When the European Space Agency (ESA) designed a spacecraft to fly closer to the sun than any other probe in history, it faced a major problem: how to shield the probe from extreme heat and radiation.
A joint mission with NASA, the Solar Orbiter launched in February 2020 and recently emerged from its first pass behind the sun. It has to be able to withstand temperatures hot enough to melt lead, as well as 13 times the radiation that reaches the Earth’s surface.
At first, the agency looked for conventional solutions, based on metals and carbon fiber, but they were not good enough, Cesar Garcia Marirrodriga, ESA’s project manager for Solar Orbiter, said Instead, the agency found the answer in a material that dates back to the Stone Age. An ancient pigment.
After ESA put out an invitation for solutions, it was approached by Irish biotechnology company ENBIO. It had developed a technique to apply synthetic bone coatings to orthopedic and dental implants, to make them more easily accepted by a patient’s body. Because the technique reduced weight and prevented issues like flaking, ENBIO thought it could be useful for the titanium surfaces of Solar Orbiter.
But the synthetic bone was light-colored and testing showed that it would darken after prolonged exposure to sunlight, changing the amount of heat it absorbed and reflected. A black coating meant its properties would be stable for the whole mission, absorbing the sun’s energy as heat and then dumping that into space.