HDPE/N2O Hybrid

[Scott_Rip]

I'm new to the forum. I just thought I would introduce myself with my current rocket project. I'm building a hybrid using nitrous oxide and polytethylene rod as the fuel. My nitrous tank is just a 20 lb CO2 tank, 4 ft long and 5 in diameter. My motor is made from 3 ft of 3 in aluminum tubing.

One idea I'm considering is using a preloaded oxidizer tank. That is, I am thinking about attaching a manual valve to my tank and filling it before putting it in the airframe and attaching the plumbing. Then, once it is attached to the plumbing, I can open the manual valve. Flow through the injector will be controlled by a second solenoid valve or electric burst diaphragm. Let me know what you think about this...

 

[Nate]

Hey man, welcome to the forum.

First, I have to warn you that your post might get deleted here because the discussion of motor design/construction is strictly prohibited. If you'd like some help with your motor, there are some very knowledgable people on both of these forums;

https://thefintels.com/bbs/

https://newtons3rdrocketry.com/forums/

That being said, you sound like you're on a good track. I know of several people who have used the pre-filled tank idea with much success. One thing though, your oxidizer volume is huge compared to your combustion chamber. Are you really planning to run 20lb of nitrous through a 3" motor, or is that just a storage tank, and you're using a smaller one for the flight?

 

[Scott_Rip]

Well, I don't want to cause any trouble. If the thread gets deleted, I'll be gooder in the future. I'll probably continue this discussion at one of those other forums, then.

 

[loopy]

I think you're fine. The main thing that's frowned on is chemical formula's for propellant.

Sounds cool! Do you have any details on the rocket itself?

 

[Scott_Rip]

I'm mainly focusing on the propulsion system first, but I have made a rough design for the airframe. I plan on using 5.5" paper phenolic tubing and aluminum supports between the motor and oxidizer tank. The total length will probably end up being around 12 ft or more. Once I get to it I'll probably need help with the DAQ and recovery systems.

Also, in reply to Nate's question, the tank and motor should be pretty well sized together. The motor will have about 5 lbs of HDPE fuel in it. From what I've seen, HDPE/N20 hybrids usually run at mixture ratios somewhere between 5 and 8, similar to HTPB.

I've got a solid model of the design in the works. I'll post a jpeg once it's closer to being done.

 

[Nate]

Ahh you're right. I didn't see how long your combustion chamber was. I was picturing a much lower aspect ratio.

It sounds like you're all set, and know what you're doing (far better than I do ) Good luck!

 

[jderimig]

Visit this forum....

hybriddyne

and post your questions there. More knowledge on this subject there.

You will get yourself killed from advice here.

 

[edwardw]

3 feet of 3" isn't that long for that kind of nitrous. I'm guessing your O/F ratio is between 5-7:1. Make sure you have a ton of head end insulation. I don't know what your injector looks like but at the head end you'll have a very oxidizer rich environment so it will take much more abuse. I don't know your web thickness but I'm betting you will need nearly and inch up there.


Edward