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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.

Unofficial multi stage world record

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SaskAlex
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Unofficial multi stage world record

Post by SaskAlex » Mon May 10, 2010 8:22 pm

Well I flew JP-2 again on Saturday. It achieved two record breaking flights that were class B compliant, except that my onboard camera decided not to work. I still haven't figured out why, but I guess that's what you get for a $20 camera. Oh, and I still did fly the camera, so there was no weight advantage.

The first flight reached 1141' and the second reached 1157' for an average of 1149'. Both flights were done at about 180 psi. Here are the altimeter logs:
may8flight1.jpg
may8flight2.JPG
I won't bother posting the ground footage because it was absolutely rubbish. If I go for another attempt at making it official, I'll definitely have to work on that.

The booster weighs 389g and the sustainer weighs 248g. With the 45g payload it comes to a total of 682 grams. Here are some pictures. The sustainer is shown without the parachute system and payload (shown here http://www.wra2.org/forum/viewtopic.php ... 1062#p8207). One interesting thing about the sustainer is that the water is stored near the front of the rocket, but the whole vessel is pressurized. The first picture shows the internal setup before the pieces were all PL'ed together. If you can't see how it works, I can post an explanation.
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Re: Unofficial multi stage world record

Post by WRA2 » Mon May 10, 2010 9:01 pm

Let everyone know if you figure out why the camera did not work. There are a lot of teams that are using that same one. I can at least add the 1157 flight to your personal best on the standings page.


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Re: Unofficial multi stage world record

Post by WTF » Tue May 11, 2010 12:05 am

Awesome job Alex! I am blown away by the performance of your little rocket! It's so small and light. When you posted your videos on Youtube I assumed you were flying a huge rocket like everyone else. I'm amazed that such a small and light unreinforced rocket has gone so high. I think you have completely nailed something nobody had ever tried before. Your idea to put the water in the front of the sustainer is pure genius! Why didn't anyone think of that before!!! That's "outside the box" thinking and I love it. My hat is off to you!



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Re: Unofficial multi stage world record

Post by wracing » Tue May 11, 2010 12:29 am

Congratulations Alex!!!!! :D :D :D



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Tim Chen
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Re: Unofficial multi stage world record

Post by Tim Chen » Tue May 11, 2010 12:26 pm

What a great idea! I've never seen anyone with the water above the air in a water rocket before. I'm embarrassed to say that I've been at this for several years and never tried anything like that before. Thanks a lot for making us so-called "experts" look like amateurs! (Just kidding). You deserve a lot of credit for this idea. I hope you have a name for this scheme so that we know what to call it.

I'm impressed!


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SaskAlex
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Re: Unofficial multi stage world record

Post by SaskAlex » Tue May 11, 2010 10:25 pm

Thanks for the positive feedback, guys. I can't really think of a name for the water storage system. How about saying the sustainer has "false-bottom water storage"? Doesn't have to much of a ring to it, so suggestions are welcome.

Interestingly, this aspect of the rocket was of little benefit on these last to flights. Some how, the seal (hot glue) between the green straw (for air movement between the two compartments) and the false bottom became damaged before these flights. Water was leaking between the top and bottom compartments, so I could only put in enough water to fill the tube going from the false bottom to the nozzle. I guess this shows that you have to be really careful when building a system like this, because it's all inside the pressure vessel and can't be repaired.

All in all, I think the lack of a staging mechanism was more beneficial to this rocket than the water storage. The sustainer is firing the whole time, and it is supported by the booster in such a way (which you can probably see from the pictures) that it can separate very easily. It requires absolutely no hardware on the sustainer. This means the sustainer separates without loosing any velocity and without having any chance to change direction.



