Mini Water Bottle Rockets!!

This project is a super fun and easy way to explore rocketry using everyday materials that would otherwise be ending up in the landfill. And unlike regular model rockets you can use it as many times as you want as it's powered completely by air and water!!

All common household items!

1. Goggles and gloves - Safety First!!
2. Disposable plastic water bottle (These use common 500ml bottles, but 2L Soda bottles can be used for bigger rockets!)
3. Bike pump + ball pump needle
4. Cork (or 3D-printed TPU plug)
5. Cardboard box - A shoebox works really well
6. Foam board/ Cardboard - For the fins
7. Tape
8. Hot glue
9. Knife

First you want to prepare the actual rocket by cutting and attaching foam or cardboard fins.

1. First use measuring tape to measure the size of the bottle. (The one in the picture is about 8 inches from the cap to the end).
2. You then want to draw out three triangular fins on your cardboard or foam. I found that ideally you want these to be approximately 60-75% the length of your bottle, but you can always experiment with different shapes and sizes.
3. Cut out your fins!
4. Glue + Tape the fins on. Starting with hot glue makes this a lot easier since it will hold the fins in place while you're taping them, but the main strength comes from the tape. Try to make sure your fins are evenly spaced around the bottle and as straight as possible.

*It helps to make sure that the bottom of your fins is level with the bottles cap as this will allow the rocket to stand on it's own.

The pressurization system consists of the cork, the ball needle, and the bike pump.

1. The first step is to prepare your cork. If using a normal cork, then you will have to drill a hole in the center of the cork to fit snugly around the bike pump pin. The hole should be 1.9- 2 mm wide to fit well. If your cork is too small you can wrap it with tape to increase it's size. (PS: If you don't have a cork you can also 3D-Print one in TPU, which is what I did)

Now you can do the first test of your rocket.

1. Push the ball pin into the pump and lock it in, then push it into the cork too. Insert the cork into the rocket and wiggle and push it in as far as it goes.
2. Then have another person hold the rocket and pump head, after reaching a certain pressure (depending on how tight you pushed the cork in) the rocket will automatically fly off.
3. I would suggest first trying this with an empty bottle before adding water, because you will get drenched!

Now we will make the base for rocket. For this you will need a shoebox (or any cardboard box) and something to weigh it down.

1. Make a tiny hole in the top of the cardboard box and stick the ball pump needle through it. Attach the cork to the other side and press them together.
2. If the cork still wiggles consider hot gluing it to the box, but this may not be necessary.
3. Connect your the head of your bike pump to the other side of the needle and lock it
4. Cut out a hole for the pump's pipe to exit the box
5. Place something to weigh the box down. I used a couple of bricks, but this could be anything.

That's it your done! Now it's time to have fun!

1. Fill your bottle about a third to halfway up with water.
2. Place the bottle on the cork (This is where having a shoebox helps since you can tilt the top sideways when attaching the bottle, so nothing spills)
3. Pump it up.
4. Watch it fly!

Me and my Brother had a lot of fun with this and I hope you do too!!!