By Felix Schmidt, Application Engineer for Space
All spacecraft must contend with radiation. High-energy, stripped atomic nuclei and particles travelling almost at the speed of light bombard satellites and gradually damage the electronics on which they depend.
Typically, manufacturers use aluminium to protect their spacecraft. Aluminium is a strong, familiar material that does provide some protection. But it isn’t equally good at stopping every form of radiation and it’s relatively heavy: for every kilogram of aluminium added, more fuel is required, and that corresponds to a higher cost for the operator.
At FibreCoat, we’ve decided to approach this problem from a different direction. What if a radiation shield could bring together several materials, each chosen for a different job, into one lightweight composite?
Different particles, different materials
We tend to talk about radiation as if it were one thing. In fact, there are different kinds, and the mix of them changes as the spacecraft’s orbit does.
Electrons, protons and other particles interact with shielding differently: some particles stop; others pass through. Radiation can also produce secondary radiation inside a shield, posing another threat to electronics.
Materials with a high atomic number, such as bismuth, are effective at absorbing X-rays and gamma rays. Materials with a low atomic number, especially hydrogen-rich polymers, can help deal with other particles and some of the secondary radiation generated inside the shield.
Together, these materials can protect against different forms of radiation. The idea is known as *graded-Z shielding*, where ‘Z’ refers to an element’s atomic number. Rather than create the thickest barrier, we aim to put the right material in the right place so that it protects the spacecraft’s electronics against the right kind of radiation – and to do so while keeping the overall structure as light as possible.
How metal-coated fibres make it possible
We developed a process that involves coating each individual glass or basalt filament with a thin, continuous layer of metal. This combines a strong fibre core with the properties of a metal.
These materials can be turned into fabrics, arranged in layers and consolidated into composite plates. Engineers can change the metal, fibre content and layer sequence to suit different missions.
Our proposed radiation shielding material contains BisCoat, our bismuth-coated glass fibre, with a space-grade, high performance polymer, such as PEEK: the bismuth the supplies the high-Z component; the polymer provides a low-Z component and binds the fibres into a solid structure.
The simulations
We’ve been working with LOFITH Composites to manufacture our material. To test the concept, our team modelled radiation in a low-Earth orbit 500 kilometres above Earth, inclined at 30 degrees. SPENVIS described the trapped radiation; GEANT4 calculated the dose reaching a silicon detector behind each shield.
Rather than treating each composite as a single block, the model represented the individual coated filaments and the polymer between them in three dimensions. This was important: how the fibres are arranged affects how particles scatter and where secondary radiation shows up. This also lets us explore changes in fibre content, coating and layer structure.
We compared three options: solid aluminium; aluminium-coated fibres in a polymer composite; and bismuth-coated fibres in a similar composite. And we compared them at four equal mass-per-area values from 5 to 20 kilograms per square metre.
The result for trapped electrons was very encouraging. In the simulations, the bismuth composite achieved the same electron dose with 30 to 40 per cent less shielding mass per unit area than solid aluminium.
For trapped electrons, the material mattered, not just its mass.
What this means
It’s important to acknowledge that these same simulations did not establish an overall mass advantage for the total radiation dose in this orbit. Energetic trapped protons dominated the dose: they passed through the shields, leaving no clear difference in the total dose between the materials.
Good electron shielding does not guarantee good protection against every radiation hazard. The results instead point to environments where electrons are a larger part of the radiation problem, as in medium-Earth orbit, geostationary orbit and the outer radiation belt. Further testing is needed.
In these simulations, we also used a hydrogen-rich polyethylene model in place of PEEK. In later work will use the intended flight material and examine more complex arrangements of layers.
From idea to orbit
A simulation is one thing; space is another.
On 1 October 2026, the LofiCoat PicoSat mission launched on board SpaceX’s Transporter-18 flight. It carries two radiation sensors: one exposed to the surrounding environment; one placed behind a BisCoat shield. Their readings will test the new shield in situ. We expect to see results in the coming months. Next will come more detailed simulations, more precise proton calculations and designs for other orbits.
Our goal, ultimately, is to give spacecraft manufacturers more choice. Metal-coated fibres amount to a highly flexible way to combine strength, useful material properties and radiation protection in one structure. Our first results are encouraging, showing that such fibres have a clear advantage over aluminium against trapped electrons. We’re now working to establish where that advantage can make the biggest difference in space.