The Unusual Connection Between D-Day and Self-Heating Soup
Written on
Chapter 1: The Strategic Importance of Pointe du Hoc
The imposing cliffs of Pointe du Hoc stand tall over the Normandy shores, where Allied forces landed on June 6, 1944. This pivotal moment marked the onset of the liberation of Europe from German occupation. The cliffs provided an ideal vantage point for artillery that could devastate any troops attempting to storm the Omaha and Utah beaches.
Anticipating this threat, Allied commanders ordered a naval bombardment of Pointe du Hoc. However, to ensure success, they also devised a contingency plan. A specialized team of U.S. Rangers ascended the 30-meter cliffs, located the enemy artillery, and used grenades to obliterate the guns. Their success hinged on the use of thermite-based charges, which differed significantly from conventional high explosives. Instead, they harnessed a chemical reaction that generated temperatures sufficient to melt steel components.
Interestingly, the thermite used by the Rangers is quite uncomplicated, consisting simply of rust (iron oxide) and powdered aluminum. When combined, these materials remain stable and safe until ignited—typically using a magnesium fuse. The reaction that ensues is remarkable, with aluminum seizing oxygen from the rust, resulting in iron production and an intense heat burst. This reaction can reach temperatures of around 2,500°C, hot enough to melt iron.
This video illustrates the thermite reaction in slow motion. Initially, the bright light is from the burning magnesium. As the fuse reaches the thermite, the spectacle becomes even more impressive, culminating in a melted tube and a pool of flaming iron.
Thermite serves as an extreme case of an exothermic reaction, which releases energy in the form of heat and light. While fire is a common example of such reactions, many of the troops landing on Normandy also had another instance in their rations: self-heating soup cans. These cans functioned as both a stove and a container, featuring a tube of cordite—typically used as a propellant for small arms ammunition—running through the center as fuel. They were quick and easy to ignite, often with just a cigarette, allowing soldiers to prepare a warm meal swiftly. However, they also had a tendency to explode, unexpectedly showering nearby soldiers with scalding soup.
Chapter 2: The Evolution of Self-Heating Technology
Since the early attempts to create self-heating cans, many efforts have been made to bring them to mainstream markets. Most of these innovations relied on less volatile reactions for heating, although some still encountered explosive challenges. A common method involved mixing quicklime (calcium oxide) with water, which generates heat rapidly. However, its efficiency is limited, producing only about 60 calories of energy per gram of reactant. This means that to raise the temperature of a drink by 40°C, a significant portion of the can’s volume would be consumed by the heating element. This is somewhat acceptable for a small beverage on a warm day but becomes impractical during colder weather when a hot drink is more desirable.
To achieve a more effective heating solution, a more robust reaction is necessary—perhaps something akin to thermite? Despite the apparent madness of including a reaction capable of disabling artillery within a can, HeatGenie is pursuing this very concept. Over the past decade, the company has filed numerous patents detailing the incorporation of thermite in self-heating cans. The reaction utilized by the U.S. Rangers was deemed too intense, leading the company to substitute rust with a less reactive, yet familiar, material: silicon dioxide. The latest self-heating cans now rely on aluminum and powdered glass.
When activated, this reaction produces an impressive 200 calories per gram of reactant and can achieve temperatures of 1,600°C. Given the potentially hazardous nature of releasing such energy, HeatGenie has implemented various safety measures in its design. These include intricate “firewalls” to contain the flamefront if temperatures escalate, energy-absorbing “heatsinks” to promote efficient heat distribution, and vents for steam release. With these precautions in place, the company claims that only 10% of the can's packaging is dedicated to the heating components, which can still deliver a warm beverage in just two minutes.
As we look back over a century since Russian engineer Yevgeny Fedorov first experimented with self-heating cans, and more than 15 years since Nestlé abandoned a similar venture, has HeatGenie finally found the solution? While their patents and funding suggest they may have resolved the technical challenges, whether they truly possess a marketable product remains to be seen.
First published in The Conversation