As you may already know, an MRE (Meal Ready to Eat) is a prepackaged meal intended for soldiers to have lightweight, nutritious food on the go. MREs are heavily engineered to be the optimal way to give a soldier a good meal on the battlefield in even the worst conditions. Food is essential for soldiers to perform at their best, so the military has invested quite a bit of time and energy in developing optimal solutions to the problem of hot, bracing food that can be made with as little effort as possible.

MREs are engineered to be as light as possible, work at all times, and be resistant to any kind of conditions that may render them unusable. One of the most impressive parts of the MRE engineering is the flameless heater, which cooks the food with a simple chemical reaction, requiring nothing from the soldier but water.

A flameless heater has many advantages for a soldier on the go. In dark conditions, building a fire or using a portable gas stove to prepare food may alert an enemy to the soldier’s presence. It can also be dangerous to use a fire in some conditions, like inside a building. Rain and wind can render flame-based cooking methods impossible. Because of challenges like these, MREs instead use a special chemical reaction that can work in almost any conditions to heat food.

Chemical reactions that create heat are not uncommon in nature. For example, though it is very slow, the process of rusting iron gives off heat. Rusting is the process of oxygen atoms bonding to a metal, which releases pent up chemical energy in the metal and oxygen. Oxidation, the chemical term for oxygen bonding to another substance, nearly always results in converting chemical energy to heat. Burning wood or charcoal is also an oxidation reaction, but a much more rapid one that gives off light as well as heat. An example of the oxidation of a metal generating heat more rapidly is thermite, which is a compound of burning metal that can burn straight through solid steel even underwater. The same principle is at work in an MRE.

Instead of using iron, which rusts slowly, MRE flameless heaters work by using magnesium, which oxidizes much hotter and faster than iron. Magnesium also carries much more chemical energy by weight than iron. However, the chemical reaction at play is exactly the same as rusting; creating magnesium oxide instead of iron oxide! As most people know, iron rusts more readily when in contact with water. The same chemical principle is utilized to start the rapid oxidation reaction of the magnesium to generate heat.

The key with an MRE flameless heater is to create an oxidation reaction that does not result in an open flame or any light being given off. This is achieved by mixing the magnesium powder with salt and a small amount of iron dust, which accelerate the reaction, and putting the whole mixture into a heat resistant flexible pad roughly the size of a playing card. When water is added, the water molecules are broken apart, releasing hydrogen gas and bonding the oxygen and half of the hydrogen to the magnesium to create magnesium oxide. In addition to the hydrogen gas and magnesium oxide, this process releases a massive amount of energy. The whole reaction takes only 7.5 grams of alloy powder and 30 milliliters of water.

Within a few seconds of adding water to the flameless heating pack, the pack becomes extremely hot. Military specifications dictate that these packs be capable of heating an entire 8 ounce meal by 100 degrees Fahrenheit in just twelve minutes. After the water has been added and the reaction has started, the pack is sealed and placed in the MRE pack with the food. The MRE is then closed, and after 12 minutes, will be hot and ready to eat.

MRE flameless heaters are very safe compared to most cooking methods. The amount of hydrogen released into the air is negligible for most cases. However, in very confined spaces without ventilation, using too many MRE packs can become dangerous in some situations. The buildup of hydrogen gas in such a situation can become a fire hazard. In particular, the United States Department of Transportation Federal Aviation Administration conducted a study that showed that using flameless heating packs like these on a passenger aircraft can release enough hydrogen gas to be dangerous to the passengers.

MREs used by the military are marvels of modern engineering. Using as little weight as possible, these meals can be safely heated in almost any conditions, all without creating an open flame, and requiring nothing more than a small sip of water. Having hot food on the go in stormy or dangerous conditions with no preparation means that soldiers can perform much better on the go than would otherwise be possible. If you would like to try how FRH works, don’t hesitate to get your MREs from us.

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