So you think keeping your coffee warm is a challenge? Try working with satellites.
When these man-made objects travel behind the Earth, our planet can block the sun’s rays from reaching them, which cools them down. In space, a satellite can face extreme temperature variation — as much as 190 to 260 degrees Fahrenheit.
Satellites have generally used one of two mechanisms to maintain warmth: physical “shutters” or heat pipes to regulate heat. Both solutions can deplete on-board power reserves. Even with solar power, the output is limited. And both solutions add mass, weight and design complexity to satellites, which are already quite expensive to launch.
Why even think about the subject?
A satellite with a temperature that falls out of optimal range can cause varied disturbances on Earth, from disruptions in tracking wildfires or other natural disasters to interference with a Google Maps app or your next Netflix binge.
In the future, however, those technical difficulties could be prevented with a material developed at the USC Viterbi School of Engineering.
Taking its temperature
Taking cues from humans whose self-contained system manages internal temperature through homeostasis, a USC team developed a new material to self-regulate the temperature of the satellite. The team, which boasts expertise in optics, photonics and thermal engineering, developed a hybrid structure of silicon and vanadium dioxide to better control the radiation from the body of the satellite. The material works like textured skin.
Vanadium dioxide functions like what is known as a “phase-change” material. It acts in two distinct ways: as an insulator at low temperatures and a conductor at high temperatures. This affects how it radiates heat. At over 134 degrees Fahrenheit (330 degrees Kelvin), it radiates as much heat as possible to cool the satellite down. At about two degrees below this, the material shuts off the heat radiation to warm the satellite. The material’s conical structure (almost like a prickly skin) is invisible to the human eye at about less than half the thickness of a single human hair, but it helps the satellite switch its radiation on and off very effectively.
The hybrid material developed by USC and Northrop Grumman is 20 times better in maintaining temperature than silicon alone. And passively regulating the heat and temperature of satellites could increase the life span of the satellites by reducing the need to expend on-board power.
Besides its function on a satellite, the material could also be used for thermal management on Earth. For example, the material could be applied over a large area of a building to more efficiently maintain its temperature.
The USC team included Michelle L. Povinelli, a professor in the Ming Hsieh Department of Electrical Engineering at USC Viterbi, and USC Viterbi students Shao-Hua Wu and Mingkun Chen, along with Michael T. Barako, Vladan Jankovic, Philip W.C. Hon and Luke A. Sweatlock of Northrop Grumman.
The study was published in the journal Optica. The research was funded by Northrop Grumman and the National Science Foundation. The development is part of a thematic research effort among Northrop Grumman, NG Next Basic Research and USC.