Welcome to the Water Rocket Forum, sponsored by The Water Rocket Achievement World Record Association.

The largest, most sophisticated and ground breaking group supporting you, the serious water rocket flyer! Whether you are a beginner or an expert, the WRA2 has something for everyone.

A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Put a high pressure in a rocket without reinforcing it

Discussion about Compressors, hose, pipes, fittings, launchers, release mechanisms, and launch tubes.
User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Mon Apr 05, 2010 5:55 am

In fact that is also a question that I have, because I can take the reinforcement from the rocket but I need an extra reinforcement for the cross-section of the nose-cone, and maybe the weigth difference will be minimal...

I don´t need 400 psi to say that this works, I only need to launch it above the burst point of the bottle.

Making the seal with the reinforcement of the cone will be hardest part of the design.


Research and Development is the soul of WR

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Wed Apr 07, 2010 6:29 am

The one major problem is that during launch as soon as I break the seal around the nose cone, the water around the outside will depressurise rapidly. This will cause the rocket to overpressurise and explode before it makes it off the end of the launch tube.

I think the solution to this problem is to mesure the maximum expansion in diameter of the bottle before it bursts.
That expansion will be in milimeters, so the 0-ring in PVC tube must be deplaced in the bottle in a way that the distance that the bottle has to move up will be less than the expansion distance.

So if the burst distance of the expansion is 4mm, the 0-ring must be 2mm inside the bottle.

Probably the 0-ring must be made of teflon and I should put a teflon tape inside the bottle´s neck, that way less friction will help to launch the rocket faster than the expansion.


Research and Development is the soul of WR

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Fri Apr 09, 2010 3:08 pm

Here is the same idea, this time the launch tube is retractable (wich will be a technological challenge) before the launch.

This way it wont have the friction of the 0-ring wich would avoid the rocket to depressurise before it explodes.

I think it won´t explode because the resistance towards the 22mm hole is less than towards the walls of the rocket, so the air will move more quickly towards the nozzle than towards the wall.

That way the rocket will depressurise faster than the burst speed (I guess...).
rocket-box2.jpg
You do not have the required permissions to view the files attached to this post.


Research and Development is the soul of WR

User avatar
U.S. Water Rockets1
WRA2 Member
WRA2 Member
Posts: 1771
Joined: Sat Feb 03, 2007 3:24 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by U.S. Water Rockets1 » Sat Apr 10, 2010 10:52 pm

What if you were to make a sabot the shape of your rocket that would hold the rocket in shape until it exits the launch tube.

We were just kicking around some ideas at out meeting and it was suggested you freeze the water in the launcher and the ice would shatter when the rocket swelled up as it exited the launch tube, but it should come out before the rocket could explode.


Team U.S. Water Rockets
Visit USWaterRockets.com
Visit our Blog
Tune in to our YouTube Channel
Visit our Facebook page
Visit our Twitter Page
Opportunity is missed by most people because it is dressed in overalls and looks like work. --Thomas Edison

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Sun Apr 11, 2010 6:38 am

The reason that I had prefered a water-box instead a sabot is simple:

- more easy to make
- the sabot can´t cover the zone from were the fins born, so that sligth area might burst.
- with a sabot it will have virtual spaces around the rocket (mm, micro...) that might burst.

The freeze idea is cool but the problem are the fins, they will get stucked in the ice.

Maybe they should be retractable so after getting out they would expand...but I dought that the expanding speed would be more faster than the launch speed.

To break the ice the fins should be strong (carbon fiber) and very thin (like the ones from the X-12).

Fins that goes from the top of the rocket to below the rocket will slide trough the ice instead of having to crack the ice that is freezed in the superior part of the fins.


Research and Development is the soul of WR

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Sun Apr 11, 2010 7:22 am

SaSkAlex said that my sealing mechanism must hold 3600lbs (= 1600kg) of pressure.
If so this project is already doomed, but I don´t know the carbon fiber strenght to hold this.


Research and Development is the soul of WR

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Sun Apr 11, 2010 8:36 am

Here is an example of a Sabot Launch.



Research and Development is the soul of WR

User avatar
RaZias
WRA2 Member
WRA2 Member
Posts: 751
Joined: Mon Jul 14, 2008 3:16 pm

Re: Put a high pressure in a rocket without reinforcing it

Post by RaZias » Sun Apr 11, 2010 12:10 pm

Any idea of a good material to make a mold from a 2 L bottle ?

I think the Sabot idea might work I just need to find a material to make the mold.


Research and Development is the soul of WR

Post Reply