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An experiment with wood that’s out of this world

This fall, the European Space Agency (ESA) will launch a satellite from New Zealand that might just catch the notice of woodworkers everywhere. That’s because the CubeSat will be made almost entirely out of birch plywood. This isn’t your average base cabinet being catapulted through the atmosphere. For a start, it’s really small. It’s a 10 cm (4”) cube of Finnish multi-ply with an accordion-arm selfie stick and some aluminum corner trim. Called WoodSat, it’s an effort to test how well plywood does in space.

The mission is a follow-up to a 2017 wooden satellite that was launched into the stratosphere aboard a weather balloon. That mission was successful, so hopes are high for this one. The concept here is that wood is a lot less expensive to work, engineer and purchase than the traditional carbon fiber composites that are used to build satellites. Also, a wooden structure should completely burn up on re-entry, leaving little or no litter in the upper atmosphere.

Some of the challenges the space engineers are facing are very familiar to woodworkers because most of them relate to moisture and wood movement. More inert materials such as metals and plastics don’t have natural grain, which offers the possibility of fissures. Think about how a board splits along the grain under impact. Wood also expands and contracts across its grain, and even though this is multi-layered plywood with cross-lamination, in the vacuum of space with no protection from radiation, it’s anyone’s guess how it will behave.

But beyond movement, the engineers at ESA are most concerned about minute quantities of moisture. As woodworkers know, there are two kinds of water in wood, bound and free. The free water usually sits inside the cells, and the bound moisture is pretty much locked inside the cell walls. ESA is using a thermal vacuum to try to dry the wood completely.

The satellite project is also going to test how various lacquer and varnish coatings behave in space. Ironically, WoodSat’s base coat is made from plywood’s nemesis, aluminum oxide, to limit outgassing, since the vapors might interfere with the satellite’s highly sensitive electronics.

Radiation is definitely going to be a big issue with using wood in space. It will darken the epidermal (outer) layer of cells and will inevitably degrade the strength of the material. Think how a veneered sideboard might react to sitting in front of a sunny south window for years. The furniture has the advantage of seven layers of atmospheric protection from solar radiation, while WoodSat is going to have a direct and essentially uninterrupted view of the sun every time it comes out of Earth’s shadow.

The experiment is going to raise more questions than it answers, which means there will probably be more wooden satellites in the future. For example, is plywood the best representative of this material or would a composite such as MDF be more stable? And should ESA be trusting this project to a bunch of engineers when everyone knows that woodworkers are far more creative? 

This article was originally published in the August 2021 issue.

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