[burpg] Fuel Grain Mixing - 1 PM

From: Ben Ha <benha@xxxxxx>
To: "burpg@xxxxxxxxxxxxx" <burpg@xxxxxxxxxxxxx>
Date: Fri, 24 Oct 2014 11:06:00 -0400
Hey Everyone,

We need a few people to mix a fuel grain for the MK IIB this afternoon in
order to remain on schedule for next week's hot fire. I will not be able to
mix the grain so we need someone to step up and take the lead on this.
Please meet in the lab at 1 PM to mix the fuel grain.

1. Clean fuel grain mold (mold top, mold bottom, and center rod). Try to
get as much of the old fuel grain off of this mold as possible. Under the
fume hood, spray the molds and the rod with mold release. Rub the mold
release around on the molds. Do this a total of three times with five
minutes of time in between each coat. One person can do this while everyone
else moves on to the next steps.

2. Setup casting area. Cover the entire area with the tarp as well as
newspapers in order to keep the fuel grain from getting on anything. Make
sure the layer of newspapers is thick enough so that even if the fuel grain
spills over, it gets only on the newspapers. Cover the large scale with
newspaper as well.

3. Place the bucket on top of the newspaper on top of the scale and zero
the scale. If you haven't yet, put on some disposable gloves.

We are experimenting with a different mixture ratio this time, so there
should be:

14.20% E744 (EW 178)
85.80% HTPB

For the MK IIB, we need about 4 lbs of fuel, so this results in:

0.568 lb E744 (EW 178)
3.432 lb HTPB
4.000 lb Total

*All weight measurements have a tolerance of +- 0.001*.

The ratio is key so if you pour too much curative, recalculate using these
percentages so that you can get the correct ratio. If you do recalculate,
record on the whiteboard your new weights for the mixture.

4. Pour the curative (E744) into the bucket and hit the target weight. You
can pour some into an empty plastic cup as it gets close to the target
weight to control it more easily. If you go over the target weight,
recalculate the new total target weight using the mixture ratio above.

5. Pour the HTPB into the bucket and try to hit the total weight. This
means that instead of zeroing the scale and aiming for whatever weight of
HTPB you need, just try to hit the target total weight which would be 4.000
lb in this case.

6. While someone is pouring the HTPB, setup the mixing apparatus and vacuum
chamber. The mixing rod should be inserted into the cordless drill and the
vacuum chamber should be tested for leaks.

7. When you are finished pouring the HTPB, move the bucket on top of the
tarp and pour about a 1/4 cup of carbon black into the mix. Do not pour the
entire cup at once. We only need enough to make the mixture black.

8. While sprinkling the carbon black in, begin to mix everything using the
cordless drill, remember to go SLOW so that we introduce as few air bubbles
into the mixture as possible.

9. Slowly mix for a total of *ten minutes*. While someone is mixing,
another person can prepare the cardboard tube. The outside of the tube
needs to be covered in tape in order to prevent any of the fuel from
contaminating the outside of the tube. You will need to make the bottom
edge of the tube extra thick with tape in order for the tube to seal with
the bottom mold. Please verify this seal with Armor. Once the seal is
verified, write on the tape with sharpie "Fuel Grain 7."

10. Move the bucket into the vacuum chamber and vacuum the entire mixture
for *12 minutes*. Start the timer when the gauge on the vacuum goes as low
as possible.

11. After the 12 minutes is up, carefully remove the mix from the vacuum
chamber.

12. Stick the cardboard tube into the bottom mold and

*MAKE SURE THE TUBE SEALS WITH THE MOLD.*
13. Stick the center rod into the groove in the bottom mold and have
someone apply pressure to keep fuel from getting under the rod.

14. Pour the mixture into the mold. Try to spill as little of the mold as
possible because 4 lbs of fuel is just enough to make the fuel grain as
well as the witness cup.

15. The mold is full once the fuel reaches about 1/4" from the top. Stick
the top of the mold on and press down to make sure the mold is sealed.
Check for leaks.

16. Fill a plastic cup about halfway with fuel and label this cup "Fuel
Grain 7."

17. Clean up and make sure there is plenty of newspaper around the fuel
grain in case it gets knocked over and spills out.

Please respond directly to me so we can know who to expect in the lab at 1
PM.

Thanks,

Ben Ha

-- 
Boston University
Mechanical Engineering 2016
BU Rocket Propulsion Group Secretary
BU IS&T Desktop Services Student Lead Tech
[burpg] Fuel Grain Mixing - 1 PM

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