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Registered Member #9197
Joined: Wed Jan 02 2013, 03:04AM
Location: MA, United States of America
Posts: 2
I am experimenting with ideas/plans/methods for building a model rocket (probably not quite high power) from scratch. The nozzle is a very important piece of a rocket, so I want to experiment with different shape and materials.
I guess I'm going to be using some sort of de Laval nozzle. I haven't been able to find much on how modifications to the different parameters of them (e.g. throat diameter, nozzle length, diameter/length of each section of the nozzle) affect how the nozzle will perform. Does anyone know a bit about the physics behind nozzles and how I can tailor one for my needs?
From my research, bentonite clay and quick setting concrete seem to be the most logical materials. However, both types involve using a machined form to create the best nozzle shape. I don't have access to a lathe, so I'm not sure how I can make a decent nozzle. I don't know if anyone has ever built a nozzle or similar type of device before, but if anyone has ideas on how to construct it, I would appreciate any advice you can offer!
If I was unclear or didn't provide enough information, please ask me. Thanks so much!
Note: I will be using PVC as a case for the motor probably rocket candy (65% KNO3 / 35% sucrose).
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I guess that before you can do any maths regarding the nozzle, you need to calculate rate of burn and volume of gas produced, then you can calculate what diameter nozzle will give mach 1, etc.
or, conversely, for a given nozzle diameter, what rate of burn will give sonic velocities in the nozzle?
EDIT: You could make the pattern in wax, then just melt it out afterwards.
Registered Member #9197
Joined: Wed Jan 02 2013, 03:04AM
Location: MA, United States of America
Posts: 2
Ash, thanks for the quick reply! You're right. I need to know more about the properties of my propellant.
This may sound like a silly question, but how exactly can I test the volume of gas produced for my propellant? I was thinking of dry packing my first motor, so burning it when it isn't packed might not yield the same results as when it is. I think this would hold true for both testing burn rate and volume of gas produced. Any ideas?
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Making nozzles
