American and Japanese scientists are preparing to launch the world’s first wooden artificial satellite next summer as an environmentally friendly alternative to the aluminum ones currently circling the Earth. With the number of satellites expected to increase dramatically in the coming years—and more than 100 trillion untracked pieces of old satellites already in orbit—researchers are worried that such debris will soon cause problems for our planet and human-made structures in space.
“We are very concerned with the fact that all the satellites which re-enter the Earth’s atmosphere burn and create tiny alumina particles, which will float in the upper atmosphere for many years,” Takao Doi, a Japanese astronaut and aerospace engineer with Kyoto University, told BBC News’ Justin Harper in 2020. “Eventually, it will affect the environment of the Earth.”
In 2020, a team of Japanese researchers launched the LignoStella Space Wood Project to test the durability of three different types of wood in space: Erman’s birch, Japanese cherry and magnolia bovate. They subjected the samples to exposure tests for more than 290 days on the International Space Station before returning them to Earth earlier this year. The team’s analysis found that despite the harsh conditions of space, the wood samples had no measurable changes in mass and showed no signs of decomposition or damage.
“When you use wood on Earth, you have the problems of burning, rotting and deformation, but in space, you don’t have those problems: There is no oxygen in space, so it doesn’t burn, and no living creatures live in them, so they don’t rot,” Koji Murata, a researcher at Kyoto University, tells CNN’s Rebecca Cairns.
Based on their tests, the team determined that the magnolia wood—or “Hoonoki” in Japanese—would likely make the best material for a satellite based on its “workability, dimensional stability and overall strength,” per a statement from the university.
Wooden satellites could have several advantages over the traditional metal ones. Unlike metal, wood completely burns up when re-entering the Earth’s atmosphere, and it doesn’t release harmful substances or debris in the process. A recent study from the National Oceanic Atmospheric Administration found that aluminum and exotic metals from rockets and satellites are present in about 10 percent of the aerosol particles in the stratosphere. This number could grow to about 50 percent, depending on how many satellites are launched into low Earth orbit, per the paper. Researchers have cautioned that these particles could damage the Earth’s ozone layer.
As of September, about 10,590 satellites were orbiting our planet, with roughly 8,800 of them still functioning. In total, the mass of all space objects in Earth’s orbit adds up to more than 11,000 tons. And that number is only slated to grow—estimates suggest 2,500 satellites will be launched each year on average between now and 2031.
Defunct satellites can pose a major risk to the ones that are still functioning or to spacecraft. In low Earth orbit, the impact speed of orbital debris can reach more than nine miles per second—over ten times as fast as a bullet, per NASA.
Wood may also prove to be an advantageous satellite material choice because electromagnetic waves can penetrate through it, meaning components like antennae could be held inside the satellite body instead of sticking out of it, simplifying the design.
But still, wooden space structures come with lots of unknowns, as Tatsuhito Fujita, an engineer at the Japanese space agency JAXA who has been involved in reviewing the LignoSat project, tells CNN.
“The use of natural resources for space hardware [makes sense] from a sustainable development goals perspective, but since wood has never been used in satellites, we cannot tell what kind of benefit we can obtain at this moment,” Fujita tells the publication.
NASA and JAXA will likely launch the joint LignoSat mission in the summer of 2024. Researchers will monitor the satellite for at least six months to see how it performs.