In this blog post we want to tell you more about our glider and give you more detailed information on the glider’s production process.
We call our glider FGU (Free Gliding Unit) and it contains the GCU (Glider-Mounted Control Unit), which we’ll be talking about in one of our next blog posts. The GCU will contain the electronics needed to fulfill all necessary tasks (e.g. GPS, attitude measuring, data transmission etc.) after the ejection. The FGU is the main payload of our experiment.
The glider will have a wingspan of 250 mm, an average chord length of 140 mm and (including the electronics) a height of 60 mm. The weight of the FGU will be approximately 50 g including the GCU and batteries. The glider will be made of depron foam material, reinforced with composites. The picture below summarises all the key parameters of our glider.
The mechanical wing structure was developed as part of the bachelor thesis “Entwurf, Fertigung und Prüfung der mechanischen Struktur des Raumgleiters REXUS GAME” by Johannes Gründig. The main focus is on the forces that occur during the rocket start, the ejection and the reentry of the glider.
To help you understand the process behind the production of our glider, we’ll be talking about all the materials we’re using as well as the techniques that are necessary to build the glider in the way we want.
The glider is made out of depron (a polystyrene hard foam), aramid fibres and carbon fibres. The foam core provides a defined distance of the fibres to the neutral fibre. The fibres have to absorb these forces during the different stages of the flight of the FGU. As a reason of the low weight requirements the fibres are placed on the depron with embroidering technology. To make clear what the process looks like, we’ve included a short video of the embroidering of the aramid fibers onto the depron.
That allows us to place the fibres in the optimal direction to counteract the occurring tensions. In the pictures below you can see the fibre placement. The yellow fibres are made from aramid and the black fibres are made from carbon. We chose this combination because aramid offers lower density at higher tensile than glass fibres. With carbon fibres the ratio is even better but carbon fibres are electrically conductive, which could lead to our antenna being shielded. This is why we want to use as little carbon fibres as possible. We will also produce and test gliders without any carbon fibres. If the test procedure shows that those without carbon fibres produce good results we will use them. Like that a glider weight of less than 20 g can be achieved.
To give the FGU its three dimensional form it is laminated in an positive form at 60 degrees inside of an oven to optimize the polymerization of the epoxy resin. You can see that in the picture below. As you might have noticed at the beginning of this blog post, we have already produced a lot of prototypes for testing. 😉