Solid propellants

[mator]

During the summer I have some experience with manufacturing solid propellant. In my opinion, I have success to got the composition with very, very good cost/efficiency coefficient.
Here video of burning one sample. It is 75% NaNo3 15% coal 10% paraffin.

[mator]

I have some progress with solid propellat engines:
first with channel and without nozzle

and with nozzle
[youtube]http://www.youtube.com/watch?v=WqtFO9eT5jw&list=UUAdbIupDMkf-1VPfprhnbIw&index=1
[/youtube]

By calculations in special programme second engine (with nozzle) must give me 10kg of thrust by 10 atmospheres in combustion chamber. But on manometer we can see only 4 atm. I will think on it further)))

[stevep]

Hi Mator,

To calculate the chamber pressure, you would have had to assume a certain burn rate for your propellant. This burn rate will vary with pressure. How have you established the burn rate curve (rate vs. pressure) for your propellant?

Also, be very careful with mixtures of more than a few percent of carbon--they tend to have high burn rate exponents and are therefore very difficult to control (leading to "boom"!).

--Steve

[mator]

Because propellant that I used is very popular, so there written a program by enthusiasts.It can calculate solid propellant motors with different construction. And i didnt know burn rate of this fuel. It is in this program)))) I used KNO3 sorbitol fuel.

[stevep]

Hi Mator,

If you used kno3/sorbitol, then the program is almost certainly not using the correct burn rate. You will have to perform a number of experiments to find the correct burn rates (which will vary according to the chamber pressure), then enter them into the program. But until you figure out the correct burn rates, no calculation of chamber pressure/thrust will be correct.

--Steve

[mator]

Ok. I think that program using quite correct rates, based on experiments and theory. I think that in my case theory and experiment are so different because of many factors as: not correct ignition, quality of propellant, initial temperature of all engine (and propellant) it was quite cold and it also can slow down burn temp of propellant. And losses in manometer connection.