aluminum powder. When mixed, they are completely safe and stable. That is until you kick the mixture by lighting a metal magnesium fuse. Then the fireworks begin. The aluminum grabs oxygen from the rust and produces iron in the process. The reaction can reach temperatures of up to 2,500 degrees Celsius. This is hot enough for molten iron.
This video shows the reaction in slow motion. The light is the burning magnesium. When the thermite is consumed, the results are stunning. A melted tube of iron and a flaming pool of iron remain.
Thermite, an extreme example of an exothermic reaction, is a chemical reaction that produces energy as light and heat. The exothermic reaction we are most familiar with is fire, which typically results from a carbon-oxygen response. There are many more. In fact, many of those same troops landing on Normandy’s beaches had a similar example in their ration pack in the form of self-heating soup cans.
The cans were a stove rolled up into one with a tube containing cordite running through the middle to serve as fuel. These cans could be easily lit by a cigarette and allowed troops to cook a meal in less than five minutes. Unfortunately, the cans tended to explode and shower the assembled squaddies in hot soup.
Self-heating cocoa. University of Cambridge
Since then, many attempts have been made to turn self-heating canned into a popular product. Has still had problems with explosions. When mixed with water, quicklime (calcium dioxide) heats quickly. It’s not very efficient. One gram of the reactant produces 60 calories. (One calorie heats one milliliter of water by 1degC).
To heat a drink to 40 degrees Celsius, you would need a heating component that is nearly half of the package. It’s fine if you want a little drink on a hot day. But in winter, when you really need a hot beverage, it is only a tepid cup of coffee.
Cans with more power
It’s time for a more effective reaction. What about thermite? HeatGenie plans to pack a can that will turn off an artillery weapon. It may sound wild, but it’s exactly what they are planning. Has filed numerous patents over the past ten years describing thermite in self-heating containers. The reaction that the US Rangers used was still too hot for them to handle. So they have dialed things down a little by replacing the rust in the cans with silicon dioxide, a material which is less reactive but not less familiar. The latest generation of heated cans are powered by aluminum and ground-up glass.
This reaction can still produce 200 calories per gram and reach 1,600degC. HeatGenie has several patents that cover safety concerns. Given the history of self-heating packaging, it is not surprising to see this much energy released from the can you hold.
The company has also designed a series of ” fire walls ” that will block the “flame front” if it gets too hot. There are also heatsinks that absorb energy and ensure the heat is effectively transferred around the drink. Vents have been added to release any steam. The company claims that only 10% of the package is taken up by heating elements. This can still produce warm coffee within two minutes.
Has HeatGenie finally cracked the self-heating can, more than a century after Fedorov’s initial efforts? The firm may have solved the technical aspect, but whether they really have a hot product is another matter.