NASA’s Space Technology Mission Directorate (STMD) has begun tests with a carbon nanotube-based Composite Overwrap Pressure Vessel (COPV), which uses a form of nanotechnology that can reduce the mass and improve the performance of aerospace systems.
Carbon nanotubes are small hollow tubes with diameters of 0.7 to 40 nanometres, and lengths generally in the tens of microns.
Despite being ultra-small, carbon nanotubes can offer major benefits, as materials manufactured from it can exhibit superior strength while also being extremely lightweight.
Carbon nanotubes can be up to 200 times stronger and have five times the elasticity of steel, while also offering highly efficient electrical and thermal conductivity.
NASA computer modelling analysis has shown that composites using carbon nanotube reinforcements could lead to a 30 per cent reduction in the total mass of a launch vehicle.
Michael Meador, Programme Element Manager for Lightweight Materials and Manufacturing at NASA’s Glenn Research Facility, said: “No single technology would have that much of an impact to reduce the mass of a launch vehicle by that much. I’m not trying to be cliché, but that is a game-changer. We’re going to use the COPV part of a cold-gas thruster system. We are one experiment in that payload, but it’s a pioneering flight. This is the first time that carbon nanotube-based composites have been tested in a structural component.”
NASA has collaborated with Nanocomp in New Hampshire to make nanotube yarns and sheets, with the space agency developing specialised processing methods to fabricate COPV’s.
Meador said: “We were not just interested in developing high-strength composites from carbon nanotubes yarns, but also in demonstrating their performance by building an actual component and flight testing it. The COPV flight will go a long way in showing that these materials are ready for use in future NASA missions.”
Emilie Siochi, a Research Materials Engineer at NASA’s Langley Research Centre, said: “This COPV represents the first large item we’ve built by turning nanotube components into yarn. We’ve had to improve the properties, improve the quantity and the quality. There’s potential for the structural properties of carbon nanotubes to be much stronger than carbon fibre composites, which is now state of the art for structural material. So if it’s stronger, we’ll be able to build lighter structures needed for access to space.”
However, there is still more to be done in terms of improving the material’s mechanical properties, as well as fabricating the yarn fibre in quantities to make it competitive with conventional carbon fibre.
Outside of aerospace applications, the use of carbon nanotube materials to cut down the weight of ground transportation vehicles could lead to huge savings from less fuel consumption while also lessening carbon dioxide emissions.
Meador concluded: “We’re not looking at magic materials. Rather, we’re finding that when you get down to the nanoscale, there are certain features of materials at that scale that give rise to new properties, new physics that you don’t see above that scale, and that’s what it’s all about, seeing how you can control and exploit these properties.”