Imagination of Lignosat in space / Photo = Kyoto University Space debris, including expired artificial satellites and rocket debris floating in space orbit, exceeds 9,300 tons. As space debris has emerged as a risk factor ahead of the era of full-scale space exploration, wooden satellites are being developed as a replacement. The satellite is scheduled to be launched into space as early as this summer.
Magnolia passes extreme space environment test
Lignosat with satellite equipment inside wood / Photo = Kyoto University According to the scientific community on the 4th, the world’s first wooden satellite, jointly created by the Japan Aerospace Exploration Agency (JAXA) and NASA, is undergoing final durability tests ahead of launch this summer. there is. The research team led by Professor Koji Murata of the Department of Agronomy at Kyoto University joined hands with Japan’s largest timber company, Sumitomo Forestry, and announced the ‘Lignostella Space Wood’ project to create a sustainable satellite using trees in April 2020.
For 290 days from March 2022 to January last year, space exposure experiments were conducted on three types of trees, including magnolia, wild cherry, and birch, at ‘KIBO’, a Japanese experiment module operated on the International Space Station (ISS). did. The biggest key to the experiment was whether it could withstand extreme conditions such as space radiation exposure tests without deformation.
Koichi Wakata, a Japanese astronaut who stayed on the ISS, personally installed trees outside the module and collected data. As a result, the wood specimen did not undergo any deformation such as cracking, bending, peeling, or surface damage, and showed no change in mass even in extreme environments where it was exposed to significant temperature changes in outer space and solar energy particle rays for 10 months.
Among the three types of wood, the tree ultimately selected for satellite production was magnolia. Magnolia was selected as a suitable tree for the wooden satellite project because it is relatively light and has greater stability than other tree species. Kuroda Workshop in Otsu City, Shiga Prefecture, which possesses traditional Japanese construction techniques, participated in the satellite production work. To reduce wood deformation and damage, we applied a traditional method of fixing it without nails or adhesives using irregularities.
The name of the satellite is ‘LignoSat’, and it is a very small satellite (CubeSat) the size of a mug. It is ultra-light, measuring only 10cm in width, length, and height, and weighing only 330g.
Securing sustainability of space development
The reason why satellites made of wood appeared was to ensure the sustainability of space development. More than 9,300 tons of artifacts, including space debris, are floating in Earth’s orbit, including non-operational satellites, fairings and boosters separated from the rocket body or rocket, and broken spacecraft fragments.
Space debris travels at a speed of 7.4 km per second in low-Earth orbit and 3 km per second in geostationary orbit. Because it is faster than a bullet, it can pose a major threat to the Earth and a normally functioning satellite at any time. Space debris is made of shiny metals such as titanium and aluminum and is considered the main culprit of ‘light pollution’, increasing the brightness of the night sky by more than 10%.
Humanity began placing artificial satellites into orbit in the 1950s. As of 2010, up to 100 artificial satellites were launched every year. However, as commercial launches have become more active over the past decade, the number of satellites launched has rapidly increased. In 2021, more than 1,400 satellites were launched into space. Rigrosat the size of a mug. It is ultra-light, measuring only 10cm in width, length, and height, and weighing only 330g. / Photo = Kyoto University Orbiting Now, a website that tracks satellite paths, calculated that the number of satellites reached 8,486 as of August last year. This includes 8,270 low-orbit satellites scheduled to disappear upon re-entry. The scientific community speculates that it may have surpassed 9,000 last month.
It cannot be said that the situation in space is not very serious yet, but it is a problem as the number of satellites launched into space is increasing at a rapid rate. Professor Eloise Marais, who leads the Atmospheric Composition and Air Quality research group at University College London, warned: “The situation in space will get worse over time.”
“The first step to reduce damage caused by space debris”
Wood is more environmentally friendly than the composite alloys used in spacecraft construction, and can be designed to be decomposed or completely burned at the end of its life. Dr. Takao Doi, a former astronaut, said, “There is no need to worry about wood rotting in space, where it does not rain and bugs and bacteria do not multiply. Rather, we expect it to be a better material for future space development.”
Even considering efficiency, there are many opinions that wood is suitable as a space material. Because electromagnetic waves penetrate trees well, the structure and shape of the satellite can be simplified by placing a satellite antenna inside. In general, after a satellite is launched, the antenna is not properly deployed and the entire satellite often becomes disabled. This problem can be avoided if the antenna is installed inside the satellite.
There are other cases in which not only Japan has jumped into the development of wooden satellites. Finnish plywood company WISA is pursuing the ‘Woodsat’ project. It was originally scheduled to head to space for the first time in the world in 2021 aboard the Electron launch vehicle of American launch vehicle company Rocket Lab, but the schedule was delayed.
Lignosat is scheduled to be jointly launched by JAXA and NASA this summer, and if successful, the world’s first wooden satellite will be created. The research team said, “We are also developing technology to allow satellites to self-decompose after their lifespan has ended,” and added, “We hope that satellites made of biodegradable materials will be the first step in reducing damage caused by space debris.” Lignosat case made of wood / Photo = Kyoto University Reporter Kang Gyeong-ju [email protected]
