how much water should be in a launch for a two liter bottle rocket?

Answer 1

I think the answer is between 1/4 and 1/2 of the bottle (which would be between 1/2 liter and 1 liter).

You should try various levels and see what works best. You have two variables: the amount of water and the air pressure. You can pretty much figure that increasing the pressure will always increase the height of the flight. But increasing the water could either increase the height (because there is more water being expelled to drive the rocket higher), or decrease the height (because the rocket is heavier, and the reduced amount of air is not enough to drive it as high).

Keep in mind that when you reduce the volume of water, you'll need to pump more air into the rocket in order to get up to the same air pressure. (If you pump it 20 times when it's half full of water, you'll need to pump it 30 times when it's 1/4 full, since the volume of the air is 50% greater, and you have to pump in 50% more air to get it to the same pressure.)

Keep track of the results of your experiments (by timing each flight and writing down how much water and air pressure you used). You should soon be able to identify the best combination of water and air pressure.

Good luck!

Answer 2

About 1/3 full. Pressure should be 40-45 psi.

Use a tubeless tire valve. It will fit the opening in the bottle and will pop out (with some help) when the pressure it right.

CHAPTER ONE
THE WATER ROCKET

It's a sunny summer weekend afternoon and after the kids have watched "Teenage Mutant Ninja Turtles, Part III" six times, and you have read every word in the newspaper including the classified and business section, total boredom sets in.

A neighbor’s dog has rudely chewed the kiddy pool and the kids' bicycle tires are all flat. Hey! The lawn mower works and has a full tank of gas.....NAH! "What can we do?", the kids ask. Well, before they contemplate acting out Dr. Suess's book, "Hop On Pop", look around the garage and in the garbage. You may find all you need to entertain not only yourself and your family, but the whole neighborhood as well.

Do you remember the water rockets you played with as a child? What ever happened to the rocket? I'll bet you still have the air pump, but the plastic rocket has undoubtedly become a part of the environment by landing in a drainage ditch or in the woods across the street. Have you ever tried to buy just the rocket without buying the air pump? Well, if you haven't, let me save you some
time and frustration. They don't sell them separately because the manufacturer has already anticipated sales based on the fact that kids will lose the rockets and parents will be forced to buy the entire package again.

What would you say if I told you that you could make your own water rocket from a 2-liter plastic soda bottle? Impossible? I think not! If you have a bicycle pump and a tubeless tire valve you've got all you need for an afternoon of wet fun!

Raw materials:
1 (or more) plastic 2-liter soda bottle

Tools required:
1 bicycle pump
1 tubeless tire valve

STEP 1
Find a 2 liter plastic soda bottle that has a separate plastic base attachment. Fill 1/3 of the bottle with hot tap water and immediately twist the plastic base off the bottom of the bottle (the hot water weakens the glue with which the base and label are attached). The sooner the base is removed after the hot tap water has been added, the less glue will remain on the bottom of the bottle. Next, turn the bottle on its side with the label seam down and slowly peel the plastic label off the bottle. To remove the remaining traces of glue from the bottle, use cooking oil and a paper towel. Gently wash the outside of the bottle with dish soap to remove any remaining cooking oil, then carefully empty the hot tap water from the bottle (to prevent unsightly wrinkles, turn the bottle upside-down with the cap slightly loose, swirl the water around in a counter-clockwise motion, and quickly remove the cap over the sink).
STEP 2
Fill 1/3 of the bottle with cold tap water, attach the bicycle pump hose to the tubeless tire valve and work the end of the valve into the bottle until it clears the narrow part of the bottle neck.


STEP 3
While holding the bottle upright, pull the tubeless tire valve snug against the inside of the bottle neck while one of the kids pumps enough air into the bottle to hold the valve in place. At this point, you should advise all
onlookers and observers to stay clear of the "launch site".

STEP 4
Carefully turn the bottle upside-down and hold it loosely near the neck while keeping the tubeless tire valve centered in the opening, then have the participating child continue to pump air into the bottle. If the pump
has a pressure gauge, pump until it reaches about 38 p.s.i. or until the valve starts to move downward. When sufficient air pressure has been pumped in, hold the bottle away from your body (and others) and slowly work the valve out of the bottle while maintaining its vertical position. To prevent possible injury, leave the pump hose clipped to the valve and make sure that you catch the valve when it ejects itself from the bottle.

The resulting launch will send the bottle soaring into the air leaving a 30 foot column of water about one inch in diameter that seems to hang in the air for a second, then comes down on the person acting as the launching pad. So, before attempting this launch, be sure that you are prepared to get yourself and your
audience soaking wet.

Answer 3

How much pressure will it hold? ☺

Doug