Mastering the intricacies of controlling matter at the nanoscale level is part of a revolutionary quest to apply nanotechnology to benefit industrial processes. A key element of that technology is the use of carbon nanotubes.
Carbon nanotubes are small hollow tubes with diameters of 0.7 to 50 nanometers and lengths generally in the tens of microns. While ultra-small, carbon nanotubes offer big-time attributes.
For instance, materials can be manufactured that exhibit superior strength but are still extremely lightweight. Think in terms of 200 times the strength and five times the elasticity of steel. For good measure, add in that they offer highly-efficient electrical and thermal conductivity.
A carbon nanotube Composite Overwrap Pressure Vessel (COPV) is to fly this month as part of the SubTec-7 mission using a 56-foot tall Black Brant IX rocket launched from NASA’s Wallops Flight Facility in Virginia. Shown here is the SubTec7 payload undergoing final testing and evaluation at Wallops Flight Facility. Credits: NASA/Berit Bland
Reduce mass, improve performance
No wonder then that NASA’s Space Technology Mission Directorate (STMD) is keenly interested in nanotechnology – an approach that can reduce the mass and improve the performance of aerospace systems.
For example, NASA computer modeling analysis has shown that composites using carbon nanotube reinforcements could lead to a 30 percent reduction in the total mass of a launch vehicle.
“No single technology would have that much of an impact to reduce the mass of a launch vehicle by that much,” explains Michael Meador, Program Element Manager for Lightweight Materials and Manufacturing at NASA’s Glenn Research Center in Cleveland, Ohio. “I’m not trying to be cliché, but that is a game changer!”
NASA worked with industry partner, Nanocomp of Merrimack, New Hampshire to produce carbon nanotube (CNT) fibers to fabricate a carbon nanotube Composite Overwrap Pressure Vessel. Credits: Nanocomp
Soon-to-fly hardware will test the tensile properties of a carbon nanotube fiber-based composite tank over that of conventional carbon fiber epoxy composites. A Composite Overwrapped Pressure Vessel – COPV for short – will take to the skies aboard a sounding rocket launched from NASA’s Wallops Flight Facility in Virginia on May 16.
“We’re going to use the COPV as part of a cold-gas thruster system,” Meador explains, noting that this involves moving the rocket’s payload during its flight, as well as spinning up the payload to improve the rocket’s aerodynamics during its descent to Earth. “We are one experiment in that payload, but it’s a pioneering flight. This is first time that carbon nanotube-based composites have been flight-tested in a structural component,” he said.
Tensile strength tests were performed in advanced of the flight test to help engineers predict the loads the article could experience before failing.
The COPV project has involved several NASA centers – Glenn Research Center, Langley Research Center, the Marshall Space Flight Center – as well as industry.
NASA collaborated with Nanocomp in Merrimack, New Hampshire to make nanotube yarns and sheets, with the space agency developing specialized processing methods to fabricate COPVs.
“We were interested not just in developing high-strength composites from carbon nanotube yarns but also in demonstrating their performance by building an actual component and flight testing it,” Meador adds. “The COPV flight test will go a long way in showing that these materials are ready for use in future NASA missions.”
A demonstration flight article is wound with carbon nanotube composites.
The suborbital rocket flight of a COPV is a first step, explains Emilie Siochi, a research materials engineer at NASA’s Langley Research Center in Hampton, Virginia. “This COPV represents the first large item that we’ve built” by turning nanotube yarns into composites. Early on at the start of the initiative, she says carbon nanotube fiber material was only available in small quantities. That needed to change.
“We had to improve the properties, improve the quality and the quantity,” Siochi points out. The NASA-industry relationship was invaluable to scale up the material for space agency use, she says, and qualifying the COPV for a flight test has assisted in maturing the technology too.
“There’s potential for the structural properties of carbon nanotubes to be much stronger than carbon fiber composites, now the state of the art for structural material,” Siochi says. “So if it’s stronger, we’ll be able to build lighter structures needed for access to space.”
COPV tank snug inside sounding rocket. Credits: NASA
Meador sees a bright and long-lasting future for carbon nanotube materials.
“When we first started to get into nanotechnology research we were looking at where did it make sense for NASA to invest…where could a huge payoff be for the agency, be it in weight savings, performance, or reduced power consumption,” Meador suggests.
There’s more work to be done in terms of improving the material’s mechanical properties, as well as fabricating the yarn fiber in quantities to make it competitive with conventional carbon fiber.
“There’s a big payoff, not just for aerospace applications,” Meador observes. Use of carbon nanotube materials, say in cutting down the weight of ground transportation vehicles, could lead to a huge savings from less fuel consumption and also lessening carbon dioxide emissions. Likewise, the insertion of the technology into aircraft is another area that deserves further attention, he adds.
“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,” Meador concludes. “And that’s what it’s all about. Seeing how you can control and exploit those properties.”
For more information on NASA’s work in nanotechnology, see this episode of NASA EDGE about how this technology is being used in sensors and various materials:
Loura Hall on June 13, 2017