CSIC Develops Nanoparticle Coating to Protect Satellites from Dangerous Multipactor Effect

Scientists in Spain have developed a breakthrough nanoparticle coating that could significantly improve the reliability of satellite communications while reducing the environmental and health risks associated with existing aerospace materials. The innovation comes from the Spanish National Research Council (CSIC), working alongside its spin-off company Nanostine with support from the European Space Agency (ESA).

The newly developed coating uses gold and silver nanoparticles to combat the multipactor effect, a long-standing challenge in satellite engineering. Laboratory tests indicate the technology outperforms the chromium-based coatings currently used across the aerospace industry, offering a cleaner and more sustainable alternative without sacrificing performance.

The multipactor effect has troubled spacecraft designers for more than four decades. It occurs when electrons multiply rapidly inside vacuum-operated components such as antennas, waveguides and radio-frequency equipment. These electrons repeatedly collide with internal surfaces, creating an avalanche that can eventually disrupt communications or permanently damage critical satellite hardware.

Because satellites operate in the vacuum of space, preventing this phenomenon has been essential for ensuring mission reliability. Even a minor failure within high-frequency communication systems can affect the performance of an entire spacecraft, making effective protective coatings an indispensable part of satellite manufacturing.

For years, the aerospace industry has relied on Alodine, a chromium-based coating that effectively limits secondary electron emissions responsible for triggering the multipactor effect. Despite its proven performance, Alodine presents serious environmental and occupational health concerns due to the presence of chromium compounds, which are considered hazardous.

European regulators have increasingly encouraged the development of safer substitutes, anticipating stricter environmental rules that could eventually phase out chromium-containing materials. However, finding a replacement capable of matching Alodine’s technical capabilities has proven exceptionally difficult.

According to Lidia Martínez, a researcher at CSIC’s Institute of Materials Science of Madrid (ICMM), the challenge lies in reducing the emission of secondary electrons. These electrons fuel the chain reaction that ultimately leads to the multipactor effect.

Previous research largely concentrated on modifying material surfaces at the micrometre scale. Although these approaches produced incremental improvements, they failed to deliver the significant reduction in electron emissions demanded by modern satellite systems.

The CSIC team instead shifted its focus to the nanometre scale, engineering an ultra-fine rough surface that fundamentally changes how electrons interact with the material. This approach represents a significant departure from earlier techniques and takes advantage of the unique physical properties exhibited by structures measuring only billionths of a metre.

Researchers produced gold and silver nanoparticles measuring between four and eight nanometres using an advanced ultra-high-vacuum process known as a gas aggregation source. Unlike many conventional manufacturing methods, this technique deposits nanoparticles without solvents or chemical residues, producing exceptionally clean metallic films.

The resulting coatings form porous metallic layers with highly controlled nanostructures. Their carefully engineered surface reduces the number of secondary electrons generated during operation, directly addressing the root cause of the multipactor effect.

Independent testing at ESA-accredited laboratories produced encouraging results. The nanoparticle coatings reduced secondary electron emissions by approximately 30 percent compared with conventional Alodine coatings, representing a substantial improvement for aerospace applications where every performance gain enhances system reliability.

Researchers also measured the cut-off energy threshold, the point at which a material begins generating more secondary electrons than it receives. Depending on the coating configuration, this threshold improved by as much as 300 percent, suggesting the new material remains stable under considerably more demanding operating conditions.

Durability testing formed another crucial part of the research programme. Satellite materials must withstand prolonged exposure to extreme temperatures, radiation and the harsh conditions of space over many years.

To simulate these challenges, scientists subjected the coatings to thermal treatments reaching 150 degrees Celsius, approximating the temperatures experienced by spacecraft exposed directly to sunlight. Additional ageing tests extended over six months to evaluate long-term performance.

Although the coatings experienced a modest decline in effectiveness after prolonged testing, they continued to outperform freshly applied Alodine. This resilience suggests the nanoparticle films could provide reliable protection throughout extended satellite missions if future qualification programmes confirm the findings.

The technology has already moved beyond laboratory research. CSIC and Nanostine jointly filed a European patent application with the European Patent Office in July 2025, securing intellectual property protection while the application undergoes examination.

Nanostine, a spin-off company established by CSIC, will oversee commercialisation of the technology. The company intends to focus primarily on aerospace customers seeking safer alternatives for satellite communication equipment and other high-frequency space systems.

Development of the coating has received financial support from the Community of Madrid through its Industrial PhD programme. Additional backing came from the ESA Business Innovation Centre, coordinated in Madrid by the Madri+d Foundation, highlighting the collaborative effort between scientific institutions and industry partners.

Despite the promising laboratory performance, researchers caution that introducing new materials into space missions requires extensive validation. Every component used aboard satellites must undergo rigorous qualification procedures to demonstrate consistent performance under launch stresses, radiation exposure and years of operation in orbit.

Martínez noted that the European Space Agency has responded positively to the project’s progress but emphasised that significant work remains before the coating can be incorporated into operational spacecraft.

The qualification process for aerospace materials typically spans close to a decade. Engineers must verify manufacturing consistency, mechanical stability, compatibility with existing satellite components and long-term resistance to the demanding environment encountered beyond Earth’s atmosphere.

If future testing confirms the coating’s current performance, the technology could help eliminate one of the industry’s dependence on hazardous chromium compounds while improving the reliability of satellite communication systems. Such an achievement would represent an important step toward more sustainable aerospace manufacturing without compromising technical performance.

As satellite networks continue expanding to support telecommunications, navigation, Earth observation and scientific exploration, innovations that improve component durability and operational safety are becoming increasingly valuable. The CSIC-Nanostine nanoparticle coating demonstrates how advances in nanotechnology may help solve engineering challenges that have persisted for decades.

While commercial deployment remains several years away, the research marks a significant milestone in the search for environmentally responsible materials capable of meeting the demanding standards of modern space missions. If successfully qualified, the technology could eventually become a new benchmark for protecting next-generation satellites from one of space engineering’s most persistent threats.