Some have dubbed NASA’s CubeSats "nanosatellites" because of their relatively small dimensions that are based on the size of a Beanie Baby box one of their inventors found in a store. The CubeSats are small, weighing in at just 1 to 10 kilograms, but they’re not nanoscale small.
While the CubeSats are not going to be shrunk down to the nanoscale any time soon, they now at least contain some nanotechnology. For the first time, researchers at NASA’s Goddard Space Flight Center have used carbon nanotubes in an epoxy resin to fabricate a mirror for a lightweight telescope on a CubeSat.
“No one has been able to make a mirror using a carbon-nanotube resin,” said Peter Chen, a Goddard contractor and president of Lightweight Telescopes, Inc., that is working with the team to create the CubeSat-compatible telescope, in a press release.
“This is a unique technology currently available only at Goddard,” he continued. “The technology is too new to fly in space, and first must go through the various levels of technological advancement.”
If the carbon nanotube-enabled telescope does make it to space, it will be part of an optical system consisting of three commercially available, miniaturized spectrometers optimized for the ultraviolet, visible, and near-infrared wavelength bands.
In the prototype the researchers have fabricated, the spectrometers are connected via fiber optic cables to the focused beam of a three-inch diameter carbon-nanotube mirror.
The use of a carbon-nanotube mirror in a CubeSat telescope provides a number of advantages over traditional materials, like glass or aluminum. Of primary importance is the lightweight nature of the carbon nanotube epoxy resin. However, the researchers also note that the material is highly stable, easily reproducible, and it does not require polishing, which is a time-consuming and expensive process.
To produce the carbon-nanotube mirrors, a mixture of epoxy and carbon nanotubes are poured into a mold that has been designed to impart certain optical properties. The mold is then heated to cure and harden the epoxy. After the epoxy has hardened, the mirror then is coated with a reflective material of aluminum and silicon dioxide.
“After making a specific mandrel or mold, many tens of identical low-mass, highly uniform replicas can be produced at low cost,” Chen said. “Complete telescope assemblies can be made this way, which is the team’s main interest. For the CubeSat program, this capability will enable many spacecraft to be equipped with identical optics and different detectors for a variety of experiments. They also can be flown in swarms and constellations.”
While the initial aim is that this mirror will be used in the small confines of a CubeSat, there is belief among the researchers that it could also be used in large-scale telescopes, such as James Webb Space Telescope’s 6.4 meter primary mirror that will take over in the role that has been held by the Hubble Telescope and which is scheduled to launch in October 2018.
In addition, the carbon nanotube resin can be exposed to an electrical field before curing that will form carbon-nanotube chains and networks. After the curing is completed, it is possible to simply apply power to the mirror and change the shape of the optical surface. This concept, which has been successfully done in the lab, could lead to “smart optic” telescopes in which each mirror segment has a number of externally mounted actuators that deform the mirrors into specific shapes that are needed for the telescope to focus on different points of space.
Chen added: “This technology can potentially enable very large-area technically active optics in space. Applications address everything from astronomy and Earth observing to deep-space communications.”