Ethanol Cold Flow
In this test, we ran water pressurized with nitrogen gas through our Ethanol tower in order to verify our system and get readings on pressure and temperature. This cold flow test was our first major checkpoint to our way to Callisto 1 and required a great effort from each subsystem.
The ethanol cold flow test hardware largely consists of valves, piping, and tanks. The valves and piping are bolted to two aluminum plates and a tower made of 8020s. The piping is layed out in a simple geometric pattern that allows us to identify and access any valve in the system.
To start off, we have a Nitrogen K-bottle (pictured yellow in the rendering below) that pressurizes the water in the cold flow test. This is secured by several cinder blocks and has valves at the top that we can open and close nitrogen flow when we want to pressurize the system or stop pressurizing.
This K-bottle feeds into the piping in the top plate, which has several valves for venting and sensors reading the pressure and temperature of the N2 in our piping.
The piping and valves on the top plate then feeds into the ethanol flight tank (pictured silver in the rendering below). This is where we would store our actual ethanol in the rocket, but since we're replacing the ethanol with water for the cold flow, this is where we store the water. We have to fill the tank from the bottom up and then open the valve between the tank and the top plate piping to allow for the water to become pressurized for the rest of the system.
This ethanol flight tank then feeds into the second grouping of piping in the bottom plate, which houses more valves for venting and sensors for pressure and temperature readings. At the very bottom of the tower, we have an opening that feeds into the injector (although since injectors are not the focus of cold flows, we could very well have not included the injector in our test). The pressurized water then sprays out of the injector (or from the final valve if we do not include the injector) and into the open atmosphere.
Below are renderings of our ethanol tower test stand, as well as the P&ID (Piping and Instrumentation Diagram).
Our very first cold flow test was a success! We were able to run water and nitrogen through our system without any major hardware or technical issues. Unfortunately, we were not able to get one of the solenoid valves (NCSV-3) that we had hoped for. However, we instead replaced it with a manual ball valve and figured out a way to operate it at a distance. We had also opted to not include the injector due to lack of machining opportunities, but we ended up making a 3D printed model of it and bolted it together on test day as a surprise. Injectors are, for good reason, not supposed to be made of 3D printed plastic, so during the actual test, the water leaked out the sides and didn't have a very good spray pattern. While we were able to get the results we were looking for in terms of the hardware and procedures, we did have some issues in terms of the programming side. Before the test, the GS (Ground Station) was not able to send commands to actuate valves with the Raspberry Pi on the test stand due to a priority error. Because of this, we ended up using data collected from the black box text files and the launch box to actuate the valves. Despite the delay in testing and failure to send commands with GS, the launch box operated correctly and we were able to complete our test.
Live stream featured at the top of this post with the video icon.