Spacecraft made with heat-resistant materials. (Credit: DALL-E)
Spacecraft surfaces can face extreme temperatures exceeding 600°C, whether from intense solar exposure to the sun or from heating when entering Earth’s atmosphere. Managing these extreme temperatures is crucial to protecting a spacecraft’s interior while preventing its outer “shell” from damage.
However, it remains to be a challenge for scientists to develop materials or coatings that can withstand extreme heat and the harsh environment of space while continuing to function without breaking down.
Cooling objects in space presents two key challenges. First, without surrounding air, familiar cooling methods such as fans or evaporative cooling do not work, leaving thermal radiation as the primary way to dissipate heat. Second, materials that efficiently emit thermal radiation also tend to efficiently absorb radiation at the same wavelengths, making it difficult to control radiative heat flow. To overcome this limitation, scientists are exploring “asymmetric” materials — structures designed to emit more thermal radiation on one side than the other.
Imagine a highly efficient structure that can dump heat by releasing infrared radiation into space, while limiting the amount of external thermal radiation emitted toward the spacecraft’s interior.
Today, scientists are still working to develop coating materials that can achieve this type of thermal asymmetry while remaining chemically stable at high temperatures and simple enough to manufacture across the large surfaces of a spacecraft.
USC engineers Michelle Povinelli and Jayakanth Ravichandran teamed up to tackle this challenge in a recent study.
They aimed to design a coating that can withstand extreme heat while precisely controlling thermal emissivity, offering a new approach to a longstanding problem with potential applications in spacecraft technology.
Launched in 2023, the research project resulted in a paper titled “High temperature oxide multilayers for broadband asymmetric thermal emission,” recently published in Optical Materials Express.
Michelle Povinelli is a Dean’s Professor and professor of electrical and computer engineering and vice chair of USC Viterbi School of Engineering and the USC Mark and Mary Stevens School of Computing and AI’s Ming Hsieh Department of Electrical and Computer Engineering (ECE).
Ravichandran is the Philip and Cayley MacDonald Endowed Early Career Chair and professor of chemical engineering and materials science and electrical and computer engineering. He holds joint appointments in both ECE and USC Viterbi’s Mork Family Department of Chemical Engineering and Materials Science.
Checking All the Boxes that Meets the Demands of Space
To create the coating, Povinelli’s team needed materials that could achieve asymmetric thermal emissivity when arranged in layers to control how heat is emitted from the coating’s two faces.
But optical performance was only part of the challenge. The researchers also had to consider whether each material—and the layers together—would remain chemically and thermally stable at high temperatures. Otherwise, the materials could undergo chemical changes, interdiffuse or crack, compromising the coating’s performance and safety.
Similarly, when stacking materials together, the researchers had to consider how materials in each layer interact with one another, and how well their thermal properties materials match as temperature changes. A material that performs well alone may react with an adjacent layer or generate damaging stress when the structure is heated. Materials such as gold, for example, can withstand high temperatures but may become unstable under extreme conditions.
The team also sought a coating that was thin, structurally simple, and potentially practical to manufacture across large surfaces. Some advanced nanophotonic designs, such as photonic crystals, rely on lithographic patterning to create intricate micro- or nanoscale features. These processes often require cleanroom equipment and multiple fabrication steps, making them expensive, time-consuming, and difficult to scale to large areas. In contrast, the proposed coating consists of unpatterned planar layers and therefore does not require lithographic patterning.
One-Way Heat Valve: Dumping Heat Into Space
The team identified a promising material system that checks all the boxes: a pairing of calcium zirconate (CZO) and strontium ruthenate (SRO) designed to radiate heat efficiently into space while limiting heat transfer toward the interior of the spacecraft.
Complementary experimental evidence suggests that the coating could withstand temperatures exceeding 600°C.
By arranging the two compounds into a multilayer structure, the researchers created a “one-way” heat radiator. CZO serves as the outward-facing layer, using its antireflective properties to efficiently emit heat into space. SRO, meanwhile, forms the inward-facing side, limiting heat from radiating toward the spacecraft’s interior.
The two materials are also expected to be compatible at high temperatures, expanding and contracting at similar rates and helping prevent the coating from cracking or peeling. Both are heat-resistant oxides that remain stable without diffusing into surrounding layers, allowing the coating to maintain its structure and function under extreme conditions.
At only about 2.1 micrometers thick, thinner than the width of a hair, the coating is also ultrathin and lightweight, addressing a key limitation of traditional, bulkier thermal-control materials. The design could potentially be manufactured across the large surfaces of a spacecraft.
The researchers recently presented their work at the Air Force Office of Scientific Research (AFOSR) and NASA Thermal Radiation Mitigation Review in Arlington, Virginia.
Published on September 25th, 2026
Last updated on September 28th, 2026