Building a water rocket that can stay for a long time in the air?

Question

My year level has to make water rockets that can stay for the longest time in the air.
The only rule we have to follow is to use a 1.5 water bottle.
I'm clueless on how to build the water rocket.
Any suggestions on how to?
Also, what do I have to add to it to make it stay longer in the air?
I have been told that we can attach a parachute to it.

Answer 1

There are two things which will determine how well your rocket does.



1. How high you can get it before its fuel (the water) runs out



2. How slow you can get it to come back down



The thrust for your rocket is provided by air pumped into the bottle to force the water out. To be able to push the water out, the air pressure inside the bottle has to be greater than normal outside air pressure. At the same time, there is a limit to the pressure the bottle itself can take without bursting.



As the water is pushed out the bottle, the air expands and the pressure drops. What you want is for the air pressure inside the bottle to be equal to normal atmospheric pressure as the last drop of water is pushed out.



That is actually quite an easy calculation. If the maximum possible pressure the bottle can take is 5 times normal atmospheric pressure, then you can fill the bottle 4/5ths with water. If it can only take 3 times normal atmospheric pressure, then you can only fill the bottle 2/3rds with water. 5 times atmospheric pressure is probably a reasonable estimate as all these bottles have to meet safety standards.



You are probably better to slightly under fill the bottle than over fill it. Too much water is just extra weigh to carry all the way up. Too little water means your rocket will start faster, but will run out of power a little early.



You could try to increase the pressure the bottle can handle by putting a few bands of tape around it.



For the parachute part, you will want the biggest you can reasonably attach. A simple pyramid shape with a whole cut in the middle will probably be good. Depolying the parachute may be a little tricky because the rocket may tip over before the parachute opens properly, in which case it will probably just get wrapped around your rocket, which will then come down just as fast as it went up!



Good luck with your efforts

Answer 2

A water rocket, as you probably know is just a plastic bottle with water in it , pressurized with compressed air.

When it is launched the expanding air forces the water out and due to Newtons Law of equal and opposite forces, the bottle is accelerated into the air.

When trying for maximum duration there are a couple of considerations.

1. The amount of thrust.

2. The duration of the thrust.

3. The mass of the rocket and fuel(water and air).



The magnitude of the thrust is determined by how much water it can force out per second.

The duration of thrust is determined by how much air and water the bottle can contain, and the size of the exit nozzle.

The mass of the rocket is mainly the weight of the water and a chute if you use one.



Unfortunately , you can't have them all at the same time.

If you put a whole lot of water in the bottle then you don't have much room for compressed air.

If you put a lot of air in the bottle then your water load is reduced.

The size of the exit hole (nozzle) has an effect on the thrust. The bigger the nozzle the faster the water will come out and the greater the acceleration, but the duration of the thrust is reduced.

If the nozzle is made smaller then it takes longer for the water to exit and though the duration of the thrust is increased the acceleration is decreased. Also the rocket stays heavier longer.

So basically what you have to do is experiment with

A. the amount of water you use

B, the amount of air pressure you can put in

C. the size of the nozzle ( you can reduce it slightly by taping a very short piece of garden hose into the neck of the bottle).

If playing around with these allows you to get a reasonable altitude then maybe a parachute might help or build some stubby wings and see if you can get the bottle to glide when it;s empty.

Good luck.

Answer 3

Learn to use google I just typed building water rockets and I came with hundred sites with movies; pictures;step by step help to make them.. here are few :

http://www.ast.leeds.ac.uk/~knapp/rockets/

http://ourworld.compuserve.com/homepages/pagrosse/h2orocketsi.htm

http://www.kidscanmakeit.com/SC0002.htm

http://dogrocket.home.mindspring.com/WaterRockets/

http://makezine.com/05/rocket/

Answer 4

one of the very gud reactions tht u cn do is betwn doctr pepper n somethng sour

oh yh haribo



the reaction betwn haribo n pepper is almost explosive n it generates alot of power