A device that will absorb wasted heat from space equipment and reflected sunlight and convert it into an energy source for spacecrafts and Mars rovers is being developed for the U.S. Air Force by a Northeastern University researcher.
“Even if it can supply only 10% to 15% of backup energy to the electronics, we can extend the lifetime of both electronics and a spacecraft,” says Yi Zheng, an associate professor of mechanical and industrial engineering and the director of Nano Energy Laboratory at Northeastern.
Zheng will work on the thermal device in collaboration with Faraday Technology Inc., an Ohio-based company that specializes in developing applied electrochemical engineering technology for the U.S. government and commercial clients.
“Our goal is to design a high-performance thermal absorber and thermal emitter that can absorb, convert and emit the energy at the desired wavelength,” Zheng says.
This technology will be suitable for short- and long-term space travel, he says, including use on the moon, Mars or even satellites launched out of our galaxy.
In the past few years, Zheng has been developing materials to harvest and store energy, waste energy and nanoengineered materials.
The primary source of energy in space, he says, is usually the sun — high-performance solar panels convert sunlight into energy to power space equipment.
Zheng’s energy source will use the waste heat generated by space equipment that otherwise is dissipated further into space, as well as sunlight that does not reach the Earth and is reflected by the atmosphere.
Spacecrafts and space equipment, Zheng says, have to operate in extreme conditions — really low temperatures (usually minus 454 Fahrenheit; or minus 270 Celsius) and nearly total vacuum. In addition, driving space vehicles requires energy resources.
“We cannot simply launch another tank of oxygen [for example] to the traveling equipment,” Zheng says.
Electronics operating on board a spacecraft or high-temperature surfaces, Zheng says, will produce thermal radiation, or infrared light, which is invisible to the eye but can be detected as a sensation of warmth on the skin. This heat will be dissipated in space and be lost.
Waste heat exists almost everywhere, Zheng says, including Earth. For example, a hot engine or a furnace heated to a high temperature dissipates some of that temperature as well.
Recovery of that energy has been studied for the past few decades, Zheng says, and his team will apply recently developed technologies in designing their thermal system.
First, they will test various human-engineered materials and surfaces — called metamaterials and metasurfaces, respectively — for the proposed thermal absorber. Metamaterials possess some properties that are not observed in natural materials. They do not exist naturally on Earth, Zheng says, and, therefore, have to be synthesized or nanomanufacturerd in the lab.
The problem with common materials, he says, is that they do not have high-absorbance or emittance properties at the desired wavelengths of infrared energy. Zheng says the wavelength of infrared light is about 1.5 to 2.5 micrometers, which is about 12-24 times smaller than the diameter of a human hair.
“So that requires some theoretical and experimental work from our group,” he says. “Actually, my research interests are focused on active and the dynamic tuning of thermal, radiative and optical properties [of materials].”
“Also, we have to balance the weight and the cost as well,” Zheng says. “We have to balance a lot of stuff. So, considering the limited selection of materials for outer space use, that kind of pushed us to think of and adopt nanotechnology to design functional materials as a thermal device.”
Even though nanotechnologies or nanomaterials are expensive, he says, they work remarkably well. Without nanotechnology, it is impossible to absorb specific wavelengths under the extreme conditions.
To fabricate nanomaterials, Zheng says, scientists use refractory, or thermally resistant materials that are stable and have a high melting point of over 2,700 degrees (or 1,500 Celsius) and a long lifetime.
One good candidate is tungsten, Zheng says, a rare metal with the highest melting and boiling points of known elements on Earth. He wouldn’t rely on this material alone, but in combination with other materials it could be useful in the extreme conditions of space.
Zheng is spending this summer as a NASA faculty fellow at Glenn Research Center in Cleveland. He’s doing research on thermal management for the Artemis campaign that aims to return Americans to the moon in preparation of the first manned mission to Mars.
“I really hope what I’m doing for both the Air Force and NASA can contribute, actually, to the future projects for longer outer-space traveling,” Zheng says.
Written by Alena Kuzub.
