Before the end of the year, two different groups from two different countries hope to launch extremely unusual but space-like experiments. These experiments (and I can’t believe I’m writing this) will test to see if wood works as a structural component of satellites.
Yes, wood. Like, from the trees.
I admit to being skeptical, this will work, but both ideas are pretty interesting, and if they do, it could change the way some satellites are made.
One group is from Kyoto University in Japan. Scientists from its Biomaterials Design Laboratory will launch a variety of special wood samples at the International Space Station sometime this year. The Japanese module from Kibo to ISS has a facility where the experiments are located out the station, exposed to space, and the samples (in a metal frame of approximately 10 x 10 centimeters) will be placed there for testing.
They will be exposed to the wide range of space temperatures, cosmic radiation, and probably most importantly, atomic oxygen. Ultraviolet light from the Sun breaks down oxygen molecules in our atmosphere, creating independent oxygen atoms around the Earth’s lower orbit. These atoms are very reactive (which, to be fair, is partly why we breathe oxygen) and can corrode equipment in space. It is not clear how the wood will react over time, so tests are being done.
The experiment is expected to last about six months, after which the board will be returned to Earth for study. The big question is almost what would you say: to what extent does the wood withstand the extreme conditions of space? Does it change its structure or its mechanical strength?
The second group does it even further. Coming from Finland, they build a wooden satellite to see how it stays in space and wait to launch it before the end of the year.
It is called Woodsat and is based on a standard Cubesat design: these are small nanosatellites measuring only 10 x 10 x 10 cm. You can grab one in the palm of your hand. In this case, however, instead of the usual metal structure, the exterior is almost entirely made of wood. Plywood and birch specifically. The only metal on the outside will be rails along the edges of the face needed to deploy it into space.
Oh, and a selfie stick, so you can take photos to send to Earth to study (ultraviolet light from the Sun can alter and darken wood chemically).
On board this small satellite will be a handful of small experiments. One of them is a thermoplastic (plastic that can be melted and molded) called PEEK (for polyether ether ketone) that can be used as a printable electrical conductor to supply energy; in this case, it will power a small LED that can light up as proof that the circuit is working and a detector that detects when the LED is on.
Another is a microbalance that will be able to detect incredibly small amounts of material that can be deposited on it from on-board electronics and wood. The third is a pressure sensor that will measure the amount of gas in the satellite shortly after launch.
The latter two are quite important. My skepticism about the use of wood is not only for structural or mechanical issues, but also for excess wood. The trapped gas is released over time even here on Earth; in space, this process will be even stronger and, if so, it coats sensitive devices or optics with debris that could damage them or be deadly to them. It could also reduce electronics.
I remember when a camera I installed on Hubble was installed in 1997, we had to wait a couple of weeks even to turn on the detectors. It used a very high voltage and the residual air coming from the space shuttle could cause a short circuit. At first, the internal pressure exploded most of the gas in the chamber when exposed to the vacuum, but when the pressure was extremely low (although it was still too high for safety), we had to wait while the atoms individuals bounced randomly enough to leave. the camera.
So it doesn’t rub with the wear and tear of the wood and I’m glad to see they have sensors on board to measure it.
To test this, the Finnish group dried some wood to the maximum in a thermal vacuum chamber, a tank from which they could remove air and heat the wood inside. They also deposited an extremely thin layer of aluminum on the wood to protect it, and then beat it with atomic oxygen to see how it held up. According to their tests, they think the wood in orbit should hold up well.
If that works, it could be quite interesting. For example, the metal walls of satellites are excellent, but when impacted by high-energy radiation from the Sun, they can expel secondary subatomic particles at high speed, such as shrapnel, and this can fry the electronics. Wood may not have the same problem. In addition, wood is light, economical and renewable in a sense, which are desirable qualities for space architecture.
I will add that the Kyoto group, pending its initial results, also plans to build a wooden satellite (called LignoSat (“ligno” means “wood-related”)) that will be launched in 2023.
The question is: will space wood work? Hopefully next year or so we will know.