Rockets

[Rxke]

as the mass of the propellant is important, too, (reactionmass is higher) would you get better results when you mixed some 'heavy' stuff into the H2O or is that cheating?

BTW Archie, they told me Polyester is a trademark name? Anyway we use polyethylene terephthalate at college, but refer to hollytex and melinex when we use the non-woven fiber variety and the thin sheet forms of the product. It *is* an amazingly versatile substance...

[Riley Montgomery]

Ok...I'm sorry I haven't responded in a while but I've been busy. I'm failing to recieve any help on how to construct this thing. I really want to make this thing fly. Let me tell show you the paper my physics teacher gave me about this Water Rocket Contest.

Requirements: Your device must have a two-liter pop bottle as its lower part of the water rocket. It cannot be damaged in any way, because we will be placing water and 80 PSI of compressed air into it. Wings and fins cannot extend below the neck of the bottel because they will interfere with the rocket launcher.

Your Device Cannot Use:
  Sharp points which may cause injury if the rocket flies off course.
  Explosive or other violent chemical reactions
  ANything other than water in the lowest two liter bottle.


That's it. Now we won't be shooting these straight up but at an angle to see who can get the farthest distance. Any advice on how to construct it?

[archiebald]

Riley, why don't you just click on the links and do some searching of your own?  Haven't we given you enough to get you started?

Rxke,
Looking through some of the links, this has been considered.  But, I guess whatever mass you put into the thing as reaction mass must also be accelerated as part of the payload so the net gain may be negligible.  Remember the rocket itself will only be about 60 to 100 grams dry and the reaction mass would be about 1 to 1.5kg of water for a 2 liter bottle.
Also, the thing to consider would be pollution, cost and possible health hazards - that's the beauty of using water.
There have been a lot of experiment done with CO2 instead of air and I also read of helium being tried.  In some cases, dry ice is used with the water to generate the CO2 pressure.

In one of the links I found, I even saw a guy had designed an electrolysis unit that splits water to charge the bottle air space with hydrogen and oxygen.  He then ignites this mixture with a spark unit to give an initial boost.  Woooohhhh!!!
http://www2.et.byu.edu/~wheeler/benchtop/hydropyro.htm

The same guy also used a 5 gallon water cooler bottle (normally PC material and not designed for pressure) to loft a pumpkin 20 meters into the air.

Nutters!!!

[Riley Montgomery]

I can't use any chemical reactions and I'm pretty sure that is a chemical reaction. I can only use water, nothing else....

[archiebald]

Riley, Have you looked at any of the vidoe clips I linked to???

Try the following experiment.

1) Buy a bottle of Cola / Beer / Champagne (whichever your age or budget will allow)
2) Shake it vigorously to loosen up the carbon dioxide molecules.
3) Open it.

If you need any further explanation, please don't ask me.