Specialty Coating Systems (SCS) presents an insightful overview of how its Parylene conformal coatings are essential in safeguarding the electronics aboard the Hayabusa2 unmanned spacecraft.
The Hayabusa2 Mission: A Journey to the Stars
Launched in December 2014 by the Japan Aerospace Exploration Agency (JAXA) from the tanegashima Space Center, the Hayabusa2 spacecraft embarked on an enterprising mission. Its objective was to reach the asteroid Ryugu, gather samples from both its surface and interior, and return these samples to Earth for analysis.
Milestones in Space Exploration
After a successful launch,Hayabusa2 traveled for three and a half years,arriving at Ryugu’s orbit in June 2018,approximately 180 million miles (290,000 km) from earth. The spacecraft conducted detailed studies and mapping of Ryugu’s surface from a distance of around 12 miles (20 km). In February 2019, it achieved its first touchdown to collect surface samples, followed by a second touchdown five months later, which allowed for the extraction of material from deeper layers of the asteroid. Despite the asteroid’s surface being weathered by solar radiation since the formation of the solar system, the subsurface samples remain pristine and are anticipated to yield crucial insights into the solar system’s origins. A capsule containing these samples successfully returned to Earth in December 2020. Hayabusa2 is now on an extended mission, set to observe exoplanets and rendezvous with another asteroid in 2031.
Protecting Electronics with Parylene Coatings
Inside the Hayabusa2 spacecraft are 20 circuit boards that support its digital and analog cameras. These circuit boards are coated with SCS Parylene conformal coatings, which shield them from the harsh environmental conditions encountered during launch, travel, and operation, including atmospheric pressure fluctuations, metallic whiskers, and outgassing.
The Advantages of Parylene Coatings
While atmospheric pressure changes during launch can be detrimental to many coatings, Parylene coatings are applied in a vacuum as a gas, eliminating voids that could allow air to infiltrate and create failure pathways. This unique application method ensures robust protection for the electronics.
Even though metal plating is considered more environmentally friendly than lead, it is indeed prone to forming whiskers due to mechanical and thermal stresses. These whiskers, typically measuring one millimeter or less, can lead to electrical arcing, short circuits, and contamination that disrupts electronic systems.While no definitive method exists to prevent whisker formation on metal surfaces, Parylene coatings have demonstrated effectiveness in mitigating this issue. Their conformal nature ensures uniform thickness across all surfaces, providing comprehensive protection against whiskers, which is vital for space applications. Manufacturers in the aerospace sector frequently choose SCS Parylene C and Parylene HT for their ability to reduce whisker formation and enhance component reliability.
Addressing Outgassing Challenges
Outgassing, the release of gases from materials, poses significant challenges for space applications, as these gases can coat sensitive electronics, leading to degradation and failure. Thus, coatings must not only protect the substrate but also avoid causing harm to other instruments. It is essential to use materials classified as low outgassing.
Standards for Low Outgassing Materials
the Jet Propulsion Laboratory in the United States has established criteria for determining a material’s suitability for space use, which can be found at outgassing.nasa.gov. To qualify as low outgassing, materials must meet two key criteria: a maximum total mass loss (TML) of 1.0 percent and a maximum collected volatile condensable material (CVCM) of 0.10 percent. Parylene C, along with its proprietary adhesion promotion systems (AdPro Plus, AdPro Poly), and Parylene HT, have been rigorously tested and have consistently met these stringent standards, confirming their classification as low outgassing materials.
Conclusion: A Partnership in Space Exploration
SCS is honored to have been chosen to supply Parylene conformal coatings for the Hayabusa2 mission, contributing to the exploration of the asteroid Ryugu. The low outgassing properties of Parylene coatings can considerably enhance the reliability of components during atmospheric pressure variations while effectively suppressing metallic whiskers. Additionally, these ultra-lightweight, uniform, and pinhole-free coatings offer extraordinary barrier properties, ensuring optimal performance in the most challenging environments.
