Introduction: 2 Liter Rocket

Picture of 2 Liter Rocket

Looking for something exciting to do? Try building a water powered rocket out of a 2 liter soda bottle! This can be completed in less than half an hour with simple household materials.

Materials:

  • 1 Two liter bottle
  • Cardboard
  • Card stock (or construction paper)
  • 1 Cork
  • 1 Schrader needle (common on most bicycle pumps)
  • Tape

Tools:

  • Excato Knife
  • Drill (or awl)
  • Scissors
  • Bike pump
  • Marker (or pen)

Step 1: The Cork Stopper

Picture of The Cork Stopper

Take a cork and stick it into the soda bottle's opening to make sure that it fits in snugly. The seal has to be tight, so if your cork doesn't fit either find a larger diameter cork, or wrap the cork with tape to increase the diameter.

Cut the cork shorter so that the Schrader needle is longer than the cork, the tip of the Schrader needle has an opening that needs to be exposed.

Step 2: Drill Into Cork

Picture of Drill Into Cork

Drill into the center of the cork all the way through. If you don't have a drill you can punch through the cork with an awl or a nail. The important thing is that the drilled hole is smaller than the Schrader needle.

Push the Shrader needle through the drilled opening, then insert the cork into the mouth of the bottle.

Step 3: The Fins

Picture of The Fins

To make the fins lie the bottle flat of its side and trace a fin shape with a marker. The fins should be about 2 inches wide at the base and 8 inches high, but you can make them any shape you like.

Cut the fins out with an Exacto knife or scissors.

Step 4: Tape Fins

Picture of Tape Fins

With the mouth of the bottle pointing downwards, attach the fins with tape, equally spaced around the bottle. I had the fins act as a stand for the bottle rocket, placed at a height to allow enough clearance under the rocket to install the bike pump into the cork.

I used strong duct tape so the fins were sturdy and would hold in place after a few rocket launches.

Step 5: The Cone

Picture of The Cone

To form the cone simply fold over the corner of a sheet of card stock or construction paper and continue rolling until you get a cone with a base that is roughly the same diameter of the bottom of the soda bottle. If it's a little larger you can trim the cone base with scissors.

Use tape to secure the cone shape, then more tape to connect the cone to the bottom of the soda bottle.

Your rocket is all ready to launch! Now is the time to decorate your rocket if you want with color or stickers.

Step 6: Take It Outside

Picture of Take It Outside

Find a suitable launching site to blast off. I went to the park, but any open area away from trees and power lines will work.

Step 7: Fill With Water

Picture of Fill With Water

Before hooking up the bike pump we'll need to add some water to the soda bottle. Since water doesn't compress, water will act as a ballast for the soda bottle and reduce the amount of area inside the bottle to be pressurized (which means less pumping).

I suggest filling about 10% with water, although, you can experiment and find what you think works best for your rocket.

Step 8: Pumping

Picture of Pumping

Insert the cork stopper into the rocket, making sure the cork has a snug fit. Place your bike pump off to the side of the rocket and start pumping.

Make sure the rocket isn't pointed at anything, especially yourself!

Step 9: Blast Off!

Picture of Blast Off!

Keep pumping, the soda bottle will pressurize and the rocket will blow out the cork and blast off!

I was able to get mine to go about 25ft high, but with experimentation on cork tightness and water ballast I'm sure you can get yours to go higher.

please share your soda bottle rocket in the comments below. Happy launching!

Comments

redrok (author)2015-08-31

Hi Hammock Boy

You describe this as a "water powered rocket".

However, this is actually a "compressed air powered rocket".

One should ask what the water is used for in these things?

These rockets go much further by eliminating the water and use only the compressed air in the bottle.

Here is the physics:

1. The energy contained in the air is proportional to the volume times the pressure. So the more water in the rocket the less air or energy contained in the rocket.

2. The lighter the rocket the greater it can accelerate. Water is quite heavy compared to the rocket body. This heavy weigh limits the maximum velocity and consequently the the maximum height the rocket can atain.

Try a series of test launches with various quantities of water including no water and compare the resultant maximum heights. To be fair, make sure each launch has the same air pressure.

redrok

dillonp6 (author)redrok2016-03-29

Yes you are correct the water only acts as mass for the bottle. The air released is what causes the bottle to fly

paul dito (author)redrok2015-09-07

Air powered? I don't think air alone would get that bottle very far, do you? Try it without water.

