In order for the Hubble Space Telescope to take incredible, never-seen-before shots of celestial bodies and then send them back to Earth, the spacecraft needs power. While in orbit, Hubble cannot plug into an electrical outlet or stop at a store for some batteries. One of the ways NASA supplies power aboard a spacecraft is by harnessing energy from the most powerful entity in the solar system: the Sun. Since the 1960s, photovoltaic technology, or technology that converts sunlight into electricity, has been instrumental in the exploration of space.
To build upon existing photovoltaic technology, NASA’s Glenn Research Center has worked on a variety of innovative designs and materials to incorporate into photovoltaic cells, the building blocks of solar power systems. One of these materials is the carbon nanotube—a tiny structure about 50,000 times finer than the average human hair, with notably high electrical and thermal conductivity and an extreme amount of mechanical strength. Such properties give carbon nanotubes great potential to enhance the reliability of power generation and storage devices in space and on Earth.
Dennis J. Flood, the branch chief of the photovoltaic division at Glenn in the 1990s, was looking into using carbon nanotubes to improve the efficiency of solar cells when he ran into a major roadblock—high-quality carbon nanotubes were not readily available. To address this problem, one of the chemists in Flood’s group came up with a process and system for growing them.
A senior chemist at Glenn, Aloysius F. Hepp, devised an injection chemical vapor deposition process using a specific organometallic catalyst in a two-zone furnace. Hepp’s group found the unique process produced highquality carbon nanotubes with less than 5 percent metal impurity. In addition, the process was more efficient than existing techniques, as it eliminated pre-patterning of the substrate used for growing the nanotubes, a timely and cost-prohibitive step.
Because Glenn was more interested in the photovoltaic technology that could benefit from the incorporation of carbon nanotubes, and not in the actual production of the carbon nanotubes themselves, the Center released the technology to the inventors—Hepp and fellow researcher Jerry Harris, associate professor of chemistry at Northwest Nazarene University—in 2005. By that time, Flood had retired from NASA, and he and his son, Dennis M. Flood, founded Nanotech Innovations in Oberlin, Ohio. They filed a full patent application, and in 2010, Nanotech Innovations was awarded a patent for the process and apparatus to grow high-quality, low-impurity carbon nanotubes.
For several years, the company has focused on improvement. Now a portable, bench-top system, the technology can make research-scale quantities of high-quality nanotubes within just a few hours. Called the SSP-354, one of the major advantages of the NASA-derived technology is that it is a single-step process. Most processes for growing carbon nanotubes require at least a two-step process, explains the younger Flood, but the SSP-354 does not require catalyst pre-deposition or expensive substrate preparation. The user simply loads the injector and presses “Start.”