Sunday, February 28, 2010


The Franken-chamber has been tested with the torch igniter. The igniter has been very reliable and easily lights the main chamber. It is easily 10 times bigger than necessary and makes over 10% of the main engine's rated thrust running by itself. However, the size of the igniter is set by the smallest practical orifice size which is 0.014" in the NOS flare jets I am using. If I switched to vapor propellants, it could be made much smaller while making the plumbing much more complicated.

Testing of the main chamber has shown the combustion efficiency is extremely poor. The easiest approach to improving efficiency is to increase chamber length. With the stainless steel chamber, it was easy to cut the nozzle end off with the band saw and weld in another barrel section. The result is sort of comical looking - yet another testament to the limits of scaling rocket engines

I hope to be able to test again soon. In the meantime, I've already starting working on the design of the next engine as this one has about reached the end of its patchwork life.

Wednesday, February 10, 2010

A Non-update

I've been testing the Franken motor as well as another igniter for a different application. Finished upgrading the test stand hardware and software with flow meters for both oxidizer and fuel. That has already been very useful as I was able to accurately determine the O/F ratio the igniter is running. It will light as rich as 7:1 but runs very rough. Smoothest operation seems to be right around stoichiometric at 10:1 or a bit leaner.

I've also been working on an avionics experiment that is coming up this spring. More on that to come soon.