Yesterday a few of the guys from Lunar Numbat and some other friends came over for a meeting about where Australian Rocketry is going. We didn't get the turn out we were hoping, so we didn't have the meeting but I fired up the engine to show the people that came.
The setup was the same as the last test, but this time I used a different type of catalyst which I heard about from a chap at ASLI. It is a zeolite, which is a type of mineral usually used for absorbing oil spills etc. The idea is that it would handle the heat better than the silica gel. There was a huge difference, and this time all of the exhaust seemed to be turn to vapour. I was quite happy with the results, I just hope that the catalyst will perform as well with higher concentrations. The reason for the wagging of the exhaust at the beginning is that the converging part of the nozzle is partially blocked with steel wool (Ashley came up with that one). I need to make a small spacer to raise the bottom of the pack up to fix this. Interestingly after the feed pressure was increased to 110PSI the problem went mostly away, although the exhaust was still quite rough. I ran quite a bit of peroxide through the engine , and it didn't show any loss in performance. Interestingly after stopping the engine for about 20 minutes while we refilled the tank the catalyst seemed to stop working. After the test we all took the engine apart and did some brainstorming about why this happened, everyone came up with so manny great theories (too manny to discuss) and it was good fun to discuss the problem with others. Thanks to trent for his help assembling the engine.
The next step is to test the engine with higher concentration peroxide. I am currently concentrating a batch which I hope to test later tonight or tomorrow if it keeps raining. On friday I got all the parts I had been waiting on, so I have been starting to assemble the new test stand a fill cart. I have decided on a armadillo style vacuum filling method. I have been so far testing the catalyst test setup with compressed air at 110PSI, because the PVC pipe used as a tank is not rated for high pressure. With %50 this works well, but I am afraid that the chamber pressure with higher concentrations will be too high. I know that ideally the flow should regulate itself to allow an amount of peroxide in to maintain the chamber pressure, but I think that the check valve will cause the flow to pulsate too much. By that I mean that that too much peroxide will get injected raising the chamber pressure above the feed, which will cause the check valve to kick in and stop any more flow, causing the cycle to repeat.