Day 27: Things are coming together!

After three injector blanks and $30 of micro drill bits, I was finally able to get a plate drilled! The design called for 6 x 0.017" inch impinging fuel jets to be drilled and that was simply not going to happen. I wound up breaking the bit on the second to last hole. Being that I was so close, I drilled it out with a 0.023" bit with the intent of reducing the injector pressure drop.

I ran about 20 flow tests at varying pressures to verify the design...but before that I had to get my daily dose of adrenaline. It turns out that 300 psi max in the lines was no joke. At about 400 this finally gave out on me right into my chest. Like a bomb went off and punched me in the chest, I found myself stumbling around my rocket lab concussed from the BANG!

My ears were ringing for at least an hour. Luckily I had a back up hose and went right back to it getting the tests done... with ear protection on this time.

The stoichiometric flow rate is ~0.02 kg/s for a 5.7:1 O/F ratio. There is no surprise about the increased diameter increasing the flow rate to about double what I designed. Further investigation shows that at an injection pressure drop of 60 psi will give me a 2.5:1 O/F ratio which offers a fuel rich combustion that can reduce combustion temperatures by nearly 1000 K while producing an ISP just over 200 seconds. I'll take it! If worse comes to worst, I can drop to ~30 psi (10% chamber pressure and still push 4:1 O/F ratio.

I got a couple good pictures of the injection pattern. It stays nice and centered. I chose an injection normal for the central oxidizer and 45 degree impingment angle for the fuel.

You can see the diamond shape in the middle of the injector stream. That is from the middle stream getting impacted by the fuel stream from the outside.

Behind the scenes

And of course when I am finally done monkeying around, tragedy strikes when I am trying to be careful. My tank fell off the top of the rocket assembly. This should be an interesting set back.

Did both ends have to break off!? Should be interesting getting that out.

Sneak peek of all the systems! It's starting to look like rocket!