ChristopherK29 (author)paul dito2015-09-30

Well by decreasing the container volume, you are increasing the gas pressure (PV=nRT). This means a greater pressure per same amount of pumps

mikiex (author)redrok2015-09-06

You do need water in these rockets to achieve a maximum height, the water is a mass that you are ejecting. The mass of the water leaving the rocket at speed will give you an equal opposite force pushing the bottle (Newtons 3rd Law). If you only have air in the bottle you will have very little mass, so the rocket won't go far at all. The optimal amount of air/water is something you do need to experiment with (unless you want to get into some maths!)

SpankyO (author)redrok2015-09-06

Here is the physics... Air is not a solid Object, like water. Question, Will a shotgun kick more if there is a slug in it , or just a blank? It has to move the Slug / water, now but that is a Solid Propellant.. well the water is. Check this out .. it will help you to understand more ..

http://exploration.grc.nasa.gov/education/rocket/BottleRocket/sim.htm

TaitS1 (author)redrok2015-09-03

There is a air/water rocket station at OMSI in Portland, Oregon. Filling with some water typically makes them go higher. There may be less energy with water in there, but doesn't the water add thrust and direction?

ecto311 (author)TaitS12015-09-06

Maybe the water helps hold pressure better than just air. Prevents some of it from leaking. Maybe if you used a gel of some sort on the cork it would work even better eliminating the weight of the water but letting it seal better also.

SameerK6 (author)2015-10-19
Hi redrok,My rocket went higher with the ballast than it did without. the water actually helps increase the weight which increases the momentum gained. This increases the height that the rocket catapults to (law of conservation of angular momentum).

SamGeek

redrok (author)2015-10-03

Come on Guys, You haven't actually done the experiment of "Water vs No Water", have you?

The energy stored in the bottle is solely contained in the compressed air. Since water is incompressible no energy is stored in it.

The water is simply excess mass. Worse yet the more water volume the less compressed air in the bottle which limits the stored energy.

redrok

ecto311 (author)2015-09-06

I made one of these years ago but used a crutch bottom on the bottle. The rubber holds tight on the cap and seals again and again. I would think the cork would be destroyed over time.

ymasullo (author)2015-08-31

Although I'm a biology teacher, I would love to do this with students to have them work together and figure out what works best. Simple idea. I love it.

JanV10 (author)2015-08-31

Download Cliff Hight Timer app on your phone for free and start the clock when your rocket start to desend. Easy way to calculate hight of rocket. Add a parashoot to your rocket.

altomic (author)2011-12-06

i saw a contest on Japanese TV which was a bottle rocket contest based entirely on distance achieved.

the winner was a multistage rocket as made here. it had launching tracks and went about 500 feet.

awesome.

Jetmaster360 (author)altomic2015-08-25

what do you mean 'multistage'? how did they do it?

SidA2 (author)Jetmaster3602015-08-30

timers that make the next bottle launch as soon as the previous stage stops

Jetmaster360 (author)SidA22015-08-30

can you please post a link?

TimB2 (author)2015-08-30

Why not use a small hobby type air compressor or portable compressed air tank to pressurize the rocket? All I've ever seen is hand operated pumps.

MichaelN (author)TimB22015-08-30

We use one of the cheap portable jump-starter packs that has a12V lead-acid battery and inbuilt compressor. Works great. I'm planning a smaller unit using a 12V $10 compressor and LiPo battery pack.

Debbi Doodles (author)2015-08-30

You rock ! My son is the same way. I just posted you all over FB and the Geeks that love good geek stuff! Thank you for your awesome ideas! :-)

chobbs1957 (author)2015-08-28

This is a great fun idea. Thanks

arothschild (author)2011-12-05

This looks really fun! Good project for holiday break!

TheGeek1984 (author)2011-12-05

For a school science class we made these. I never got to see mine go up though. It went the highest from what I was told, but I wasn't in school that day because unfortunately the night before was my grandfather's memorial service and my mom turned off my brother's and my alarm clock. She didn't want to make us go to school the following day, she thought it would be too hard. Anyway, my science teacher was also the photography teacher, and even though she set my rocket aside so I could see it fly, her photography students threw it out. I've been meaning to make another, but didn't have any way to get it in the air.

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Bio: From solder to zip ties, lead acid batteries and LEDs, and especially Legos, putting things together has always fascinated me. The more challenging the better ... More »
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