The test stand has taken way more time to put together than I imagined. In fact, it's taken about 5X more time than the design and fabrication of the uncooled engine.

I finally finished the failsafe control unit. It's purpose is to control the various remote devices (relays, solenoids, ignitor, etc.) during the test. It also provides for a remote control box that includes a dump switch and some status indicators. The card interfaces to a National Instruments PXI-6527 isolated DIO board and will be controlled by the test program in LabVIEW.

I used Eagle Schematic for the drawings. It runs in Linux and Windows and they also have a free version (which I'm using). I have hand sketches of the overall instrumentation setup which I'll convert over to Eagle when I get some more time.

I added a separate fill port to the LOX tank to make it easier to get it closed back up after filling based on my tests with LN2. The internal threads on the tank got iced up real bad and I couldn't thread the burst disk fitting back all the way in. The new tube connector has external threads on the top so it is much easier to cap it off after I'm done filling it.