So I've been wanting to make a rocket engine for a long time now and after lots of delays, I finally finished my first one. Originally it was going to be a small liquid engine but that was becoming more and more complex and after hearing about Copenhagen Suborbitals' work with [URL="http://www.copenhagensuborbitals.com/public/GALCIT_Report.pdf"]Galcit rocket propellant[/URL] I decided to make a solid rocket motor instead.
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000257.JPG[/t]
[B]What did you make it out of?[/B]
Just some steel pipe fittings.
[B]How big is it?[/B]
The pipe is 3 inch steel with ~1/4 inch think walls so it's about 3 1/2 inches in diameter. The nozzle exit is 1 1/2 inches in diameter (on the inside). Overall it's about 16 inches long.
[B]It's not done! There's no exit cone piece on the nozzle![/B]
I wanted to make a diverging nozzle piece but I don't have to tools to do it.
[B]Did you weld it yourself?[/B]
Nope. My dad did because I'm really bad at welding.
[B]What will you use as the propellant?[/B]
It's going to use [URL="http://www.copenhagensuborbitals.com/public/GALCIT_Report.pdf"]Galcit propellant[/URL]. My propellant mixture is going to be slightly different than in the link. It's going to be a mix of potassium nitrate (oxidizer), [del]vaseline[/del] candle wax (paraffin; fuel), and roofing cement (various hydro-carbons; fuel and binder) at approximately 60, 15, 25 percent volume, respectively.
[B]What will be the grain configuration?[/B]
[IMG]https://dl.dropboxusercontent.com/u/13781308/ShareX/2013-08/2013-08-05_10-30-25.png[/IMG]
This configuration has an initial short-duration high-thrust burn followed by a long-duration low-thrust end burning section.
[B]Will the rocket fly?[/B]
No. It's really heavy (29 lbs without propellant) and I don't know how much thrust this will produce. Instead it's going to be mounted to an extra piece of I-beam my dad has and static-fired. If it produces enough thrust I might look into making a tube body for it.
[B]How will you ignite this?[/B]
Not sure yet. I need to make some sort of electronic pyrotechnic igniter (like a model rocket igniter) but it needs to be able to get the entire inside really really hot.
[B]You're crazy!
[/B]:v:
[B]Do you have any more pictures?[/B]
Of course!
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000171.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000175.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000176.JPG[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000189.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000191.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000199.JPG[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000201.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000203.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000215.JPG[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000218.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000225.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000228.JPG[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000229.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000232.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000234.JPG[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000245.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000246.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/P1000255.JPG[/t]
I'm excited to see more
'I'm somewhat surpeised there aren't more comments in this thread.
Then again I guess there isn't much to discuss since the OP already answered a bunch of questions in the OP, that and most people here probably don't know much about rockets.
I guess I should contribute some questions then...
Do you have any kind of estimate on power output?
Do you have any plans to measure the power output during the static fire?
How do you measure power output? I've always wondered that.
[QUOTE=OvB;41798205]How do you measure power output? I've always wondered that.[/QUOTE]
I'm not sure myself, but if I had to guess, I suppose you could attach it to some sort of a device on the top that works as a sort of inverted weight scale?
Maybe an accelerometer in the jig that holds it? or mount it to an arm that has a certain amount of give, and then measure how far it bends?
I made a rocket engine once.
It was cardboard with match propellant. The paper boat is was supposed to propel bow dived and the thing lit on fire.
Fire and explosives are fun. How much stress is the thing going to be under though?
Also I'd say your best bet for an igniter is a blowtorch on a stick.
Just ordered 6 lbs of potassium nitrate. I also decided to change the fuel from vaseline to candle wax (paraffin).
[QUOTE=chipset;41797698]Do you have any kind of estimate on power output?
Do you have any plans to measure the power output during the static fire?[/QUOTE]
Nope. Figuring out the thrust requires knowing what the burn rate of the propellant mixture is and I don't know that. I might make up a small amount of propellant and stuff it in a pipe to 1) figure out a burn rate, and 2) test an igniter.
I would like to somehow measure it but I don't think I will be able to make something up to do so. I would like to do something like what LarparNar said and make a spring scale that work by compressing the spring and seeing how much it gets compressed. But that requires make a sliding sled type thing for the engine and I don't think that'll happen. Maybe in a later test.
