Aerospace Explores Nanotube Applications for Space
The Aerospace Corporation is pioneering space applications for an exciting new technology that holds the potential to revolutionize several industries.
Carbon nanotubes, commonly referred to as CNT, are cylindrical carbon forms that are one of the strongest materials found on Earth. They also have exceptional electrical, mechanical, thermal, and optical properties that make them highly anticipated and valuable, said Dr. Don Walker, senior member of the technical staff, Energy Devices, Energy Technology.
“All CNTs are not alike,” he said. “They can be multi-walled or single-walled. They can be metals or semiconductors. They are stronger than steel and more thermally conductive than copper. They have all the great properties.”
“It is that magical; it’s a wonder material,” he added.
Currently, nanotubes are used in some clothing and as a composite material (mostly carbon fiber) to help strengthen marine paint, wind turbines, and sports gear, like skis, ice hockey sticks, surfboards, hunting arrows, bicycles and baseball bats. Nanotubes are expected to make an appearance within electrical circuits, electrical cables and wiring, actuators, within radar absorption equipment, telescopes, a broader expanse of textiles, the medical field, speakers and headphones, ultra capacitors, solar cells and hydrogen storage for future fuel use.
Aerospace’s interest in the technology centers around the potential for use as a coating for the solar panels that help protect and power space vehicles, Walker said.
“These are a big deal,” Walker said. “They are thin, conductive and flexible. Because it is so pervasive, we can use them in almost all spacecraft technology.”
The group’s goal is to find a way to use nanotube technology successfully as a stronger, lighter conductive coating for solar panels, allowing the panels to be thinner, lighter, stronger, and flexible, while still protecting the panels against electrical arcs that can render them inoperable. The coating that spacefaring solar panels currently use darkens with time and exposure to radiation, hindering the performance of the solar cells.
The Aerospace team exposed the nanotubes to radiation to test how much or how quickly they would darken when exposed to the sun’s radiation in space. Not only did they learn the nanotubes will not darken, but they also stumbled upon an unexpected problem.
The radiation forced the semiconducting CNT material to switch from being conductive to ten times more resistive. The semiconducting CNTs nanotubes will be one way on Earth, and become the opposite once in space. The metallic CNTs remained roughly the same conductivity.
“These are extremely sensitive to the chemical environment,” Walker said. “Much of our own common knowledge is based on how these react in an oxygen-rich environment. What is true here on earth won’t be true in space. The requirements in space are different than here on Earth.”
The team is also working to mitigate two other issues, both of which resulted from attempts to use nanotubes in bulk.
The nanotubes’ recorded strength properties are from tests done on single tubes. Much of the strength is lost when the tubes touch, and there is a resistance to conductivity where they are joined.
“What we have to try to do here is discover how we can bridge from nano scale to bulk scale,” Walker said. “We need to understand the differences in behavior in space and figure out how to eliminate these problems.”