Water Rocket Forum

SaskAlex wrote:

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.

Are you launching by yourself? One of the reasons that Air command's videos look so good is that he has a whole crew of "launch personnel" (family) to run cameras/chase rocket etc. If you are doing this by yourself it is going to be difficult to launch the rocket, record the ground video and track the rocket with the camera and chase it if it drifts. You are also flying higher so it is more difficult because as it goes higher it gets smaller. Be careful when zooming. the more you zoom the shakier the video will be. Your best bet is to start with the camera zoomed out and then slowly zoom in as you track the rocket. You could also make one of the camera booms like Anti Gravity Research used for their flight of 1242 feet. (that may help you keep the the rocket centered in the frame).

Try and at least get the launch and the landing on your video.

Good luck on your next flights

SaskAlex wrote:

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.

I thought you said the water barrier inside the rocket didn't work and so the water wasn't in the front of the rocket for the recent flights. If that is what you said then the find must be sufficient to make it stable.

SaskAlex wrote:

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.

I was also wondering how big the nozzle is on the sustainer. It seems to thrust for a fairly long time.

Reinforce the rocket with Kevlar and pump with a 12V 300 psi compressor, then you will have a higher record.

If try this careful because it can explode from positioned reinforcement.

RaZias wrote:Reinforce the rocket with Kevlar and pump with a 12V 300 psi compressor, then you will have a higher record.

If try this careful because it can explode from positioned reinforcement.

I'm not sure how much weight reinforcing will add. His boosters are pretty big which is going to go over the weight limit of the rules.

Plus, you're potentially breaking the law by flying a rocket that heavy. The weight limit is not some random number someone made up, it's the limit most countries place to separate a hobby rocket from a professional rocket. If you break that law there's some places which will classify the heavy rocket as a weapon! In this time in history, you'd have to be more than a touch loopy to be flirting with laws that relate to terrorism!

WTF wrote: I thought you said the water barrier inside the rocket didn't work and so the water wasn't in the front of the rocket for the recent flights. If that is what you said then the find must be sufficient to make it stable.

Since the false bottom was leaking I had to put in very little water. It was only around 100ml or less, just enough to fill the tube going from the nozzle to the false bottom. Since it was in this tube, it was not right at the bottom of the rocket. Also, it really wasn't much mass. If I had had the planned 500-600ml right at the bottom of the rocket, it certainly would have been unstable.

Oh, and the nozzle is around an 1/8". I can't remember exactly what it was, but I can check if you want. The small nozzle and long thrust are another reason you really need it to be stable with the water in it.

SaskAlex wrote:

WTF wrote: I thought you said the water barrier inside the rocket didn't work and so the water wasn't in the front of the rocket for the recent flights. If that is what you said then the find must be sufficient to make it stable.

Since the false bottom was leaking I had to put in very little water. It was only around 100ml or less, just enough to fill the tube going from the nozzle to the false bottom. Since it was in this tube, it was not right at the bottom of the rocket. Also, it really wasn't much mass. If I had had the planned 500-600ml right at the bottom of the rocket, it certainly would have been unstable.

Oh, and the nozzle is around an 1/8". I can't remember exactly what it was, but I can check if you want. The small nozzle and long thrust are another reason you really need it to be stable with the water in it.

I understand your thinking now and it makes it clear to me that this truly is a novel approach that has never been tried before but will surely be copied. Combining the idea of putting the reaction mass in front of a small nozzle sustainer with boosters gives the following advantages:

1. Stability during boost phase.
2. No need for foam or slosh baffles.
3. Stability over a long duration of thrust.

I believe that this combination of ideas is brilliant!

Thanks for contributing this idea!

Holy shit dude, that's a amazing set of flights. Sorry you didn't get the video. I hope you are going to fly again soon and set a new record for us "bottle" guys!

Alex,

This is a really great design. As stated earlier in the thread, you have combined several ideas that had been tried before and found to be of little advantage. The difference is that you were able to combine the ideas in a way that nobody else thought of before to exploit their benefits in ways that were not done before. It's doubtful that anyone could get a rocket with such a powerful booster to fly as well without putting the water in the front.

We ran the numbers back when we were trying to design our first rules compliant rocket and we believed that it would be possible to set a new record using bottles only. It's great to see someone has finally proven that is true after all these years!

I do not fully understand how your rocket actually works. I see a tube on the inside of the rocket. But where do you put the water?

Greath respect for the height! :-)

Daan.[D&P]Rockets* wrote:I do not fully understand how your rocket actually works. I see a tube on the inside of the rocket. But where do you put the water?

Greath respect for the height! :-)

The tube runs up the middle of the rocket and is connected to an enclosed water 'tank" in the top of the rocket. The "tank" is made by gluing a bottle top section inside the pressure vessel to make a divider.

The water is filled into the area above the bulkhead and is confined to the top of the rocket by the bulkhead. When air is filled into the rocket it pressurizes the empty space below the bulkhead. A tube on the wall inside is used to allow the air to enter the water compartment but the tube is placed above the water fill level so the water cannot escape into the air chamber below.

When launched, the air pressure goes from the lower air chamber through the side tube and above the water level and pushes the water down out the central tube and out the nozzle in back.

By putting the water in front, the sustainer is completely stable as soon as it launches, which contributes to the efficiency of the rocket and results in the amazing altitudes.

Does that help clear things up?

Congratulations, Alex! You have really done great! I want to see you beat Antigravity Research with plain bottles! That would really set the world on it's ear!

Hi everybody, my first post

I think that easy method to hold water on top of the rocket is to put smaller 0.5l-1l bottles INSIDE bigger bottles and position that smaller bottle, in the middle and to top of rocket, and run pipe from smaller bottle down to rocket nozzle. Inner smaller bottle contains water and outer bottle air, you can left smaller bottle open on top, near top of the rocket, so you do not need any additional and possibly leakin airtubes. Ofcourse there may be problem that water may slosh over the smaller bottle to bigger.

I hope that you undestand what I try to explain

MK_Rocketry wrote:Hi everybody, my first post

I think that easy method to hold water on top of the rocket is to put smaller 0.5l-1l bottles INSIDE bigger bottles and position that smaller bottle, in the middle and to top of rocket, and run pipe from smaller bottle down to rocket nozzle. Inner smaller bottle contains water and outer bottle air, you can left smaller bottle open on top, near top of the rocket, so you do not need any additional and possibly leakin airtubes. Ofcourse there may be problem that water may slosh over the smaller bottle to bigger.

I hope that you undestand what I try to explain

Hello, MK_Rocketry. Welcome to the forum!

You idea sounds like a refinement of what Alex had done to his rocket which might be an improvement. Are you planning on building your idea? It would be interesting to see if the concept works as well as the design Alex flew.

How about a false bottom foaming rocket? Foam rockets have a reputation of long burn durations. Problem is HOW TO PRODUCE FOAM. Ahhh, upper splice is half filled with water.