ESA is Testing How Iron Burns in Weightlessness

What happens when you burn iron in space? The European Space Agency is torching iron powder in microgravity, to find out. They aren’t doing it for the fun of it, but to understand something called “discrete burning.” It turns out that this process might enable more efficient iron-burning furnaces right here on Earth. It could eventually join other renewable energy sources as a way to combat the release of greenhouse gases in our atmosphere.

So, why burn iron? In astrophysics, when a hugely massive star gets to the “iron-burning” phase, it spells catastrophe in the form of a supernova. That’s because it takes more energy to consume the iron in the star’s core than the star can put out. But, “burning” iron in microgravity is a different chemical process.

When you burn something, you’re adding oxygen to the material you want to burn. The process gives off heat, plus other byproducts. If you’re burning wood or something like that, the by-products are ash and carbon dioxide (a greenhouse gas).

When iron (or other metal) powder burns, it reacts with air to form oxides. In the process, they create a lot of energy (and light). In the case of iron, the leftover is basically iron oxide—good old rust. And, people can reprocess the rust to remove the oxygen. Essentially, you get iron back. No carbon dioxide gets produced and no other dangerous gases show up in the process.

“The best way to reduce carbon emissions into the atmosphere is not to emit it at all,” explained ESA engineer Antonio Verga, who worked on flying the team’s experiments aboard TEXUS sounding rockets.

How To Burn Iron, ESA-Style

Most of us have experienced burning metals when we set off fireworks or played with sparklers during holiday celebrations. Those are great toys, but they’re also mini-energy sources. What happens if you scale up such iron- and metal-burning processes? You get heat and energy on a much larger scale. That’s what the ESA scientists wanted to test, for reasons relating to future exploration of the Moon and beyond.

Here’s what it looks like when iron dust is burned in a controlled chamber. It gives off heat and light. This is the process of discrete burning. Courtesy ESA.

To test the iron-burning process, the agency sent up a series of parabolic flights on zero-g aircraft and rocket launches. Onboard “ovens” contained iron dust that floated free and ignited discretely. Such discrete burning is rare here on Earth, but the physics of it is worth researching for space-based use. The idea was to see if discrete burning could be a useful technology in such places as lunar bases. To get a mental image of the process, think of a forest fire where one tree burns, and then when things get hot enough, the fire jumps to a neighboring tree.

Video of iron burning on an ESA parabolic flight aboard the Falcon-20 aircraft of the Canadian National Research Centre. The view shows iron metal dust igniting as it reaches combustion temperature. The view is slowed down 30 times. Courtesy ESA.

High-speed cameras captured views of the experiments onboard the aircraft and rockets. The images and data were then fed into computer models that scientists are using to understand if iron-burning plants are possible in various environments.

Applications in Space and on Earth

Metal-burning processes might seem unusual to many people—almost science-fictiony. It’s not a completely new idea, though. A whole community of researchers is looking into the process here on Earth for sustainable energy production. And, it’s not new to the industry. In the Netherlands, the Swinkels Family Brewery embraced iron burning several years ago to convert its brewing process from fossil fuels to a more ecologically sustainable process.

In space, while there are no colonies or stations on the Moon yet, ESA scientists see a time when sustainable metal-burning energy plants will be needed there as well. One possible scenario is to use solar energy to produce aluminum and silicon powder from lunar minerals and get hydrogen and oxygen from lunar ice. The hydrogen would be used to convert lunar dust that is high in iron and titanium to produce water and iron powder. The metallic powders and oxygen from the water ice could be turned into propellants for rockets or ground transportation and the water by-product becomes drinking water.

The iron fuel demo plant in Eindhoven, The Netherlands. Courtesy ESA.

The sustainable fuels industry is seriously looking at metal burning as a future source of “clean energy.” There’s already a demonstration plant up and running experiments in the Netherlands, near Eindhoven. The goal is to find out how much of this energy can be generated as a replacement for fossil fuels. It uses iron powder and generates about 1MW of steam. Based on this experimental model, other companies are looking into metal burning for heavy industrial uses.

For More Information

Metal Fuel for Carbon-free Energy on Earth
Any Old Iron
Iron’s In the Fire

Carolyn Collins Petersen

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