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rp181

Thu Apr 17 2008, 01:33PM

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

I plan on making a rocket for some extra credit (reading Rocket Boys, aka October Sky), and it has to be completley hand made, so no rocket motors.

The book uses rocket candy, and zinc dust and sulfur, but i want to use rocket candy due to the availability of chemicals. What recipe works best? Ive see alot on the web, and dont wanna waste.

The casing, in porportion to the book, is 1" wide tubing 2' high steel EMT conduit. How much should i fill it?

Would ceramic work as a nozzel? what shape? I cant make a metal one, because school dosnt have a metal lathe.
EDIT: this shouldve been in chemistry.

Dr. Shark

Thu Apr 17 2008, 06:46PM

Registered Member #75 Joined: Thu Feb 09 2006, 09:30AM
Location: Montana, USA
Posts: 711

You definitely want to follow Richard Nakka here

here is one of the most experienced people in this subject. Also check

as he has a nifty method of dissolving the ingredients in water before heating them, which apparently helps mixing the ingredients.

Make sure you know what you are messing with, experimental rocketry is a dangerous undertaking an in fact most rocketry associations WILL NOT allow you to fire a "homebrew" rocket at one of their events.

Ceramic is a great material for a nozzle, but how the hell are you going to machine that if you don't even have access to a metal lathe? I think some people had success with a concrete nozzle, maybe that would work for you.

[Edit: Broken URL]

Bored Chemist

Thu Apr 17 2008, 08:49PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

Dr shark,
I think that pre bronze age cultures managed to make stuff out of clay without any of the trappings of modern technologhy (apart from a fire).

However the point about how dangerous home made rockets can be is still valid.
As far as I can see this guy is making a pipe bomb by accident.

ramses

Thu Apr 17 2008, 09:21PM

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

I've read that book too, good read. As I recall, they initially had problems with not packing the tube well enough, resulting in air bubbles. you might get in serious trouble if your rocket blew up, especially after all the media crap about everyone being a terrorist. if anyone gets hurt, even remotely, expect the worst (expulsion). I would pack it all the way, and make sure you do a test launch at home if possible.

ask your teacher, they may want you to blow it up at the peak of it's path, to keep a 2' long hunk of hot steel from landing on anything sensitive. I've heart the ground kitty litter can be pressed into a nifty nozzle, just make sure you put the propellant in first. just make sure there is a hole dead center in the clay.

ramses

Dave Marshall

Thu Apr 17 2008, 09:33PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Under federal law, making any rocket that intentionally explodes without a pyrotechnic license is at best a serious misdemeanor, especially given the power that would be required to effectively fragment "a 2' long hunk of hot steel".

Give it an ejection charge and a parachute like every other model rocket on the planet. It isn't hard. A few grains of F gun powder on the top end of the motor that pushes the nose cone off.

In my experience, PVC is very capable of containing your typical candy rocket. I've launched motors weighing in excess of 3 pounds in 2" PVC. Its lighter, cheaper, easier to work with, and less likely to do catastrophic damage if it hits something.

Ceramic will work as a nozzle. You could build a small wood or propane fired kiln in your back yard that could get hot enough to effectively fire a ceramic nozzle. A 55 gallon drum, some fire bricks, and a sawzall should just about do the trick. I'm thinking if people who were still using sharp rocks for tools could do it, you shouldn't have too much trouble.

Dave

rp181

Thu Apr 17 2008, 09:33PM

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

one, this is not going to be lauched at school, itle be launched somewhere else and videotaped. I was planning to make the nozzle out of clay and firing it. Wouldn't blowing it up just send shrapanel everywhere? that would be a pipe bomb in midair. No one would be there, just us 3 working on it.

Making the hole in the center wont be a problem, making it on the potters wheel will make it easy to tell. How am i going to attach the clay nozzle? i was thinking welding on a metal ring once the nozzle's in, making it stay. ILe make sure its packed really well.

Are there any laws concerning homemade rockets?

Dave Marshall

Thu Apr 17 2008, 09:36PM

Registered Member #16 Joined: Thu Feb 02 2006, 02:22PM
Location: New Wilmington, PA
Posts: 554

Heh, posted right as you did rp181.

Yes, there are a number of laws regarding the manufacture, procurement, storage, and handling of rocket motors and their chemical components. Generally speaking candy rockets in their simplest form avoid most restrictions so long as the fuel is mixed on site and the engine is below a certain size.

There are a number of sites on the web that detail these laws. Most sites regarding experimental rocketry link to them in some form or fashion.

Dave

rp181

Thu Apr 17 2008, 09:41PM

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

Hmm, well i made this concerning making it blow up in midflight, but thats against the law, so i guess this will work to:

By knowing the burn rate of the fuel, i can pick the right thickness of the top of the fuel. On top of it, the ejection charge would be placed, so once it burns through the rocket candy, itle burn the ejection charge.

EDIT: forgot about the PVC comment. I thought that PVC would break with the pressure, on top of that, PVC is a good fuel, so wouldnt it burn? Also, PVC is toxic when burned. If it works, ile use it, does the 1in have to have a certain pressure rating?

Billybobjoe

Thu Apr 17 2008, 10:51PM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

rp181 wrote ...

By knowing the burn rate of the fuel, I can pick the right thickness of the top of the fuel.

What is the burn rate of the fuel? Making rockets is all about finding the burn rate of the fuel and avoiding making the whole thing a smoke bomb or worse, pipe bomb. And what's going on in that picture?

rp181 wrote ...

PVC is a good fuel, so wouldnt it burn? If it works, ile use it, does the 1in have to have a certain pressure rating?

It will burn, ideally much more slowly than your fuel. Solid core 1 inch pipe usually has a pressure rating of 480 PSI (its stamped on the tube). Foam core, which is no good, will usually say "cellular core" on it and is not designed for pressure.

I don't know why everyone is talking about firing a clay nozzle. I suppose its possible but I've never heard of it being done. Get some bentonite (or just regular dry powdered clay) and look up some information about rocket tooling (see below) to see how it is rammed into a solid mass (nozzle).

I would recommend David Sleeter's book

It covers mainly blackpowder engines but there is a powdered rocket candy propellant listed as well. It may be the most information packed book I've ever read. There is nothing left for the reader to guess - shows how to make tooling and everything else, and gives proven-to-work engine dimensions. This may be a bit much to do for your extra credit project but if your interested in rocketry as a hobby definitely check it out.

Bored Chemist

Fri Apr 18 2008, 06:09AM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

"I was thinking welding on a metal ring once the nozzle's in, making it stay. "
Really, welding on a fueled rocket?

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