Hydrogel is something that most of us are familiar with from it being used in contact lenses, burn dressings, and hair gel. In future, it might also be used to shield astronauts from the hazard of deadly cosmic radiation on long space voyages.
One of the major hazards of space travel is prolonged exposure to radiation. Outside of the Earth's atmosphere, an astronaut aboard the International Space Station (ISS) is exposed to about 72 millisieverts (mSv) of cosmic radiation during a six-month tour of duty, or the equivalent to several years of exposure that they'd absorb on Earth.
It's even worse on one of the planned missions to Mars when the interplanetary spacecraft ventures beyond Earth's protective magnetic field. If such a voyage took three years, the crew would take in over 1,000 mSv, which is almost 200 times Earth exposure.
Speed can help to minimize this exposure but the main protection is some kind of shielding that can absorb the radiation before it can do any harm. With its density and abundance of hydrogen atoms, water is particularly effective. Line a spacecraft with tanks of it and that would simplify matters nicely.
The problem is that water is a liquid. That's bad enough when there's gravity but in the weightless conditions of space, water can slosh around as it likes, leaving gaps in the shielding. Worse, water can leak, which can cause all sorts of mischief, from shorting out electrical circuitry to posing the novel threat to astronauts of drowning in deep space.
Based on new research by scientists at the Polymer Chemistry and Biomaterials Group (PBM) at Ghent University in Belgium, one solution is to trap the water inside an advanced super-absorbent polymer (SAP) that soaks up water like nobody's business. Expose it to water and the SAP increases in weight several hundred times as it forms a hydrogel. Form it using 3D printing and you have your radiation shielding.
According to ESA, such a hydrogel would not only act as a shield for spaceships that wouldn't slosh or leak, it could also be used to line spacesuits. This is particularly important because a shielded spacecraft isn't much good once an astronaut leaves it. Shielded suits would allow crews to spend more time on spacewalks or planetary EVAs. Even if the suit was punctured, the hydrogel would remain in place, allowing the wearer time to reach safety. It might even, conceivably, be configured to act as a sealant – much like that used in military aircraft fuel tanks.
"There is a constant search for lightweight radiation protection materials," said Peter Dubruel. "In our Discovery activity we successfully demonstrated that hydrogels are safe to use under space conditions. In this follow-up project, we are applying different techniques to shape the material into a 3D structure and scale up the production process, so that we can come a step closer to industrialization."
Source: ESA