[QUOTE=A_Pigeon;41804242]Fire and explosives are fun. How much stress is the thing going to be under though?
Also I'd say your best bet for an igniter is a blowtorch on a stick.[/QUOTE]
I'm not sure about the stress because I'm not sure about the pressure (because I don't know the burn rate) but this is quarter inch steel so If anything fails, it will be the flange gasket or the nozzle melting.
As for an igniter, I'm gonna try lighting a bunch of match heads with a model rocket igniter and see if that works.
maybe try throwing a firecracker/match bomb/flaming axe can. depends on if you need a prolonged burn or not.
Just attach it to a bike or a long board!
I remember some member at the Space thread in GD was making a rocket with their college and they just stuffed a lit sparkler up the thing for the ignition but they were using liquid fuel not solid. That might be considerably more dangerous with solid.
And another thing with the igniter; it needs to get the entire burn surface really hot as evenly as possible. So stuffing a sparkler in there would cause one section of the burn surface to start burning before the other sections so you would end up with an uneven burning of the propellant grain. If I were to toss a firecracker in there it might damage the grain. So I think I'm gonna go with something like a match bomb.
Made some propellant to test out igniting and to go over the propellant making process.
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_145257_577.jpg[/t]
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_173042_989.jpg[/t]
Doesn't really burn. Adding more oxidizer as we speak.
More images and videos to come.
[editline]poop[/editline]
As promised.
Boiling water for the hot water bath
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_170338_428.jpg[/t]
Melting the wax
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_171037_684.jpg[/t]
Putting in the roofing cement
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_171353_766.jpg[/t]
Roofing cement heating up and mixing in
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_171556_027.jpg[/t]
Potassium Nitrate mixed in
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_172901_222.jpg[/t]
First burn
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_190020_315.jpg[/t]
Unsuccessful attempt
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant/IMG_20130825_194041_950.jpg[/t]
[video=youtube;-1umbGylXpU]http://www.youtube.com/watch?v=-1umbGylXpU[/video]
So, first I took a small bit on the end of a sliver of wood and that seemed to burn alright. However, when I took a pile of it and tried to burn that it didn't do anything. So I tried using a bigger torch but that just smoldered and went out. So I reheated it and put in more oxidizer (% mass of KNO3 went from 60% to about 75%). I tried again with the big torch and it smoldered a bit more and a bit longer but it just went out.
Since adding mroe oxidizer seemed to help, what I think the problem might be is that the environmental pressure is below the propellant's deflagration limit. The deflagration limit is the minimum pressure that a propellant can burn at and self-sustain combustion without requiring additional input energy. This is just a theory though so I emailed Copenhagen Suborbitals to see what they might think.
[QUOTE=Pelf;41966957]So, first I took a small bit on the end of a sliver of wood and that seemed to burn alright. However, when I took a pile of it and tried to burn that it didn't do anything. So I tried using a bigger torch but that just smoldered and went out. So I reheated it and put in more oxidizer (% mass of KNO3 went from 60% to about 75%). I tried again with the big torch and it smoldered a bit more and a bit longer but it just went out.
Since adding mroe oxidizer seemed to help, what I think the problem might be is that the environmental pressure is below the propellant's deflagration limit. The deflagration limit is the minimum pressure that a propellant can burn at and self-sustain combustion without requiring additional input energy. This is just a theory though so I emailed Copenhagen Suborbitals to see what they might think.[/QUOTE]I think that's exactly it, this seems to be behaving like rifle powder outside of a cartridge. It's sort of sputtering and not really being very enthusiastic in it's burn. Also, are you mixing it properly? It seems to be somewhat inconsistent, so maybe you have a mixing issue too.
Any updates or?
I never got a response from CS but I'm pretty sure the issue was just the deflagration limit. I've got a bunch of propellant lying around (about 1kg worth) so I'm going to make a small test motor to test out an ignition system, determine (roughly) the propellant burn rate, and to confirm whether the deflagration limit is truly the cause for the propellant not burning before.
