Armadillo Aerospace News: Tank burst test, Engine scale-up, Plasma cutter

We hydrostatically tested one of the Structural fiberglass tanks this weekend. The 24” x 50” tanks we use on the subscale vehicle have plastic screw threads, which we were confident would be the first thing to go, so I ordered a somewhat larger tank that had a bolted flange. I had hoped that the single flanged tank would have a complete fiberglass overwrap on the non-flanged end, but it turned out that it has a cast aluminum integral piece that was probably used to hold the tank during the winding process. To my surprise, it had a few pockets of exposed liner on this bottom flange, which I expected to be the first part to let go.
We filled the tank with water, then filled our trailer test tank with water, and connected that through a very small orifice line to the top of the tank, then began pressurizing it. As always, these tanks make a distressing amount of snapping and popping sounds as the pressure is increased. We took it up 50 psi at a time to 600 psi, let it sit there for a while, then relieved the pressure. We took it back up slowly again, which it did without much popping, and let it sit at 600 psi for a little while. When we took it up 50 psi more, the bottom flange burst. When we looked at the bottom, it appears that the aluminum flange broke before the liner could extrude through the holes, although there were significant visible stress lines on the exposed liner. Read More