The BBC reported in 2020 that Japanese firm Sumitomo Forestry had embarked on a joint development project with Kyoto University, Japan, to test using wood to build satellites. Meanwhile, Finnish company Arctic Astronautics is scheduled to launch the first wooden satellite into space in 2022. But what are the potential advantages of wooden satellites? This article explores the novel materials science behind wooden satellite projects around the world.
Standard Cubesats. Image Credit: FoxPictures/Shutterstock.com
First Wooden Satellite in Space
Arctic Astronautics, a Finnish aerospace education company that sends CubeSat satellite kits to students, is testing plywood panels for space exploration with its WISA Woodsat mission.
The company has previously developed a wooden CubeSat which is launched into the outer reaches of Earth’s atmosphere on a weather balloon. However, that mission did not put a wooden satellite in space, as the balloon did not pass the Karman line where the atmosphere is generally accepted to give way to space. The technology developed – and lessons learned – in that mission led to Arctic Astronautics creating the first-ever wooden satellite designed to go to space.
The WISA Woodsat is a nanosatellite, a class of satellites measuring under 10 cm3 and weighing less than 1 kg. This small satellite class now represents the majority of human-made objects in space. The CubeSat standard is a satellite design that can be built with over-the-counter technology and materials, and which can share rides into space with hundreds of other satellites in rocket-pool launches.
The satellite uses a specially coated plywood manufactured by WISA Plywood, an advanced wood products manufacturer headquartered in Lahti, Finland. The mission’s primary purpose is materials science: plywood panels are being tested in the extreme conditions of space to answer questions about how suitable the material is for future extraterrestrial missions.
Arctic Astronautics used regular birch plywood – just like you would find in a hardware store – to construct the satellite’s outer panels. However, untreated plywood is too humid for use in space. The Finnish engineers put the WISA plywood into a thermal vacuum chamber to get as much moisture as possible out of it, first. Then, they added an ultra-thin aluminum oxide layer with atomic layer deposition.
WISA WOODSAT Trailer HD
Video Credit: UPM Plywood/Youtube.com
Aluminum oxide is a chemical compound typically used as a housing material for electronics. In the Woodsat satellite, it will stop the wood from releasing any gases into space as well as protect the surface from exposure to atomic oxygen, a corrosive gas found at the edges of the earth’s atmosphere.
Atomic oxygen was first discovered when it was encountered by NASA’s early Space Shuttle missions. It is formed when strong ultraviolet (UV) radiation from the sun splits regular oxygen molecules, and it was strong enough to damage the thermal blankets of those early NASA missions.
WISA Woodsat will be powered by nine small solar cells. The satellite has two cameras on board, one on a metal selfie stick. The cameras will enable the team to watch how the plywood surfaces on the satellite are affected by the harsh conditions of outer space.
A secondary purpose for the WISA Woodsat mission was to carry an amateur radio payload to let hobbyists relay radio signals and images around the world. However, the authorities recently declined Arctic Astronautics’ request to license an open radio frequency for the mission.
That decision has put the launch date back by a few months. Initially due to launch from Australia on a Rocket Labs rocket in November 2021, engineers have confirmed the launch date will now be some time in early 2022.
Testing Wood for Space
Meanwhile, Japanese forestry company Sumitomo Forestry is working with Kyoto University researchers to test the use of wood in satellite construction. Reports on the new partnership from 2020 quoted plans to put a wooden satellite in space by 2023.
CUTE: Characterizing Exoplanet Atmospheres with CubeSats
The low-tech material is a somewhat surprising candidate for aerospace engineering applications. However, it has excellent low thermal conductivity, meaning its structure is not affected by temperatures between - 150 and 150 °C. It is also not affected by near-vacuum conditions encountered out of planetary atmospheres.
One of the key potential advantages of using wood in satellites is that it does not block the electromagnetic radiation wavelengths used by satellites for communications. Communications signals can pass through the outer panels of a wooden satellite, potentially rendering external antennae useless.
Researchers at Kyoto University’s Biomaterials Design Lab are sending various wood samples to the International Space Station (ISS), where they will be placed outside in space by astronauts working in Japan’s Kibō research module on the ISS.
The ultimate goal for the team, however, is to build a wooden satellite – LignoSat – which is scheduled for launch in 2023.
Are Wooden Satellites a Solution to Space Junk?
Some news outlets have reported that wooden satellites could be a solution to the space junk problem: the more than 3,600 defunct satellites littering Earth’s orbit. Wooden satellites, they claim, would completely burn up upon reentry.
It is unlikely that wooden satellites can present a realistic answer to the space junk problem, however. There are two main reasons for this.
First, wooden satellites will still contain metal and plastic materials: electronics, payloads, and the main structural frame. Detachable rockets and blasters used to get the satellite into orbit in the first place would all continue to create debris in space after they fulfill their use.
Second, if satellites were re-entering the atmosphere then there would not be a problem with space junk cluttering up the low-Earth orbit. Part of the problem with space junk is the difficulty of getting defunct satellites out of orbit and back into the atmosphere. Wooden satellites would still need to come with fuel and motors to get back down to Earth, just like their aluminum counterparts.
References and Further Reading
Harper, J. (2020). Japan developing wooden satellites to cut space junk. BBC. Available at: https://www.bbc.co.uk/news/business-55463366.
Johnston, H. (2020). Wooden satellite to launch in 2023, glowing thread is made from wood. Physics World. Available at: https://physicsworld.com/a/wooden-satellite-to-launch-in-2023-glowing-thread-is-made-from-wood/.
Pilkington, B. (2021). Space Debris: New Technologies to Clean Our Orbit. AZO Quantum. Available at: https://www.azoquantum.com/Article.aspx?ArticleID=224.
Pultarova, T. (2021). The world's first wooden satellite will launch this year. Space.com. Available at: https://www.space.com/first-wooden-satellite-will-launch-in-2021.
Timmer, J. (2020). Coverage of “wooden satellites” misses the point. Ars Technica. Available at: https://arstechnica.com/science/2020/12/wooden-satellites-an-intriguing-idea-but-wont-solve-space-junk-problems/.
WISA Plywood (2021). The launch of WISA Woodsat is delayed due to frequency licensing. WISA Plywood. Available at: https://www.wisaplywood.com/news-and-stories/news/2021/10/the-launch-of-wisa-woodsat-is-delayed-due-to-frequency-licensing/.
Yirka, B. (2020). Japanese pairing looking into using wood to build satellites. Tech Xplore. Available at: https://techxplore.com/news/2020-12-japanese-pairing-wood-satellites.html.