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Re: Unofficial multi stage world record

Post by air.command » Tue May 11, 2010 10:55 pm

Very nice work Alex. Those are some very impressive flights!
Tim Chen wrote:I hope you have a name for this scheme so that we know what to call it.
One of the names given to this system is "Hydrocephalus". Here are some examples of it:

The following relevant text was archived from the old mailing list:
Perhaps :
http://perso.numericable.fr/~fbouquetbe ... fusees.htm
or
http://www.planete-sciences.org/espace/ ... ersee.html
or
http://www.passaero.info/e-invers.1.html


also some more discussion about it here:

The following relevant text was archived from the old mailing list:
Basicly, water is stored in an upper chamber that has a tube connecting to the
nozz. And there's stand pipe(s) that allow air to flow into the upper chamber
from the lower fuselage to push the water out. The stand pipes stop the water
from falling into the lower chamber but allow air to feed into the upper chamber
above the water. So the weighty water only sits higher in the fuselage until
it's ejected.

My first build is a couple of similar circumfrence bottles as the lower fuselage
and an upper bottle turned neck down. Some drinking straws pierce the upper
bottle funnel area as stand pipes. A piece of 1/2" pvc pipe connects the neck
of the upper bottle to the lower nozz. All is glued with PLP.

The buld in progress involves some new bottles i failed to describe in my last
posting. These bottles are 1/2l and 2.34" (Cool! Huh!) diameter, with a
slightly wider base area. Happens that the base is a perfect outside fit for
the other end of the bottle. (Iceland Sping water) I happen to have collected
some thinwall kite stut tube tha fits a gardena nozz just right and also
pressfits a sport cap slider+ cap.

Since the strut is 3' long, that dictates a spliced assemby of about 5 bottles
in the lower chamber; a sports cap to seal the upper chamber bottom and the
strut sticks out of the Garnena nozz. The strut becomes the actual nozz, and
the Gardena becomes the launch release I think the i.d. of the tube may be
8or9mm.

Essentially, it looks like a black tube inside a spliced fuselge that reaches
from the nozz to about 80% of length of the fuselage and terminates in the neck
of another fuselage section. I figure the water in the tube plus the water in
the top chamber can varied from about 25% or lower in relation to the air in
the under chamber.

One thng I question is what forces and restrictions will that long 'nozz' have?
And another...how nuch stand pipe feed will be needed; especially when using
bigger nozz..

I've been working on a sketch of it and should post it to the group pictures
soon.


http://www.AirCommandRockets.com

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Re: Unofficial multi stage world record

Post by ninja_iga » Wed May 12, 2010 12:18 am

hi Alex!

congrats on the record flight!

uh, i'm slightly lost here, for my benefit,
can you explain, how come putting the water higher in a WRocket is better? :D
really appreciate it! :)


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Re: Unofficial multi stage world record

Post by WTF » Wed May 12, 2010 1:36 am

air.command wrote:Very nice work Alex. Those are some very impressive flights!
Tim Chen wrote:I hope you have a name for this scheme so that we know what to call it.
One of the names given to this system is "Hydrocephalus".
That sounds a little bit too pornographic. This is a family forum!



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Re: Unofficial multi stage world record

Post by WTF » Wed May 12, 2010 1:43 am

ninja_iga wrote:hi Alex!

congrats on the record flight!

uh, i'm slightly lost here, for my benefit,
can you explain, how come putting the water higher in a WRocket is better? :D
really appreciate it! :)
It would put the weight in the front of the rocket and would help it be stable in flight. It would be like a dart, where the point is metal and would make sure it was stable after it was thrown, even if you throw it badly the dart corrects itself because the weight. I assumed this was perfect for a boosted rocket. It would let it throw the rocket like a dart.

Apparently it doesn't make a difference, so nevermind.



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Re: Unofficial multi stage world record

Post by Brian » Wed May 12, 2010 2:29 am

congratulations! thats a nice looking rocket. i once designed something the same for the reason that you could use the a longer launch tube as a good piston inside the inner tube.
you might be able to squeeze a few more metres out of your record (unless your already using a launch tube).
whens your next record attempt.


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Tim Chen
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Re: Unofficial multi stage world record

Post by Tim Chen » Wed May 12, 2010 9:18 am

WTF wrote:
ninja_iga wrote:hi Alex!

congrats on the record flight!

uh, i'm slightly lost here, for my benefit,
can you explain, how come putting the water higher in a WRocket is better? :D
really appreciate it! :)
It would put the weight in the front of the rocket and would help it be stable in flight. It would be like a dart, where the point is metal and would make sure it was stable after it was thrown, even if you throw it badly the dart corrects itself because the weight. I assumed this was perfect for a boosted rocket. It would let it throw the rocket like a dart.

