Sunday, 3 June 2012

Thruster Test + Vehicle Components

Yesterday we tested the new engine, and we got some good load cell data but disapointingly the engine only produced about 3Kg of thrust. There could be a few reasons for this but I think we the most likely thing is that the engine isn't getting enough peroxide and we need a bigger solenoid. Other factors which could have caused less recorded thrust are that the thruster was firing on a slight angle and could have gotten slightly jammed in its sleeve but I tried to calibrate the cell recreating these and it is fairly clear that something is not working properly. I would like to try another test this week with using a larger solenoid. Playing with the engine is still pretty novel and I pulse the engines a few more times than I need to. I noticed a small amount of leakage from the engine which I think is because the engine flange is too smooth and the copper ring doesn't bite into it enough.

For the above test we used 1L of %90. We were actually going to use %85 but at the time we couldn't figure out how much water to add (its harder than it seems). Here is a excel spreadsheet my friend Robert Walker wrote to do it, I thought someone might find it usefull.

I was quite happy with how the test went and how everyone performed running the test but there definitely room for improvement on the logistics side. Firstly it was raining pretty heavily, and although everything was under a tent the water did make the test more difficult the it would have been otherwise, so no more testing in the rain. The tent should be for protecting everything if it rains, not for testing in the rain. It made the suit fog up and we couldn't really hear Buren read out the fill steps so he mostly went alone. Following on from that we need a better method of communicating with the person  filling. I will getting a radio with a VOX headset. The filler should also wear a sweatband or something on his head so he can wipe any moisture on the inside of the suit.

We actually planned on doing two tests but when filling for the second test Buren found the tank only sucked a small amount of peroxide before it wouldn't take anymore which gave us all quite a fright as it could have meant that there was decomposing peroxide in the tank. We used the small amount of peroxide and vented and I decided not do try again but instead to disassemble and check everything. As it turned out the reason the system wouldn't take any more peroxide was because it had sucked a bunch of air initially (the tube wasn't properly in the peroxide container) but I thought it was better to be safe. Also we hadn't changed anything since the first test and the went fine so I don't think any contaminants could have gotten into the system. To deal with this I will install a pressure gauge on the system so in the unfortunate event there is peroxide decomposing in the system we know as it is happening.

We also need to stop doing nigh tests as it doesn't make things any easier.

I have also been working on components for the vehicle, and have now finished the three base plates. I managed to get the plates into the lathe with some difficulty as I couldn't find any other way of making decent holes in them.

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