The Launching of the World’s First Wooden Satellite Possibly Opens an Era of Sustainable Spacecraft

An unusual collaboration between Kyoto University and Japanese homebuilder Sumitomo Forestry has delivered the world’s first orbital satellite made primarily of wood to the International Space Station, as the focus of an experiment that may herald the end of the use of aluminum as the main ingredient in spacecraft construction. Using such an unconventional material has the goal of improving the ecological sustainability of disposable spacecraft, allowing the organic material of the craft burn up entirely when it eventually re-enters the Earth’s atmosphere, instead of increasing the amount of metal pollutants in the atmosphere that traditional aluminum-built satellites leave behind.

Named using the Latin word for wood, LignoSat2 was launched as part of a cargo delivery mission to the International Space Station on November 5, and will be deployed in orbit from the station for a six-month mission. The miniature cubesat’s goal is to measure how well the wood in its construction withstands the harsh environment of space, where the temperature of an object frequently shifts between 100°C and -100°C (212°F and -148°F) as it passes from day to night over the course of its 90-minute orbit.

Weighing only 900 grams (32 ounces) and measuring 10 centimeters (3.9 inches) on each side, LignoSat2 is made primarily of wood from a magnolia tree native to Japan called hoonoki (Magnolia obovata), and constructed using traditional Japanese methods eschewing glue or screws. Hoonoki was favored as the material of choice after a 10-month experiment conducted aboard the ISS found that it, a wood traditionally used to build katana sheaths, was best suited for spacecraft construction.

While one might assume that a biological material like wood might not be suited to survive in the harsh conditions of space, the airless environment lacks water that would be required for it to rot, and without oxygen the material can’t be burned, even though it is unlikely to reach the 250°C (482°F) required for wood to ignite to begin with.

The concept behind making spacecraft out of wood is to reduce the amount of metallic debris that can pollute the atmosphere when a satellite breaks up during re-entry; aside from the danger posed by components that might be large enough to survive their fiery plunge and impact the surface, aluminum oxide particles that ablate off of metal satellites can linger in the atmosphere long after the rest of the craft has burned up, harming the ozone layer and contributing to a host of health problems for those living on the surface, such as respiratory issues, neurodegenerative disorders and cancer.

Wood, on the other hand, would simply be charred to carbon compounds when exposed to the extreme heat of re-entry, by-products that are far less harmful to the environment and human health. While spacecraft will still require numerous metal-based components, that amount could be dramatically reduced using wood. LignoSat2’s hoonoki will also be evaluated for its ability to protect electronic components from space radiation, as wood is known for its ability to absorb high-energy ionizing x-ray and gamma radiation.

“Satellites that are not made of metal should become mainstream,” according to astronaut Takao Doi, who is a professor at Kyoto University. Doi also speculates that “metal satellites might be banned in the future” if alternative materials prove to be viable for use in spacecraft.

“It may seem outdated, but wood is actually cutting-edge technology as civilisation heads to the moon and Mars,” stated Kenji Kariya, a manager at Sumitomo Forestry Tsukuba Research Institute. “Expansion to space could invigorate the timber industry.”