Saturday we fired the 250 Lb motor with a new all copper pintile injector. The top end of the motor and the chamber wall worked fine. The Throat/end closure leaked and we melted the bottom end of the motor. It ran for 24 seconds, but the video camera died 20 seconds into the firing. The video is here.
After looking at the data, the chamber pressure started declining almost immediately, so I think the throat was coming apart as soon as we started. We still did not get any load cell data, the load cell worked in the shop, but not when the rocket was running. We have gotten this result twice. The Fuel feed pressure was also very noisy. In the chart below the Tank pressure sensors measure the tank pressure and the feed measures the pressure at the input to the motor after the throttle valves. At the end of the run the Lox tank and feed pressure drops quickly as we vent the tank, but the fuel pressure does not seem to change much. This is because we vent the fuel tank utalage into the motor for purge.
We will make a solid copper throat/chamber assembly and either test next weekend or the following week. It will depend on if I can find a 1st class Pyro op for this coming Saturday.
(It looks unlikely).
Today I started seriously looking at the paperwork necessary for my AST license. It seem like an appropriate day to start ;-) I wrote the beginnings of a hazard analysis and started looking at the procedures and verification processes necessary. Toward that end I also made a slightly more accurate rendering of the vehicle.
3 comments:
Paul,
Is your chamber pressure transducer packed with krytox? I was just wondering if the slow pressure decrease might have been some thermal effect at the sensor.
--- Carl
Why use krytox for the chamber transducer ? Lithium grease usually works fine I think, and is much cheaper for sure.
Good read always prefer to read the quality content testing erp
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