Saturday, June 30, 2007, 05:32 PM
This week we added several layers of Bondo to the outer surface of the motor's ablative liner and we also mated the injector to the combustion chamber.
The following picture is an action shot of Bondo being applied to the ablative liner. The Bondo was added to fill the gap between the fiberglass ablative liner and the inner steel wall of the combustion chamber. The Bondo was used to fill this void since it is much easier to lathe than the fiberglass, will not see high temperature combustion gases, and is not in a location that carries a load.
Later in the day, we drilled and tapped eight holes in the injector attachment ring on the combustion chamber to attach the injector body. Here you can see the assembled unit.
Obviously we still have some work to do on the combustion chamber!
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Saturday, June 23, 2007, 07:16 PM
Today the team finished applying fiberglass to the ablative liner and then vacuum bagged the part. The vacuum helped drive small bubbles out of the resin while the resin hardened and also helped hold the proper shape during the cure. Here is a picture of the part while on the vacuum pump:
In the next picture, you can see the finished product just after the vacuum bag was removed. Note the ridges of resin where the bag wrinkled...next time we will do a better job of using less resin and tightening the fiberglass weave prior to applying the vacuum!
Later in the day, Jason and Chris mapped out the locations of the eight bolts that hold the injector to the combustion chamber and drilled them on the press:
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Saturday, May 19, 2007, 06:20 PM
Today the propulsion team worked on the rocket motor's ablative liner. This fiberglass tube lines the inside of the rocket motor's combustion chamber, protecting the steel walls from the 6000 degree flame inside the rocket motor. The tube is designed to burn away (ablate) during the motor's operation, and must be strong and uniform.
Today, the team applied layers of fiberglass cloth impregnated with epoxy resin to a mandrel, which is sized to the exact inner dimension of the ablative liner. In this picture, you can see Ed (volunteer) demonstrating proper epoxy application technique to the students:
These strips were applied to the mandrel at a 45 degree angle to the expected direction of combustion, decreasing the rate at which the ablative will burn away. In the next picture, you can see Amanda (volunteer) helping the students apply wet fiberglass to the mandrel:
Once the outer diameter of the ablative liner had reached the correct size, the still-wet ablative was vacuum bagged and allowed to cure. On the next work day (mid-June), the ablative will be cut down to the correct outer diameter (using putty to backfill voids, if necessary), polished, and then removed from the mandrel.
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