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Rocket Candy

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LAN_403

rp181

Fri Apr 18 2008, 01:55PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

im not that stupid, the top will still be open, so fueling would be done after, the the nose cone put on.

ramses

Fri Apr 18 2008, 05:57PM

Registered Member #1208 Joined: Thu Jan 03 2008, 05:30PM
Location: Chesterland, OH
Posts: 154

sorry about the blow it up comment. I assumed that you knew the law in your area, and I thought you would be setting it off on school property, infront of your class. SCH 40 3/4" is rated to aroung 350PSI

ramses

rp181

Sat Apr 19 2008, 03:31AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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anyone know the mass to power ratio for rocket candy? For now, my nozzle is just a smaller diameter hole. a 3/4in closure plug fits into 3/4in coupler, pvc is then put on for the actuall chamber, and a small ring is inserted into the bottom to make sure it doesnt blowout. Im worried that it is too heavy to liftoff, it consists of ~14in of 3/4in pvc, 2 couplers, a cap, and 2 metal closure plugs. only ~10in of 3/4in pvc is where the rcandy goes.

johnf

Fri May 02 2008, 08:08AM

Registered Member #230 Joined: Tue Feb 21 2006, 08:01PM
Location: Gracefield lower Hutt
Posts: 284

A cheap nozzle can be made from tig welding nozzles they are a few dollars each threaded at the wide end to screw onto the torch and several differnet exit diameters are available. All nozzles are made from alumina or similar and can take 2000 degrees Celsius easily
Stay safe

rp181

Sun May 04 2008, 06:38PM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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just updating, the rocket is about 2 1/2' tall including nose conem the CoG is above the CoP, and im going to make the rocket candy today and hopefully do a static test.

The nozzel is coated on the inside with Specialty Heat Epoxy putty sort of as a sacrificial coating i can replace. Ignition is a piece of nichrome wire inside the rocket candy pwoered by a 9v.

Backyard Skunkworks

Sun May 04 2008, 10:06PM

Registered Member #1262 Joined: Fri Jan 25 2008, 05:22AM
Location: Maryland, USA
Posts: 451

I doubt a 9V battery will provide enough power to heat the nichrome very fast. I'd go for maybe 10 NiMH AAs in series or a SLAB. Once I tried setting Estes Cs off with two 9Vs in series and nothing happened. Even if you do manage to set the rocket off, the 9V will die after a few launchs, which is quite a waste unless its NiMH rechargable, in which case it should put out enough current to work.

rp181

Thu May 15 2008, 01:53AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Posts: 1529

Time to bump this thread :)

I made some rocket candy, didnt work well, and remelted and let it dry. Both times, the rocket candy dosnt stay alite. The KnO3 and Sugar were measured out but the cornsyrup was just approximated, could this be the problem.

I also crushed some dried rocket candt and lit it with [impressive] results. heres youtube links:

Seems much better in RL :)

Firefox

Thu May 15 2008, 02:15AM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

As a note, commercial APCP propellants do not burn well outside of their casings. This is because the 5+ atm of pressure inside of the casing keeps the propellant alight. The reason the crushed rocket candy worked well is because you gave it a large surface area to burn on, allowing the heat of the candy around each other to provide enough heat to keep the reaction going. Try putting the candy in a thick (I mean very thick) steel pipe with a high temperature steel alloy "washer nozzle" screwed/bolted (make sure its well secured) to the end. Then bury all but the end of the motor and try lighting that with a remote ignition system, I believe toaster wire shorted across a car battery will work. If not, use the toaster wire to ignite magnesium powder from those fire starter blocks (flint on one side, Mg on the other).

rp181

Thu May 15 2008, 02:36AM

Registered Member #1062 Joined: Tue Oct 16 2007, 02:01AM
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Why very thick steel? My rocket is 1/2 inch copper (thin, but coppers expensive) and nozzel is a coupler going down to 1/4in

Firefox

Thu May 15 2008, 10:37PM

Registered Member #1389 Joined: Thu Mar 13 2008, 12:50AM
Location: Pittsburgh, PA
Posts: 346

I am saying for a testing casing. I meant thick walled, the inside diameter of the pipe is up to you. A thick walled steel pipe is unlikely to burst, and then you can work from the results of that test.

Also, I would suggest a thick cardboard, cardboard+fiberglass, cardboard+carbon fiber, or pure carbon fiber tube for the body of the rocket. When the Rocket Boys flew, rocketry was an up and coming hobby, and the distinction between model/high power rocketry and amateur rocketry had not been defined, and probably did not need recognition. Now it is crystal clear.

From the NAR website:
"General sport rocketry is distinct from "amateur rocketry," which is generally recognized as anything involving design and manufacture of non-commercial motors and propellants, or rockets whose construction is not in conformance with the NAR Safety Codes."

Model/High Power rocketry enthusiasts (with a few exceptions made when people have many years of flying, more experience than a NASA technician, and are flying M+ rocket motors) are required not to use metal for any part of the airframe or structure of a rocket. I feel comfortable allowing the elders of my other hobby to use such materials, because they know what they are doing, and they abide by the safety codes set down by the National Association of Rocketry (no amateur rocketry) and the Tripoli Rocketry Association (amateur rocketry is allowed). In Tripoli, amateur rocketry is done at specialized events, where safety boundaries are increased, and launches are declared as experimental.

I may be coming across as a bit harsh, but the rocketry hobby as a whole has come under a great deal of fire from people who do not copletely understand it, and would like nothing better than to get it banned outright. This is why I do not like the idea of an inexperienced rocketeer dabbling in amateur rocketry, and I will outright implore you not to use metal for anything but the casing of the motor. This is also why I will be willing to help you to the best of my ability. What the hobby doesn't need is a big news story and legislation to do it in, once and for all. Help keep it that way, please.

Last but not least, please read up on these things:
-Tripoli Safety Code

-NAR Safety Code

-NAR High Power Safety Code

My last question is, why does the motor have to be home-brew? It seems unreasonable for a teacher to ask you to do something that is so dangerous for extra credit. Check again if you cannot just build the airframe and insert a commercially made motor. I, along with many other enthusiasts in the model/high power rocketry hobby, would greatly appreciate you getting a bit more experience under your belt before you try your hand at amateur rocketry. However, if you decide that you wish to keep going in this pursuit, I wish you the best of luck, and I am sure I don't need to remind you to be safe, but I will anyway. Be safe.

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