Project Starship: Innovations in Metallurgy for Science Fiction

Science fiction loves to find ways to stretch the limits of a material’s properties and, as scientists, we can learn from the creativity of these authors to continue to expand our knowledge and applications of these ancient materials. When Dr. John Mauro invited me to contribute my metallurgy expertise as part of Project Starship, I was excited to delve into how we can marry the imaginative and the technical.

My background in metallurgy started with an interest in alloy design, or combining different metals into a single component to form novel properties. My interests further expanded not only into novel properties, but also novel methods of processing these metals to create materials that have only been dreamed of. It requires thinking big in both aspects of metallurgy to even begin to get close to what science fiction has made reality in the pages of a book.

Metallurgy: Ancient Art or Novel Technology

Metals, one of humankind’s oldest materials, defined the ancient ages—think the iron age, the bronze age. It’s hard to imagine what more there is to discover about metals if it has been studied for so long. Yet, there is so much more that we can learn.

Let’s start by defining what a metal is. Metals are crystalline materials that have atoms that are arranged in specific order that gives metals their strength. These atoms can be arranged in different ways to produce very different properties—from lightweight but strong titanium, to strong and corrosion resistant stainless steel. In most applications, we don’t commonly use the pure form of a metal, but rather an alloy. Alloys typically have a primary element and then other elements are added to change the properties of the materials. This is where the magic happens with metals, in my opinion.

Going as far back 500 AD, we saw the discovery of Damascus steel, a carbon steel that was stronger than its standard steel counterpart. It is theorized that this was an accidental discovery, as steel smiths would use coal in the smelting process, introducing small amounts of carbon into the molten metal. Thus, one of the first steel alloys was formed. Another example is the very commonly used stainless steel. By adding just a small percentage of chromium to steel, we are able to take a material that would oxidize if the air is too humid and transform it into a material that can withstand even the most corrosive environments.

This is where we can start getting creative when it comes to the materials starships are made of. In Graham McNeill’s world, his 40k ships are made of many different materials, including ceramite, a high strength steel immune to heat. To get such properties, we would start looking at high melting temperature materials to alloy with steel. Refractory metals, such as molybdenum and tantalum are already alloyed with steel, typically for corrosive resistance, and they become even more prevalent in super alloys. These are typically iron-nickel, nickel, or cobalt based alloys that are designed to withstand even the most extreme environments [1]. Could these be enough to withstand the Warp that McNeill’s starships must endure? While we can’t know for certain, we do know that researchers are constantly on the hunt for metal alloys that can withstand more and more extreme environments.

However, when we start alloying metals together, the new material could be made of new phases, or arrangement of the metal atoms. Not all of these phases come with favorable properties. Iron, the base for steel alloys, has a tendency to become very brittle when it’s alloyed with different metals. Striking the right balance is what gives us materials like carbon steel and stainless steel. Get off balance and the results are disastrous.

Overcoming Compositional Issues through Processing

That leads to the questions of how can we overcome these compositional issues. I’ve discussed alloying, where the mixing of materials occurs at the atomic level, but what about macroscopic ways of combining material. In the inaugural Project Starship article, Graham McNeill brought up the importance of his starships to be able to withstand travel through the Warp. He approached this through a materials selection lens but I invite you to also think about it from a materials construction lens.

Traditional methods of combining metals, like welding, have been used for centuries and are very robust. They are used to connect metal components for all sorts of applications, from stair railings to spaceships. We can’t deny that they are well-studied and well-executed process. However, nothing is perfect. Any sort of join, especially abrupt ones, like a weld, can produce weak spots where materials can fail. For starships, the last thing we’d want is to have a catastrophic failure as enemy fleets are descending upon the ship.

These are all questions that metallurgists are asking themselves in the wake of emerging technology. Additive manufacturing, or 3D printing, opened up the door to a whole new way of processing materials in general, but also metals specifically. 3D printing allows us to create components layer by layer, with layers as small as 0.1 micrometers thick. To put that in perspective, that is about the thickness of human hair. We can create complex shapes that come out from the printer nearly ready to go. I am already imagining how just this aspect of the technology would be game-changing for starship design. No longer bound by the limitations of subtractive machining, starships could include any number of complex designs that have already been imagined by authors but could now become reality.

Beyond the shaping capabilities of 3D printing, there’s another aspect that is of interest for starship design—small scale changes in chemistry over a longer length scale. This gradient like change in composition opens up a wide array of possibilities for joining materials over longer length scales with the specific goal of avoiding some of the issues that crop up with welding and other traditional joining methods. That is not to say that this method is without flaws. Part of the research in this field is all about planning pathways to jump between materials without encountering those undesirable phases discussed earlier [2]. Ongoing research is working towards using fundamental scientific principles to better understand these pathways and enable continued innovation in this field.

3D printing also allows us to combine materials with different properties to create components that have different properties at different locations. For example, we could have a material that is particularly corrosion resistant in a location that’s continuously exposed to extreme environments and another part that has a low coefficient of thermal expansion in a location that cycles through large temperature changes.

Looking to the Future

So where does this leave us? While it may seem like some of these starship designs are lightyears off, in reality, the innovation toward novel materials is well underway. Metallurgy is an ancient art but also a novel science. This field of functionally graded materials is still new, but research is ever evolving. I imagine that with time it would reach the capabilities to be able to spatially tailor exact properties for specific locations within the 3D printed part. Combining this processing technology with that of alloy development opens the door for the innovative materials and designs that are assumed to be the stuff of dreams in science fiction.

This article was first published in Grimdark Magazine Issue #42

References

[1] Jr., William D. C., David Rethwisch. Materials Science and Engineering: An Introduction, 10th Edition. Wiley, 2018.

[2] Bobbio, L. D., Bocklund, B., Simsek, E., Ott, R. T., Kramer, M. J., Liu, Z. K., & Beese, A. M. (2022). Design of an additively manufactured functionally graded material of 316 stainless steel and Ti-6Al-4V with Ni-20Cr, Cr, and V intermediate compositions. Additive Manufacturing, 51, 102649. https://doi.org/10.1016/J.ADDMA.2022.102649

 

 

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