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-   -   Sugar Rocket Motor Mods (http://www.oldrocketforum.com/showthread.php?t=15841)

wjwj 03-12-2016 01:16 PM

Sugar Rocket Motor Mods
 
Hi,

A question for any of you rocketry/chemistry experts out there. I am a radio-control enthusiast who has recently been experimenting with rocket motors. What I am trying to do is create a "rocket plane", but unlike typical rocket planes, I am putting much time and care into making a craft that is both light and aerodynamic to achieve high flights.

Here is my question: I want to use sugar motors (KNO3 and sucrose) to power this thing. I have made a few already, but the problem is that they burn way too fast with too much thrust. What I want to do is modify the motor to slow the burn. Here is my idea:

Add baking soda to the KNO3/sucrose mixture since baking soda is non-flammable. I know this is done to create a delay charge, but I don't want it to burn that slow. Also, I would probably decrease the nozzle diameter to accommodate the pressure decrease.

What are your thoughts on this? Does it seem doable? Are there any formulas/methods for determining how much baking soda to add? If I could extend the burn from ~2s to ~10s then I would be happy.

Thanks for your help!

stefanj 03-12-2016 01:43 PM

This probably isn't the best forum for motor-building questions. I'm sure some here have dabbled in it, but you won't find the concentrated expertise of . . . well, I'm not sure what to suggest!

It is an interesting project, though. I'd love a super-low-thrust motor for airplane uses; a modern Jetex without the clunkyness.

luke strawwalker 03-12-2016 05:19 PM

Quote:
Originally Posted by wjwj
Hi,

A question for any of you rocketry/chemistry experts out there. I am a radio-control enthusiast who has recently been experimenting with rocket motors. What I am trying to do is create a "rocket plane", but unlike typical rocket planes, I am putting much time and care into making a craft that is both light and aerodynamic to achieve high flights.

Here is my question: I want to use sugar motors (KNO3 and sucrose) to power this thing. I have made a few already, but the problem is that they burn way too fast with too much thrust. What I want to do is modify the motor to slow the burn. Here is my idea:

Add baking soda to the KNO3/sucrose mixture since baking soda is non-flammable. I know this is done to create a delay charge, but I don't want it to burn that slow. Also, I would probably decrease the nozzle diameter to accommodate the pressure decrease.

What are your thoughts on this? Does it seem doable? Are there any formulas/methods for determining how much baking soda to add? If I could extend the burn from ~2s to ~10s then I would be happy.

Thanks for your help!


Try here... open discussion of EX motors, without the stupid "kid-proof" forum garbage on TRF...

http://www.rocketryspot.com/index.php

YORF doesn't discuss EX motors either... for whatever reason. Guess there's not a huge interest.

Best of luck! OL J R :)

wjwj 03-12-2016 06:12 PM

Thanks guys. I already looked at TRF, but apparently it is against their rules to post anything about rocket motor manufacture (which is ridiculous of course.) I'll try your suggestion, "The Rocketry Spot." If you happen to think of anything, though, please don't be afraid to share your thoughts!

Ltvscout 03-12-2016 06:35 PM

Quote:
Originally Posted by luke strawwalker
YORF doesn't discuss EX motors either... for whatever reason. Guess there's not a huge interest.

Best of luck! OL J R :)

It might not be discussed, but I don't ban it like TRF does. It really doesn't pertain to the theme of this forum which is why people don't talk about it here.

/// 03-12-2016 07:33 PM

Hi wjwj,
Before trying a burn rate modifier, have you considered different grain geometries?
C-slot, moonburner, end-burner?

tbzep 03-12-2016 09:44 PM

You can make smoke bombs with the same ingredients, so the mix ratio, surface area (grain geometry), and nozzle will make a huge difference in thrust and burn time.

luke strawwalker 03-12-2016 11:20 PM

Quote:
Originally Posted by Ltvscout
It might not be discussed, but I don't ban it like TRF does. It really doesn't pertain to the theme of this forum which is why people don't talk about it here.


Yes, didn't mean to imply otherwise...

I'm glad that you take the stance that such discussions are "allowable"... (I put that in quotes because I don't accept the premise that topics of discussion should be allowed to be controlled by a third party, or that "permission" is required to discuss such things).

I also can understand that YORF is primarily about "classic rockets" and therefore not, by definition, likely to include much about high power or experimental motors. I'm glad that such topics CAN be discussed, but also that YORF focuses more on the MODEL rocketry part of the hobby rather than high power and experimental motors, which seem to dominate the discussions in other boards like the Terribly Run Forum (TRF), the Rocketry Center, and Rocketry Spot...

While those discussions are interesting, the model rocketry content is small enough to be "drowned out" by the greater volume of such discussions...

Later! OL J R :)

wjwj 03-12-2016 11:36 PM

Here is a page that I found which seems to be exactly what I was looking for.

http://www.jamesyawn.net/endburner/

Could someone read this and help me decipher this guy's methods? My main questions are:

- What fuel (specifically) is used? It says KN/sucrose/Fe2O3, but how much of each?
- Can 3/4" PVC pipe be used for the case?

Also, I am trying to figure out how simply using an end-burner motor increased the burn time from 1-2 sec to nearly 7 sec. Does that make sense to you guys?

ghrocketman 03-13-2016 12:25 AM

End-burning KNO3/Sucrose or KNO3/Dextrose results in a Smoke-Bomb with zilch for thrust.

Try experimenting with room temperature mixed Epoxy Glue (instead of Sugar) for the fuel with KNO3.


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