The cold flow was a bit of a flop. Or at least an unconvincing gush. I spent the day inside, working on the camera bay (pics to come), but followed the buzz of GroupMe messages as the plumbing and engine team set up, filling the water and liquid nitrogen to replace the actual fuel and oxidizer to as it would be on launch day.
When the countdown did come, it ended in an instant pressure loss and a water fountain of leaks in different locations. Yikes. We had 4 main problems:
1. The two orings between the printed injector plate and the chamber of the rocket engine weren't installed. I was particularly alarmed by this oversight, as this would have resulted in a destructive failure of the engine. This was mainly a procedural error. Because the rocket engine was not actually firing, it wasn't given the same attention that it would have for an actual launch. This meant that the cold flow video showed a disk of water gushing out of where the seal should have been.
2. In addition to the mistake with the engine preparation, the valve that we redesigned failed. This was due to the aluminum handle which translates the force from the firing piston to the steel torque rod which attaches internally to the ball valve. Because of the differential in the expansion between the steel and the aluminum, the pressed connection between the lever and the driving axle slipped on the cryogenic side. Our intended fix is swapping out the aluminum handle for a steel one and welding the two together once we press fit it.
3. In addition to all of this, the AN fitting on the fuel into the engine wasn't tightened all the way, so water sprayed out of this during the firing. Another procedural error.
4. Finally, the liquid nitrogen tank hardly filled - either our dewar pressure is too low, or the head on it is too large, and the height difference between the tank inlet and the dewar is enough to prevent filling. Because the jump to the next pressure dewar that we can order from the school is significant (around 260 psi, I believe), we would rather find a way to fill with the higher pressure dewar. So the fix we have in mind for now is to simply lift the dewar up higher using a shop lift. If this works, we will find a way to do this safely at the launch.
I am not encouraged by the results of this cold flow - there doesn't seem to be much procedural oversight, and simple mistakes that could instantly destroy the entire rocket should not be taken lightly. This is especially the case when they occur in pairs with other, even more alarming hardware failures. I am hoping that a visit from 7 of NASA's Engine Testing engineers will assist us in overcoming some of these aspects. It will take several resounding successes to convince me not only of the viability of the system, but the familiarity with the complete launch preparation procedures.
The recovery, camera bay, and avionics portions of the rocket are progressing as planned, albeit at a slower rate than anticipated. Pictures and an update on that portion of the rocket coming soon.