Introduction: How to Make a Rocket Using PET Bottles

About: Hey! I'm Natanael Prado, a 21 years old boy who was born curious! I like technology, robotics, and of course, I love to make and invent things too! 😄

Hey guys, in this project I will show you how me and my friends, Larissa and Karine made some PET bottle rockets and a rocket launcher for a national competition in Brazil called MOBFOG, together we are the Propulsion team. So, The Brazilian Rocket Show (MOBFOG) is an entirely experimental Olympics, as it consists of obliquely building and launching rockets from a rocket launcher as far away as possible. These rockets can easily reach 100 meters (328 ft) away, and up to 300 meters (984 ft) with some improvements. So let's get started!!

Step 1: Materials

So to make this project I will basically split it into two parts, the rocket part, and the launch rocket part.

To make the ROCKET you will need to have:

  • Two 1,5 L returnable PET bottle
  • A TEKBOND 793 glue
  • An insulating tape
  • Sandpapers
  • Durepoxi (an epoxy adhesive)
  • school folder
  • spray paints and other things to decorate your rocket

To make the LAUNCH ROCKET you will need to have:

  • 8 Aluminum tubes
  • 20mm PVC Pipe
  • Copper fittings
  • Pressure gauge
  • ½ drawer register
  • 45mm PVC glove
  • 6 Meter String
  • A Nail
  • Durepoxi
  • Nylon Clamps
  • Metal ring clamp

Step 2: Building the Rocket

So let's start building the rocket. But first, take the two 1,5 L returnable PET bottles and use sandpapers to sand both bottles. Then let's move to the next step.

1. Cutting the bottles

Take one of the previously sanded bottles and cut it in the middle, then you will have something like the second image below.

Now we'll have to build the rocket nozzle using the top of the bottle that has been cut, for that you will have to use "Durepoxi" which is an epoxy adhesive and then shape the mass at the tip to form the tip of a rocket with the rest of the bottle, see the image below.

Once you've made it, let's glue this part into the bottom of the other bottle, so wrap the TEKBOND 793 around the bottom of the bottle, then put the rocket nozzle in it and tape around it. Now your rocket is starting to take shape as you can see in the image below.

Now have fun painting and decorating your rocket any way you like ;).

2. Making the Fins

To finish your rocket you have to make the fins of your rocket, to make it you will need a plastic school folder, you can use other materials too, but only make sure that it's a light and rigid material. Exist different tips of fins elliptical, trapezoidal, square, rectangular, etc... In this project, we made 3 trapezoidal fins. See the images below.

When you finally cut the fins put it in your rocket and it will be done. The images below show 2 of our rockets that we launched, on the left, you can see the rocket Canopus and on the right, you have the rocket Andrômeda.

Step 3: Making the Rocket Launcher

Now it's time to make the rocket launcher, particularly this was the hardest part for us, so my father helped us. In our rocket launcher, we put a record so that if something went wrong at rocket launch time we could abort the launch (that is very important for your safety) and we put a manometer to measure the pressure inside the rocket before launching it.

1. Connecting the pressure gauge on record

Let's start accomplishing the pressure gauge in the ½ drawer register, to make that you will need three pipe nipples, two Female Connector Copper 22 x 1/2 and a T pipe. The structure should look like the image below. You should also use some kind of Joint Sealant Engine and Teflon ribbon to glue the connections.

2. Connect the Aluminium tubes

Once you've made it you have to connect the aluminum tubes into the other connections making the entire structure of the rocket launcher. The structure we made is in the image below, but you can do it differently if you want.

As you can see there's a nail on the tip of the PVC pipe to which the bottle will be placed, this nail serves to pop the vinegar ballon which will be placed inside the rocket and thus starting the reaction inside the rocket that will make it fly, but we will talk about the chemical reaction only in step 4, there is also a hole in the tube that allows the rocket's internal pressure to be measured by the pressure gauge.

3. Eliminating the gap between the tube and the rocket mouth.

The Launch tube diameter (20 mm) is slightly smaller than the inside diameter of the rocket nozzle. This will be under high pressure and there can be no air leakage, so we suggest the following procedure to remove the “gap” that exists between the tube and the rocket mouth. 8 cm above the “tee”, along with the 25 cm tube place the ring of a 6.5 ”birthday balloon nozzle. About this nozzle place, a full loop of 5 cm wide cotton tape tightly attached to the tube. Remember to wipe soap or soap over the tape and inside the bottle mouth before rubbing over the beak of the birthday balloon that is under the sticking plaster. This lubrication is fundamental.

4. Making the trigger

To get the rocket off the base only when we want it, we need to firmly attach it to
release base. For this, we suggest putting 8 nylon clamps, with 3.6 mm heads placed symmetrically around the release tube. Note that the “chin” of the nylon cuff head should be 1 cm above the balloon tip, so the “tail” of the cuff will be 9 cm from the beginning of the tee. To attach the nylon clamps use one or two metal clamps opening up to 1 inch, However, this still does not hold the rocket when pressurized at the launch pad. To do this cut a piece of white pipe, 4 cm in diameter and 4 cm in length and drill two diametrically opposed holes one of its ends. Tie a 20 cm long string between these holes and Then tie another one about 4 or 5 m long from the 20 cm. When pressurized the rocket, stretch the 4 or 5 m string behind the rocket and at the end of the count. regressive pull the string enough to lower it. At this moment the rocket will violently exit the release base.

Step 4: Prepare Rocket Fuel

A rocket doesn't fly without fuel right?! So The last step is to make the fuel, for that, you need to have Vinegar 4% and baking soda, when these two-ingredient are mixed, it makes a chemical reaction that will release CO2, which will generate pressure inside your rocket. So when you pull the rocket trigger the pressure will be released and your rocket will fly towards the sky.

Step 5: Launch Your Rocket and Enjoy It

Now you can finally launch your rocket, you have to put approximately 60 grams of baking soda inside the rocket, and then fill a party balloon with approximately 945 milliliters of vinegar and put it inside the rocket too, when docking the rocket in the launchpad you have to rock the rocket in the launch pad until the nail pop the party ballon, when this happens the reaction will start and release pressure, be sure to check if the trigger is holding the rocket and if no pressure is being leaked, and of course be careful and stay away when pulling the trigger.

Note: I've attached a pdf of this same project here in PT-BR which is my native language! :)