Building, building, and almost there!

So, "what happened over spring break?", you may ask.

Fabricating.  The rocket system is finally coming together!  First, I cut the stainless steel base plates that are mounted to the testing cart.  Little did I know, when cutting steel with a chopsaw (I had only ever cut wood and tile with one before), the friction between the saw blade and steel produces enough thermal energy to melt the steel.  Forget to pull the saw back and you sling bright orange molten metal around a workshop full of people/chemicals.  I later drilled holes in the steel plates with the drill press, and those were then mounted on the test cart (pictured below).

The mount for the rocket assembly

   The bent vertical component is standard aluminum.  After this, I finally got the prefabbed rocket cases I need! That was the highlight of the week. However, the bulkhead and injector were inadequate.  So as you probably can guess,I made it work.  With grinders, blowtorches, solder, copper tubing, more drills, and epoxy, the injector's orifice shrunk from 1/8in to 1/16in... I am happy with the result.

Pre-modification Case

Modified bulkhead (top view)

  I also used the chopsaw to cut the beautiful phenolic tube into ten small baby tubes... Apparently their true color is yellow!  Last post I made remarks about the phenolics' red-brown color; the red-brown arises as a result of exposure to ultraviolet light.  The same phenomenon occurred with the old Space Shuttle booster rockets: UV turned the colors over time.

About to cut the Phenolics

Ten 4.5in Phenolic tubes, almost ready for casting

My nitrous valve also came in.  What that leaves left to do is fabricate the graphite nozzle (the lathe at the shop is too big!  Gotta find a smaller lathe somewhere.), finish up my control box (built with automobile accessory switches and a three-dollar Walmart "trinket box" that I'll likely spray paint black to make it look more professional).  The tubing is all left, but won't be too hard.  And last, but certainly not least, is to cast the fuel grains.  Finally I jump into the chemical engineering. Aluminum, magnesium, polyvinyl chlorate, more aluminum, and a vast array of hydrocarbons lay ahead.  I'm so excited.

Oh, one last thing... to measure pressure vs. time during the testing, I'll need to fit a pressure transducer into the bulkhead of the rocket.  That's likely prove horrifically inconvenient.  But we'll see...

Tomorrow, if I am lucky, I will cast my first HTPB (that's hydroxyl-terminated polybutadiene, for those of you who forgot) fuel grain.  Also, the warning on the casing told me the pyrotechnic igniters that I made (matches, BKNO3, wire) were not to be used.  But rules are meant to be broken.  Sorry, printed label, I do not take my orders from you.

  Jury-rigged pyro igniter    

"Ignite by Electrical Means Only"... eh, no thanks.

If all goes well, I could be firing next week. Fire, smoke, nitrous, and technical analysis lay ahead!