Apparently it doesn't make a difference, so nevermind.
I was under the impression that it worked so well mostly because the idea prevented the water from sloshing to the top of the rocket the second the boosters stopped thrusting, and so you don't need to use foam to stuff the entire rocket with reaction mass that doesn't move around. I'm not a big fan of foam because even the cheap store brand soaps are expensive, and it is bad for the environment and kills the grass. I want to make sure not to leave brown spots where I launch because it's not my property.

If it's true the last launches didn't have the water on top, then I wonder what keeps the sloshing from breaking up the thrust. I hope Alex can get some good ground footage next time.


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Re: Unofficial multi stage world record

Post by WRA2 » Wed May 12, 2010 4:26 pm

Tim Chen wrote: If it's true the last launches didn't have the water on top, then I wonder what keeps the sloshing from breaking up the thrust. I hope Alex can get some good ground footage next time.
Maybe you should make a new sustainer without the "extra hardware" inside which will make the rocket lighter and possibly go higher. Keep up the good work Alex, you are getting close to the altitude that Anti Gravity flew in 2003 and have beaten some very famous water rocket teams to 1000 feet! 8)

Speaking of ground videos Alex, You do not need to have a professionally produced documentary for a record submission. Since the WRA2 requires the onboard video, the ground video is less important. An easy way to produce an acceptable ground video is to place your camera in a fixed location to film the launch. Then after you have launched you can take the camera and film as much as the descent as possible. If you look at most water rocket videos you will see that no one can track the rocket through it's entire flight without it drifting out of frame or landing behind tress, etc. Since the onboard video is required you do not need the film the entire flight from the ground and keep the rocket "in frame".


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Re: Unofficial multi stage world record

Post by SaskAlex » Wed May 12, 2010 7:48 pm

Tim Chen wrote: I was under the impression that it worked so well mostly because the idea prevented the water from sloshing to the top of the rocket the second the boosters stopped thrusting, and so you don't need to use foam to stuff the entire rocket with reaction mass that doesn't move around. I'm not a big fan of foam because even the cheap store brand soaps are expensive, and it is bad for the environment and kills the grass. I want to make sure not to leave brown spots where I launch because it's not my property.

If it's true the last launches didn't have the water on top, then I wonder what keeps the sloshing from breaking up the thrust. I hope Alex can get some good ground footage next time.
Actually, the way the sustainer sits on the booster there is absolutely zero force holding the sustainer onto the booster. The moment the booster is done thrusting, the only forces on the sustainer are air resistance, gravity, and its own thrust.

The advantage in having the water near the top is that the rocket can be made stable with much smaller fins. With a rocket this short and light, I don't think I'd ever be able to make fins big and solid enough to keep it stable if the water was at the rear end of the rocket.



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Re: Unofficial multi stage world record

Post by SaskAlex » Wed May 12, 2010 7:57 pm

WRA2 wrote: Speaking of ground videos Alex, You do not need to have a professionally produced documentary for a record submission. Since the WRA2 requires the onboard video, the ground video is less important. An easy way to produce an acceptable ground video is to place your camera in a fixed location to film the launch. Then after you have launched you can take the camera and film as much as the descent as possible. If you look at most water rocket videos you will see that no one can track the rocket through it's entire flight without it drifting out of frame or landing behind tress, etc. Since the onboard video is required you do not need the film the entire flight from the ground and keep the rocket "in frame".
I know I don't need a great video, but in mine I really only caught the launch. I tried air command's tip of sighting down the top of the camera and it kept the rocket in frame really well. However, since I was fully zoomed out and my rocket is so small, it appears as just a tiny dot in the frame, which you can only see at certain times, and if you know where to look. I guess next time I really have to zoom in more. It just might be hard to find it in the frame, let alone keep it there.



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