Hybrid Rocket Motor Nozzle Tests

Update on my senior project here at Cal Poly San Luis Obispo. This video is intended primarily for my advisor, but to anyone else who isn't familiar with what I'm doing:

This is a demonstration hybrid rocket motor in our propulsions lab, employing oxygen as the oxidizer and plexiglas (polymethylmethacrylate) as the fuel, with propane as the ignitor. The purpose of this motor is DEMONSTRATION of hybrid motor characteristics, NOT thrust performance. As such, the thrust is intentionally low (this is also good for safety).

My senior project is to design a rocket nozzle or two that will sufficiently demonstrate to students the higher performance that can be expected from the use of a nozzle, particularly in the form of increased thrust.

Cal Poly's motto is "learn by doing." I am doing exactly that. Machining new fixtures and nozzles, testing the nozzles, collecting the data, and doing everything else myself has been a learning experience, allowing me to see the design process from conception to application.

If you have any questions about Cal Poly, their aerospace engineering department, or hybrid rocket motors, let me know and I'll be sure to get back to you.

Category:

Howto & Style

Tags:

• hybrid
• rocket
• motor
• engine
• calpoly
• cal
• poly
• oxygen
• propane
• plexiglas
• fuel
• grain
• oxidizer
• nozzle
• aerospace
• engineering

[cabagesoup714]

That is great, just the information that I needed. I am making a hybrid rocket motor, using gaseous oxygen as the oxidizer. The nozzle is the hardest part for me, I have a lot of machining experience but am too poor to buy materials other than steel. I was worried that the steel would melt, but this resured me. I don't know if you have any tips, that would be great.

[mark8v35]

Well, I would warn you that the combustion temperature stayed below steel's melting point only because the combustion pressure was so low. If you up the pressure to get any kind of decent thrust, you're going to increase the combustion temperature and thereby run a good chance of melting a steel nozzle. It also depends on how long you run it - even aluminum would last a second or two. It also depends on what you are using for the fuel... so many variables. Let me know if I can help you out.

[irishguy20007]

What is the difference with producing a much larger rocket engine.Will the same principals apply as one sizes up or are there different principals involved.I was inspired when I was in Chicago in 1994 and seen one of the captures rocket engines at a university.

[mark8v35]

The same fundamental principles apply, although new issues are almost always introduced with scaling.

[Fenrisulfir]

0,075 inches, 0,175 inches... tss these are really nice numbers to calculate with. Haver you ever heard about a thing called metric system?! Makes your life much more easier.

[dudebot09]

I can imagine the shop blowing up and the narrator saying "that's a pretty standard burn"

[LTF85199]

Thanks for sharing this video.. very useful

[Dragonsintuxcedos]

Is the combustion chamber made of glass?

[llllXeallll]

hello i'm new to rocket making and you probably hear this alot but where is a good site/book to go read to learn the fundamentals. i understand alot of what your saying but i wouldnt be able to figure that stuff out myself yet and i'm really interested in learning more. Any help would be greatly appreciated!!!

[nickalisse]

@Fenrisulfir Pretty good video & explanation, but I'm all with you. Metric system is lot easier to calculate!!!

[chaosopher23]

@cabagesoup714 Use the kind of clay that fires in a 2500* kiln that can be reheated and reheated... it's cheap, and can be machined if you're slow and careful, and it doesn't melt easily. Estes does it all the time.

[psyclistic]

A few questions:

1) What kind of steel are you using for your nozzles?

2) What's the material of your combustion chamber walls?

3) What are you using for fuel / oxidizer?

I'm an aero engineer but not an expert on this stuff. Maybe your nozzles/orifices aren't melting because there's enough thermal mass for a lot of the heat to be conducted away from the region where the steel comes in contact with the exhaust.

[noxnflame]

What is the clear tube made of in the middle of the engine? I would think glass but that melts way below the temperature it's at.

[emilen2]

Nice nough, though seriously you ought to get an F for Failing the metric system.

[fookthefrench]

Your analogy is flawed.  The OP and his professor know the metric system. They just didn't use it for this project.

[Alexpaths]

@nox665 Most CalPoly engineers use metric unless specifically told otherwise. Many times we use English units since we are told to by industry such as Boeing, Lockheed Martin and Some others for presentations; have you ever had good momentum in a presentation that is brought to a sudden stop because some old engineer can't use metric? Really we want jobs.