As for the ignition system, this is what I was thinking:
[t]https://dl.dropboxusercontent.com/u/13781308/ShareX/2013-09/2013-09-17_17-38-05.png[/t]
(pardon the poor diagram)
There is a model rocket igniter located inside the engine. A propane tank (or possibly an acetylene tank from an acetylene torch) fills the motor with propane (or acetylene) gas. The gas supply is cut off, removed from the nozzle, and the model rocket igniter is [URL="http://www.youtube.com/watch?v=bti7XgFT-Lg"]ignited[/URL], hopefully causing the gas to explode, making the inside of the motor really hot and increasing the pressure enough to overcome the deflagration limit.
Today I went through my dad's pipes and stuff to find threaded steel pipe caps for a test motor. He only had 1 inch and 3 inch caps. Since 1 inch is too small I went with the three inch. My dad can only put threads on segments longer than about a foot so the test motor was going to be 3x12 inches. But then I realized that my engine that I already welded up was the exact same dimensions so I decided to forget the test motor; I'll just use the actual engine for testing.
In the meantime, since I don't have a tripod for my camera, I made a little stand for it:
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/IMG_20130921_173343_766.jpg[/t]
[editline]21st September 2013[/editline]
I asked my dad about the igniter idea and he didn't think it would get hot enough for long enough to start combustion. He said it would probably just make a loud bang but not be enough to set it off. So I looked around online for some injector ideas and I found this site: [URL]http://www.nakka-rocketry.net/igniter.html[/URL]
That guys says he uses black powder and the designs there are pretty similar to a model rocket engine. Since I have some extra Estes engines, I'll try putting one of them in the nozzle of my engine and setting it off. It'll be hot, and should raise the pressure enough, and it'll sustain it for a second or two which should be plenty to ignite my engine.
So that basically puts everything in place. I'm going to try to fire it off tomorrow.
[editline]21st September 2013[/editline]
Maybe I'll try my igniter idea anyway. Couldn't hurt.
Loaded the engine with propellant.
The workstation
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_100331_370.jpg[/t]
Breaking it out of the bucket with a screwdriver
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_100302_210.jpg[/t]
Putting pieces in a dish
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_100317_684.jpg[/t]
More pieces
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_101350_889.jpg[/t]
Halfway there
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_101403_033.jpg[/t]
Filled and tamped down
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_103128_088.jpg[/t]
Removing the pipe
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_103313_558.jpg[/t]
Pipe removed
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/IMG_20130922_103406_845.jpg[/t]
Neatened the edges of the hole
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/P1000331.JPG[/t]
Close-up
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket Engine/Propellant Loading/P1000329.JPG[/t]
The hole is a little off-center but it'll only make the burning a bit uneven. No big deal there. At least for what I'm doing. If this were launching any kind of rocket then that unevenness wouldn't be acceptable.
[editline]e[/editline]
Rocket set up and ready to test. Will fire in a little bit and post results. Video later tonight.
Tried 3 times; all failed.
[video=youtube;xeHtUlKQ4yU]http://www.youtube.com/watch?v=xeHtUlKQ4yU[/video]
I used model rocket engines for the igniters. This is the first test. The model rocket was placed in the nozzle shooting in.
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/1-IMG_20130922_151424_548.jpg[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/1-IMG_20130922_151937_391.jpg[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/1-P1000332.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/1-P1000334.JPG[/t]
For the second test I tried placing the model rocket engine at the bottom of my engine shooting out.
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/2-IMG_20130922_154724_478.jpg[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/2-P1000337.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/2-P1000341.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/2-P1000342.JPG[/t]
At this point I figured the issue was probably the pressure so I took a blank flange and drilled a 1/4" hole through it. I used the same igniter setup as the last test.
[t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/3-IMG_20130922_164615_350.jpg[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/3-P1000343.JPG[/t][t]https://dl.dropboxusercontent.com/u/13781308/Rocket%20Engine/First%20Test/3-P1000346.JPG[/t]
I'm thinking it's probably a bad batch of propellant. I'll make some more next weekend and see if I can do any better.
Have you thought about trying out rubber as the fuel? if you grind it down into a fine powder it will readily melt and mix with the oxidizer, if i remember we used ammonium perchlorate. for just plain rubber rockets I used it using oxygen from a welding gas bottle as the oxidizer. produced some pretty powerful thrust.
I also heard of using iron oxide based propellant, but never got round to trying it. there is a pretty good site for different types of fuels and their applications.
[URL]http://www.pyrocreations.com/rocket_propellants1[/URL]
Sorry, you need to Log In to post a reply to this thread.
