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Pneumatic Rocket for my school Project

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Unread postAuthor: psycix » Thu Nov 08, 2007 6:49 am

The design looks nice! (omgimgonnastealitlolnojoke)
But I think it can be inproved.
Your big center main part of the rocket just only counts up for weight and air resistance.
Make it an engine too!
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Unread postAuthor: Skywalker » Thu Nov 08, 2007 8:23 am

Yeah dude, I've built tons of water rockets, you're going to want to use something lighter than PVC. Also, you will never make a two-engine configuration like that work -- the thrust won't be the same and the rocket will not fly straight. But if you could make a two-stager work (it's been done) that would be impressive.

As for non-electronic parachute deployment, only one way to go: airspeed flap. I made one work once; it's tricky but you can do it it, and it's quite impressive.
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Unread postAuthor: jrrdw » Thu Nov 08, 2007 8:43 am

If the rocket falls with the bottem pointed down, a open body mite let the air flow from falling push out the nose cone.

I don't quit understand how you plan to use quick disconnects. Pull the cord and that disconnects them giving a wide open throttle from the start?

That would be a short ride for the size of you design.
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Unread postAuthor: Zen/// » Thu Nov 08, 2007 9:12 am

Yeah, pvc is just too heavy and you really only need 1 engine.
Like that episode of mythbusters on the rockets on the swing.
The two rockets dident fire at the same time and caused the dummy on the swing to twirl instead of going around the swing. The two rockets were fired a fraction of a second out of sink (lol whats the real spelling?) .
Then they decided to just use 1 rocket.
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Unread postAuthor: psycix » Thu Nov 08, 2007 11:49 am

Its just too hard to get the thrust right with multiple engines.
Also, pvc is too heavy
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Unread postAuthor: jackssmirkingrevenge » Thu Nov 08, 2007 12:02 pm

I still think it would be a better idea to use the launcher as opposed to the actual rocket for propulsion - that way, you save a lot of weight on your actual rocket enabling you to easily fit any recovery gizmos you might want to add.
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Unread postAuthor: jrrdw » Thu Nov 08, 2007 1:55 pm

jackssmirkingrevenge wrote:I still think it would be a better idea to use the launcher as opposed to the actual rocket for propulsion - that way, you save a lot of weight on your actual rocket enabling you to easily fit any recovery gizmos you might want to add.


Thats a really good point. Maby build a mini launcher just for launching rockets of this type. Have the best of both worlds, engines on the rockets that go off 50' or so after launched????
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Unread postAuthor: LikimysCrotchus5 » Thu Nov 08, 2007 3:09 pm

Yea but you need to somehow configure your mini launcher to be compatible with water because you need propulsion and using air is not going to be enough because it will be light and since it wont have alot of weight then the speed in the air will screw it up. An example, if you have ever used a coke bottle, the wind will carry it once its out of water cause its light.

Or B, I just thought of this :idea:
Maybe make a mini launcher, a mini rocket, but you have some weight on the rocket which will cause it to fly better. Like make this rocket out of pvc and have it fit down the barrel snuggly.

@ammosmoke: well i think it would be better to have more surface area with high pressure so that you can distribute the propulsion better. Take for example a real rocket. It usually has three engines plus two side engines, and the engine takes up the whole bottom of the rocket. So i would say go with more surface area, but no bigger than the rocket and you will need a good amount of pressure to give it a nice boost.
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Unread postAuthor: Maniac » Thu Nov 08, 2007 5:00 pm

off topic but it was a funny coincidence the exact same thing is happening to me i had the same idea and every thing else too
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Unread postAuthor: Thursto » Thu Nov 08, 2007 9:46 pm

Hey all, well thanks for the comments, i dont think my school would let me bring in a launcher like jacks idea, because a barrel could be attached and anything that fits in it could be fired so then they'll be all angry and get cops n crap involved, but i might just do that, hae a under over design with a good old ball valve and yeah.

With the disconnects its hard to explain, lok on google, and find someone who made one of those bottle type rockets, and how they have the garden connector thing and they attach string to the bit that you pull down, and the pressure launches the rocket out of the socket when the latch is released. its hard to explain.

And maniac, did you try it out, and if so did it work?

and i know PVC is heavy but what else could i make it out of that would hold 50-100PSI?
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Unread postAuthor: ammosmoke » Thu Nov 08, 2007 10:01 pm

LikimysCrotchus5 wrote:Yea but you need to somehow configure your mini launcher to be compatible with water because you need propulsion and using air is not going to be enough because it will be light and since it wont have alot of weight then the speed in the air will screw it up. An example, if you have ever used a coke bottle, the wind will carry it once its out of water cause its light.

Or B, I just thought of this :idea:
Maybe make a mini launcher, a mini rocket, but you have some weight on the rocket which will cause it to fly better. Like make this rocket out of pvc and have it fit down the barrel snuggly.

@ammosmoke: well i think it would be better to have more surface area with high pressure so that you can distribute the propulsion better. Take for example a real rocket. It usually has three engines plus two side engines, and the engine takes up the whole bottom of the rocket. So i would say go with more surface area, but no bigger than the rocket and you will need a good amount of pressure to give it a nice boost.



I didn't know how big his rocket was.... How big is it? I don't really see what was wrong with my suggestion.... (!?!) I never said one way or another about engines and their placement, at least I don't think so...

But seriously, just a suggestion, use something like 1/4" quick connect instead, because you won't have water to slow down the flow. And put it up to about 400psi....
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Unread postAuthor: LikimysCrotchus5 » Thu Nov 08, 2007 10:34 pm

EditEDIT: Oh, I forgot the part about quick disconnect hose things. Depending on how large your rocket is, you may want to use something with a smaller hole.


Im was just basing what i said off of this. The more surface are would be good but what your saying will also work. I was just using real rockets as an example. So the open part of the engine has more surface area becaus there is three, its just a idea. But i think you would do better with some type of liquid propulsion, such as water.
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Unread postAuthor: Thursto » Thu Nov 08, 2007 11:42 pm

I posted in the main topic that these were the dimensions:

Approx dimensions:
Engines:
length: 20cm
Width: 2"
Main Section (middle area):
Length: 50cm
Width: 3" DWV (because DWV pipe is ligher, plus its not storing pressure.)

EDIT: Heres the pics

Image
Still attached to my garden connections but we have some spares in the shed, but yeah u get the point, the gold part will be attached to he bottem of the rocket, an will act as the nozle in witc the water sprays out of.

Image
Here it is disconnected

And also i'll get a few picturs up of what i mean by garden disconnects.
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